Reply With QuoteThe 11.3 compression will run much stronger.
You can mix the 92 and 110 when you are not out of town. Keep the timing in it. 50/50 mix.
If you go out of town you can fill up with the 110. Run the tanks half way down and fill it back up with 92.
I'm trying to figure out what Pistons I should use. I'm building a 408 sbf with 60cc afr aluminum heads. I have the choice of 9.73 which should be fine for pump gas (22cc dish) or flat tops yielding 11.3 comp ratio. I've always been able to keep a consistant water temp of 165 with my jetboat.
With 11.3 comp, what kinda gas would I have to use? Could I get away with mixing 110 or av gas with 92 premium, and at what ratio? I don't want to use straight 110 for the expense and fact I can't fill up with it when I go on vac for a week with the boat. Could be willing to bring some 110 to mix with 92 if I can get away with a 4:1 / 92:110 ratio or something similar.
I currently run a 351w at 10:1 on 92 with iron heads no problem. I have a 250hp plate NOS kit which I switch to a different tank with 110 and use a timing retard, when I use it.
Thanks for any advice,
jd
The 11.3 compression will run much stronger.
You can mix the 92 and 110 when you are not out of town. Keep the timing in it. 50/50 mix.
If you go out of town you can fill up with the 110. Run the tanks half way down and fill it back up with 92.
Thanks info, I guess I can always try and reduce the mix and read plugs like I did with the nos to see what I can get away with. I'm always leaning toward more power, as I always seem to build too conservative. (never done higher comp or blown, that'll prob be next winter though idea )
jd
I agree with running the 11.3 c/r and that you can run a 50/50 blend of the 92/110 octane fuels.
Your jet boat will benefit largely with the additional 1.6 points of compression and you should be safe with the 100 octane fuel blend.
I, too, am careful about running adequate octane fuel; I have about 10.5:1 c/r and blend fuel in my 11 gallon tanks at 8 gallons/3 gallons (91/110).
LO
hey lakes, I feel like i'm in an institution when I have a cleanroom suit on at work also (assume thats what you got going on in the avitar)
jd
Cant you run higher comp ratio with alum heads as they get rid of heat alot faster??
Are you interested in using ceramic coatings? With coatings, I run 10.8:1 and 36 deg timing on 91 octane. Haven't had any problems yet with detonation.
do you just send the pistons/heads (combustion chambers) out to have them coated? Whats it run and what kinda warranty? I'm guessing I'd still have to run a little higher than 92 oct with 11.3 comp.
Thanx,
jd
blown, I've been told with alu heads I can get away with about 10.4 comp before I have to start limiting timing, getting funky camshafts that reduce effective comp ratio, and running the motor on the edge and robbing a little power. I've never run above 10:1 and only used iron heads before on my motors so I'm just taking peoples advice till I put the new motor together and then I'll test and see what I get away with.
jd
Why do you want to run such a high compression ratio? Why not just run a 8.5:1 compression ratio with turbos? If you do it that way you can run pump gas and lower boost when AV gas isnt easily available or you can run AV gas and higher boost when AV gas is available.
I'd think that in the long run you'd save money over all because you wouldn't be spending $4 a gallon on gas all the time. You would probably also get better fuel efficiency with turbos.
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