# Knocking noise when running



## axesever (Apr 22, 2010)

Hey guys, so I have a 67 GTO and I just rebuilt a 400 engine for it and dropped it in. It was fine, it had a slow knock (like, not fast enough to be a rod and the speed didn't change) at low idle and then completely went away at higher rpm (anything about an idle really).

The bad news though, is that the very first day I was able to drive it, when I parked it, the electric fuel pump got left on along with my floor pedal being slightly stuck down (it popped out when i pulled on it later) and my carb filled with too much gas (I was unaware) enough to where there was gas all over the engine. When I went to start it, (unaware of the fuel issue at this time) it ignited, lighting my engine mildly on fire and thankfully i had an extinguisher nearby. Anyways, long story short, I towed it home, pulled out the spark plugs (fuel came pouring out), turned the engine very quickly to make sure it wasnt locked up (it wasnt) and left it to sit two days to dry (fuel was EVERYWHERE and a very strong aroma). I came back to it, replaced the oil (tons of fuel in it), turned it over to blow out extra fuel, changed some minor things burned (negative battery cable, oil pressure gauge line, and it started right up. But now, that knock is there constantly. When I put my hand on the distributor I can feel the knock better than anywhere else, its a brand new KEI distributor, but I am clueless as to the problem, hoping its minor. I've spent over 4 months rebuilding this thing.

Any advice helps, but please dumb it down a little as I am not a mechanic and only 21, I've had the car since 16 and I really care deeply for it. I call her Eve. So this whole thing breaks our hearts. Any advice is deeply welcomed.

(Photo is pre-fire, but its the same. Enjoy.)


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## Rukee (Feb 8, 2007)

First off hook up that fuel pump to a keyed power supply.
Then to aid in finding the noise, use a long screwdriver or metal rod of some sort and put one end on different areas of the motor and listen through the other side with your ear on the end of the rod/screwdriver. I'd start back there by the distributer. If the noise is coming from the distributor, maybe the cap is not on straight/square.
You might wanna change the oil again too right away to get that gas out of there. It will damage the bearings.


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## axesever (Apr 22, 2010)

Yeah its keyed, I just didnt shut the key off all the way. I know, I kick myself for it.

I'll check for the knock this weekend (at a different house).

I checked the oil and it doesnt smell like gas at all, but I might reflush it again soon. Just sucks being the fourth time I've changed it this WEEK.


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## mikes06goat (Jan 13, 2009)

I know this seems like a strange question but are the flexplate bolts tight? My brothers Firebird was doing the exact same thing. The noise went away at higher RPMs. It's a long shot but just one more thing to check.


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## 66tempestGT (Nov 28, 2009)

mikes06goat said:


> I know this seems like a strange question but are the flexplate bolts tight? My brothers Firebird was doing the exact same thing. The noise went away at higher RPMs. It's a long shot but just one more thing to check.


:agree definitely worth checking.


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## 66tempestGT (Nov 28, 2009)

i bought a camaro very cheap because it was knocking. turns out the flexplate was broken around the bolts. made some easy money on that deal!


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## axesever (Apr 22, 2010)

Ok I checked it, and the valley pan in back underneath the distributor is where the noise is coming from. 

Flexplate is fine.


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## jetstang (Nov 5, 2008)

Look for a bent pushrod. May have bent when it tried to open the cylinder with the motor hydrolocked, and the noise would come from the valley pan as the pushrod makes contact with the valley.

You may have bent a connecting rod. Disconnect 1 spark plug wire at a time and see if the knock goes away. Turn the engine off before disconnecting. 

I just went after a lifter tap and ended up with 2 dead cam lobes. I'm hearing of failures of new lifters as they are chinese and don't make it through break in. A weak lifter can tap at idle, then pump up when the oil pressure comes up.


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## axesever (Apr 22, 2010)

I did the spark plug trick already, no result. I have a feeling its a bad lifter as you stated. I will drive it a little and see if it stops, else I will replace the lifters.


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## jetstang (Nov 5, 2008)

check the pushrod first, a lifter you will here in the valve cover, not in the valley.


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## Too Many Projects (Nov 15, 2008)

axesever said:


> I did the spark plug trick already, no result. I have a feeling its a bad lifter as you stated. I will drive it a little and see if it stops, else I will replace the lifters.


I don't recommend running the engine anymore than is absolutely necessary to determine the knock. If you are loosing a lifter/cam lobe all that metal is going into the oil and onto the bearings of a new engine. 
Did you use a break-in supplement such as ZDDP, EOS ?


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## axesever (Apr 22, 2010)

That makes sense, thanks. Do you have any clue the cost and time I would be facing for a pushrod?



Too Many Projects said:


> I don't recommend running the engine anymore than is absolutely necessary to determine the knock. If you are loosing a lifter/cam lobe all that metal is going into the oil and onto the bearings of a new engine.
> Did you use a break-in supplement such as ZDDP, EOS ?


Yes I used it, and it improved quite a bit. And the engine isnt new, it's used. Still, I see your point.

