It pings under acceleration; need advice
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 2,675
Likes: 13
From: Sudbury MA
The gentleman who built the motor looked it over today and said all is well and done correctly. He said the problem is that the engine was built to 1968 specs with 11:1 compression and in those days octane was higher so it ran fine. Nowadays, 93 octane is not enough for this engine. He said Octane boosters are a waste of money ( I think Lars said same thing) Told me to drive the car and put approx 1,000 miles on the engine then redo the timing and vacuum and all the other stuff.
He said if I put in racing fuel it would probably run great. He suggested a Sunoco station in a nearby town that sells racing fuel for $6.50 per gallon, went to look for it and couldn't find it so don't know if that would work. Also, hard to find racing fuel if you take a trip.
I guess I have no choice but to drive it and let the engine break in and then revisit the problem. He did tell me to drive in such a way that it doesn't ping, in other words accelerate easy. Not my idea of how to drive a Vette but guess I'll try. Will also retard the timing to 4 degrees to see if that helps. I asked if the cam gear could be off one tooth and he said absolutely not or it wouldn't idle as smooth as it does.
There you have it,
Kurt
He said if I put in racing fuel it would probably run great. He suggested a Sunoco station in a nearby town that sells racing fuel for $6.50 per gallon, went to look for it and couldn't find it so don't know if that would work. Also, hard to find racing fuel if you take a trip.
I guess I have no choice but to drive it and let the engine break in and then revisit the problem. He did tell me to drive in such a way that it doesn't ping, in other words accelerate easy. Not my idea of how to drive a Vette but guess I'll try. Will also retard the timing to 4 degrees to see if that helps. I asked if the cam gear could be off one tooth and he said absolutely not or it wouldn't idle as smooth as it does.
There you have it,
Kurt
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
Kurt
no offense but i think he is full of crap.
my '65 has the L76 327/365hp motor and it's full factory spec including the 30-30 cam which is actually a very radical cam for the street.
I have NO problems at all running 93 octane fuel at the factory listed timing specs and I get ZERO pinging.
also, telling you to continue driving the car at all, let alone for 1,000 miles with it pinging, is ludicrous and dangerous to the motor. Does he plan on tearing it down and rebuilding it all over again AT NO CHARGE when you end up destroying the pistons from detonation.
Personally I think he doesn't want to admit that he may have made a mistake somewhere on his original build OR he doesn't know enough to recognise a problem or how to solve a problem that staring him in the face and is playing it off as nothing.
If it was my car i'd take it to someone else to get a second opinion.
An L79 is not an overly radial motor so it should run fine on 93 octane fuel as factory timing specs or maybe 2 degrees below that.
If it takes more than that to retard the timing enough to eliminate pinging than there is a problem somewhere.
Personally, if it's pinging that bad I wouldn't drive it TEN miles until I got it corrected, let alone a THOUSAND!
About the only thing that I believe of what he said is about the octane boosters - they ARE a waste of money.
no offense but i think he is full of crap.
my '65 has the L76 327/365hp motor and it's full factory spec including the 30-30 cam which is actually a very radical cam for the street.
I have NO problems at all running 93 octane fuel at the factory listed timing specs and I get ZERO pinging.
also, telling you to continue driving the car at all, let alone for 1,000 miles with it pinging, is ludicrous and dangerous to the motor. Does he plan on tearing it down and rebuilding it all over again AT NO CHARGE when you end up destroying the pistons from detonation.
Personally I think he doesn't want to admit that he may have made a mistake somewhere on his original build OR he doesn't know enough to recognise a problem or how to solve a problem that staring him in the face and is playing it off as nothing.
If it was my car i'd take it to someone else to get a second opinion.
An L79 is not an overly radial motor so it should run fine on 93 octane fuel as factory timing specs or maybe 2 degrees below that.
If it takes more than that to retard the timing enough to eliminate pinging than there is a problem somewhere.
Personally, if it's pinging that bad I wouldn't drive it TEN miles until I got it corrected, let alone a THOUSAND!
About the only thing that I believe of what he said is about the octane boosters - they ARE a waste of money.
Drifting
Joined: Mar 2006
Posts: 1,526
Likes: 2
From: Oak Ridge NC
Originally Posted by 427Hotrod
The mods aren't that hard to do really once you know how. You would need to find someone who understands what they are doing. The old dist curve kits actually allowed you to get most of it done. Run a search on "Lars' here on the Forum and see if he still sells the kits he used to have. He used to recurve dist's to...but I think he's slowed down on the side stuff lately.
You usually can't pull your car up there to get it. You need to take a bunch of 5 gallon cans out there and load up. That is usually no issue..just don't talk about using it on the street. The only reason it is an issue is because they don't collect highway use taxes on it.
AV gas has a few peculiarities...but if you added 5-8 gallons per tank full it would likely take care of issue. I know other folks who buy a 55 gallon drum of race gas and keep at home to add small amounts throughout the summer as needed for cruise season. If you used 5 gallons per tank of good race gas...that would likely get you through your cruising season.
JIM
You usually can't pull your car up there to get it. You need to take a bunch of 5 gallon cans out there and load up. That is usually no issue..just don't talk about using it on the street. The only reason it is an issue is because they don't collect highway use taxes on it.
AV gas has a few peculiarities...but if you added 5-8 gallons per tank full it would likely take care of issue. I know other folks who buy a 55 gallon drum of race gas and keep at home to add small amounts throughout the summer as needed for cruise season. If you used 5 gallons per tank of good race gas...that would likely get you through your cruising season.
JIM
