Oil viscosity affects pinging?
Thread Starter
Pro
Joined: Jul 2004
Posts: 668
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From: Platteville WI
Oil viscosity affects pinging?
Someone told me over the weekend that I could try a couple things to reduce pinging. First is a heavier oil. Second is a colder plug. I am also looking for a way to try higher octane fuel. The best I can find is Shell 93.The first two suggestions don't sound plausable to me. Any thoughts?
Advanced
Joined: Nov 2005
Posts: 96
Likes: 0
From: Baton Rouge Louisiana
Definately plugs and octane, but a heavier oil? That is one I have not heard before. Carbon deposits in the combustion chamber can cause pre-detonation, I guess a heavier oil would have a harder time finding its way into the cylinder.
I'd work on plugs and octane first.
I'd work on plugs and octane first.
Pro
Joined: Apr 2006
Posts: 625
Likes: 49
From: Southern California
Someone told me over the weekend that I could try a couple things to reduce pinging. First is a heavier oil. Second is a colder plug. I am also looking for a way to try higher octane fuel. The best I can find is Shell 93.The first two suggestions don't sound plausable to me. Any thoughts?
Thin oil can find its way into the combustion chamber, where it can make pinging more likely than with fuel alone. This is due to the increased likelyhood of carbon build-up on everything inside the combustion chamber. This ups the compression ratio in general, as well as creating potential hot spot areas that could get you into pre-ignition/detonation issues, even with a properly timed engine. That's what they were talking about, when they said to use thicker oil, it can help prevent undue build-up. But if you have already gotten into a pinging condition, then changing oil now is sort of like closing the gate after the horse got out. What weight oil have you been using with the pinging?
Last edited by 540 RAT; Apr 30, 2008 at 08:27 PM.
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Don't believe the oil viscosity story causing detonation. Most likely your timing map is not spot on or you are running lean.
Safety Car
Joined: Oct 2004
Posts: 3,725
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From: Minnesota
I don't know the background of your problem but in case you haven't already done so you need to make sure the advance mechanism on your distributor is working properly. The easiest way to get rid of predetonation is to retard the timing which is very easy to do.
Melting Slicks
Joined: Dec 2006
Posts: 2,669
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From: Kingston Ontario
Octane and spark plugs, yeah! 
Not sure of the oil viscosity, but if it's causing a carbon build-up in the cylinders then yes, it could be a factor.
Also suspect; could be a vacuum leak or incorrect timing. How is the ignition system (distributor and spark plug wires in good shape)?
Not sure of the oil viscosity, but if it's causing a carbon build-up in the cylinders then yes, it could be a factor.
Also suspect; could be a vacuum leak or incorrect timing. How is the ignition system (distributor and spark plug wires in good shape)?
Drifting
Joined: May 2006
Posts: 1,425
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From: Seattle Wash.
I don't see the correlation between oil viscosity and pinging. That would mean inversly, a thinner/lighter oil would cause a properly timed car to start pinging. Not gonna happen. In most cases, pinging is caused through timing and / or lean settings on your carburetor.
If I were you, I would put the correct heat range plugs in, check all elements in your ignition system, and use that as a baseline to start with and make any other adjustments after that.
If I were you, I would put the correct heat range plugs in, check all elements in your ignition system, and use that as a baseline to start with and make any other adjustments after that.
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Thread Starter
Pro
Joined: Jul 2004
Posts: 668
Likes: 3
From: Platteville WI
Thanks for all the replies. I'm using 10W30 oil. Can't remember which plug part numbers are in there. Anyone know what "cold" plug I should be using? They need to fit with Hooker Super Comp headers.The timing is set at 14 initial and 34 total. The EGR is disconnected. I've asked the Chevy dealer to fix it and they refused, saying that the engine will run better without it. Hmmmm. Any thoughts on an easy way to make my own 94-95 octane gas?
