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#1
07-05-2006, 12:30 AM
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Engine Pinging Badly at Proper Ignition Timing
Hey guys, I've got kind of a problem. I've got an '84 Caprice Classic with a 4 bbl Rochester Q-jet and a 700 R4 Tranny. About a month agot I converted the car to be a non CC car, which required me to install a vacuum advance HEI distributor and a non-CC Carb (another Q-Jet) It ran great for a while, very responsive etc etc, well its started to ping when it was warmed up recently, so I retarted the timing a little from 4 degrees over TDC to about 6 hoping it'd help well itd helped for about a mile, then got bad again with the pinging, so i retared it more to 8 degrees, same issue, well i got it to stop pinging finally, but its off the charts how retarded it is, and the engine has NO power now because of it. Why would it suddenly want to ping so badly at the proper timing and why do I have to retard it so drastically to get the ping to stop? New plugs by the way, and the Vacuum advance Hei was freshly reconditioned. The carb on the other hand was off of a '78 Caprice and had been sitting in a tool chest for 12 years. Would the carb have an effect on the bad ping? Any help would be great guys, and thanks so much in advance!
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Last edited by PeteA216; 07-05-2006 at 09:58 AM. Reason: misleading title 
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#2
07-05-2006, 11:07 AM
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Re: Engine Pinging Badly at Proper Ignition Timing
I have no idea, but i'd make sure you arent advancing the timing instead.
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#3
07-06-2006, 10:55 PM
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Re: Retarded Timing, Still Pinging.
well, you were right about the lean mixture... i got tired of messing around with the Q-Jets, and got myself an Edelbrock performer carb w/ electric choke. That fixed the lean problem so I was able to advance the timing now, it gave the car a TON of pep, and really woke up that 305. Its still no 350, but it sure beats the Q-Jets. They're not bad carbs, I've had 3 of em, one of them pre-CC... but they just don't seem to put out as much as this Edelbrock does. The car's never ran this good before, even with a freshly rebuilt Q-Jet.
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#4
07-07-2006, 08:37 PM
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Re: Retarded Timing, Still Pinging.
the 80's Q-jets were actually superior in CC form to most holly, or otherwise, "Performance" carbs. they can flow up to 750 cfm (i think) on demand.
since you went with non CC, i'd say that a "Performance" carb would help a LOT. if the pinging problem did not start right when you installed the 78 carb, than it wasnt the carbs fault. i'd try checking your distributor and vaccuum advance. if you have even a small vaccuum leak it could throw the whole timing curve way off.
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#5
07-08-2006, 10:09 AM
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Re: Retarded Timing, Still Pinging.
Is the EGR working? EGR failure of some kind (clogged passages, bad valve) is often the reason for pinging. Another is excessive carbon buildup in the combustion chamber. Have you drizzled water into the running engine lately to steam clean the chambers?
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#6
07-09-2006, 10:15 PM
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Re: Retarded Timing, Still Pinging.
I've done the water thing a few months ago (helped a little), And the EGR valve is sort of *cough* no longer attached to the car. I replaced it with a steel plate and gasket a little while ago. As for vacuum leaks, I noticed the gasket off the base of the Q-jet was cracked all the way through, and might have been the source of the lean mixture.
Yesterday I noticed the ping was back a little bit here and there, at 4 degrees OTDC, so instead of retarding it again, I tried a higher octane fuel and that fixed it. Oh and if it makes a difference, it ONLY pinged after the engine was fully warmed up.
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#7
07-09-2006, 11:20 PM
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Re: Retarded Timing, Still Pinging.
Try using the GM top engine cleaner or Sea Foam - methinks you still have a bad carbon problem. You might also have a burned valve which is presenting a sharp object to the combustion chamber - this tends to generate a detonation condition due to hotspots.
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#9
07-12-2006, 01:17 PM
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Re: Retarded Timing, Still Pinging.
also if the gasket on the base of the carb was cracked, you should replace it. it'll cost maybe ten bucks.
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#10
07-13-2006, 03:42 PM
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Re: Retarded Timing, Still Pinging.
What do your spark plugs look like? If you have that much of a ping issue you should be concerned with detonation. To agree with silicon, you may have something that is acting as a hot spot in the combustion chamber.
Something as simple as a funky buildup on the spark plug can do it. Plus the plugs may no longer be correct for your engine with all the things you've changed on it. Bob
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#11
07-13-2006, 04:38 PM
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Re: Retarded Timing, Still Pinging.
clean and re-gap your plugs. if they are black and sooty, you may have a carbon problem. use LOTS of seafoam. first warm up the engine. run the engine at idle and pour it down the carb slowly at first then stall it by pouring it fast. if you have a 4bbl, you will need to pour somewhat evenly from two bottles. once it stalls, let it sit for an hour or so (the bottle says fifteen minutes, this doesnt work), then start it up and GO. it'll smoke like hell, and you want to be able to run it flat out for a while, so i'd try and do it somewhere you can do this. it should help a great deal. every time i do this, my engine feels more responsive and more powerful.
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