Posted awhile back about my truck poping through exhaust pipes, well I realized its only during deceleration. Also it has recently started popping through the carb went hittin the gas from a stop. I dont know whats wrong can someone please help. Timing is at 12 degrees, distributor is stock but new, plugs and wires are new, carb was just rebuilt. what else do i need to fix, lol?

 

Play with your timing. You may be getting an incorrect reading from the damper. You have a sorta strange problem. You may need a valve job.

 

I think its the heads too as long as the carb is clean.

 

I think it could be timing too. (Just a story I wanted to share -- I knew a guy who thought he set the damper to 0 degrees and TDC, but turned out it was actually at 10 degrees and not checking the #1 for TDC). Anyway...his FE didn't run so well at first.

May want to start timing at 6 or 8 degrees and advance it from there. Keep us all posted...and good luck with it!

 

it sounds like your heads to me. but if its spitting out of the carb it could be timing also . my bet its probably both causing you this grief !!

 

either way even if you didnt set the timing to the dampner degrees, you can set the timing reletivly close just by ear and common sense. when a motor is old you will not likely get accurate time. I think if you stick a light on it you can get it close enough by feel.. to figure out whats wrong.

 

Scott: I would check your camshaft timing. The gears and the chain wear and stretch over use. The gears installed by the factory, aluminum with plastic teeth, were soft, designed to eliminate noises. The teeth often fell off, and the aluminum wore down, retarding the camshaft timing.

The chain accumulates all this wear. The following is an easy check to determine the amount of slack, slop or wear, in your timing chain.

It is not necessary to remove any components as long as you can see the timing marks clearly. It can be done with one person, but a second person can be helpful if the distributor cannot be easily seen while turning the cranskshaft from the front of the engine. This test cannot tell if a chain has jumped; it can, however, tell you if there is enough slop in the chain to have let it jumped.

Tools: Breaker Bar with socket to fit the front crankshaft bolt

1. Mark the TDC or 0 mark on the damper clearly. Ensure the rest of the timing marks can be clearly seen; clean them if necessary. You may find it useful to scrape a little chalk over them to highlight them.
2. Remove the distributor cap and place it out of the way. You must be able to see the rotor while turning the engine with the breaker bar. It usually is not necessary to remove the spark plugs, but some high compression engines may require it to get an accurate reading.
3. Turn the engine in its normal rotational direction until the TDC or 0 mark is lined up with the pointer.
4. IMPORTANT: Do NOT turn the crank backwards just to line it up. Doing so will give erroneous results. You MUST rotate the crank in ONE direction only. If you overshoot, just go around again. This is where it may be helpful to remove the plugs.
5. Once the TDC and 0 marks are lined up and while watching the rotor, rotate the crank in the opposite direction. When the rotor begins to turn, STOP. It may help to have a helper push against the rotor's direction of rotation. (Remember, it will be going backwards at this point.) They can feel it begin to move more accurately than you can see it begin to move.
6. Note the value of the timing mark the pointer is indicating. It will be BTC, because you went in reverse of normal rotation.
7. This value is the amount of slop your timing chain has in degrees of rotation. Anything less than 10 is safe, but performance begins to fall off after 5.
8. If you have anything over 25, STOP driving that motor and get the chain and gears replaced! I have seen motors run with up to 45 degrees - but I wouldn't risk it myself.

 

How likely are heads to mess up after 4000 miles, The heads were just rebuilt new valves, seats, springs, retainers, everything.

 

trust me it happens, specially with new seats installed, sometimes when they put new seats on, they dont get sealed properly and well come loose, i had this happen on a 390 that had 20,000 on it, good luck

 

Try changing the dist. cap. It could have a hairline crack or carbon tracking.

I had that happen to me once and I couldn't figure what was wrong for anything. I had the air cleaner off listening through the carb for bad intake valves when it let go with a carb. backfire that sounded like a cannon. I almost passed out from the noise and then hit my head on the hood getting out from under there.

When I came to I changed the cap and it ran like new.