Pinging Problem.....help
Thread Starter
Racer
Joined: Jan 2009
Posts: 353
Likes: 2
From: Cuyahoga Falls Ohio
Pinging Problem.....help
I recently purchased a '66 427/425 coupe and have test drove the
car a few times. Had a pinging issue right off the bat and decided
to put a bottle of lucus octane booster and 4 fresh gallons of premium
fuel to invigorate the old fuel in the tank. My guess is the fuel in
the tank is a combination of 3 years of light driving by the previous
owner.
Still having pinging issue on flat land and horrible up a hill under light
throttle so I played with the timing last night. I was able to reduce the
pining just a bit no matter what setting I place the timing at...???
Next step is draining the fuel tank and putting in a very high octane
fuel..... agree ???
What am I missing ????
What is the minimum octane for a 11:1 compression 427/425 ??
Thanks
car a few times. Had a pinging issue right off the bat and decided
to put a bottle of lucus octane booster and 4 fresh gallons of premium
fuel to invigorate the old fuel in the tank. My guess is the fuel in
the tank is a combination of 3 years of light driving by the previous
owner.
Still having pinging issue on flat land and horrible up a hill under light
throttle so I played with the timing last night. I was able to reduce the
pining just a bit no matter what setting I place the timing at...???
Next step is draining the fuel tank and putting in a very high octane
fuel..... agree ???
What am I missing ????
What is the minimum octane for a 11:1 compression 427/425 ??
Thanks
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
I recently purchased a '66 427/425 coupe and have test drove the
car a few times. Had a pinging issue right off the bat and decided
to put a bottle of lucus octane booster and 4 fresh gallons of premium
fuel to invigorate the old fuel in the tank. My guess is the fuel in
the tank is a combination of 3 years of light driving by the previous
owner.
Still having pinging issue on flat land and horrible up a hill under light
throttle so I played with the timing last night. I was able to reduce the
pining just a bit no matter what setting I place the timing at...???
Next step is draining the fuel tank and putting in a very high octane
fuel..... agree ???
What am I missing ????
What is the minimum octane for a 11:1 compression 427/425 ??
Thanks
car a few times. Had a pinging issue right off the bat and decided
to put a bottle of lucus octane booster and 4 fresh gallons of premium
fuel to invigorate the old fuel in the tank. My guess is the fuel in
the tank is a combination of 3 years of light driving by the previous
owner.
Still having pinging issue on flat land and horrible up a hill under light
throttle so I played with the timing last night. I was able to reduce the
pining just a bit no matter what setting I place the timing at...???
Next step is draining the fuel tank and putting in a very high octane
fuel..... agree ???
What am I missing ????
What is the minimum octane for a 11:1 compression 427/425 ??
Thanks
If your engine is built and tuned to factory 425 hp specs, it should run on 93 pump gas just fine.
What does the timing curve look like?
Melting Slicks
Joined: Oct 2004
Posts: 3,345
Likes: 87
From: Northern MN
St. Jude Donor '13-'14-'15-'16-'17
Where do you find 93 octane??? In MN or at least in my area, we only have 91. Wouldn't a better solution for now be to get some VP/Cam2 or some other racing fuel to supplement what is in his tank. That will burn out the old stuff and he can then start to experiment with his available fuel. JMT.
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,147
Army
Can get 93 octane all over Florida....I run it in the '61.
I can't figure out if the OP says he has 3 year old fuel in the tank or not.
If so, its volatility is way down I'm sure. Its certainly fuel, timing or both.
I can't figure out if the OP says he has 3 year old fuel in the tank or not.
If so, its volatility is way down I'm sure. Its certainly fuel, timing or both.
Pro
Joined: Jul 2008
Posts: 622
Likes: 24
From: Clermont Florida
If it pings under heavy throttle, you may have lost the rubber advance limiting bushing.
You need to power time the engine, to check max advance. You will need a timing light with advance capability. Chevys, up to 1971, are designed to have approximately 50 to 54 degrees total advance with the vacuum hooked up. If you have the correct advance can the timing will lose 15 or 16 degrees from those numbers, with vacuum disconnected. So, if your timing is set right, and the distributor is the right one for the engine, your total timing should be about the numbers I mentioned.