Keep in mind I have about 10 miles on the engine since putting it in.


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## Too Many Projects (Nov 15, 2008)

axesever said:


> Hey guys, so I have a 67 GTO and I just rebuilt a 400 engine for it and dropped it in. It was fine, it had a slow knock (like, not fast enough to be a rod and the speed didn't change) at low idle and then completely went away at higher rpm (anything about an idle really) now, that knock is there constantly. I've spent over 4 months rebuilding this thing.





axesever said:


> That makes sense, thanks. Do you have any clue the cost and time I would be facing for a pushrod?
> Yes I used it, and it improved quite a bit. And the engine isnt new, it's used. Still, I see your point.
> 
> Keep in mind I have about 10 miles on the engine since putting it in.


I guess I'm a little confused.....first you state you spent 4 months building it and now it's used ?? what's used, the cam and lifters ?? If that is the case and the lifters weren't kept with the exact same lobe they came off of, then you still have a lifter problem, especially if the supplement changed/helped lessen the noise. That doesn't indicate a push rod issue. Oil or additives won't change a bent rod.
If the cam is used, do you know the history of it ?


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## jetstang (Nov 5, 2008)

axesever said:


> That makes sense, thanks. Do you have any clue the cost and time I would be facing for a pushrod?.


Pull the valve cover off, start engine listen for a tick, look for a rocker that isn't moving as much as most. Pushrod costs under $5, and a valve cover gasket, easy stuff.
So, it's a used motor you detailed and installed or had built?


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## axesever (Apr 22, 2010)

Yeah sorry I wasnt detailed enough.

The engine I bought from a guy that had a 66 GTO that was caught in a house fire and the rear of the car was totaled by the roof crashing down. It sat for a couple years, so exterior items like the intake manifold and valve covers were USABLE and in rough condition (I wanted it looking nice) so I used my old ones (there were in great condition). I tore down the engine most of the way, without actually tearing down any of the mechanical stuff inside because it was all still in great condition. I flushed out the engine with carosine and then about 10 qts of oil to get out any of the residue. I deep cleaned any of the parts that were reusable, bought some (like the water pump), and was also able to use some of my old parts (my old engine was a pontiac 389). 

Does that make better sense? I'm sorry this was my first time doing any of this so I apologize if I explained it wrong.


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## jetstang (Nov 5, 2008)

axesever said:


> Yeah sorry I wasnt detailed enough.
> 
> The engine I bought from a guy that had a 66 GTO that was caught in a house fire and the rear of the car was totaled by the roof crashing down. It sat for a couple years, so exterior items like the intake manifold and valve covers were USABLE and in rough condition (I wanted it looking nice) so I used my old ones (there were in great condition). I tore down the engine most of the way, without actually tearing down any of the mechanical stuff inside because it was all still in great condition. I flushed out the engine with carosine and then about 10 qts of oil to get out any of the residue. I deep cleaned any of the parts that were reusable, bought some (like the water pump), and was also able to use some of my old parts (my old engine was a pontiac 389).
> 
> Does that make better sense? I'm sorry this was my first time doing any of this so I apologize if I explained it wrong.


Yep, better. Used motor with new gaskets. Sounds like you have a lifter that won't pump up, or the cam is going, same process as listed before. Odd thing you said is that it doesn't change speed with RPM, that is odd, all noises go up and down with RPM. But the cam spins half as fast as the motor, so it would seam slower, but changes. When I bought my 454 SS it had a knock like this, wasn't crank and wasn't lifters. I found 4 pistons with the sides scrubbed off, 1 piston had metal covering all the rings. Motor came out and got complete rebuild.








Then I put a supercharger on it








Still gotta figure out the duct work and find an 1/8th mile long extension cord.


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## 66tempestGT (Nov 28, 2009)

come on, i know you have room for a generator in the bed.


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## jetstang (Nov 5, 2008)

66tempestGT said:


> come on, i know you have room for a generator in the bed.


Man, where have you been? Never thought of that. I had about 150 ft of cord, but then bang, unplugged and all gains gone. I'm trying it tomorrow, still have to clearance the hood.


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## injn37 (Nov 16, 2008)

Three things.....

1. First thing I thought of was a push rod /collapsed lifter for the noise.

2. As for electric fuel pump. Get a pressure switch to put in a T with the oil sender. This gets wired in series with fuel pump. Also, with this switch, there is a normally closed contact that gets wired to the solenoid. This way, when you start the car, solenoid power fires the fuel pump. When motor on 'run' oil pressure ( normally open), powers the fuel pump. If engine stalls or key turned on and no oil pressure, fuel pump shuts down. This is a great safety, and prevents filling the holes and pan with gas. Only way to do it right with an electric fuel pump, period!

