# Peculiar exhaust note



## Captainfish#1 (Dec 31, 2017)

Hello all, I have an unusual problem hoping that the expertise here can help resolve. I have a new build in my 1970 GTO. 455 40 over, 10.00 compression 614 heads and Crower 60245 cam, original RA IV manifolds and intake with Race Pro mufflers. Car runs great and pulls willingly to 6000 rpms. The problem is that at idle I have a popping or whooshing along with the expected rumble. It is bad enough that I find it an embarassment . Switched off from Q jet to Holley and popping remains. Two sets of plug wires and two sets of Autolite 85 plugs yet popping persists Cap and rotor are new. Is it possible that the mufflers are defective? I know it sounds ridiculous but running out of variables. Readjusted lifters and all cranking compression was almost exactly the same around 178. Anyone else experience anything like this?


----------



## BearGFR (Aug 25, 2008)

Could you post a video with sound so we can hear?


----------



## Captainfish#1 (Dec 31, 2017)

BearGFR said:


> Could you post a video with sound so we can hear?


Will try


----------



## Sick467 (Oct 29, 2019)

Double check you spark plug wires and cap. Wires on the wrong plugs, arcing wires, & contaminants in the cap can all cause misfiring. If the misfire is when the exhaust valve is open...you'll get some popping out the tailpipes.


----------



## geeteeohguy (Feb 2, 2008)

Video would help. I would hook up a vacuum gauge and look for a flickering needle when it pops. Could be exhaust valves leaking due to timing issues, etc. 6000 rpm is, IMO, too high an RPM for a stock-ish big-journal engine. I burnt up a 428 that way once. YMMV....


----------



## PontiacJim (Dec 29, 2012)

Captainfish#1 said:


> Hello all, I have an unusual problem hoping that the expertise here can help resolve. I have a new build in my 1970 GTO. 455 40 over, 10.00 compression 614 heads and Crower 60245 cam, original RA IV manifolds and intake with Race Pro mufflers. Car runs great and pulls willingly to 6000 rpms. The problem is that at idle I have a popping or whooshing along with the expected rumble. It is bad enough that I find it an embarassment . Switched off from Q jet to Holley and popping remains. Two sets of plug wires and two sets of Autolite 85 plugs yet popping persists Cap and rotor are new. Is it possible that the mufflers are defective? I know it sounds ridiculous but running out of variables. Readjusted lifters and all cranking compression was almost exactly the same around 178. Anyone else experience anything like this?




Automatic or manual trans? If auto, 2,500 RPM or better stall converter?

Did you dial in the cam to verify cam specs using a degree wheel?

Engine vacuum?

1.5 or 1.65 ratio rocker arms?

Checked valve train geometry?

Zero lash the lifters using the stock double nut rocker arm nuts or poly locks?

Rhoads lifters, anti-pump up lifters, or standard hydraulic lifters?

What type/weight oil are you using?

What valve springs/open/closed pressures were used and what was the installed height?

Stock points distributor or other?

What is your Initial Timing, Total Timing @ "X" RPM, and how much vacuum advance does the vacuum can provide? Ported vacuum or direct manifold vacuum to the vacuum advance?

Idle speed?

As you raise/ease engine speeds up in neutral, is there an RPM where the popping stops?


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> Will try


Sorry Bear, Not smart enough to figure out how to do that.


Sick467 said:


> Double check you spark plug wires and cap. Wires on the wrong plugs, arcing wires, & contaminants in the cap can all cause misfiring. If the misfire is when the exhaust valve is open...you'll get some popping out the tailpipes.


Thanks,Will do


BearGFR said:


> Could you post a video with sound so we can hear?





BearGFR said:


> Could you post a video with sound so we can hear?


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> Sorry Bear, Not smart enough to figure out how to do that.
> 
> Thanks,Will do


Crower cam saver lifters,1.65 rockers,full manifold vacuum, 10 degrees VA , 1/2 turn past zero lash idles great at 800, just the popping. I know that 6000 is a lot of revs for this engine, it just got there when tires broke loose. Tried ported advance- no difference. Trying to get you all a video from my photos but struggling with that also. Thanks for input. Must be something trivial because engine runs well, better than when the RA IV was brand new Almost forgot,timing at 13 btdc and points distributor.

.


