Hey all, first post on this forum but I’ve been lurking for a while on my journey of fixing up a ‘63 C10. The issue I’m currently facing is what I believe to be pinging coming from the engine (it’s a pinging at idle and higher rpm / also some backfire coming from the exhaust manifolds) This is my first older car that I’m working on so I’ll list everything I’ve done so far and specs of the truck. First off it’s a 1963 C10 with a 4x4 conversion done to it I’m ***uming late 60s or early 70s. It has a divorced Rockwell T221 transfer case, Dana 44 HD front, 10 bolt rear, SM420 4 speed trans, and a 350 SBC in it (don’t know much about it so I’m ***uming internals are stock). When I first got the truck I got it running the way i got it and we enjoyed it for a few weeks. Recently I went through and replaced the carb, intake manifold and distributor. I thought pinging could be from an exhaust leak at the exhaust manifold where it mated up with the engine so I went ahead and replaced on those but the pinging is still there. I timed the engine with a total of 34 and initial came to 12. Timing was done with the distributor vac*** advance disconnected. (Since this is the first time I’m timing an engine like this I hope I did it right lol) I put a vacuum gauge to the carb and I currently have 15 at idle. not really sure where else to look at this point or if this is not even an issue to be worried about in these engines. Thanks for the help in advance!!
Here are a few things to look for. Timing too far advanced. Running too lean or too rich. Valve adjustment too tight or burned exhaust valve. Worn lobe on the cam. 12 degrees advance at low idle seems awfully much. Slow the idle and try backing it off to about 4 degrees advance and see what happens. Depending on al***ude where you live, 15 inches of vacuum should be okay. Higher al***ude = less vacuum. It seems to have a slight miss. In the dark, run it and look for "lightning" at the plug wires. Especially where one touches another one. If the engine is stock it should idle smoothly at 500 RPM. Check carefully for leaks at intake and exhaust manifolds. Spraying WD-40 around all places where you can see a gasket edge should not change any function. Do this on a COLD engine to avoid a flash fire! Don't spray the exhaust gaskets! The carbs on these are famous for leaking at the base gasket/manifold juncture. When checking the timing, plug the vacuum line after disconnecting it from the distributor. Idle speed must be properly set before setting the timing. I believe these have a mechanical advance in addition to the vacuum. Check the vacuum advance pot on the distributor for function. A bad diaphragm = vacuum leak. It should pull back and hold under suction.
Heard the tick sound, almost sounds like a lifter, after 40 years as a mechanic, the only time I heard a ping at idle was due to a big chunk of carbon bouncing around in a combustion chamber. Check your valve adjustment, you may have a worn cam lobe, that maybe the noise and backfire part. Pull the plugs, check color, anything else unusual about appearance may narrow it down to a cylinder in particular.
I was going to add, warm it up, check plugs and do a compression test, any one reading not matching others within 10/15 psi or more warrants closer inspection , your average SBC will be fine with 10-15 degrees timing at idle, with a hot cam, more, here's another case, recently had SBC come in for constant rod knock, did the basics first, compression test showed a small burn through of head gasket between 3 and 5, new head gasket, "rod knock" gone.
Just a couple of suggestions, check for a broken valve spring (had an outer break, leaving the flat section inner spring to do all the work) or a broken/cracked rocker arm (at the ball pivot area..
Doesn’t sound like pinging to me,,,,,it’s not running steady,,,that for sure . Was it doing this before you swapped all the parts ? Tommy
Thanks for all the replies! I’ll get after some of the suggestions today. Tommy, I was thinking about when it started last night. My wife and I took the truck for a spin last Saturday after all the parts were replaced and I verified float levels, timing, etc. she was running great and we stopped at a circle k to top her off. I powered super unleaded in the tank. The drive home was normal but then I decided to take her out the next day to the parts store and that’s when the “pinging”/ backfire under load or when revving started. Not sure if maybe the fuel can be causing this? Would the engine not like a higher octane level and would it cause this unsteady/backfire?
Also, I can post a video when I disconnect the vacuum advance from the distributor and plug it. It seems that the unevenness settles a bit. Not sure what can be going on with the distributor to cause this.
First, study up on vacuum advance hooked up to manifold, ported, or not hooked up at all. Plenty of articles on google and this site about that. On one truck I have I set it at 36 full advance and I don’t care about idle. And it runs best this away. No vacuum advance. noises can travel threw engines. From the flexplate to a fuel pump rod and all in between. But does sound lifter ish. You can run the motor with valve covers off, and see if you can isolate. plugs need to be checked for sure. And no, higher octane shouldn’t change a motor. And I agree it’s not pinging. It’s knocking.
Jalva , If it was good before,,,,I would suspect the fuel . Now a days there are so many different blends,,,,who knows what you might be buying . You might have topped off with E85,,,,,,the tankers deliver the fuel,,,,,,could have put in wrong underground hole,,,,? Just an idea,,,,,,try the fuel first,, before chasing a lot of things and spending money on parts . Try an additive to see if it will clean up the fuel,,,,of try to burn what you can out,,,,or drain it . it’s worth a try ! Tommy
AH ha, that may be telling you something. ***uming the vacuum advance is using manifold vacuum, the vacuum advance , at idle, has the timing advanced. Disconnecting wile allow the timing to retard somewhat. Perhaps try , with engine at idle, retarding the timing until engine "labors". Now increase until it just smooths out and and sounds "free". See how you like that. Ben
Running with open headers? If so connect the exhaust and see if it still does it. Scavaging is all over the place at low rpm and throttle openings.
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