Pinging even with low timing
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Advanced
Joined: Nov 2013
Posts: 69
Likes: 6
From: Raleigh, NC
Pinging even with low timing
Need help with pinging under heavy acceleration. I believe it's not a timing issue at this point.
1970 350 10.25:1 compression with HEI distributor. Automatic.
New ACdelco plug wires and ACdelco R45ST plugs (could these plugs be "too hot" and cause the pings?)
Initial timing: 10 degrees with vacuum advance plugged (I had initial and total timing much higher before but kept going down due to the pings)
Total timing: 25 degrees with vacuum advance plugged
Manifold vacuum advance gives 15 degrees at idle (I disconnected it once during test drive and it still pinged)
Mechanical advance gives 15 degrees at 2000rpm (a bit early, but not sure if this would cause pinging? Even so, I'd think my very conservative initial timing should help.)
93 octane premium gas most of the time, although I made a mistake using 86 and pinging got worse. Added Gumout octane booster and it helped slightly.
Seamfoam in both fuel tank and sprayed into Quadrajet throat - didn't help.
Other than the pings, car runs very well. 21.5in vacuum at 925rpm in park. 625rpm in drive. Steady rpm needle (+/- 5 to 10rpm)
I have R44ST plugs coming in as my next fix...
Thanks in advance for your help!
1970 350 10.25:1 compression with HEI distributor. Automatic.
New ACdelco plug wires and ACdelco R45ST plugs (could these plugs be "too hot" and cause the pings?)
Initial timing: 10 degrees with vacuum advance plugged (I had initial and total timing much higher before but kept going down due to the pings)
Total timing: 25 degrees with vacuum advance plugged
Manifold vacuum advance gives 15 degrees at idle (I disconnected it once during test drive and it still pinged)
Mechanical advance gives 15 degrees at 2000rpm (a bit early, but not sure if this would cause pinging? Even so, I'd think my very conservative initial timing should help.)
93 octane premium gas most of the time, although I made a mistake using 86 and pinging got worse. Added Gumout octane booster and it helped slightly.
Seamfoam in both fuel tank and sprayed into Quadrajet throat - didn't help.
Other than the pings, car runs very well. 21.5in vacuum at 925rpm in park. 625rpm in drive. Steady rpm needle (+/- 5 to 10rpm)
I have R44ST plugs coming in as my next fix...
Thanks in advance for your help!
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
What cam is in it? Have you run a compression test? Has engine been rebuilt? It's got a lot of vacuum....so cam is pretty mild or timed/installed wrong.
What engine temp?
Not sure on rear gearing etc......but since there's a swapped in HEI with an advance curve that comes in pretty quickly.....I'd throw some heavy springs on it to slow down the curve a lot. Typically I'd limit total advance and use more initial to get it back up to at least the mid 30's at WOT and high RPM.
Is it pinging under light/moderate throttle or WOT with some RPM...like 4000-5000?
Plug heat range is fine.
JIM
What engine temp?
Not sure on rear gearing etc......but since there's a swapped in HEI with an advance curve that comes in pretty quickly.....I'd throw some heavy springs on it to slow down the curve a lot. Typically I'd limit total advance and use more initial to get it back up to at least the mid 30's at WOT and high RPM.
Is it pinging under light/moderate throttle or WOT with some RPM...like 4000-5000?
Plug heat range is fine.
JIM
Safety Car
Joined: May 2001
Posts: 4,754
Likes: 1,642
From: Fairfax Virginia
Pinging or detonation can be heard when an engine has excessive carbon buildup inside the cylinder. On lower compression engine this can be a real issue and a PIA to resolve.
VW Air cooled engines would ping when they developed carbon on the piston crown or the cylinder head. The most effective way to remove it in the old days was to pour "cool water" into the carburetor while holding the throttle open enough to keep it running. The cool water would break up the carbon and most would come out of the exhaust system as the carbon continued to break up.
If this doesn't help then I would be very suspicious that you have a slipped outer ring on the balancer. This causes the the timing marks/numbers to mean nothing as the parts have come apart and spun, how much nobody knows. From here you need to re-establish the TDC marks to get it set properly.
