# Cold Start Phenomenon?



## Sick467 (Oct 29, 2019)

A brief intro so that my current project does not turn anyone off,

I will be restoring my fist car once the current project is complete (resto starts in a year or so). My first car was/is a 67 GTO and I fell in love with the Pontiac 400 motor so...

I have a Pontiac 400 in my 72 Chevy truck restomod and it gets hard to crank over once it gets fuel.

The motor is built to have about 350 HP and run on 87 octane...nothing too high performance. Stock parts from the oil pan to the intake, Edelbrock 4B carb, and a street/strip cam. It would be a long story, but in short...it has parts that range from 70 to 76...the block being a 70 and the heads being 76.

If the engine has not been started that day, a fresh battery will crank the engine over nicely at the first turn of the key for about 2 or 3 turns and then the rpm's drop drastically like the starter is having a hard time turning the engine. I suspect it's the time at which the cylinders are getting fuel. At this point the engine rpm drops to a lope...whop....whop....whop (3 to 6 "whops")...then it fires up and runs very nice. Once the engine has been started and then shut off, it can be fired back up with out near the whopping lope.

I have messed with the timing such that I can significantly reduce this whopping, but then it runs poorly once started. Mainly rough idle and some backfiring. I don't know the timing settings as I have just bumped the dizzy to and fro until it seems to work the best for starting and idling...more so for idling I guess.

The project is still not ready for the road so I don't know how it does at speed, but it moves itself around the shop and yard like I would expect. It just has this hard time of cold starting without dogging down the starter.

Any thoughts?


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## BLK69JUDGE (Jun 10, 2010)

if it were mine ..........
I would do a spark plug check ... for color ..and look for a clean plug..... possible coolant leak into cylinder
from sitting and its barely hydrolick ing... ?? slowing the rpm of engine turning over...

but it sounds like it turns over for a couple seconds b4 the lag .....
probably not likely leaking ..usually when this happens, it will turn over but not a full revolution and lag or slow down.. but...

then the possibility of sticky weights n springs in the distributor advancingthe timing?
and firing b4 tdc ....

then I would head to the starter ..if it engages quietly and isnt a whiner when engaged
have your original rebuilt IF its a high torque unit ...

thats all I got for now ...

doubtfull dirty battery connections would do it but a small diameter positive cable
may do it ...

Scott


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## bigD (Jul 21, 2016)

A mini-starter such as a Summit brand will eliminate starter problems, IF the starter is the problem. Have had a couple on 455 racing engines. No problems. 

If it's a weak battery problem, you could hook up jumper cables, to another good batt. I wouldn't even try a batt that has less than 800 cold cranking amps, for a Pontiac engine. I actually use 2 of those on my 455 bracket engines, so I won't have to run an alternator. 

Need to put a timing light on it, so you'll know exactly where it is, when it runs good & when it don't. 

A correctly functioning vacuum advance will allow you to reduce timing for cranking, but will quickly increase timing, for a better idle. But, without a timing light, there is no way to know what timing is, either with or without vac advance hooked up.


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## PontiacJim (Dec 29, 2012)

We like it when someone puts a PONTIAC engine in a Chevy - there's a guy who knows what a real engine is. :cheers

Reading the post, I would say it is a timing issue. It sounds like it'll spin faster when cold, gas then enters the cylinders, spark is trying to ignite the mixture, but the badly off timing is just not allowing it to catch. Then when it does, because the engine/cylinder/plugs are hot, you have the easier starting.

BUT, it could be other.

Assuming fully charged battery and fairly new? Don't know what 1976 heads you used to lower compression. Lower compression should not be an issue as compared to something like 10.5 compression. Just for fun, you might pull all the plugs, and with coil wire pulled, spin the engine over and see how fast it'll spin. With no plugs, there will be no compression and the engine should wiz right over fairly quickly.

If not, then it could indicate the battery, starter, bad connection/corrosion of the cables, something grounding out, or even something binding/dragging mechanically. You want a good heavy battery cable as some of the store bought replacement cables are small gauge and will get by, but are not delivering all the current you need. Make sure the engine is grounded to the frame and body. Poor grounds can cause problems and these are often left off when installing an engine.