Captainfish#1 said:


> Sorry Bear, Not smart enough to figure out how to do that.
> 
> Thanks,Will do


Got video uploaded to you tube but not published yet. The springs were set to the 1.81 standard RA IV height, 10 /30 oil and manual trans
No breaking up or misfires of any type at anything above about 11 or 1200 hundred rpms


----------



## PontiacJim (Dec 29, 2012)

Captainfish#1 said:


> Crower cam saver lifters,1.65 rockers,full manifold vacuum, 10 degrees VA , 1/2 turn past zero lash idles great at 800, just the popping. I know that 6000 is a lot of revs for this engine, it just got there when tires broke loose. Tried ported advance- no difference. Trying to get you all a video from my photos but struggling with that also. Thanks for input. Must be something trivial because engine runs well, better than when the RA IV was brand new Almost forgot,timing at 13 btdc and points distributor.
> 
> .
> 
> ...


OK, so looking at it all here is *my opinion.*

The factory RAIV cam specs state 15 degress BTDC and manual transmission idle speed of 1050 RPM's. Your 800 RPM's are too low - and as you stated, 1,100 RPM's no issues.

So here is what I feel is happening. You have a BIG cam.

1.) Due to the differences in cylinder head, intake, and exhaust configuration, there is a great deal of sensitivity to the cam *OVERLAP*. More overlap will decrease low RPM efficiency by *increasing raw fuel escaping into the exhaust*.

2.) Late exhaust valve closing will allow some of the *new intake air/fuel charge to escape out the exhaust system*, decreasing fuel mileage and increasing emissions.

3.) Longer stroke cranks dwell the piston longer near top dead center and hence *tend to make the engine act like it would if overlap was increased.*

4.) With two engines of the same displacement operating at the same engine speed and being of the same displacement but different strokes, *the longer stoke engine should require a larger duration camshaft.*

My thoughts are that the popping is from the unburned raw gas that is being pulled from the fresh intake charge entering the combustion chamber during valve overlap and being ignited - supported by No.'s 1,2,& 3 and the fact that the popping goes away at 1,100 RPM's and the RAIV cam's idle was 1050 RPM's.

The efficiency of the flow of the 614 heads coupled with the long stroke/longer piston dwell at TDC increasing more overlap than advertised is part of the mix in the popping cause.

A wider Lobe Separation Angle of 114, maybe even 116, _may have been_ a better choice instead of the 112 LSA your Crower cam has.

That all said, the popping sound may be simply a symptom of the cam selected and too low of an idle speed. You should have an electric idle solenoid that when energized in the "RUN" ignition position increases idle speed to 1050/1100 RPM's and when the key is turned "OFF" to shut down the engine, the plunger retracts dropping the idle speed/closing the throttle so the engine shuts down and does not "diesel" and keep running.


----------



## coyote595 (Dec 4, 2019)

Does your exhaust pop on decel in gear? Like if you shift down a gear and use the engine to slow the car? I am also into motorcycles, and this is common if there are any leaks in the exhaust system that allow fresh oxygen to enter the hot exhaust system and assist any unburnt fuel to ignite. 

Also, just curious, You are running 614 heads, which are 72cc 1970 RAIV, and your displacement is about 464 Cu In. Are you running dished pistons? How are you keeping the compression low enough?


----------



## Captainfish#1 (Dec 31, 2017)

PontiacJim said:


> OK, so looking at it all here is *my opinion.*
> 
> The factory RAIV cam specs state 15 degress BTDC and manual transmission idle speed of 1050 RPM's. Your 800 RPM's are too low - and as you stated, 1,100 RPM's no issues.
> 
> ...


Thanks Jim. Sounds very plausible as the pop is not to be heard anywhere except at splitter exit. While raise idle next time I have hood up. Shaker 455 sent me a properly set up points distributor and it is willing to idle even happily even lower once it was installed.


coyote595 said:


> Does your exhaust pop on decel in gear? Like if you shift down a gear and use the engine to slow the car? I am also into motorcycles, and this is common if there are any leaks in the exhaust system that allow fresh oxygen to enter the hot exhaust system and assist any unburnt fuel to ignite.
> 
> Also, just curious, You are running 614 heads, which are 72cc 1970 RAIV, and your displacement is about 464 Cu In. Are you running dished pistons? How are you keeping the compression low enough?


I have Ross 27 cc dished pistons and the heads are at 68 cc, from a long time ago. No popping on decel , only at idle. Thanks for response


----------



## PontiacJim (Dec 29, 2012)

Captainfish#1 said:


> Thanks Jim. Sounds very plausible as the pop is not to be heard anywhere except at splitter exit. While raise idle next time I have hood up. Shaker 455 sent me a properly set up points distributor and it is willing to idle even happily even lower once it was installed.
> I have Ross 27 cc dished pistons and the heads are at 68 cc, from a long time ago. No popping on decel , only at idle. Thanks for response


Sounds like the engine is set-up right and is a real torque monster. Yep, I think that is what you are experiencing and the lower RPM is where it will be worse. The RAIV heads have a good flowing exhaust port compared to other heads. You may want to also consider some type of rev-limiter to make sure your don't over rev the engine and do damage. Just takes a second on for the tires to break loose on a patch of sand when jumping on the pedal or even a missed shift. I won't run a healthy engine without one.

