[steve25]

In my mind there are only 3 or 4 possibilities left for this issue.

1) the Intake valve is bad in cylinder #2

2) the head gasket between 2 and 4 is bad, and both of these could be further confirmed by a compression test.

3) crossfiring by many means is lighting off number 2 when it should not be .

4) the firing order is wrong.

[Cliff R]

It's been at least 10 years ago now but I had a customer bring a vehicle here with a "fresh" 455 in it built by one of the "gurus" who used to frequent this Forum.

Part of the rebuild of the engine included a running test before picking it up. The engine was installed and the customer was not happy with it. It was WAY down on power and if you hit the throttle quickly it would "pop", but seemed fine for "normal" driving and getting into the throttle slowly.

He had several very knowledgeable folks close to him look at it and try to troubleshoot the issues, they all said it was something in the carb and/or distributor. Since I did both of those parts for the project I got them back and they were fine on my engine but didn't work on the customers 455.

He finally decided to bring me the entire vehicle as he'd exhaust all efforts locally and the engine builder had washed his hands of the whole deal. So the car is brought here some 800 or so miles and backing it off the trailer I told Ray it sounds like the cam is "out of phase". I listened to it for a few minutes, removed the air cleaner, propped myself up over the carb and hit the throttle quickly. This resulted in a very quick and immediate "pop" and "back-fire" up thru the carb.

Next we verified the timing mark on the balancer and ignition timing, it was fine. I removed the drivers side valve cover and rotated the engine paying close attention to when the #1 cylinder intake valve opened. It was WAY off so we removed the timing cover and found the issue. The "builder" had installed a 9 keyway Rollmaster timing set and advance it 4 degrees or 2 keyways on the drive sprocket. Problem is he used the same "dot to dot" as he did with no advance on the lower sprocket instead of going back two teeth to the left and using a different place on the lower sprocket for alignment.

I'm guessing he degreed it "dot to dot" decided it needed advanced 4 degrees, then used the wrong tooth to align things and just buttoned it up without re-checking the ICL.

It was a quick and easy fix and the engine made great power when we go the cam back in phase and no popping anyplace. I'll also note here that even with the cam being off quite a bit it really didn't idle or run all that bad, just way down on power and "popped" when you stuck the throttle.........Cliff

[Formulas]

The evidence inside your cap is from secondary voltage / current IE. Voltage / current that should travel to a spark plug to fire off a cylinder

So anything in the secondary chain just after the metallic conductor face on the coil is suspect

Suspect of what you asked. Suspect of having to much resistance for the current to travel to the right place to do the right job

You could have high resistance China button, cap terminals, rotor, spark plug wires or spark plugs themselves

And as always with new builds engine ground wires one of the module hold down screws provides a ground path but if the distributor and hold down clamp is freshly painted is your distributor body getting a good ground or an incidental one.

Something is amiss from the original GM engineering or that system would not of been produced very long.
And if current designed to reach a sparkplug cant get to it, it will go where it can

[John Milner]

Thanks for the replies everyone. So far I have not burned the second cap while testing. I'm thinking it may have just been crappy made in china parts that led to the melting. I did change the plugs just to rule those out. It is just odd that the popping noise goes away when I take the #2 plug wire off and rev the engine up. The popping noise is there when I take off any other plug wire with #2 wire connected. It's also odd that the #2 exhaust port gasket blew out. The exhaust manifolds were surfaced flat before I installed them and the head surface was in good shape as well. I would say that it is a bad valve or incorrectly adjusted valve but I don't think both sets of heads have a bad valve on #2 cylinder. The second set of heads I put on are a good set of heads that I personally put roughly 10,000 miles on before I did a head swap on another one of my cars. I did not find anything obvious when I ran a compression test. It will be a day or two before I can get back to working on it. I will take a closer look at the manifold and if that has no restrictions, I may re-check the cam timing and look at replacing the two lifters for cylinder 2.

[KEN CROCIE]

Check lift on #2 ex.
Does the new cap show arcing residue like the previous cap?