Fresh gas? Ethanol laced gas goes bad quickly, so you need fresh gas to eliminate that as a problem.

Flooding. Smell any heavy gas fumes? When it strains to fire, you might not let it catch at that point and pull a couple spark plugs to see if they are wet. Once the engine is warmed up, it may not be quite the problem.

What distributor? Points, HEI, or other? Could be electrical.

Spark plugs gapped to .035"?

Valve adjustment. Maybe valves are too loose/tight? Did you go with factory rocker arm studs and nuts? Torqued down to 20-25 ft lbs? Did you check pushrod length seeing the engine is an assortment of parts? Or did you opt for polylocks?

How big on the street/strip cam? Specs? Did you degree the cam?

Timing gears not lined up correctly. Are you sure you lined up the cam gear and crank gear correctly? It's not a Chevy, so the Dot's don't face each other Cam gear @ 6 O'clock & crank gear @ 12 o'clock - although some reference books will show it this way as this was done on the earlier engines. You want Cam gear Dot at 12 0'clock, crank gear Dot at 12 O'clock. BUT, the engine will work either way. The 12/12 O'clock alignment will have the No 1 spark plug firing at the typical No 1 terminal in the cap. With the 12/6 O'clock (Dot's facing each other), the No 1 spark plug firing will be placed in the No 6 position on the cap.

Pontiac distributor rotates Counter Clockwise (CCW). Advance timing by turning distributor to the right going into the CCW rotor movement. Retard timing by turning CW away from the rotor movement. Retarded timing will cause the engine to start hard and run hot.

Make sure all wires are in their correct position on the cap and none are touching/crossing over and causing a spark jump from one wire to the other.

Vacuum leak? Check to make sure all intake/carb bolts torqued down. Does the center exhaust heat crossover on the intake cover the exhaust heat outlets on the heads? Usually an earlier intake with late heads won't close up the port, some is left open on the head.

PCV valve connected and operating?

Initial timing at the crank balancer would be 9 degrees at idle - factory/ with points. But, you most likely want about 10-12 degrees. This is with vacuum plugged to the distributor. Once you connect the vacuum advance, timing at idle should jump up about 10-12 degrees more, giving you about 20-ish degrees.

New harmonic balancer? An old balancer can move around. The outer ring is bonded to the inner hub and the bond can deteriorate and cause the outer ring/timing mark to move out of position giving a false reading.

That should keep you busy checking a few things for a while. Then get back to us and we can go from there. :thumbsup:


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## geeteeohguy (Feb 2, 2008)

I'm with these guys. My gut tells me it's a timing issue, but verifying you don't have a coolant leak into one of the cylinders is an easy check. The very first thing I would do is verify that the distributor is in correctly and not off a tooth, and verify that the mechanical advance is not binding up. (BTDT). The fact that it fires up easily when hot pretty much eliminates starter/cable/battery issues, as these get worse with a warm engine. 
Try this: disconnect the coil wire next time you go to fire it up cold and see if it slows down when cranking with no spark. If it doesn't slow down, you will KNOW it is a timing issue. If it acts the same, and DOES slow down, you will know it is NOT an ignition issue. Keep us in the loop and let us know what happens.


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## Sick467 (Oct 29, 2019)

OK, I'm am going to start assuming that I have multiple issues, but this is what I did last night...First off thanks for jumping in and advising the new guy!

1.) Got it started with the traditional "spin fast at first, slow down whop, whop, whop... fire and run procedure. NBD

2.) Checked the timing with a light with the vac advance line disconnected and plugged...it was about 45 degrees before TDC. That would be about 9 o'clock looking at it from the front. Jeez!

3.) Rotated dizzy to get timing at 12 degress BTDC.

4.) Hooked vac line back up and adjusted idle down to 700 rpm. Seemed like a good place for it, much lower and it would sound like it might stumble.

5.) used the ADV button on my timing light to bring the balancer mark to ZERO on the indicator. The advance setting read 31. Engine sounded fine, but different obviously. I guess I used that timing light function properly to determine total advance...you tell me.

