Vacuum at idle is around 20 - Is it steady ? Bouncing needle is indicative of several other problems. With vac can on dizzy disconnected, what's the timing do ? Steady or bounce?
If you had an exhaust manifold leak,it should have changed its sound when the plug leads were removed. Doe's i have a 350 oil pan ? i built a 350 once and put a 283 pan on and a rod was just touching the windage tray....just a thought. JW
It be an open lakes header flange leak ( if I'm understanding the posts here) and I think anyone would be hard pressed to hear a flange leak with the collector end just a few inches from the flange. I'm of the opinion that all Headers are guaranteed to leak eventually. The noise and the bouncing timing may be related and steming from one issue or two completely desperate issues. One could be a causation of the other also.
It has an old mr. Gasket aftermarket pan. The 350 has the passenger side dipstick which would rule out an earlier sbc pan right? Posted from the TJJ App for iPhone & iPad
As soon as I'm confident that e neighborhood is wide awake, I will check everything that you all have suggested. Thanks for all the advice Posted from the TJJ App for iPhone & iPad
Really sounds like your timing chain is sloppy, and sloppy enough to be touching the cover. I'd be changing it, or go ahead and do the engine you want.
So I got the timing to stabilize by fiddling with everything. I'm not sure exactly what I did, but I'm getting about 21.5" of vacuum at idle at 12* initial advance. The problem I'm now having is the advance won't come in all the way unless I rev to the moon. I'm getting 28* around 3000rpm. Do I need lighter advance springs? Also, the bad news is I still have the tick/knock sound.. The engine seems to be happy otherwise runs at 175* and no oil pressure issues, no glitter in the oil. I'm not heavily invested in the engine so if it craps out so be it. The knock sounds like it is coming from the front of the engine around the lower middle of the block as best as I can identify. Thanks for all the great advice Posted from the TJJ App for iPhone & iPad
Stretched timing chain caused erratic timing on a 65 GTO I had in college. Suspected when timing. Finally jumped time and would not run at all. Unfortunately it happened 1200 miles from home. You might have more than one issue with yours.
Timing has stabilized. I now need to adjust total advance and figure out the tick. Posted from the TJJ App for iPhone & iPad
Man they are hard to fix and diagnose over the Internet. Especially if you don't know what fiddle lead to the fizzle. First and foremost, the numbers being posted are of little value unless you've verified the TDC mark with a piston stop. Them balancer rings can and do move around quite a bit.
are you sure the rotor isn't moving around or the vacuum advance? Do you have a plugged vacuum line? Line collapsing? It reminds me of my issue I just had: http://www.jalopyjournal.com/forum/showthread.php?t=813678 Did you time it with vacuum advance unplugged? They sell the vacuum advance units at the store btw, should only be about 10-15 bucks. Worth a try if you suspect it being the issue. I would really just swap the vacuum line and check to see if you have a leak somewhere or not enough suction from the carb (something maybe plugged)
I think the ignition is sorted except the advance. It's the rest of it now lol! Posted from the TJJ App for iPhone & iPad
Erratic timing: HEI distributor? Check the pivot holes in the advance weights and the pins on top of the distributor mainshaft. This is a common area for wear and there used to be a repair kit available with new weights and pin bushings. Try putting a narrow stripe of white paint somewhere on the balancer hub, rubber damper ring and the face of the iron inertia ring. Check it from time to time to make sure the inertia ring isn't slipping. Tapping/knocking noise: Did you try unbolting the fuel pump and moving it away from the block? The pumps can get noisy as already mentioned. You just need to run it a few seconds on the fuel in the float bowl to see if the noise goes away. You may have just knocked a piece of carbon loose in the combustiom chamber while sorting out your tune-up. Some combustion chamber cleaner or water blasting may clear it out. Or it may just go away on it's own.
The balancer timing has been verified via timing stop. I will check the fuel pump. Thanks Posted from the TJJ App for iPhone & iPad
How close was the factory marK? Now's the time for the full length witness mark mentioned a few posts back by ClayMart, to track any balancer shift for the next time it's running poorly.
OK, 20-22 inches of vacuum is very good. If the mark is moving 30-40 degrees and the engine continues to run good it sounds like it's time for a balancer.
Many years ago I bought a 60 dollar 70 Impala for the 350 to use in my 67 C20,after getting it in the truck it had what sounded like a lifter tick that would not go away with adjusting the rocker arms. About a week later the timing chain jumped and when I got it apart I noticed the timing chain was slapping the cover.
Just a shot in the dark, but who knows. I was driving my '46 Chevy with a SBC in it on a very choppy expressway and it began to tick, loudly. I could hear it in the car at expressway speed. I pulled off and checked under the hood and didn't see anything Wrong till I happened to put a hand on the dipstick. I could feel the tapping through the dipstick and when I tried to pull it put it would only move a half inch or so. I yanked hard on it and it came out minus the last couple inches, and the ticking/tapping stopped. The only thing I could figure is that the choppy road got the dipstick moving and it touched the crank and got bent over and was getting hit by the crank. I replaced the dipstick and the old broken piece is still in the pan.
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