One of the guys at work has a modern Nissan Z-350 and he has 3 different factory exhaust sound settings with a flip of a button. One of the settings allows the exhaust to pop/backfire when you let off the gas after revving it/decelerating. When younger, we learned that if you turned the key off briefly and then turned it back on as you were driving down the road you could create that nice backfire. Sounded "cool" unless you had a weak muffler and blew it up - and then had to explain to your dad why the muffler was all swollen up. LOL


----------



## Captainfish#1 (Dec 31, 2017)

I know this is really going to sound Bush league but is there any muffler likely to mitigate or mask this? As I have stated before I find it embarrassing to have it sound like this


PontiacJim said:


> Sounds like the engine is set-up right and is a real torque monster. Yep, I think that is what you are experiencing and the lower RPM is where it will be worse. The RAIV heads have a good flowing exhaust port compared to other heads. You may want to also consider some type of rev-limiter to make sure your don't over rev the engine and do damage. Just takes a second on for the tires to break loose on a patch of sand when jumping on the pedal or even a missed shift. I won't run a healthy engine without one.
> 
> One of the guys at work has a modern Nissan Z-350 and he has 3 different factory exhaust sound settings with a flip of a button. One of the settings allows the exhaust to pop/backfire when you let off the gas after revving it/decelerating. When younger, we learned that if you turned the key off briefly and then turned it back on as you were driving down the road you could create that nice backfire. Sounded "cool" unless you had a weak muffler and blew it up - and then had to explain to your dad why the muffler was all swollen up. LOL


What had me perplexed Jim is that I ran the HC -03 cam in it as a 400 and never heard this
We had the HO cam profiled and it was very close to this Crower but showed wear so builder went with this Crower. The only difference was that as a 400 I ran headers
.


----------



## Captainfish#1 (Dec 31, 2017)

Anyone have any suggestions as to exhaust then. Maybe the Race Pro mufflers are amping up the pop. Would adding headers again make a difference or changing mufflers? I really can' t let it stay like this but really like the performance over 4000 rpms so I do not want to change cam. Rhoades are an option also if no other options seem viable. Thanks


----------



## BearGFR (Aug 25, 2008)

Captainfish#1 said:


> Got video uploaded to you tube but not published yet. The springs were set to the 1.81 standard RA IV height, 10 /30 oil and manual trans
> No breaking up or misfires of any type at anything above about 11 or 1200 hundred rpms


Where's the link?


----------



## coyote595 (Dec 4, 2019)

A turbo style muffler might mask it a little bit, but if you like the exhaust loud, they might not be noisy enough for you. I have used both the Dynomax Super Turbos and the Pypes Turbo Pros and I like them both. The Race Pros are a straight through baffled pipe, so there is nothing there to conceal your pops. The Turbo routes the exhaust through an S pattern. This type of muffler has a deep mellow tone, but is quieter than what you have now.


----------



## Captainfish#1 (Dec 31, 2017)

BearGFR said:


> Where's the link?


Mistakenly had video flagged as private on YT. Will supposedly premiere 12 am tonight. Hopefully. Once on YT getting it to the forum will be next obstacle. Thanks for interest.


----------



## Captainfish#1 (Dec 31, 2017)

coyote595 said:


> A turbo style muffler might mask it a little bit, but if you like the exhaust loud, they might not be noisy enough for you. I have used both the Dynomax Super Turbos and the Pypes Turbo Pros and I like them both. The Race Pros are a straight through baffled pipe, so there is nothing there to conceal your pops. The Turbo routes the exhaust through an S pattern. This type of muffler has a deep mellow tone, but is quieter than what you have now.


Not interested in exhaust being loud ( 70 years old ) but am concerned about flow. Builder wanted headers as we saw a considerable loss of power with the RA manifolds already. May ultimately end up with headers anyway


----------



## coyote595 (Dec 4, 2019)

A good turbo muffler has plenty of flow. In the old days, I ran Cyclone Sonic Turbos in my Firebird on a modified solid cammed RAIV engine that would spin freely to 6800 rpm. Those were 2.5" mufflers with 2.25" full tail pipes. If you were concerned with the Turbo being restrictive, you could just step up the muffler to a 3 inch in your 2.5 inch system, if that is what you have.


----------



## PontiacJim (Dec 29, 2012)

Captainfish#1 said:


> I know this is really going to sound Bush league but is there any muffler likely to mitigate or mask this? As I have stated before I find it embarrassing to have it sound like this
> 
> What had me perplexed Jim is that I ran the HC -03 cam in it as a 400 and never heard this
> We had the HO cam profiled and it was very close to this Crower but showed wear so builder went with this Crower. The only difference was that as a 400 I ran headers
> .