*At this point, I am thinking that all looks good...do you agree?*

6.) I shut the engine off and immediately tried to start it. I got a lesser version of the whop whop, but it started quickly. This would be normal as it has just been running and the engine is primed to fire up rather quickly.

7.) I did step 6 a couple times and then the starter just said "NO MORE". No trying, no clicking, no humming...nada.

I now suspect my starter to be expired. I swapped in a very new Interstate battery...it is a high CCA battery also, just new this year and even tried the battery charger jump start mode on my Schumacher charger (200amp). Checked all the connections, found a loose screw on a temporary ingition switch and tightened it...no change in the starters attitude.

I will be pulling the starter tonight and bench testing it with jumper cables and go from there. 

Maybe while the starter is out I can get to PontiacJims questions that I don't know. Here's what I do know...

6X heads , pretty much stock compression minus what was freshened up off the deck. IIRC the comp ratio is at 9:1 so that it would run good on 87 octane.

Gas is pretty fresh, but I'm sure the few gallons I recently added was on top of a gallon of 1 year old gas.

I don't get any strong smell of raw fuel during the starting process. Flooding does not seem to be one of its problems.

Factory studs, rockers, and nuts. It's been too many years to admit since they were installed, but I assure they were done properly back then. Loosen while running until they click - tighten back down 1/4 turn past the stop of the clicking.

HIE ignition parts all stock. #1 plug on cap is near the firewall. Plugs are in good order and isolated from one another and in the right spots.

Vacuum leaks are non existent and PCV is coorect and functioning.

Pretty sure the harmonic balancer is NOT new...I'l deal with that if I have too if the time comes.

I do not expect a coolant leak as the short pipes on the manifolds dump right on the ground and any coolant in the cylinders would show up there I would think.

You folks have given me some homework to do...good thing I like studying old cars!

Here's what I'm dealing with so there is some "show" to go with my "tell"...


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## PontiacJim (Dec 29, 2012)

Pontiac starters have a bad habit of solenoids going bad from exhaust manifold heat. It may simply be the solenoid, or it could be the starter itself. I would have the starter you have in-hand rebuilt, if it comes to it. It fits/works with the engine and if you go with another stock starter, you might have to play around with shims - not a big deal, but just extra frustrations.

Second option is the mini-starter route.

Timing sounds like it may have been your issue. 45 BTDC was way too much. 12 is good, but 700 RPM's may be too low with the street/strip cam. 800-850 may be better, but you can try it as long as the truck doesn't creep too much or you don't have to stand hard on the brake pedal with trans in Drive. I suspect a little adjustment on the carb may improve things as well, so you might want to tweak the carb and play with the idle mixture screws and fast idle screw. 

With 12 degrees BTDC, when vacuum added, you should see another 10-12 degrees at idle. Depends on if you have direct manifold vacuum or ported from a fitting on the carb. Revving it up and using the dial back feature of the timing light, with vacuum disconnected, you want around 34-36 degrees total at around 3,000 RPM's. Your 31 may be fine, but you may be giving up a little power. You may not get 34-36 degrees with the HEI. They can be modified, but I have never worked with an HEI. Here is an article on how to modify the advance: Changing the Advance Curve on HEI Distributors

Adjusting the valves the way you did is fine, but you need the polylocks. Factory nuts will back off on you. I even tried the crimped factory style lock nuts, they still backed off. Polylocks are what is needed.

I would deep six the gas. Get fresh gas in the tank and add some Stabil 360 to it. This is what I do. The Stabil 360 in general seems to make the engine run a little better - my opinion.

Nice looking truck. I like those having the 2-tone paint scheme. Will look good with the chrome installed. Silverado? :thumbsup:


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## Lemans guy (Oct 14, 2014)

Yep...I agree your starter is toast!.......and 45 degrees base timing advance will cause that drag......

So cranking it with the advanced timing might have killed the solenoid.....

You have a vacumn can pulling in 19 degrees.......many do that but it is way too much.....

Get a Standard Motor Parts SMP VC 302 vacumn can and change it out.......it will pull in 10 degrees of vac at a low vacumn....hook it to full manifold Vacumn.....base 12 + 10 Vac will be 22 @ idle where you need to be. You still have to work on your centrifigal advance but that comes later...

