GAP

Hi,
I have a 427 tripower during acceleration I have an octane knock. The highest octane gas near the area I live in is 93. Does the octane booster really work. Anything else I can do to reduce the octane knock.

wer2xu

A knock is a knock. Retard the timing.

Octane boost=snake oil.

Go to the airport and buy av-gas, 100 or 110 no lead...not Jet A-1.

Grumpy 427

Is this an aluminum head motor? Or cast heads? I had a 427 with 11.25-1 compression with aluminum heads and a big hydraulic roller cam 585/585 lift with .245/.255 @ .050 on a 112 LSA and i ran 34 degrees total timing. I ran it on 92 octaine with no pinging at all.

GAP

Guys,
Thanks for the info, I have a 427 400HP with cast heads. I also could have gotten water in the gas at my last fillup. It stated after the fillup.

Grumpy 427

A bigger duration cam will get rid of some of the static compression and help with that as well.

TimAT

Add a couple bottles of HEET or something to collect any water you may have gotten. Since it just started at the last fillup, I'd try a different station before working on re-tuning. It's not impossible that the station got a load of low octane (or lower than it's supposed to be) gas.

capevettes

My 427/390 runs fine on 93 octane and yours should too if it's basically in a stock configuration. You may have a lean condition or your timing map is not right.

KB9GKC

Hello,

Do some research on Xylene. A lot of work has been done finding the correct ratios of gas/xylene to increase octane rating of gasoline.

With my 1972 454 93 octane is always fine with the lower compression, 1970 and earlier high compression engines should all have knock with 93 octane and they may experience problems with the valve seats etc because lead not only added octane but was a lubricant as well.

Good Luck,
Douglas in Green Bay

Jeff_Keryk

My 68 L36 is similiar to your engine. In sunny CA, we have crappy 91 octane. I run the stock initial 4*. The stock distributer has 16* mechanical advance. So, 4 + (16 * 2) = 36. If you post your distrubuter numbers, I can tell you the stock advance curve. Get a timing tape and plot your curve. I bet you have too much vacuum. I say start with the stock settings, bring in the curve a little faster, but no more. If you can hear ping, you are well into trouble. Just my 2 cents...

GAP

Thanks,
Everyone for the advice, went to adjust the timing, when I pulled the chrome top off the distributor box I found the little culprit causing my knock problem, one of the new plug wires came loose from the metal distributor insert and the rubber cap. I re-crimped the wire and adjusted the timing a couple of degrees, runs like a top with out the knock.
thanks again guys.

68/70Vette

Agree. I've used av-gas. Also, look for a performance shop in your area. You can buy car racing gas. It's expensive, but you probably don't need but a few gallons in a 20 gallon tank to bring the octane up. If you don't have cats, you can get leaded racing fuel if you want. Here in Cali, the highest octane is 91. I buy unleaded racing fuel so I can put it either in my 68 (no cats) or 08 (cats).

Oh, about av-gas. At first I had to bring gerry cans to the local municipal airport. After a few trips, and the guy there got to know me, he just pumped the gas right into the car!. My 69 (11.5:1) needed 5 gallons of av-gas and 15 gallons of pump gas to run on. I would fill the entire tank with av-gas, and as the fuel went down a little, I'd put pump gas in it. This way I could easily go two or three tanks full. Certainly enough to get to Las Vegas and back with no octane problem.