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Message started by Commando_Al on 10/04/05 at 07:24:29

Title: Compression
Post by Commando_Al on 10/04/05 at 07:24:29

Anyone ever tried to raise the compression on a Savage engine? Am I correct in thinking that a higher compression aftermarket piston is not available? What about planing the head?

Title: Re: Compression
Post by lancer on 10/04/05 at 09:37:41

If you take the head off the engine and turn it over, you will see that there really is not any metal that can be machined off. I have wondered if the top of the cylinder could be machined...which would give a similar result...maybe...maybe not.
However, there is a way to raise compression a little without doing any machine work, and that is to use a thinner head gasket. The Savage head gasket is made of 3 aluminum layers which are 0.15mm each, for a total thickness of 0.45mm. The outside layers of that set do have the outside edges molded a little so that when the head is bolted down there is a "crush" effect that will aid in sealing.

If, instead of using the gasket as it is, take it apart and use only one or two of the layers...affectively lowering the head and raising the compression.
However, the result would only be about 1 or 2 tenths of a point...not enough to make a difference.

I have seen in the parts books that the Savage and DR650 used a common piston in the mid-90's, so perhaps there is one for the DR that might work for the Savage.

Title: Re: Compression
Post by Max_Morley on 10/04/05 at 22:10:19

Remember on a OHC engine if you reduce the distance between the crankshaft and camshaft you affect the cam and valve timing slightly. Even with new gears, chain and tensioner you would have the cam lagging behind what it was designed to do. Better to try and find a piston that is shaped to not hit the valves that is taller. Also unless you can find a way to change the ignition timing, not much advantage will be gained. Timing is fixed by the position of the pickup and the trigger on the flywheel and the electronics in the ignitor box. Not a simple fix. Maybe if they decide to go to FI then ignition mapping may be possible but not cheap. Max

Title: Re: Compression
Post by patryuji on 10/06/05 at 17:32:21

Find a reputable shop for doing headwork and have them weld in some aluminum into the combustion chamber. Then it can be ported back out for a more optimum "anti-knock" shape (such as clover leaf or pentroof) and it can be ported somewhat close to the compression you want.

I know Dan Paramore of DPR racing down in Los Angeles does this kind of work...but at a premium price. A custom piston would be cheaper.