87 or 91 octane

[tripowerguy]

There is an article in an old Chevy Hi- Performance about making 400hp on 87 octane gas. They used a 355 small block 9 to 1 compression and a Comp cams 268h. They said that you make more power with 87 vs 91 because it burns faster, just as long as you don't have detonation. What I'm wondering is if you try running 87 in an engine can you do damage even though you can't hear the rattleing? : Roy

 

[dq409]

Fraid so,,,,,,,,,It`s like the oil pressure lite,,,when it comes on,,,IT TOO LATE !!!
I think the only way you can do that is build your engine around it. if you are running 9-1 should not be a problem. Also in a lower compression engine running higher octain will not increase horse power,,,,dq

 

[tripowerguy]

Well my engine is a 9 1/2 compression with composition gaskets so I figure that the real compression ratio is somewhere around 9 or 9 1/4 to 1. Am I right? I have a 268h cam in the motor and I would like to see if 87 octane would increase HP but not at the expense of blowing up a motor. When the magazine ran the engine on the dyno they had a knock sensor. I don't have such an animal so all I have is me and my hearing aids.: Roy

 

[dq409]

My guess is you should be OK,,,,Give it a try ,watch your timimg and listen for that knock and ping. I would also try the power brake method and listen that way also. 9 1/2 should be Ok. ,,,dq