Ive been trying to put together the parts for my BUDGET 406 build-up. Summit sells a rebuild kit with forged pistons for $409 dollars. THe only problem is that with those pistons id be running a very high compresion ratio with my 58cc heads. Could i have a machine shop shave like 15cc's off of every piston?

 

Depends on the piston style and make. A typical flat top piston could have a bit shaved off the top but not much. The pistons could be flycut. That's where they cut out the valve reliefs deeper to allow higher lift cams. The removal of metal will have the same results.

For the cost of having the pistons machined, it would be cheaper to just buy the proper pistons for the compression ratio you desire. Either that or buy some heads that have larger combustion chambers. Larger chambers also allow for larger valves and there's more room to unshroud the valves.

 

Just buy dished pistons if you need lower compression. I use KB Hypereutectic 12cc D-dish pistons which preserve the quench area but keep compression reasonable on large cube (383 or 400) motors. Plenty good for a "budget" engine.

If you are dead-set on forged flattops and you still want the compression lower AND head work to enlarge the chambers in't your bag then use thicker head gaskets. Going from a typical FelPro .039" gasket to a ~.055" thick gasket will knock 1/4 point off your compression.

It'll give you the same effect as shaving the piston faces down, but for a lot less money and hassle.

 

I second Damon's advice, that's exactly what I would do.

12.5cc dish 400 under 64cc chambers with .039" gaskets and stock deck clearance gives about 10.4:1 CR, barely usable on pump gas. I use the Fel-Pro 1044 head gasket which is .050" instead of .039", which knocks off another couple of tenths.

Any time you get custom machine work done, you have automatically exceeded your budget. Avoid that if at all possible by spending a bit more if necessary for the right parts up front. $2 a piston or whatever it is won't kill you, and you can't get machine work done for that price.

 

I did a search on hypereutectic pistons in the power adder foruem, I found for the most part i should run forged piston when useing a large shot, i plan on doing 150-200. Ill punch in some compression ratios in a formula and see what i can get with a thicker head gasket.

 

its gonna take a 20cc dish to get the compresion right. BTW what should my deck height be unmachined?

 

Unmachined decks are usually .020"-.030". It varies a lot. Some can be as deep as .050"

 

how do i measure the height? the blocks being machined right now so ill have to wait till wedensday or so before i can measure it