My 4.2L engine is not stock. It has a 10:1 compression ratio, aluminum fly wheel, race hardened pistons, triple Webers. This is about all I know, because I am far from being a “gear head!” I run the car with premium gas without ethanol. I am unaware of the ability to get any racing fuel in my area. (Green Bay, WI)
Twice a year I go to Road America in Elkhart Lake for the vintage races. I tour at noon. I like to push the car as much as I can get away with. You can’t be stupid, nor break any rules, or you will be “black flagged,” and escorted off the track.
Does anyone know of, or recommend a good fuel additive that boosts octane? I would really just like to get rid of the “knocks” when I have the pedal to the floor!
Probably nothing you can buy over the counter. The stuff you can buy in the “Mechanic-in-a-Can” section of the auto parts store largely does nothing but allow you to part with some dollars.
Short of acquiring some tetraethyl lead have you tried LL100 avgas, available at your local airport?
I was totally unaware of this! I will have to check out how I go about getting this from the local airport. It is not like there is a drive up pump for planes!!!
Just a quick look at Google and it appears that there may be more negatives/problems with using AvGas than there would be benefits. If you want to scare yourself, read about the engine damage that can occur!
Five gallon gas cans. I’ve never bought avgas to put in a car; I was always sticking it in the wing tanks of a Cessna. Some smaller airports have self service pumps that take credit cards.
Octane additives are garbage. They all advertise “increases octane by X points”. But read the fine print. What they call a “point” is 0.1 octane. So, unless you half-fill the tank with additive, you’re adding nothing of value.
The proper solution to your problem is a put in a thicker head gasket, and get your actual compression ratio down to 9.1:1, where it belongs. XKs WILL ping above about 9.4:1. In the meantime, the only meaningful thing you can do is run on AvGas. Keep in mind, putting AvGas in a car is a violation of federal law. But, it WILL eliminate pinging at 10:1.
Oh, and I don’t know where you are located in Wisconsin but self service 100LL at Burlington Municipal airport, for example is going for $3.79/gallon. And as Ray points out using it in a car is not strictly legal since avgas isn’t taxed with state and federal road taxes.
Ran avgas in many an engine–a couple of Formulas Vee, and my ITC Datsun-- not for its ability to withstand hi-compression, but just because it ran better, more consistently, and smelled good!
Also ran it in Tweety, back in its racing days, and never suffered any damage.
I suspect the alleged damage came from people not aware of how to time or jet properly.
have you looked for turbo blue or cam 2? haven’t used either in a few years but had a corvette with 11:1 that ran MUCH better running 1/4 race gas. I had to retard timing a few degrees without it. also had an atv with 13.5:1 and needed 1/3 cam 2 mixed with premium. the octane boost in a can never maid a difference that I could notice. 0.1 point octane is a joke, you would need 20 times that to even tell it was added.
Go on line and find a VP racing fuel distributor in your area. There will be somebody I virtually guarantee it. Mix that with your gas - start with approx 15% racing fuel and go from there.
I DO have a VP distributor in Green Bay. They can get racing fuel from a VP wholesaler in Slinger, Wisconsin. They have trucks that go twice a week! Racing fuel available in 5 gallon plastic pales, 30 gallon and 55 gallon drumbs. In stock they have C12 and Motor Sport 105, both of which I could run. They also make a leaded VP “Vintage” fuel that I am going to see if I can get. I haven’'t had time to respond to the e-mail from one of the sales reps!
Any reason that I can not run this stuff straight, rather than mixing with pump gas?
By the way, my mechanic thinks I am wasting my time, and that my performance will be no better with racing fuel than what I can buy at the pump? At least with the lead, I won’t have the nocks!!! Don’t know about advancing the distributor, changing jets, etc.
get a new mechanic! the knocks are detonation, definitely nothing to overlook. I high compression engine requires higher octane. yours isn’t very high, but high enough that your getting engine knock so you need higher octane. retarding the timing was only suggested as an option when running lower octane to prevent knock. you will lose performance doing so. you likely only need 95 or 96 so running higher than that will have no benefit but raising from pump gas to the required amount will, without any doubt, improve performance and save some melted pistons in the process.