Jay
Jay
Melting Slicks
Joined: Aug 2003
Posts: 2,135
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From: Dayton Oh
Jay-Dog: Would help if we know a little more about your Vette. Have you done any mods to the engine that might contribute to pings such as smaller cc heads, flat top pistons, or anything related to the distributor or carb?
Burning Brakes
Joined: Feb 2004
Posts: 924
Likes: 2
From: Kearneysville West Virginia
Thin oil can find its way into the combustion chamber, where it can make pinging more likely than with fuel alone. This is due to the increased likelyhood of carbon build-up on everything inside the combustion chamber. This ups the compression ratio in general, as well as creating potential hot spot areas that could get you into pre-ignition/detonation issues, even with a properly timed engine. That's what they were talking about, when they said to use thicker oil, it can help prevent undue build-up. But if you have already gotten into a pinging condition, then changing oil now is sort of like closing the gate after the horse got out. What weight oil have you been using with the pinging?
Race Director
Joined: Nov 1999
Posts: 10,643
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From: Foxfield CO 1970 Convertible
Your timing sound about right. You shouldn't have pinging unless you've upped the compression or something. Is the engine stock? To see if higher octane fuel will help, you get get octane boost and add to your gas. Or go to a station that has race fuel, but I think that's wasting money...
Thread Starter
Pro
Joined: Jul 2004
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From: Platteville WI
.20 over 355. Comp Cam 477 intake 480 exhaust, 268 duration. Plugs are AC #2 aka R45-TS, Hooker Super Comps, everything else pretty much stock. 14 initial timing, 34 all in. Running vacumm adv but not EGR. Shell 93 w/ 10% ethanol. I've been putting in a bottle of octane boost w/ each fill-up.
Drifting
Joined: Aug 2005
Posts: 1,682
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From: League City TX
I am not sure if you are asking this for general knowledge, or if you think that is what I asked about.
Leak down tests are used to find a percentage of leakage past rings & valves.
Its usefull for finding out if your engine is worn out, among other things.
What I asked, is have you measured your cylinder pressure during cranking.
Since we know the motor has been rebuilt, we know that the compression ratio might not be stock.
Without knowing an actual compression ratio, you need something to get an idea of what it might be.
If you do a compression test and it shows 230 psi, you arent going to tune around that.
If its 180 or less and you are pinging, then its probably something you can fix without going into the motor.
Leak down tests are used to find a percentage of leakage past rings & valves.
Its usefull for finding out if your engine is worn out, among other things.
What I asked, is have you measured your cylinder pressure during cranking.
Since we know the motor has been rebuilt, we know that the compression ratio might not be stock.
Without knowing an actual compression ratio, you need something to get an idea of what it might be.
If you do a compression test and it shows 230 psi, you arent going to tune around that.
If its 180 or less and you are pinging, then its probably something you can fix without going into the motor.
Thread Starter
Pro
Joined: Jul 2004
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From: Platteville WI
Yes, I am seriously trying to learn in general how this works.
Thanks.
Jay
Drifting
Joined: Aug 2005
Posts: 1,682
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From: League City TX
Does this high reading merely indicate a nice tight combustion chamber regardless of it's size? Or do you think I would get a high reading if the chamber was too small? As in small bowl and/or zero relief/flat top piston resulting in a relatively high ratio of compression? I did not build the engine. Not sure if pistons are flat top. Heads are original.
Yes, I am seriously trying to learn in general how this works.
Thanks.
Jay
Yes, I am seriously trying to learn in general how this works.
Thanks.
Jay
I actually used 230 as an extreme example. I doubt you are that high.
But somewhere around 200 psi of cranking compression you get an engine that
doesnt like to run on pump gas without pulling lots of timing out.
When your Vette was new the stock cranking compreesion probably measured around 160.
Raising the compresion ratio without installing a larger cam will make that number go up.
Thread Starter
Pro
Joined: Jul 2004
Posts: 668
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From: Platteville WI
Update: Compression came in between 170-175 all the way around. I switched to a colder plug. From R45TS to R43TS. Also picked up a timing light. Will re-check timing next weekend.
Jay
Jay
