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Fuel Mixing?

1239 Views 6 Replies 4 Participants Last post by  CutawayAl
So, I'm more or less a complete Novice.

Never fully rebuilt a engine before, or tranny/t-case

But I'm going to some mud drags this weekend, and it was suggested to me that maybe i should mix in some AV gas and play with timing, to see if i can get a boost.

1973 Ford F-450 Frame (shortened... ALOT)
1975 Jeep CJ5 Body
1971 Lincoln 460 DIVE-6015-A2B Block
C-6, NP205, 6.72 geared Rockwell Top Loaders
47" Super Swamper LTB's
TOPS 4300-4500 # loaded (with Fuel, and Me)

*EDIT* Forgot, Motor is stock, minus the Rebuild (all bearings 10 over, and overbore of 0.030)

I was plenty fast last year, But i want to see what i can weasel out of this puppy. Any thoughts on AVgas mixes, like AV+87/89/92, and in what ratios?

Also, what sort of timing adjustments should i make for that mixture?

Any help is appreciated, I'm just a n00b :p Thanks!
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What is compression and did you have hardened seats installed for the exhaust valves? If you did not have hardened seats installed then I would run a 50/50 mix of av-gas all the time. That is 50%premium/50% av-gas.
Running a higher octane on an otherwise stock motor proly will not make that much difference if any. If it runs good on 87 it proly wont run any better on 93 or 100 or 110. Might even just be a waste of money.

As far as i know, Compression is stock, minus whatever difference the 0.030 overbore made. And i was given a set of rebuilt heads, and told they were Standard Rebuilds. If hardened seats are a regular on head rebuilds, then I'm sure i have them. If not, then no :p


That may be True, Actually it probably is. But, I figured may as well try it once, see what happens. Motor is plenty strong, and is already scaring me sometimes - But thats part of the fun

So, 50/50 mix. What should i do with the timing? Advance, or retard? How far? Realisticly, following through this those, what would you expect it to pick up? Stock ratings i've found for the 68-81 Lincoln 460's were already rating 365hp and 380-400tq at the flywheel, though I'm probably wrong.
The amount of hp depends on the heads, what heads do you have? The increase in octane will allow a bump in timing, how much depends on what the motor wants.
Well, The heads are ported/polished rebuilt heads, not sure from what. Forgot i had a edelbrock performer intake, and i forgot that my standalone engine management system compensates timing/fuel stuff for me. Threw in av gas bout 60/40 mix, thing flew. When the fuel pump worked :)
The increase in octane will allow a bump in timing, how much depends on what the motor wants.
If the timing is retarded from max/ideal due it insufficient octane, more octane will allow the timing to be advanced to it's optimal setting. If the timing is already at the optimal setting, additional octane and/or more advance will not result in more power.
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