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My truck has developed a poping/pinging noise at cruising speed. It doesn't do it if I let off of the throttle, or if I'm really hard on the gas, only when cruising. My Dizzy is new, have Petronix, coil is new, carb is rebuilt, just put new timing chain and gears in, plugs are new, wires are new, replaced cap due to corrosion and still didn't help. What is the problem? Is it timing, I think I'm at 6 degrees before I believe. I am also thinking maybe a flattened lobe on the cam or lifter???? Any thoughts, my truck is stuck and I don't want to drive it anywhere till this is fixed. It also does it when I am in neutral.
Is the vacuum advance hooked to manifold or ported vacuum?
How many degrees of mechanical advance?
How many degrees of vacuum advance?
Do you have an EGR valve?
Were the jets changed in the carb during the rebuild?
Did you set the camshaft at TDC? I am thinking your camshaft may be advanced. This is easy to fix, but you would need to pull the front cover. Most timing chain sets have three slots cut in the crankshaft gear. You should be using the one for "strasight up" camshaft timing. Initial advance should not ping at around 10-12 initial at idle.
It's a 65' 352. Vacuum advance is hooked to the port in the Edelbrock carb. Timing chain is in correct, there's only one way it will go in and the marks were all lined up. One other thing, when I retard the timing ALOT! I can get it to stop popping all the time so that it is drivable. It still pops a little bit, but not nearly as bad. Could I have a burnt valve????
After it gets warmed up drizzle some water down the carb to clean out the carbon. This seems kinda wierd for it to just start happening. Doesn't sound like a burnt valve to me. When you retard the timing ALOT does it loose A LOT of power? Your balancer may be reading incorrectly.
Check the firing order one more time, then look for a vacuum leak. I think you have a lean backfire. Rotten hoses and a sticky PVC are also possibilities. Use a hand held propane torch, unlit and spray propane around anywhere a vacuum leak could develop. When you find the leak using propane the idle will pick up.
Yes Rat, it looses a lot of power. Hard to get up a hill and it's killing my gas mileage. I originally thought that it was the timing chain and gears, so I replaced that, and still no luck. William, I don't have a PCV, I have a draft tube, and there is only one vaccuum hose on my motor and it's brand new. What else could it be? Cam? Lifters?
If that is what you have, you could have a valve guide that is real loose. It will 'sometimes' just not hit the seat right, and pop back. POW POW POW and then run OK for a while. THe whole car will kind of shake and buck and then smoothe out.
Check fuel pressure & volume.. could be lean backfire. Make sure the timing marks on the damper are still right. Roll engine to TDC and check the timing marks. Rubber damper can move around...
tom
Unlikely but it could be a problem that a compression test, or a vacum test could indicate.
Have you tried the brrom handle from you ear to the motor trick? Works really well if you take the fan off first.
I did a compression test today and found my problem. My #3 cylinder only has 30 psi in it. Stuck or burnt valve. How much does it cost to get a head reworked???
mwc4275, the machine guy I use would charge $250 to totally rework one head. That would include new valves (stock) springs, seats, guides, deck leveling and porting if you like. But I don't know where you are, but that's what it would cost me for one head. Would kind of hate to have one head with springs at one pressure and have a different valve lash on the other side. Just my opinion. Doc.
Originally posted by ADSf100 What is the wet compression of the bad cylinder?
Good point!!!! Check the cylinder with a shot of oil to see if you have a broken ring before you pull the head so you can plan your attack. You might need new rings etc, etc, etc.