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Looking for input on fuel to run in the 30 hp (31.8cu in) motor that I have been piecing together.
It’s been slow going. Parts are not as interchangeable as I thought.
I had the block oversized 0.030”
No other mods to the block.
I have played with some heads.
A stock head on a standard bore block, yielded 120psi.
0.060” off a head and some clearancing got me to 135psi.

I found a head from an old motor that had looked to have less cc’s but actually had more. Only made 115psi on my standard bore block. I planed a bunch off and made some clearance for the piston and got 145psi. When I put the head on to the 0.030” over block, the pistons hit. So I carved some more off the head and now I have 165psi.

Do any of you run octane boosters or race fuel?
Any timing suggestions welcome to.

does this motor have compression relief?

All my 2 strokes gets Shell high test, no matter what compression. My 4 strokes gets all high test from what ever gas station I happen to stop to.

i dont know much about 3 cylinders,, in my v6 165 would be too high compression to run 91. 100ll works... c12 is the awesome but probably wont need near that much octain with 165psi.

Thanks everyone.
There is no decompression on the motor.
I always use shell premium in all my small engines.
I have some 100ll
I have a lot of friends that race dirt track, so may see about picking up a drum of fuel. Just not sure what blend.