Your Timing comes in at a fairly early point, that could be aggravating the problems. I try to get my full timing in at 3000 rpm and I bring it in more gradually which keeps my 427 from detonating.
The "Timing Paper" might be something you need to read as it helps you get the car to run at its best. Someone here can point you to the author so you can request a copy of it.
VW Air cooled engines would ping when they developed carbon on the piston crown or the cylinder head. The most effective way to remove it in the old days was to pour "cool water" into the carburetor while holding the throttle open enough to keep it running. The cool water would break up the carbon and most would come out of the exhaust system as the carbon continued to break up.
If this doesn't help then I would be very suspicious that you have a slipped outer ring on the balancer. This causes the the timing marks/numbers to mean nothing as the parts have come apart and spun, how much nobody knows. From here you need to re-establish the TDC marks to get it set properly.
Your Timing comes in at a fairly early point, that could be aggravating the problems. I try to get my full timing in at 3000 rpm and I bring it in more gradually which keeps my 427 from detonating.
The "Timing Paper" might be something you need to read as it helps you get the car to run at its best. Someone here can point you to the author so you can request a copy of it.
Race Director
Joined: Mar 2016
Posts: 14,351
Likes: 8,158
From: Napa Valley California
Is the pinging something that just started on its own?
Have you made any recent modifications to the engine and that’s when the pinging started?
Did you tune the car recently and immediately noticed the pinging?
If you just tuned it, did you check to make sure you tightened the distributor and hooked up the vacuum advance line to the correct port?
Have you made any recent modifications to the engine and that’s when the pinging started?
Did you tune the car recently and immediately noticed the pinging?
If you just tuned it, did you check to make sure you tightened the distributor and hooked up the vacuum advance line to the correct port?
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,053
Likes: 4,402
From: Marlton NJ
Congrats on a nice car.
A 1970 300HP automatic would have come std with a 3.08 gear.
That low gear, the mild cam, the high vacuum, and the 10.25 CR make this engine pretty knock prone on today's gas.
You have a lot of cylinder pressure at low rpms.
You do not want a fast performance curve with this combination. You want a stock slow curve, and likely a adjustable vacuum can.
It will not like a fast performance curve unless you have 97 octane gas.
I have had 2 L48s, and a blue-printed '70 LT-1, and tuned lots of cars.
My suggestions below. This should get you close:
A 1970 300HP automatic would have come std with a 3.08 gear.
That low gear, the mild cam, the high vacuum, and the 10.25 CR make this engine pretty knock prone on today's gas.
You have a lot of cylinder pressure at low rpms.
You do not want a fast performance curve with this combination. You want a stock slow curve, and likely a adjustable vacuum can.
It will not like a fast performance curve unless you have 97 octane gas.
I have had 2 L48s, and a blue-printed '70 LT-1, and tuned lots of cars.
My suggestions below. This should get you close:
- Verify TDC with a mechanical piston stop, and then verify balancer TDC matches, and has not slipped. Very common.
- Buy a timing curve kit and an adjustable vac can.
- Get a Lars timing limiter or make your own.
- Initial settings: ~10* initial timing. no vac can.
- Remove one or both timing springs, rev engine until timing stops climbing, measure total centrifugal advance. Suggest setting to 30* Make sure more revving does not make it climb.
- Recheck idle timing. If more than 10* report back. If less, ok for now. As long as it is over 4*.
- Install various springs in your distributor until the 30* timing comes all in at 3600-3800 rpm. I would not go with a much lower rpm with your combo at this time.
- Install vac limiter. Limit vac advance to 12* at idle. This is one of the most important steps for your part throttle pinging.
- Adjust vac can until it starts to lower the timing from maximum reading, once you lower the vacuum to 12-13" Hg. This is easiest to set with a mity-vac hand pump. Based on your saying you had 15" Hg Vac at idle. These cans adjust with a hex screw inside the port fitting.
- Then take it for a test ride and see if it is better.
- If it still pings, cleaning the carbon out with some water that may help improve it. Make sure you rev it, add it slowly, and do not stall the engine.
- If it does not ping, you can try slowly adding some of the mechanical timing back, 2* at a time, at idle.