The HC-03 is the 041HL (high lift). There seems to be a number of variations on this cam depending on year purchased. But basically the same specs as the factory 041, but .520" Int/Ex lift with 1.5 ratio rockers and .571" with 1.65 ratio rockers, and another version says .498"/.512" w 1.5 rockers and .548"/.563" with 1.65 rockers.

Crower lift is .562"/.575" @ 1.65 rocker ratio.

I am going to say that the original HC-03 grind was the 041HL, same as as factory specs but with the higher lift w/1.65's as pointed out and then the other versions were for those engines that did not have/use the RA IV heads because the ratio of intake to exhaust flow was pretty good whereas the standard D-port head is not as good and typically had more duration/lift on the exhaust valve to compensate.

The 041 advertised duration is 308/320 and 231/240 @ .050" lift, HC-03 308/320 and 244/252 @.050" lift, Crower advertised duration is 311/316 and 248/252 @ .050" lift.

The 041 and HC-03 have a Lobe Separation Angle(LSA) of 114 (113.5 actual), and your Crower cam has an LSA of 112.

O41 has an Intake Centerline(IC) of 112, HC-03 IC is 108 and Crower IC is 108.

Based on the advertised durations which is seat timing:
041 & HC-03 Valve overlap - 87 degrees.
Crower Valve overlap - 89.5 degrees.

But using seat timing of .050" to measure valve overlap -
use the formula Ex closes ATDC + Int opens BTDC = overlap @ .050"

*RAIV* - Ex 6ATDC + Int 3BTDC = *9 degrees of valve overlap *where the intake and exhaust valve are open at .050". True overlap will be slightly more.
*Crower *- Ex 10ATDC + Int 16BTDC = *26 degrees of valve overlap *where the intake and exhaust valve are open at .050". True overlap will be slightly more.

With the above differences @ .050", in my opinion, indicating that the cam's lobe ramps are designed as "fast" ramps lifting the valves open/closed much faster than the slower/easier lobe ramps of the stock cam.

A narrower Lobe Separation Angle (102-108) provides more valve overlap. As overlap increases and manifold vacuum decreases, idle speeds need to be increased just to keep the engine running. At idle the intake air charge is moving at a very slow speed and there is plenty of time during the overlap period for the exhaust gas to move back up the intake tract and dilute the incoming charge - producing that nice rough idle many like to hear. As the RPM's begin to climb into the power band, there is little time for the exhaust gas to do anything except exit the exhaust port. Add the inertia of high-speed air/fuel mixture entering the cylinder as the intake valve opens at higher RPM's and overlap can be very useful for pulling in that column of air into the cylinder. 

So that's how I see it, the good flowing RA IV exhaust ports, the tighter LSA, more valve overlap at .050" - more raw gas going out the exhaust at the lower idle RPM's to give you that fuel ignition pop out the pipes. 

Wow, how did I ever put together an engine in my youth without knowing all that I now know about cams? Think I might start my own cam company.


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> Mistakenly had video flagged as private on YT. Will supposedly premiere 12 am tonight. Hopefully. Once on YT getting it to the forum will be next obstacle. Thanks for interest.






Here is the video link


----------



## geeteeohguy (Feb 2, 2008)

The exhaust is so loud and the cam is so lumpy I can't really hear anything. A slight rattle that could be a loose harmonic balancer, etc....no real popping, at least to my ears. 
Very cool looking/sounding car!!!


----------



## Captainfish#1 (Dec 31, 2017)

BearGFR said:


> Could you post a video with sound so we can hear?





BearGFR said:


> Could you post a video with sound so we can hear?


B


geeteeohguy said:


> The exhaust is so loud and the cam is so lumpy I can't really hear anything. A slight rattle that could be a loose harmonic balancer, etc....no real popping, at least to my ears.
> Very cool looking/sounding car!!!


Thank you, loo
ear, Finally got video posted post # 21


----------



## Captainfish#1 (Dec 31, 2017)




----------



## geeteeohguy (Feb 2, 2008)

Did you hook up a vacuum gauge? I've run into popping like this out of the exhaust when the initial timing was too far advanced.....


----------



## coyote595 (Dec 4, 2019)

Is it easy to remove your exhaust splitters just to see if that makes a difference? It does not really sound like a pop caused by ignition of exhaust gasses to me. Your description of peculiar is certainly accurate. If the splitter removal is easy, give it a try. Can't hurt.


----------



## Captainfish#1 (Dec 31, 2017)

geeteeohguy said:


> Did you hook up a vacuum gauge? I've run into popping like this out of the exhaust when the initial timing was too far advanced.....


