12:1 Piston

[missouritrailrider]

what kind of gains should I expect over a 10.25:1 and does it have to run race fuel? Race fuel is expensive but I could manage if I got great gains from it

 

[dave76]

Well with each point in compression you get about 4% gain in power. So lets say your making about 25HP now, 8% gain only gives 2HP, now a long duration cam and ported heads and properly mixed fuel you'll probably see 33 34HP. IMO not worth the dealings with the race fuel. A properly set up 366 motor with a JE 10.75 compression piston and a Web .390 cam or for more upper RPM power a Megacycle 252X1 will put you around 28 29HP assuming you have a good exhaust, a ported head puts you at about 30 to 32. Jasonp will probably chime in on this, he has probably the most solidly built stock stroke motor you'll find on here.

 

[missouritrailrider]

See, i have a grizzly 660 12:1 and i dont run the race gas in it, just 93 octane it seems to run perfect with no prob im sure race gas would help a lot but is it necessary?

 

[dave76]

See, i have a grizzly 660 12:1 and i dont run the race gas in it, just 93 octane it seems to run perfect with no prob im sure race gas would help a lot but is it necessary?

The Raptor engine is liquid cooled, and the Warrior is air cooled. The cylinder and head temp of the Warrior probably runs in the 250°F to 275°F range on some hot summer days. The Grizz runs around 190° to 210°F and 12.1 to 12.5 is probably the highest compression you can get away with on a liquid cooled cycle engine. The Warrior won't tollerate much more then 11.1 compression on pump gas. As the temperature increases so the chance for detonation.

 

[jasonp]

See, i have a grizzly 660 12:1 and i dont run the race gas in it, just 93 octane it seems to run perfect with no prob im sure race gas would help a lot but is it necessary?

as dave said..
there are many things that effect what compression ratio you can run and dentation restance. IE. Shape and design of the combustion chamber, piston shape/design, what material the head and piston are made out of, camshaft specs, deck height, alitude, jetting, type of cooling, timing advance and so on...
What it comes down to basically is that the new stuff with liquid cooling and there four valve heads can have a much higher compression ratio because of the fact that they are more dentation restant. The shapes are much smoother inside the combustion camber and the liquid cooling helps pull the heat away.
The grizz is ment to run 93 high test octane stock from what I've been told and read.. I would be very careful running anymore then the stock compression with out racing gas.
http://www.popularhotrodding.com/tech/0606phr_understanding_compression_ratio/photo_06.html