3. Electric cord, 1/8 mile long. I like it. A great safety device for the shutdown!!! Don't even have to brake, just coast! :rofl:

rich


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## jetstang (Nov 5, 2008)

I was going to put the oil pressure switch on mine, bought it, never installed it. Because if you put the switch in there, then the fuel pump wont pump until oil pressure builds, so you crank for a few seconds, fuel pump turns on, then you get fuel pressure. If you have a weak battery and the car doesn't start quick, you'll kill the battery. On my truck, I listen for the fuel pump before I crank the car.
Hook up a QUALITY 4 post relay, like a foglight relay, hot in, hot out, ground, ignition, ignition switch turns on relay when you hit the key. Cheap foglight relays don't last, trust me, I carried spares all the time and replaced them once a week. Now, quality Carquest relay hasn't quit yet. I'm running a Holley Blue pump, now with a red pump spring in it to reduce pressure so it doesn't kill relays. Relay was the problem. Run 10 guage wire from the battery to the relay, then to the pump. You can run a straight hot to the pump with a switch in the cab if you want to run the oil pressure cutoff switch and you have starting problems, or the car has sat and drained the bowls. Don't run a toggle for your fuel pump only, as you know what happens.:cheers


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## injn37 (Nov 16, 2008)

The way to do it without relays or having pump not run when starting is the following.
Use a oil pressure switch such as a NAPA # OP6611. This switch has a 1/4 NPT thread, so you will need to reduce to a 1/8 NPT.
Ok. now the switch has 3 contacts. 'P' contact is common, 'SP' contact is Normally closed, and 'I' contact is normally open.
Connect fuel pump to the 'P' contact ( common), the ignition powered +12 for the fuel pump to the 'I' contact (normally open) and the solenoid (purple) power wire to the 'SP'contact (normally closed).
Done.
Now when the key is turned, power to the starter solenoid is also sent to the fuel pump, pressurizing the fuel system, power is running from the solenoid thru the normally closed contacts ( they are closed because there is no oil pressure yet). Engine starts. You let go of key. There is enough fuel in the bowl to keep engine running until oil pressure is above 2-5 psi( most likely, pressure is built enough during cranking to switch to the pump power), when the normally open contacts are made, now powering the fuel pump from the power line with fuse that was set up for the fuel pump in the first place.
If engine stalls, pump shuts down when the pressure drops below the 2-5 psi threshold. You can also try a NAPA OP 6610 switch (1/8 NPT), but check to make sure that none of the contacts are electrically to ground ( the metal case).

This is the best and safest way to go with an electric pump!!
If need, I can draw a schematic for any one that doesn't understand above.

Class dismissed:cheers

rich


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## jetstang (Nov 5, 2008)

injn37 said:


> The way to do it without relays or having pump not run when starting is the following.


Why wouldn't you want to run a relay? I run relays on my ignition and fuel pump, 10 guage wire from battery to relay and then to pump/coil. 16 guage wire to turn it on. NO heavy amp loads running into your car and burning up switches and connectors?
Really good info though, nice.


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## Rukee (Feb 8, 2007)

What he's saying is basically an oil pressure driven relay instead of an ignition switch activated. Either way would be good, however, for things like the electric choke circuit I like to use the oil pressure switch so no voltage goes to that choke until the engine is running.


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## jetstang (Nov 5, 2008)

Rukee said:


> What he's saying is basically an oil pressure driven relay instead of an ignition switch activated. Either way would be good, however, for things like the electric choke circuit I like to use the oil pressure switch so no voltage goes to that choke until the engine is running.


But without the choke, the engine isn't going to be running? 
I had a 78 427 Vette that would kill a battery before it started, so my cars I concentrate on getting them started quickly, no man made interuptions that burn starters up and kill batteries..
After 2 years of ownership, replaced the starter and carb and it started great everytime, just saying.
Oh, and on my 454, we have a 5 mile bridge that my truck died on 4 times in a row because of the electric fuel pump, holley blue. It was easier to replace the relay than to hunt a burnt wire or blown fuze.


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## injn37 (Nov 16, 2008)

Jetstang,
Nothing wrong with relays, I run a lot of them also for high load items. I guess it is just a preference that I have. I have run the oil pump switch scenario on 3 streets rods with never a problem, so I guess I like that method. Both work. Come to think of it, I don't like 10 gauge wire! It s-#ks to work with it, especially under the dash! Yah, I know, it is necessary to keep the smoke level down!

rich


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## Rukee (Feb 8, 2007)

jetstang said:


> *But without the choke, the engine isn't going to be running? *
> I had a 78 427 Vette that would kill a battery before it started, so my cars I concentrate on getting them started quickly, no man made interuptions that burn starters up and kill batteries..
> After 2 years of ownership, replaced the starter and carb and it started great everytime, just saying.
> Oh, and on my 454, we have a 5 mile bridge that my truck died on 4 times in a row because of the electric fuel pump, holley blue. It was easier to replace the relay than to hunt a burnt wire or blown fuze.


No power goes to the choke unit unless the engine has oil pressure. That way if your sitting in the driveway, working on the car or the radio and have the key 'on', the choke element is not heating up before the engine does.


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## axesever (Apr 22, 2010)

Ok now the speed of the knock does change. I gets quieter but quicker. Hard to explain, but at an idle its louder as if it is hitting a hallow metal box sound with an echo.


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