Timing is at 14btdc. Yesterday advanced it alot and it made no difference. Vacuum at 800 to 850 rpm about 7.5 inches


----------



## Captainfish#1 (Dec 31, 2017)

coyote595 said:


> Is it easy to remove your exhaust splitters just to see if that makes a difference? It does not really sound like a pop caused by ignition of exhaust gasses to me. Your description of peculiar is certainly accurate. If the splitter removal is easy, give it a try. Can't hurt.


Thank you, good idea


----------



## Captainfish#1 (Dec 31, 2017)

geeteeohguy said:


> Did you hook up a vacuum gauge? I've run into popping like this out of the exhaust when the initial timing was too far advanced.....


My bad. I misread your response. Good idea. Will take back initial 6 or 8 degrees and hope for best. Will let you know


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> My bad. I misread your response. Good idea. Will take back initial 6 or 8 degrees and hope for best. Will let you know


Set initial back to 6- 8 btdc did not have any impact. Had to raise idle of course. Than tried advancing and it also had no effect other than speeding up idle .


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> Here is the video link


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


>


How and why are these videos being pulled down? I am not doing it


----------



## Captainfish#1 (Dec 31, 2017)

BearGFR said:


> Could you post a video with sound so we can hear?





BearGFR said:


> Could you post a video with sound so we can hear?


----------



## Captainfish#1 (Dec 31, 2017)

PontiacJim said:


> The HC-03 is the 041HL (high lift). There seems to be a number of variations on this cam depending on year purchased. But basically the same specs as the factory 041, but .520" Int/Ex lift with 1.5 ratio rockers and .571" with 1.65 ratio rockers, and another version says .498"/.512" w 1.5 rockers and .548"/.563" with 1.65 rockers.
> 
> Crower lift is .562"/.575" @ 1.65 rocker ratio.
> 
> ...


Thanks for the thorough explanation.. I could not understand how such a small increase in .050 numbers could have such an impact when adding 64 cubic inches of displacement. Really thought this was more of an old school slow ramp cam. Been schooled again by the forum. Think I will work on masking it somewhat with mufflers and or headers. I really appreciate all the input I receive on this forum. By the way any input on muffler that will not totally destroy flow? Thanks again


----------



## geeteeohguy (Feb 2, 2008)

I run Walker Turbo mufflers on all my old stuff and have for over 45 years. Quiet enough, no annoying droning, reasonable, good quality, etc.


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> Thanks for the thorough explanation.. I could not understand how such a small increase in .050 numbers could have such an impact when adding 64 cubic inches of displacement. Really thought this was more of an old school slow ramp cam. Been schooled again by the forum. Think I will work on masking it somewhat with mufflers and or headers. I really appreciate all the input I receive on this forum. By the way any input on muffler that will not totally destroy flow? Thanks again


Probably will be Race Pros for sale soon


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> Probably will be Race Pros for sale soon


On you tu


----------



## Captainfish#1 (Dec 31, 2017)

On you tube there is a 73 TA 70455HO #64headslarge cower cam( spelled crowerwrong)flat tap. He has it idling at750 soundingperfectly normal ,same cam as mine 60245. That video is what persuaded me this cam is acceptable. Something else is going on here. I have heard 290 B-6 cams,The Lunati 705, the XE284 and none sounded as bad as mine. Will try to post that you tube link. Thanks for all the input


----------



## Captainfish#1 (Dec 31, 2017)




----------



## PontiacJim (Dec 29, 2012)

Captainfish#1 said:


> Thanks for the thorough explanation.. I could not understand how such a small increase in .050 numbers could have such an impact when adding 64 cubic inches of displacement. Really thought this was more of an old school slow ramp cam. Been schooled again by the forum. Think I will work on masking it somewhat with mufflers and or headers. I really appreciate all the input I receive on this forum. By the way any input on muffler that will not totally destroy flow? Thanks again



Here is another thought I found while web researching since you are running points:

*Weak Spark *- At low rpm the spark at the plug is not strong because the alternator is working at low RPM. Electronic ignitions keep the spark at the same voltage no matter the RPM.


----------



## Captainfish#1 (Dec 31, 2017)

PontiacJim said:


> Here is another thought I found while web researching since you are running points:
> 
> *Weak Spark *- At low rpm the spark at the plug is not strong because the alternator is working at low RPM. Electronic ignitions keep the spark at the same voltage no matter the RPM.


Although coil is new I know that is no guarantee nowadays. Is there a way an amateur can check for spark intensity?


----------



## Captainfish#1 (Dec 31, 2017)

geeteeohguy said:


> I run Walker Turbo mufflers on all my old stuff and have for over 45 years. Quiet enough, no annoying droning, reasonable, good quality, etc.


