Highest Safe Compression ratio running on 87

[pipnit]

Hey guys, so what would be a very SAFE compression ratio on 87 and where do I start to stand next to the edge of the cliff? I'm thinking 9.2:1 right now but figured I'd ask you guys for your opinions.

THX

[mrfixxall]

Hey guys, so what would be a very SAFE compression ratio on 87 and where do I start to stand next to the edge of the cliff? I'm thinking 9.2:1 right now but figured I'd ask you guys for your opinions.

THX

8.5-1,,9.2 go tp 89 minimum..

[BUIZILLA]

iron or aluminum heads?

[MOP]

I am running 9:125 on my 383 for about four years now, I have tried higher grades and experianced loss of performance. "Griz" God Bless his soul explained how higher test fuel in lower compression engines degrades performance, I can attest that mine runs noticeably better on 87. I have run ignition as high as 34 degrees with no ill effects, I am currently running 31 degrees due to concerns with alcohol content.

[LKSD]

Id recommend the better fuel as well..

[Carl C]

There are other variables such as what Buizilla asked and is it EFI or carb. Combustion chamber design is no doubt a factor. The 525 EFI is a surprisingly low 8.75:1.

[CHACHI]

I am running 9.7 and using 89 with no issues on the street in a BB Ford with iron heads.

Ken

[Fishermanjm]

9.8-1 in my 1998 2500 ram truck with a mild cam, ported , blue printed, i haul a good size slide in camper with it an run the cheepest fuel i can get. No issues at all,,, a mopar engine that doesnt ping,,, when u get up higher than that with a comp cam or somethin like that thats when u will run into issues marine engines seem to run cooler not sure if that is entirely true butt they seem too

[pipnit]

Guys,

I have a constraint here, that's why I'm asking the question. Of course I don't want to run 87 but that's ALL I can get at the two gas docks and towing the boat to the pump isn't an option for me. If I could have my druthers, they'd have 100 octane at the pump and I'd run 11.5:1, no brainer but that's not the case, all I can get is 87 and I'm not going to be mixing Toluene or anything like that.
Also, it's not a car motor, it's a boat motor, unfair comparison. How often do you run WFO with your street car for extended periods of time? Probably not very often, if ever.
I'm going to be using Aluminum AFR heads with Inconel valves, diamond pistons (-18) full seal rings, stainless marine manifolds and bring the pipes almost to the transon. If I get a set of 75cc combustion chamber AFR's and mill them to 70cc, that'll bring me to 9.17:1 with this setup. I'm thinking 9.5 might be getting me to the hairy edge. Thoughts?

[pipnit]

BTW, the cam (Marine Kinetics) and the carb (Nickerson) are going to be built around the motor. I imagine we'll add a couple degrees to the exhuast side to try to expell heat the best we can.

[Carl C]

What kind of engine? I agree with fixx. I think you will be too high and should keep it under 9:1 if you want to run hard on 87 octane. JMO, there are others who know a lot more about this but I think we need to know what engine we're talking about since there are people here who know a lot about a particular set-up.

[Fishermanjm]

so the marine engine doesnt really run cooler,,,, u sound like u have it well under control,,, nope deffinantly don't run the truck WOT at all but the engine is under tons of strain haulin the camper

[mrfixxall]

BTW, the cam (Marine Kinetics) and the carb (Nickerson) are going to be built around the motor. I imagine we'll add a couple degrees to the exhuast side to try to expell heat the best we can.

I think you should ask bob @ marine kinetics..

[pipnit]

I think you should ask bob @ marine kinetics..

Oh yeah, I'm picking his brain to the point where he's going nuts. What a nice guy, too, man, a fountain of knowledge too! I just wanted to throw the question out here too, fun conversation and wanted to see what people think and what they've experienced themselves, first hand.

[mrfixxall]

Oh yeah, I'm picking his brain to the point where he's going nuts. What a nice guy, too, man, a fountain of knowledge too! I just wanted to throw the question out here too, fun conversation and wanted to see what people think and what they've experienced themselves, first hand.

my opinion,,Dont mill the heads,surface the deck of the block,, have it Zero decked and leave the cylinder heads alone,moving the piston closer to the combustion chamber will give you a more complete burn..If you have not bought the pistons yet i would ditch the diamond pistons idea,,go with SRP which are made by JE pistons or ROSS pistons,you may spend a little more but they have been out their far longer then any piston mfr and have been proven to last..