I have a question about compressions........why do you want a specific compression?? Why not just get the most compression they make?? Lets say 15:1 or 10:1........why not just get 15:1?? I just need some more explaining on these things, I know some about this stuff, just need some reassurances.


Also, anyone know what the pred's stock compression is??



Thanks,
Brad

 

Predator has 11-1 compression stock as i remember.(Something that keeps it's 500 cc motor putting out similar power levels to a certain 9-1 660) If not that, something very close. You don't want to go to 15-1 because you will have problems with finding high enough octane fuel, your cooling system not being able to keep up, and keeping the top end of the motor sealed. You can stretch head bolts and blow head gaskets.

 

So would I even notice a change in going from 11:1 to 11.5:1??? Or is it more the point of having a good(not stock) piston in there??


Thanks NJ....

Brad

 

I would go higher than an 11.5 - 1. I've heard of people having good results on 12.5 or 13 to 1. Another advantage to a different piston is it prob is lighter, and can be modified to be even lighter. Less reciprocating(sp) mass.

 

I've seen up to 14:1 in raptors without blowing the top off every few days. Higher compression means more power, specifically more low end and midrange grunt. You also need, as was said, higher octane gasolines to resist pre-detonation. But incresased compression puts more stress on most of your engine components and systems and will lessen reliability and engine life.

You sacrafice for speed and power. I only run 11:1 but thats because I dont want to have to run race gas. If you want to be faster then you can bump your compression up, just be ready to deal with the consequences.

 

pred compression stock is 10.5:1 i have 13.5:1 but if i go with the 580 kit i will bump down around 11.5 -12.5:1

 

are any of you really high compression guys having cooling problems?

 

actually my fan hardley ever kicks on...but doug put a special sleeve in to help with cooling, it's the same sleeve he uses in his quads...it waslike an extra 250

 

14:1 - daggone - almost run diesel in that baby!

 

or a really close ignition curve.