Ordered them today #17748 Thanks


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> Although coil is new I know that is no guarantee nowadays. Is there a way an amateur can check for spark intensity?


Jim, would it be harmful to temporarily run a 12 volt line directly from battery to coil to see if it helps popping?


----------



## PontiacJim (Dec 29, 2012)

Captainfish#1 said:


> Jim, would it be harmful to temporarily run a 12 volt line directly from battery to coil to see if it helps popping?


I don't think it would hurt for a short time. It is how you can jump start a car.

You can also pull a plug wire, insert a screw driver or some tool into the boot end so it makes contact with the brass plug, and then hold it about 1/4" away from the exhaust manifold or some other good grounded metal piece, and watch the spark/arc. It should be a nice blue snappy spark. If it is orange, it is a weak spark.

I would do this test in dim light or at night so you can really see that spark jump and see the color.

Make sure the screw driver has a plastic/wooden handle cause if not, that 12V going to the plug can bite pretty good if you become the ground. That's how I got all my curly hair.


----------



## Captainfish#1 (Dec 31, 2017)

PontiacJim said:


> I don't think it would hurt for a short time. It is how you can jump start a car.
> 
> You can also pull a plug wire, insert a screw driver or some tool into the boot end so it makes contact with the brass plug, and then hold it about 1/4" away from the exhaust manifold or some other good grounded metal piece, and watch the spark/arc. It should be a nice blue snappy spark. If it is orange, it is a weak spark.
> 
> ...


Thanks, Think I will just use a clip from batt + to hot side of coil for a few seconds. Will let you know. Right now hot side of coil is showing 6 volts when running


----------



## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> Thanks, Think I will just use a clip from batt + to hot side of coil for a few seconds. Will let you know. Right now hot side of coil is showing 6 volts when running


No Bueno. Ran 12 volts to hot side of coil, in essence nullifying the resistance wire, no difference in popping


----------



## Captainfish#1 (Dec 31, 2017)

12 volts directly to hot side of coil - still popping


----------



## PontiacJim (Dec 29, 2012)

Captainfish#1 said:


> 12 volts directly to hot side of coil - still popping



Ok, no change. Now check the spark getting down to the plug. Still could be an issue within the coil, distributor, or even the wires. If you get that nice blue snappy spark, then that rules out anything from the coil to the plug.

What plug heat range are you using? Right off the top of my head, I believe the RAIV used R44S, 4 bbl engines got the R45S, and the 2 Bbl engines got the R46S


----------



## geeteeohguy (Feb 2, 2008)

Captainfish#1 said:


> Timing is at 14btdc. Yesterday advanced it alot and it made no difference. Vacuum at 800 to 850 rpm about 7.5 inches


14 btdc is about twice the spec from the factory, but your car is modified. Also, a stock engine would have about 18-20 inches hg at 800-850 rpm. 
My '65 389 with a fairly big (490 lift) single pattern Sig Erson cam produces about 12" hg at 900 rpm. Your vacuum is really, really low. When it
pops, does the needle on the vacuum gauge move or flicker or does it remain steady? I would love to see this thing on an ocsilliscope and look 
at the ignition pattern!!


----------



## Captainfish#1 (Dec 31, 2017)

PontiacJim said:


> Ok, no change. Now check the spark getting down to the plug. Still could be an issue within the coil, distributor, or even the wires. If you get that nice blue snappy spark, then that rules out anything from the coil to the plug.
> 
> What plug heat range are you using? Right off the top of my head, I believe the RAIV used R44S, 4 bbl engines got the R45S, and the 2 Bbl engines got the R46S


Started out with A/C Delco 43. Then went with Autolite 85. Will check spark at plug. Going this afternoon to get a plug puller. Two new sets of wires not crimped on enough to withstand removal without separating. Thanks


geeteeohguy said:


> 14 btdc is about twice the spec from the factory, but your car is modified. Also, a stock engine would have about 18-20 inches hg at 800-850 rpm.
> My '65 389 with a fairly big (490 lift) single pattern Sig Erson cam produces about 12" hg at 900 rpm. Your vacuum is really, really low. When it
> pops, does the needle on the vacuum gauge move or flicker or does it remain steady? I would love to see this thing on an ocsilliscope and look
> at the ignition pattern!!