Or, you can get a mirror, and look under the advance mechanism, above the points. There is a pin in a slot. That pin should have a rubber, or plastic, or brass bushing around it to shorten its travel in the slot. If that is not there, that is your problem. If there is a brass one, your distributor has been curved, and may have to be recurved.
Also, curved distributors most often do NOT use the vacuum advance, as it causes pinging under light throttle. Try disconnecting the advance and road test it. Rich
BTW, Octane booster is pretty much useless.
You need to power time the engine, to check max advance. You will need a timing light with advance capability. Chevys, up to 1971, are designed to have approximately 50 to 54 degrees total advance with the vacuum hooked up. If you have the correct advance can the timing will lose 15 or 16 degrees from those numbers, with vacuum disconnected. So, if your timing is set right, and the distributor is the right one for the engine, your total timing should be about the numbers I mentioned.
Or, you can get a mirror, and look under the advance mechanism, above the points. There is a pin in a slot. That pin should have a rubber, or plastic, or brass bushing around it to shorten its travel in the slot. If that is not there, that is your problem. If there is a brass one, your distributor has been curved, and may have to be recurved.
Also, curved distributors most often do NOT use the vacuum advance, as it causes pinging under light throttle. Try disconnecting the advance and road test it. Rich
BTW, Octane booster is pretty much useless.
Last edited by landshark 454; Apr 2, 2009 at 10:06 AM.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
Where do you find 93 octane??? In MN or at least in my area, we only have 91. Wouldn't a better solution for now be to get some VP/Cam2 or some other racing fuel to supplement what is in his tank. That will burn out the old stuff and he can then start to experiment with his available fuel. JMT.
93 octane is available almost everywhere in the country. Even at that, the engine should run okay on 91 with a little tinkering at most.
His best solution is to find out what he really has in the way of engine and tune and then go from there. There is no telling what he has in the way of either without looking.
His words: "Still having pinging issue on flat land and horrible up a hill under light throttle".
Something is way wrong but it may be something simple to fix. May not.
Safety Car
Joined: Mar 2009
Posts: 4,191
Likes: 951
From: Corpus Christi, TX
My 427 is detuned to 10.25 compression and BARELY makes it on 93 octane. When it's hot (damn near every day in Houston), it pings. Mechanical advance is stock (425HP) and vacuum is limited to 8 crank degrees. I was able to cure it with 104+ octane boost. Lucas octane boost didn't seem to work too well, nor did NOS octane boost.
Try the 104+.
Try the 104+.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Corvette & Porsche 911: How Two Icons Conquered the Last 25 Years
Joe Kucinski
2027 Chevrolet Silverado 1500 First Look: Everything You NEED to Know!
Michael S. Palmer
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
It made your wallet lighter, that should help.
Thread Starter
Racer
Joined: Jan 2009
Posts: 353
Likes: 2
From: Cuyahoga Falls Ohio
Landshark 454
Car has a vacuum advance and to my knowledge original distributor.
I can slip a mirror under the vac. advance but do not understand
how I can see the points from here ? There should be under the
distributor cap right ? Car has Transistor Ignition which was mandatory
with the 427/425.
Don't follow your mirror trick. Do you mean I need to very small mirror
to look through the small metal door of the distributor ?? to try to find
the rubber bushing ???
Sorry that I am lost.
thanks
I can slip a mirror under the vac. advance but do not understand
how I can see the points from here ? There should be under the
distributor cap right ? Car has Transistor Ignition which was mandatory
with the 427/425.
Don't follow your mirror trick. Do you mean I need to very small mirror
to look through the small metal door of the distributor ?? to try to find
the rubber bushing ???
Sorry that I am lost.
thanks
Drifting
Joined: Jul 2007
Posts: 1,671
Likes: 10
From: california
i don't see any good answers in the previous posts.
detonation (pinging) will kill your engine in short order.
here is what i would do:
1-if you are not POSITIVE about the gas in the tank, drain it. it may have turned into 50 octane moose ****.
2-check to make sure the timing mark on your damper is at true TDC, this can be done with a dial indicator or the positive stop method.
3-check the spark plugs to make sure your not running lean (dirty carb, lean jets, low float levels etc)
4-pull the cap off the distributer and check the mechanical advance weights and springs under the rotor (clean and lube as needed), check the dist. shaft for wobble and end play.