Thread Starter
Advanced
Joined: Nov 2013
Posts: 69
Likes: 6
From: Raleigh, NC
What cam is in it? Have you run a compression test? Has engine been rebuilt? It's got a lot of vacuum....so cam is pretty mild or timed/installed wrong.
What engine temp?
Not sure on rear gearing etc......but since there's a swapped in HEI with an advance curve that comes in pretty quickly.....I'd throw some heavy springs on it to slow down the curve a lot. Typically I'd limit total advance and use more initial to get it back up to at least the mid 30's at WOT and high RPM.
Is it pinging under light/moderate throttle or WOT with some RPM...like 4000-5000?
Plug heat range is fine.
JIM
What engine temp?
Not sure on rear gearing etc......but since there's a swapped in HEI with an advance curve that comes in pretty quickly.....I'd throw some heavy springs on it to slow down the curve a lot. Typically I'd limit total advance and use more initial to get it back up to at least the mid 30's at WOT and high RPM.
Is it pinging under light/moderate throttle or WOT with some RPM...like 4000-5000?
Plug heat range is fine.
JIM
No idea if the engine has been rebuilt nor what cam it has. As far as I know it's completely stock but I'm the second owner so it may have been rebuilt before.
190 thermostat and the engine runs at a steady 190. I've heard 190 is too hot for 10:1 compression? I bought an 180 just in case.
It pings 4 - 5k rpm (flooring it). Normal driving has zero pings.
Thread Starter
Advanced
Joined: Nov 2013
Posts: 69
Likes: 6
From: Raleigh, NC
Pinging or detonation can be heard when an engine has excessive carbon buildup inside the cylinder. On lower compression engine this can be a real issue and a PIA to resolve.
VW Air cooled engines would ping when they developed carbon on the piston crown or the cylinder head. The most effective way to remove it in the old days was to pour "cool water" into the carburetor while holding the throttle open enough to keep it running. The cool water would break up the carbon and most would come out of the exhaust system as the carbon continued to break up.
If this doesn't help then I would be very suspicious that you have a slipped outer ring on the balancer. This causes the the timing marks/numbers to mean nothing as the parts have come apart and spun, how much nobody knows. From here you need to re-establish the TDC marks to get it set properly.
Your Timing comes in at a fairly early point, that could be aggravating the problems. I try to get my full timing in at 3000 rpm and I bring it in more gradually which keeps my 427 from detonating.
The "Timing Paper" might be something you need to read as it helps you get the car to run at its best. Someone here can point you to the author so you can request a copy of it.
VW Air cooled engines would ping when they developed carbon on the piston crown or the cylinder head. The most effective way to remove it in the old days was to pour "cool water" into the carburetor while holding the throttle open enough to keep it running. The cool water would break up the carbon and most would come out of the exhaust system as the carbon continued to break up.
If this doesn't help then I would be very suspicious that you have a slipped outer ring on the balancer. This causes the the timing marks/numbers to mean nothing as the parts have come apart and spun, how much nobody knows. From here you need to re-establish the TDC marks to get it set properly.
Your Timing comes in at a fairly early point, that could be aggravating the problems. I try to get my full timing in at 3000 rpm and I bring it in more gradually which keeps my 427 from detonating.
The "Timing Paper" might be something you need to read as it helps you get the car to run at its best. Someone here can point you to the author so you can request a copy of it.
I've also used Seafoam in both fuel and the QJet. No change as far as I can tell.
I'm hoping with the new weights/springs, octane booster, and colder plugs (R44ST) will help with the situation. For now I'll do one thing at a time. Thank you for your comment!
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Thread Starter
Advanced
Joined: Nov 2013
Posts: 69
Likes: 6
From: Raleigh, NC
Is the pinging something that just started on its own?
Have you made any recent modifications to the engine and that’s when the pinging started?
Did you tune the car recently and immediately noticed the pinging?
If you just tuned it, did you check to make sure you tightened the distributor and hooked up the vacuum advance line to the correct port?
Have you made any recent modifications to the engine and that’s when the pinging started?
Did you tune the car recently and immediately noticed the pinging?
If you just tuned it, did you check to make sure you tightened the distributor and hooked up the vacuum advance line to the correct port?
