When I put the motor in the Vette, I used nothing but Chevron 91. No additive and no ping. It's a 10:1 stroker with cast iron heads and maybe I was just lucky.

Twice this month I've made the stooooopid mistake of putting 'other' gas in the car. This morning I was late for work and determined to drive the Vette. I unwrapped her, warmed her up, and pulled out on the road only to see the thing was on empty. Only gas between me and the freeway is Shell so I put in 10 bux and off I went to work. This afternoon on the way home it was a perrrrfect San Diego day at I think about 75 degrees and bright sun. But when I got on the freeway coming home, I took her up to 5,000 then heard that dasterdly noise. PING! :mad :smash: :bb

It's just now, really well broken in but it sure doesn't like any other fuel but Chevron 91. The Shell is supposed to be 91 octane too but my baby don't like it! :nonod: :rant:

 

Didn't we just talk about how the gas sucks out here?

 

With iron heads you are just on the limit. I put a ZZ4 motor in my 80 and with the aluminum ehads it's much more forgiving for a 10:1 motor.

I do find that without the EGR valve and on days when the temp hits about 95 and I have pinging problems but mainly at part throttle. I replaced the vacuum advance with one that pulls in less advance and the problem went away.

 

My first thought is if you can hear pinging at 5,000 you must have some very quiet mufflers and a silenced intake. My second thought is, unless the pinging were occuring in only one or two cylinders, at that rpm the sounds of it wouldn't wouldn't sound like a ping. Are you doing 5K rpm at light throtte and high speed or at WOT? At light trottle you would probably have max vacuum advance on top of total. If at wot, you'd have just total advance.

Can you better descibe the sounds, feeling, conditions, etc., when this happens? It could very well be an issue related to the different fuels but I suspect that it isn't.

 

I had the same problem with my Trans am any time I’d use a gas other then Sunoco ultra 94 it would ping. The best thing to do is jump out at the next intersection and retard the timing a bit, seemed to work for me.

 

Didn't we just talk about how the gas sucks out here?



Yea we did!! But I just had to rant. :bs

 

My first thought is if you can hear pinging at 5,000 you must have some very quiet mufflers and a silenced intake

I respectfully disagree. Often, I've heard performance motors ping at high rpm and WOT.

In my case it is accompanied by an immediate drop in power. It's significant - and it sure does make me back off.

My car is not quiet at all, but when I'm on the freeway usually I have windows up and tops on. That was the case yesterday when I got on the Interstate after work.

Today once the fog lifts, I'll be topless all the way up the coast highway to Laguna with my lady. If the fog don't lift, we'll have to stop by and visit the weather man on the way. I'll have her beat him into compliance with her purse! :lolg: :boxing :lolg: :boxing

 

I just have a plain jane grandma type crate engine, so I don't really have that problem, but have you considered an inside timing retard gizmo like MSD sells? It might take care of your pinging on those rare occasions.

 

If you have a vacuum advance connected you can disconnect it if you have a plug to seal the port. I carried a golf tee to plug the tube when mine was in use. As a long term solution you may want to install the MSD adjustable timing advance recommended above.

 

If you have a vacuum advance connected you can disconnect it if you have a plug to seal the port. I carried a golf tee to plug the tube when mine was in use.

How can that help at WOT? Are you not operating off of mechanical advance under that circumstance?

 

Paul, pinging is most likely to occur when the engine is at, or near, maximum advance while under some load but not enough load to cancel vacuum advance. "Pinging" sounds like a hammer tapping metal but would likely be inaudible at 5,000 rpm and WOT over the sound of even a stock exhaust. If it's not pinging at 2,000-3,000 rpm under medium load, I doubt that it's pinging at 5,000 and WOT. If you are experiencing detonation rather than preignition (pinging) then, yes, it may be loud enough to hear over the other sounds. If that is the case, melted plug electrodes will be a major clue.

Considering the rpm that you're talking about and considering the power drop, I suspect valve float. If the intake valves float, you will hear a popping through the intake. If the exaust valves are floating, you will hear a popping through the exhaust. While the sound will vary depending upon which valves are floating and at what rpm, at 5,000 rpm I'd expect a sound similar to a an old slow firing machine gun. If float were occuring at 7,500 rpm it would sound more like an M16 on full auto.


[Modified by Vetterodder, 9:55 PM 6/15/2003]