4A-check with a timing light (with the vacuum advance disconnected and plugged after all of the above things have been corrected) and plot the CENTRIFIGUL advance timing every 500RPMs from idle to 4000RPMs (should all be in by 3000RPMs, but some stock dist. advance are extremely lazy)
if you do all this it will pinpoint your pinging problem. what ever your pinging problem is, you need to fix it NOW...
detonation (pinging) will kill your engine in short order.
here is what i would do:
1-if you are not POSITIVE about the gas in the tank, drain it. it may have turned into 50 octane moose ****.
2-check to make sure the timing mark on your damper is at true TDC, this can be done with a dial indicator or the positive stop method.
3-check the spark plugs to make sure your not running lean (dirty carb, lean jets, low float levels etc)
4-pull the cap off the distributer and check the mechanical advance weights and springs under the rotor (clean and lube as needed), check the dist. shaft for wobble and end play.
4A-check with a timing light (with the vacuum advance disconnected and plugged after all of the above things have been corrected) and plot the CENTRIFIGUL advance timing every 500RPMs from idle to 4000RPMs (should all be in by 3000RPMs, but some stock dist. advance are extremely lazy)
if you do all this it will pinpoint your pinging problem. what ever your pinging problem is, you need to fix it NOW...
Race Director
Joined: Oct 2005
Posts: 12,470
Likes: 1,548
From: Camp Verde AZ
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
In general, the closer you are to sea level, the higher chance you have 93 octane, go up 1500 feet MSL elevation and you find 91 octane, go up 5000 feet and your premium is often 89 or 87 octane.
Higher altitude=less air=less compression.
3 year old gas will suck, run it out or drain it and put in new.
Doug
Higher altitude=less air=less compression.
3 year old gas will suck, run it out or drain it and put in new.
Doug
Instructor
Joined: Nov 2008
Posts: 131
Likes: 0
From: Greenbank Queensland, Australia
Timing
I agree with everything from mechron & AZDoug, I've just been through the same problem and don't even think about running fuel that may be 3yr old, drain it.
I might just add these links, they sure helped me...
http://forums.corvetteforum.com/c1-a...-recurved.html
http://http://www.splashedpaint.com/...VacAdvSpec.pdf
http://www.lbfun.com/warehouse/tech_info/ignition%20system/Distributor%20Installation.pdf
http://www.lbfun.com/warehouse/tech_...101Article.pdf
http://www.lbfun.com/warehouse/tech_...%20ADVANCE.pdf
http://www.lbfun.com/warehouse/tech_...t%20Timing.pdf
I might just add these links, they sure helped me...
http://forums.corvetteforum.com/c1-a...-recurved.html
http://http://www.splashedpaint.com/...VacAdvSpec.pdf
http://www.lbfun.com/warehouse/tech_info/ignition%20system/Distributor%20Installation.pdf
http://www.lbfun.com/warehouse/tech_...101Article.pdf
http://www.lbfun.com/warehouse/tech_...%20ADVANCE.pdf
http://www.lbfun.com/warehouse/tech_...t%20Timing.pdf
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
A better solution would be to find out where you're at so you know where you're going wouldn't you agree?
Why throw more variables in the game? The first step is to map out the timing as suggested before way back in post #2 as one of the "no good answers". This is easy and very simple to do. You may find your problem right there. You may not. Worst case, you may find the engine has some hot rod Harry stuff in it and you'll have to tear the engine down and change parts to eliminate the pinging in order to run pump gas.
Draining the gas is not a bad idea. I don't think that's the problem though.
93 octane is available in Ohio last I was there. As I said, that engine would probably run okay on 91 if it's stock OEM build and tune.
Last edited by MikeM; Apr 3, 2009 at 08:34 AM.
Drifting
Joined: Jul 2007
Posts: 1,671
Likes: 10
From: california
fdreano, i know you know your stuff, so no offense intended. but in his origonal post he said "high octane gas" so i figured he already knew that. i was just telling him what to look for mechanically on these 40+ year old engines. 
Thread Starter
Racer
Joined: Jan 2009
Posts: 353
Likes: 2
From: Cuyahoga Falls Ohio
CabSav
Thank you very much for the tech links on timing, and distributor
placement. Will change the old, old fuel first and see if that helps any.
Will investigate under the dist. cap and check timing set.
Thanks again....!
Dave
placement. Will change the old, old fuel first and see if that helps any.
Will investigate under the dist. cap and check timing set.
Thanks again....!
Dave