Distributor is tightened well and I've reverified initial and total timing a few times - they stayed consistent.
My vacuum advance is currently hooked to manifold. I've heard huge debates about it but it idles very nicely (much better than before) and would only ping when I floor it.
Thank you for your comment!
Thread Starter
Advanced
Joined: Nov 2013
Posts: 69
Likes: 6
From: Raleigh, NC
Thread Starter
Advanced
Joined: Nov 2013
Posts: 69
Likes: 6
From: Raleigh, NC
Congrats on a nice car.
A 1970 300HP automatic would have come std with a 3.08 gear.
That low gear, the mild cam, the high vacuum, and the 10.25 CR make this engine pretty knock prone on today's gas.
You have a lot of cylinder pressure at low rpms.
You do not want a fast performance curve with this combination. You want a stock slow curve, and likely a adjustable vacuum can.
It will not like a fast performance curve unless you have 97 octane gas.
I have had 2 L48s, and a blue-printed '70 LT-1, and tuned lots of cars.
My suggestions below. This should get you close:
A 1970 300HP automatic would have come std with a 3.08 gear.
That low gear, the mild cam, the high vacuum, and the 10.25 CR make this engine pretty knock prone on today's gas.
You have a lot of cylinder pressure at low rpms.
You do not want a fast performance curve with this combination. You want a stock slow curve, and likely a adjustable vacuum can.
It will not like a fast performance curve unless you have 97 octane gas.
I have had 2 L48s, and a blue-printed '70 LT-1, and tuned lots of cars.
My suggestions below. This should get you close:
- Verify TDC with a mechanical piston stop, and then verify balancer TDC matches, and has not slipped. Very common.
- Buy a timing curve kit and an adjustable vac can.
- Get a Lars timing limiter or make your own.
- Initial settings: ~10* initial timing. no vac can.
- Remove one or both timing springs, rev engine until timing stops climbing, measure total centrifugal advance. Suggest setting to 30* Make sure more revving does not make it climb.
- Recheck idle timing. If more than 10* report back. If less, ok for now. As long as it is over 4*.
- Install various springs in your distributor until the 30* timing comes all in at 3600-3800 rpm. I would not go with a much lower rpm with your combo at this time.
- Install vac limiter. Limit vac advance to 12* at idle. This is one of the most important steps for your part throttle pinging.
- Adjust vac can until it starts to lower the timing from maximum reading, once you lower the vacuum to 12-13" Hg. This is easiest to set with a mity-vac hand pump. Based on your saying you had 15" Hg Vac at idle. These cans adjust with a hex screw inside the port fitting.
- Then take it for a test ride and see if it is better.
- If it still pings, cleaning the carbon out with some water that may help improve it. Make sure you rev it, add it slowly, and do not stall the engine.
- If it does not ping, you can try slowly adding some of the mechanical timing back, 2* at a time, at idle.
I thought 2.8k all in on mechanical advance is good, but interesting that you suggested 3.6k instead. I'll definitely consider that. But considering how ping-prone my car is I think what you say makes sense.
A lot of it is also my fault for trying out lower octane gas this last fill up - it made it so much worse.
Thank you again for your comment and guidance.
Race Director
Joined: May 2006
Posts: 18,710
Likes: 2,574
Wow, your instructions are incredibly helpful - thank you!
I thought 2.8k all in on mechanical advance is good, but interesting that you suggested 3.6k instead. I'll definitely consider that. But considering how ping-prone my car is I think what you say makes sense.
A lot of it is also my fault for trying out lower octane gas this last fill up - it made it so much worse.
Thank you again for your comment and guidance.
I thought 2.8k all in on mechanical advance is good, but interesting that you suggested 3.6k instead. I'll definitely consider that. But considering how ping-prone my car is I think what you say makes sense.
A lot of it is also my fault for trying out lower octane gas this last fill up - it made it so much worse.
Thank you again for your comment and guidance.
Race Director
Joined: Jan 2000
Posts: 13,015
Likes: 2,260
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Verifying the balancer is still accurate is a good idea. I changed one for a friend a while back which had slipped several inches! Of course...it only slipped a little at a time...so yours might be in same situation.
JIM
JIM