Offshoreonly.com - Whats the Max Compresion you can run on 87 Octane?

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MrHorsepower...........Bad .....Avitar

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Originally Posted by Revd Up (Post 2372437)

MrHorsepower...........Bad .....Avitar

Do you have something against Outerlimits?:D

This past summer I ran 10.0-1 static on my 355 cube smallblock with AFR aluminum heads and 34* total timing. 142* Tstat and oil cooler. Oil temps 190-230 depending on load. Used mostly 87 all summer with a few tanks of 89 and 93. Transom would get really sooty running the higher grades. Plugs and performance were great on 87 and it did not leave the back sooty. 136 hrs worth.

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Originally Posted by Chris Sunkin (Post 2371776)

Dean,

How much difference do you consider the aluminum heads make in offsetting compression? Are they equivalent to a 1 point drop?

The Aluminum heads will allow you to run higher compression. Yes I would say .5-1.0 of static compression. As we all know aluminum exchanges heat rapidly, plus the advantage of having millions of gallons of fresh water to pass through the engine really helps .

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Originally Posted by Panther (Post 2372208)

Dean, have you been jetting (carbs) for extra fuel with the E-10 fuels???? My thinking is that alcohol, although it's higher octane, requires lower A/F ratios....

So anyway....hearing the horror stories of people this past year with the fuels...I decided to go up one point in the jets on my secondaries....just to be safe...

What are your thoughts on the crappy fuel we've been getting and the increased amount of detonation that's been ocouring across the board? Is it from fuels sitting too long or the alcohol A/F ratio theory?

Yes Frank I usually jet up 2-3 numbers in jet. I run my stuff as "crisp" as possible when it comes to A/F. Alcohol does require richer A/F ratios do to it's burn rate.

I am not running a thermostat for either water or oil. Engine builder didn't want to install one for some reason. I do have trouble getting oil to 180-190, water is usually around 130. I haven't seen any signs of water on dip stick or oil fill cap. Water pressure never gets about 12 psi. Any concerns?

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Originally Posted by Rebel_Heart (Post 2372583)

Everything sounds good- water temp great, oil temp is fine , and water pressure is perfect! As long as your not seeing any condensation upstairs your looking good with what you have. Oil temp would be on the low end of the range- I like to see 180- 230 being the high side. We have had race boat engines that in flat water races run upward of 250-260 with no problems in lower end. Bearings are perfect after 18 -100 mile races.

Thanks for the comment, Dean. I can rest a little easier!

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Originally Posted by whodathought38SS (Post 2371977)

THANKS for all the help!!
Now I just hope the Bigger NA motor will not make me miss my blowers!
Does it seem reasonable to be able to get 650-700hp out of a N/A 548 at 5500 max rpm with 87 octane and these specs:

Chevy MK IV BOW TIE Block bored to 4.530
Scat 4340 4.250 Crank
Scat 4340 H-beam rods 6.385
JE/SRP flat top pistons 9.5:1
Crane roller cam P/N 139021 with roller rockers too
Chevy BOWTIE 861 casting aluminum heads with 2.25 & 1.88 valves with some porting on the runners and chambers.
Dart intake with some mild porting and matching
Holley 1050 dominator marine carb
Thunder bolt IV ing with MSD box set to 34 max
Keith Eickert Cast Aluminum Exhaust Headers
BIG oil cooler and stainless marine cross over

Any thoughts from the experts would be great, that is my plan so far.

I think you projected HP is just a touch high. It wouldn't be a problem on 93 octane, but on 87 I think you will be 630-650 hp. The last 540 I did at 9.5:1 made 632 hp at 5300 rpm with a fairly small cam. With a little more cam and a few more rpm, you should be able to hit 650 hp. My 540's at 10:1 make 675hp at 5300-5400 rpm on 93 octane. My 555 ci will make 690-695 hp at the same rpm and octane. Hope this helps, Eddie.

Right on--- 548ci 10.2/1 comp. 93 oct.fuel, 1150 carb. nice hyd/roller cam, merlin iron heads & intake, 36* total, some port & bowl work, dyno @ 648 hp. ;)