The vacuum Guage is not steady at idle at all. Hovers around 7.5 at 800 rpms. I was expecting more also as you can see that you tube video with the Transam even running power brakes with this cam. I would love to see this thing also receive a precise diagnosis,but shops around here are hopeless and hapless,but they are very good at running my credit card. What I am really banking on is a fellow in Jacksonville, that has facilities and is a Pontiac guy. He has me waiting my turn sometime in May. He runs a 535 in a 63 Tempest and works on beautifully restored Pontiacs,both his and customers. It is about a three hour drive and I am somewhat apprehensive about the trip. I probably do not have 10 hours on this motor yet. I really, really appreciate all the input I receive here but it is difficult to diagnose remotely. I will try a new coil tomorrow as Jim is leaning towards ignition. As far as the vacuum the only thing I can think of is pushrod length. When the engine was being built we could not get the head gasket wanted so heads had to be shaved to make sure we had adequate compression. I do not know if this changed pushrod requirement. We are using the Melling RA IV 9.212 rod


----------



## PontiacJim (Dec 29, 2012)

Captainfish#1 said:


> Started out with A/C Delco 43. Then went with Autolite 85. Will check spark at plug. Going this afternoon to get a plug puller. Two new sets of wires not crimped on enough to withstand removal without separating. Thanks
> 
> The vacuum Guage is not steady at idle at all. Hovers around 7.5 at 800 rpms. I was expecting more also as you can see that you tube video with the Transam even running power brakes with this cam. I would love to see this thing also receive a precise diagnosis,but shops around here are hopeless and hapless,but they are very good at running my credit card. What I am really banking on is a fellow in Jacksonville, that has facilities and is a Pontiac guy. He has me waiting my turn sometime in May. He runs a 535 in a 63 Tempest and works on beautifully restored Pontiacs,both his and customers. It is about a three hour drive and I am somewhat apprehensive about the trip. I probably do not have 10 hours on this motor yet. I really, really appreciate all the input I receive here but it is difficult to diagnose remotely. I will try a new coil tomorrow as Jim is leaning towards ignition. As far as the vacuum the only thing I can think of is pushrod length. When the engine was being built we could not get the head gasket wanted so heads had to be shaved to make sure we had adequate compression. I do not know if this changed pushrod requirement. We are using the Melling RA IV 9.212 rod


If you have the stock vacuum can on the distributor, it will be incorrect for your super low vacuum reading. The stock can needs 15-17" Hg. So in effect, your vacuum advance may not be working at all, or barely anything.

Swap it out for a B-28 vacuum can which is used for low vacuum, big cam, engines. Local parts stores should have them, look for Wells _DV1810._

If you milled the heads, depends on how much. Since you have the adjustable rocker arm nuts used on the RAIV, you should at least be able to compensate a little if the pushrods were long by "zero lashing" the lifters with the engine running at idle. Messy, but in my opinion the best way to do it - then you know you have the lifter plunger adjusted correct, and I only use 1/4 tun after the rocker stops clicking, not 1/2 turn.

Many ways to run power brakes with low engine vacuum, so just because you see power brakes, does not mean he doesn't have an electric vacuum pump or other means.

Hopefully your Pontiac guy will sort it all our for you. let us know what he comes up with.


----------



## Captainfish#1 (Dec 31, 2017)

PontiacJim said:


> If you have the stock vacuum can on the distributor, it will be incorrect for your super low vacuum reading. The stock can needs 15-17" Hg. So in effect, your vacuum advance may not be working at all, or barely anything.
> 
> Swap it out for a B-28 vacuum can which is used for low vacuum, big cam, engines. Local parts stores should have them, look for Wells _DV1810._
> 
> ...


Jim,Do not have the factory vacuum canister. Distributor was dialed in about a month ago with I think a Crane unit. Starts pulling I think at 10 inches. Will put in new delco coil this afternoon, I know it is a shot in the dark. New Walker turbo mufflers arrived last night. Thinking may not install them yet till Gary-the Jacksonville Pontiac man-can hear exactly what I am. I agree vacuum is unexpectedly too low but the propane torch method did not reveal any leaks. Will let you know.


----------



## BearGFR (Aug 25, 2008)

If it still happens with the can disconnected and the source plugged, should eliminate the can as the cause. Another easy thing to try would be to disconnect and plug ALL manifold vacuum sources and see if that changes anything. 

I admit I haven't followed this thread all that closely, so if I cover ground that's already been covered please forgive me.

Just going over in my mind what kinds of things could cause a popping sound in the exhaust. 
If it actually is happening in the exhaust, then I'd expect it to be 'the loudest' listening at the rear of the car by the tailpipes - is that the case or is it 'loudest' when listening from somewhere else?
Can you tell from how often the popping happens whether it's likely just one cylinder or more (if just one, there should be one 'pop' for every two crank revolutions).

