427 Octane knock
Thread Starter
Cruising
Joined: Jun 2000
Posts: 10
Likes: 0
From: Beachgrove Tennessee USA
427 Octane knock
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.
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.
Melting Slicks
Joined: Oct 2008
Posts: 2,154
Likes: 69
From: Regina Sk Canada
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.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
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.
CF Community Team
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From: Cape Cod, Mass.
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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.
Burning Brakes
Joined: Jul 2008
Posts: 923
Likes: 37
From: Green Bay Wisconsin
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
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Drifting
Joined: Feb 2005
Posts: 1,879
Likes: 38
From: Los Gatos CA
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...
Thread Starter
Cruising
Joined: Jun 2000
Posts: 10
Likes: 0
From: Beachgrove Tennessee USA
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.
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.
Team Owner
Joined: Jul 2004
Posts: 40,380
Likes: 788
From: Redondo Beach, California
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.
