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Old September 22nd, 2005, 12:36 PM
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Pinging under full throttle...

Under full throttle, above 3500 rpm, Chammy pings at certain times. I think maybe the heads get too hot internally after a few bursts of throttle on a country road, and then the pinging starts. Coolant temp in aforementioned conditions is 200 or less. If I continue to drive it hard, the pinging gets worse, almost scary! At throttle though, it doesnt ping at all. I was wondering if maybe its a bad sensor coolant temp sensor or fuel temp sensor delivering bad data to the chip. Ive replaced the lambdas just now, no change. Im running a huge 21X7 oil cooler before that was installed Id have dieseling sometimes after shut down. Timing and advance are fine. Plugs replaced. Thoughts?
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  #2  
Old September 22nd, 2005, 01:03 PM
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Hans Haase
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Have you tried backing the timing off just a hair? Could also be that your vacuum advance is going bad. Also, what octane are you running? Were the new plugs possibly a different heat range, and the gaps are good? Maybe some cross-induction through the wires?

Other than that, maybe try some fuel injector cleaner, could be a case of a clogged injector or dirty valve.

-Hans
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Old September 23rd, 2005, 12:21 AM
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Running 91 octane plus booster. I should get some magnacore wires and try them.

Hans, I can try backing off the timing. How do I check the vacuum advance -- under no load it seems fine, but how do you check it under load?

Doug W.
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Old September 23rd, 2005, 01:35 AM
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Got something that can create vacuum, like maybe one of those little hand pumps? Then throw a timing light onto it, add some vacuum to the distributor and see if the timing changes. They are one of those things that either work, or they don't. Just sucking on the hose can sometimes work, that all depends on how sensitive the advance mechanism is.

Also, you might want to see if your timing marks on the dampener are where they should be, I've seen a few places that mention that some of them aren't quite where they should be... mine is about 5 degrees off.

Here's another thought, since your engine isn't quite stock. Does your distibutor run the factory advance curve on the weights? If you bumped up your compression, you might be advancing TOO much. Maybe try just disconnecting and plugging the vacuum line for the distributor and see if that helps.

-Hans
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  #5  
Old September 23rd, 2005, 10:07 AM
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Chris Davis
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What distributor are you running? On my Mallory, it has both mechanical and vacuum advance--I talked with Century Performance and they said that they don't use their vacuum advance since it adds something like 20 or 30 degrees on acceleration (something like that, don't quote me). So I tied off the vacuum advance and all my symptoms went away. I would clamp off the vacuum advance tube and run the engine--that will tell you right off the bat if it is it.

Best regards,
Chris
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Old September 23rd, 2005, 12:12 PM
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I'll do the advance test this weekend. Chris>> Is your Mallory an easy install? What part # and where best to source?

Doug W.
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Old September 24th, 2005, 01:12 AM
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Century Performance was/is the best deal, and they can offer alot of advice on these motors since they are experience both on the rover and the buick/race-buick front. I believe the gentleman's name is Ron, although it has been a spell. It is definetly a short name, 3 letters I believe. Won't matter, just call and it will most likely be him. Knows his stuff.
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Old November 20th, 2005, 01:16 PM
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Well I backed off the timing a while ago and that made a definite improvement, enough to notice that now the pinging is just happening when the engine temp gets high and outside air temp is above 80 degrees. So I just installed colder spark plugs and we'll see....

Interesting to note that stepping down to the next colder plug is supposed to reduce the combustion chamber temperature by 70 to 100 degrees...

More news on this channel later.

DW
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  #9  
Old November 20th, 2005, 01:47 PM
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Hi Doug,

I have the *EXACT* same problem. I started a thread about this about a month ago (you can probably search the threads and find it). Since we are both in LA, maybe it's the nice clean air we have been getting with the Santa Ana's lately?

This began for me when I had my heads done - I think that the combination of mild shaving of the heads required to re-deck them in combination with using the metal head gaskets bumped up my compression enough to make a difference.

Stock compression is 9.35:1, and 9.5:1 is generally the highest you can go on regular gas. Another reported that using the composite gaskets made the difference for him between ping and no ping (thicker, slightly lower compression).

I tried disconnecting the vac advance and it helped, but did not solve the problem. Eventually I had to back the timing back to 0 TDC (from 5 deg advanced stock setting) to get the pinging to go away with 91 octane. With 87 I still get it under heavy throttle exactly as you mention, but I haven't heard it happen with 91. And, yes, hotter days are noticeable worse!

Makes me want to install OBD-II - knock sensor should eliminate this problem!!

I'll be interested to hear your results. I've begun the building of a 4.6L, so I'm not too concerned with any more work to be done on this engine -- it just needs to not explode for a few months...
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Old November 20th, 2005, 06:39 PM
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Well, I had her out in 90 degree weather today. Pinging is almost gone -- almost! I'm going to go down to NGK B9es plugs and try again. Remember, my rig has a bored and stroked 5.0 so compression might be pretty excessive.

DW
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  #11  
Old November 29th, 2005, 11:02 AM
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Now I have B9ES in for a couple of days (changed this weekend) and zero pinging (so far!). I need a nice hot 85 degree day to know for sure.

Each colder plug lowers the combustion chamber temp by about 80 degrees. Drawback is that colder plugs fowl easier. Only time will tell....

Doug W.
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