Exhaust valves opening "too early" while there's still significant combustion taking place in the cylinder(s). 
Ignition timing "too late" (has similar effect as above).
Severely incomplete combustion allowing raw fuel to get into the exhaust system, and subsequently ignited by heat or by "the next" exhaust event.
Possible causes of the first two assuming that the popping is happening in the exhaust system: Some combination of - lifters adjusted "too tight", timing not advanced enough, exhaust valve(s) leaking/not sealing, hydraulic lifter failed/failing in a "weird" way. 
If significant combustion is still going on when the exhaust valves open, then I'd expect it to also have a strong tendency to overheat/run hot. Is that the case?

Speaking of timing.. are you absolutely certain that when the balancer marks indicate TDC that it really _is_ TDC? Balancers with elastomer rings have been known to slip, and I've seen brand new balancers that had the marks "off" by as much as 6 degrees.

Pull the dipstick and take a whiff of the oil --- do you detect any 'gasoline' smell at all? You shouldn't be able to. If you do then it's running extremely rich and probably dumping raw fuel into the oil and also into the exhaust. That could be what's popping. Even if you don't smell gas in the oil, it still might be in the exhaust. Check the color on the spark plugs. Black/sooty is a clue. 
If you smell gas in the oil that's very bad --- it'll dilute the oil and put you at risk of taking out the bearings. 

If it seems to be just one pop per crank revolution, then try running it on 7 cylinders. Remove just one plug wire and see if you can find one that, when removed, makes it stop. It'll miss, and shake, and run like crap but that might help you find "the one" that has the problem - if it is just one.

Now that you know how to provide video, see if you can get one from closer to wherever the sound seems to be the loudest and most noticeable. 

Cheers,
Bear


----------



## geeteeohguy (Feb 2, 2008)

BearGFR said:


> If it still happens with the can disconnected and the source plugged, should eliminate the can as the cause. Another easy thing to try would be to disconnect and plug ALL manifold vacuum sources and see if that changes anything.
> 
> I admit I haven't followed this thread all that closely, so if I cover ground that's already been covered please forgive me.
> 
> ...


This is a great piece of advice that we all overlooked. Good for detecting which cylinder has a loose connecting rod, or other issues as well! The milled heads/stock pushrods have me thinking this could be a valve issue hanging open a bit. Would LOVE to be in the area and throw my hands on it for a bit to try to solve the issue.


----------



## Captainfish#1 (Dec 31, 2017)

coyote595 said:


> Is it easy to remove your exhaust splitters just to see if that makes a difference? It does not really sound like a pop caused by ignition of exhaust gasses to me. Your description of peculiar is certainly accurate. If the splitter removal is easy, give it a try. Can't hurt.


Coyote you nailed it. Removed splitters and you will not believe what I found. Took picture of passenger side and will have wifey try to post it


----------



## Captainfish#1 (Dec 31, 2017)

RESOLVED, Thanks for all the responses. Tons of knowledge divulged. Will try to post picture that explains what was happening. Passenger side splitter was folded over itself to allow installation inside of tailpipe instead of outside. Done by muffler shop in the early 80's. Actually discovered by wifey when she jammed a towel into outside outlet of passenger splitter and popping stopped. Now going to try to find out how to post picture-


----------



## geeteeohguy (Feb 2, 2008)

I never in a million years would have suspected that! Great find, and goes to show that nothing is too far-fetched.


----------



## Baaad65 (Aug 29, 2019)

Captainfish#1 said:


> RESOLVED, Thanks for all the responses. Tons of knowledge divulged. Will try to post picture that explains what was happening. Passenger side splitter was folded over itself to allow installation inside of tailpipe instead of outside. Done by muffler shop in the early 80's. Actually discovered by wifey when she jammed a towel into outside outlet of passenger splitter and popping stopped. Now going to try to find out how to post picture-
> View attachment 152708


Gotta like quality work 🤪 so glad you found it without tearing anything apart, so frustrating I bet.


----------



## Sick467 (Oct 29, 2019)

Not exactly a banana in the pipe, but a similar effect! Real glad it was not engine related...whoohoo! 🍌


----------



## Captainfish#1 (Dec 31, 2017)

Sick467 said:


> Not exactly a banana in the pipe, but a similar effect! Real glad it was not engine related...whoohoo! 🍌


Once again, thanks all. Still can not stand the now normal sounding Race Pro mufflers. Dynomax turbo mufflers going on later this week


----------



## BearGFR (Aug 25, 2008)

Wowsers, that's a new one on me. Time to file this thread away under the topic, "Stuff that can cause weird things to happen".

Bear


----------



## coyote595 (Dec 4, 2019)

Great! Glad it worked out. It just did not sound like popping to me. It sounded like exhaust gasses blowing past a sharp edge or something. That is why I suggested to pull off the splitters, since they may have a sharp edge where they split if not made right. I had no idea you would find something as bad as you did. That is awful! Now enjoy that beautiful sound.


----------

