hi, i have a automotive question, whats the best way to change my low compression engine to high compression?

Question

iv read somewhere you can shave the head or put dome pistons but not sure about that. by the way this is for drag racing. thanks

Answer 1

Shaving metal off the head and the top of the block is the usual way - but be careful. This puts the valves much closer to the pistons, and you may need top cut grooves in the pistons to stop them from hitting the valves. This in turn could weaken the piston crown, so you might need pistons with a thicker crown. Domed pistons do the same thing - they reduce the volume of the combustion chamber when the piston is at the top - but it also can foul the valves, so be careful. Always measure your valve-to-piston clearance before attempting to start the engine. Otherwise, you'll need all new valves, probably all new pistons, and possibly a new head. Also, what cam you are running makes a big difference. Fuel can only be compressed so far before it explodes - not what you want in your engine (unless you're running a diesel! How much compression you can have also depends on what octane fuel you can use in your class.

Of course, the more valve overlap your cam gives you, the less actual compression you will get - and the higher your revs, the less efficiently you will be able to fill the cylinders - this is why you can have a theoretical compression ratio that is higher than the pressure that fuel spontaneously combusts (I've seen as much as 12:1 on stock cars.) And if you're running a supercharger or a turbocharger, you actually want less compression, so that the extra pressure supplied by the compressor doesn't push the fuel to ignite itself.

Good luck!

Answer 2

Just have your engine rebuilt and altered to whatever you want

And as the one above me said, Forced Induction, Turbo, or super charged you want LOWER compression