I use a RobbMc mini starter,...check his web solid equipment, will spin it right each time.

Batteries must be load tested, and lose power easy in cold weather, even a new battery can be low from sitting on the shelf, so verify.:nerd:


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## Sick467 (Oct 29, 2019)

Great support folks...I can tell I am going to learn a few things about timing and tuning. It's about time, I'm 50 and can't put it off any longer.

The starter was removed and bench tested..it was hit and miss...meaning I had to hit it with a hammer to get it to do anything and then it would miss an attempt here and there. I did put it back on and got it to start the motor a few times with a good show of improvement, but it started NOT spinning again and it's at the rebuild shop now. "My man" is going to rebuild it. He said what I had was high-torque starter to begin with and he could likely improve upon that. I probably shortened it's life (drastically) due the many years that it has been hard to start due to my lack of attention to getting advise from folks like y'all (and getting back around to the project) . I may have it back tomorrow for this weekend to do some tuning. When I get it back on, I will get some better timing numbers at the different RPM's ad such and throw them out here.

I can't wrap my head around how the advanced timing caused this drag or sudden drop of rpm of the starter turning the motor. I heard no combustion firing, backfiring...nothing, just the sound of the motor slowing down and then after a hand full of "whops" it would fire right up. My thought was that it was harder to compress the air AND fuel mixture compared to just the air, but I certainly don't know that for sure...I'm open for conversation/learning

Another note regarding the engine: My old notes suggest that the compression should be around 8.8:1 and I have yet to find the cam specs.

Until then...


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## Lemans guy (Oct 14, 2014)

A rich mixture will not cause drag or kickback but over advanced timing will....cause one or both...you had 45 degrees base timing...

So your spark was igniting too far down the compression stroke, it fires and wants to push the piston back down, where as if it fires just right the piston has enough forward and upward position to continue over the top and use the power to force it down after TDC....

Too early and and I tries to force it back, where it “drags” or “Kicks back”.........

At least that’s my story and I am sticking too it:nerd:


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## Sick467 (Oct 29, 2019)

That makes sense to me LG that an early ignition of the fuel mixture would try to push the piston back down on it's up stroke and slow the rpm's of the spinning motor making it hard to crank over quickly (even get kick back which I did not get), but wouldn't I hear the noise from the firing of the fuel mixture? I only have short straight pipes on the exhaust manifold (no mufflers) and I get no popping from it whatsoever until it starts and then it's just loud. One more thing...why have some said that retarded timing can cause this issue too? That would seem to me to make for easier and faster cranking.

I'm not doubting anybody, just confused by the relative silence of this phenomenon and the dynamics of it all.

Another point of concern...I pulled a plug last night and broke the stem off. I don't know what went wrong but it's broke so time for some plugs. They are the AC R45TSX plugs and the two plugs I checked were gapped at 0.05" plus. The engine has about 5 hours of run time on it over the last several years...the plugs are black with mild soot and I did some wondering around the net to find that spark plug details (gap and type) are a matter of mixed opinions. I am sure that I gapped my plugs according to my motors manual for a mid-70's 400 w/HIE, hence the larger gap. Question is...should I buy all new plugs? What plugs? and What gap? OR just buy one R45TSX for now and test an tune some more before changing too much up at once...The latter is my opinion.


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## Lemans guy (Oct 14, 2014)

Well it would me making a very inefficient and incomplete burn, a fizzle really,....some of the fuel would ignite causing pressure but a total burn

A fizzle......you may not hear it, retarded timing too much gives a very innefficient burn as well, so the spark may be to advanced or retarded both both are very inefficient.....maybe, we are just analyzing here.

Maybe it is just your weak starter solenoid that gives out real fast......after multiple cranks with too much timing....where it will not want to easily start

As for the plugs yes good idea change the one and check the others and regroup

I like a .035 gap,.....050 can cause.......get ready hard starts,...it takes more power to jump the bigger gap, and your plugs are always going toward wider gap by wear constantly

Wider gaps make sense if you are a racer, many reasons to burn the mixture at those high and constant RPM’s.....

