Octane

[Anonymous]

I've been wondering about this for a while, I bet you guys can clear this up for me.

My 82 Fairmont has never been able to run on 87 octane gas, even set to factory specs. Pings and diesels like a fiend. I've tried everything, tinkered with timing, rebuilt carb, make sure the plugs are always good, wires, etc.

It runs great if I use 93 octane gas, can even put a half tank of 89 in once it gets down a bit, but it runs like crap with 87. Am I missing something? I put a hotter coil (Accel) in it, and it goes down the road like a champ.

I'm wondering if I have a lot of carbon buildup, or maybe I just need to back off the timing and live with it?

I'm all ears, you guys have a lot of experience here.

 

[ASMART]

1. Try getting the carbon out. Ther eis something that Autozone and Kwick Kar sell called RXP. 1 or 2 tanks of that should clear the carbon. If that doesn't do it, backing off of the timing should help.

 

[Anonymous]

Yeah, I probably need to be more realistic, and just set the timing back a few degrees until I can run the 87. There's also the possibility that the timing marks aren't that accurate at this point anyway.

It runs great on 93, no pinging at all. I just hate to dial it back and lose that little extra bit of driveability. I was just wondering what everyone else is running in their machines.

It's a stock 200 w/Accel coil and a little bit freer flowing exhaust. It's not a performance machine, but a good running daily driver.

 

[Anonymous]

I'm running 87 with 12 degrees initial and 9.4.1 compression, no pinging.

Don't ask why cause I don't know.

Was running 14 degrees initial until the kickback killed the starter and I had to replace it.

 

[xctasy]

I cant prove it, but I'd bet money that decking the block 30 thou, even if it raises the compression, should reduce pinging. Ford purposely built in a huge piston deck shortfall to avoid stuff ups on the production. The result is the special detail work from the Power Train engineering team got diluted by the production boys. The result is a heated annular edge around the top of the block, which hurts the knock resistance. A blue printed engine has very good knock resistance, and lots of people here are running above the 9's for compression. A trick from the Schnedahl boys (Ford Falcon Six Performance), Mark P (ex Ford ignition engineer), Mustang Geezer (Ford service guy) and other people who now the special Ford handshake.

Check out Mark P 's comment on how 'squench' and gasket selection improve combustion performance. The yellow gromet Duraspark post, the Holley 1946 tricks, and lots more. It's very important to get the details right, because many millions of dollars of work was done by Ford, and got hidden away by some laid back production tollerances .