[Gary H]

Originally Posted by John Milner

Thanks for the replies everyone. So far I have not burned the second cap while testing. I'm thinking it may have just been crappy made in china parts that led to the melting. I did change the plugs just to rule those out. It is just odd that the popping noise goes away when I take the #2 plug wire off and rev the engine up. The popping noise is there when I take off any other plug wire with #2 wire connected. It's also odd that the #2 exhaust port gasket blew out. The exhaust manifolds were surfaced flat before I installed them and the head surface was in good shape as well. I would say that it is a bad valve or incorrectly adjusted valve but I don't think both sets of heads have a bad valve on #2 cylinder. The second set of heads I put on are a good set of heads that I personally put roughly 10,000 miles on before I did a head swap on another one of my cars. I did not find anything obvious when I ran a compression test. It will be a day or two before I can get back to working on it. I will take a closer look at the manifold and if that has no restrictions, I may re-check the cam timing and look at replacing the two lifters for cylinder 2.

What's the #2 spark plug look like? Also, have you pulled a valve cover off the passenger side and looked at your valve heights. You could have a stuck valve partially open from too tight a valve guide.

[John Milner]

I’ll check the lift numbers on that #2 exhaust valve. The lifter does appear to be spinning just fine. Just by watching the valve movement with the valve cover off, there is nothing obvious. I didn’t see any evidence of the white chalky substance under the cap yet. I will keep an eye on it though.

The plug really didn’t look bad. The valve height was in good shape on both sets of heads I have tried.

[bluebandit]

Swap the #2 plug wire with another then see if it pops on the cylinder you exchanged it with or stays on #2.

[DiamondJim]

Have you driven this car any distance? I had a similar problem years ago with a vehicle that had a non vented cap on the fuel tank. Scratched my head for about a week. Motor was getting enough fuel to idle and it would gradually rev up but it would run out of fuel if you hit the accelerator pump hard and it would pop. I Drilled a hole in the cap and problem solved. I’m not saying that this is your problem I just wanted to share. It would be easy to check by removing fuel cap while running.

[Dynoking]

Check for cross fire caused by ignition wire routing.

[STEELCITYFIREBIRD]

Do you have battery voltage at the dizzy power wire? Factory HEI equipped vehicle?

[John Milner]

I haven’t driven it down the road yet. It does have a factory hei and is running the factory run wire but I have not checked the voltage output from it. I believe I have found the problem though. The port on the exhaust manifold was completely plugged up that ran to the #2 exhaust port. I don’t know what it was but it had the consistency of cement. I took a hammer and a punch and broke a lot of it out. There is no way I’m putting this exhaust manifold back on though. I’ll be buying a new one. That was a lot of work just to find that the exhaust manifold was plugged. I should have checked it out better before I bolted it on.

[pastry_chef]

Originally Posted by John Milner

The port on the exhaust manifold was completely plugged up that ran to the #2 exhaust port

That would do it for sure.
Let us know when you have the new manifold on.

[steve25]

Man, that would do it with out question and that would have been the very last thing I would have thought of!!!

You don't need to buy a another one, just take it to a auto machine shop that can do Glass beading and it will look like new down that runner!

[Formulas]

Possible Mud Dauber issue if they are in your area
The mud may of hardened further with the heat similar to making a brick

[track73]

I have a 69 RA 4 pass side exhaust manifold. PM if you are interested.

[lust4speed]

Photo makes it hard to see what's actually there. In 1985 I pulled and rebuilt my '67 H.O. engine. The #2 exhaust passage in the exhaust manifold was 2/3 plugged with something in the bend closest to the head. Screwdriver probing quickly revealed it was casting sand that hadn't been cleaned out back when it was originally cast. How it survived 18 years is a mystery.

[ta man]

Wow..same effect as having a flat cam lobe on that exhaust valve...engine should run really good once it is fixed!

[firechicken]

Originally Posted by ta man

Wow..same effect as having a flat cam lobe on that exhaust valve...engine should run really good once it is fixed!

Yup, last time a thread was started about popping through the carb I suggested a flat exhaust lobe but was wrong.

Kept my mouth shut this time and would have been wrong again haha!

[John Milner]

Just to update, this thing is finally fixed. I fired it up this morning and it sounds great.