And the Petronix says wider gaps, I have run all the gaps, for me best is .035 and I use a flamethrower 2 coil and Petronix module..

I use NGK plugs, heat range 6 I believe.....make sure you have cool plugs as too hot causes detonation!

You can change em anytime...


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## Sick467 (Oct 29, 2019)

Just a quick update: Added a new plug to replace the broken one, gapped them all to 0.035", did a cold-dry compression test while the plugs were out...consistently in the 130 to 140's with one up around 160 (kinda odd), put the rebuilt starter on (needed to add another shim for some reason) , and all is working much better. No rpm stalling during starting and it starts very quickly, revs and idles very nice. BIG THANKS FOR THE SUPPORT!

Initial timing is still 12 and Advanced is still 31 (vac adv hose hooked to manifold port on Edlebrock 1407 carb).

Idle has been upped to 800 to resist cold idle stumbles,

Air-fuel screws started to stumble the engine at a half turn out so they are now at a full turn out each.

Found my cam specs, they were recommended by a Pontiac drag car builder and racer out of Blue Springs, Mo. knowing that the engine was going in a 72 Custom 10 truck .. for those who like to talk cams...See Attached.

I have reached my goal of an easier starting project and my confidence has been greatly improved. I probably won't be doing too much tuning beyond this until the vehicle can be driven on the street. Poly locks will be done this winter along with new plug wires as the current ones are 20 years old and the "make yourself' type. Oddly enough, nobody in town had a set for the 400. I guess I'll be looking to Summit...

any recommendation for plug wires and poly locks?

EDIT: it's been too long to remember, but I believe the rocker studs are stock for the 6X heads and the original rocker nuts are being used along with the original rockers...I'll verify before ordering polylocks at any rate. It's tempting to add roller rockers, but this is a very streetable build and they might be overkill.


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## PontiacJim (Dec 29, 2012)

You are making headway.

The 6X heads should have screw-in studs, right? Replace them with the better and stronger ARP 7/16" big block studs. Then get the 7/16" polylocks. 

Pontiacs like a split overlap cam, more duration or lift on the exhaust side to compensate for the poor flow of the exhaust port. Those cam specs look more like a Chevy. If you look at the specs on a factory cam, you will see the exhaust has more duration. Many cams will also have a little more lift on the exhaust valve as well. But, it is what it is and if your buddy has used it successfully in a Pontiac, then that's good enough.

On the carb, most carbs I adjust I back the idle mixture screws out 2 1/2 turns to begin with. Then turn one idle mixture screw in at a time until is begins to run poorly, and then back it back out until it smooths out again and you should be about right. Then repeat with the other mixture screw.

Keep at it. :thumbsup:


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## Lemans guy (Oct 14, 2014)

I use Harland Sharp roller rockers,...they are a bit more money but sure are smooth!


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## Sick467 (Oct 29, 2019)

It's time to thank everyone again as the 72 Pontiac Truck is on the road! I swapped out the valve studs and added the polylocks per Jim's advise. It's a good thing I pulled the valve covers to do this as I had a broken valve spring retainer. It was broke in two pieces, but still doing its job, kinda. Turns out that my local parts store recommended the wrong ones and they were all destined to have trouble. Dodged a bullet there, I guess. I had to pull the engine out of the truck do deal with a leaking rear freeze plug, so I took the opportunity to freshen the engine up and add some new paint and bling as well.

I will be fine tuning my timing and carb tuning skills this week. The carb has an off idle stumble that I hope will be remedied by moving the accelerator plunger hole location. I think I will start with the ignition timing so that I can achieve the proper idle speed and go from there. Depending on my tuning success/failure, I may post a new thread if I get confused.

Anyhow, Just wanted to show thanks to the forum and it's members with a few show-off pics of the final product and let everyone know I am gearing up to pull my 67 GTO into the shop and figure out where to start it's resurrection and I'm looking forward to spending more time with the Pontiac folks here...


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## Sick467 (Oct 29, 2019)

Oh, I forgot to throw in a photo of the GTO. It's in so much better shape to begin with compared to the other two vehicles I have redone...it should be a much quicker build...This is her good side. I'll do a build thread, I'm sure, and show all the bad stuff as I go...


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