Pistons vs jug cut

[vej]

So, I know they say cut the bottom of the jugs to raise your compression, but I was wondering why not put high compression pistons in instead? Has anyone done that instead of cutting the jugs? Pros? Cons?

 

[V]

Well i thought you needed to mill .040 off the top of the jugs to get to the factory spec of 10.2/1 comp. Then if you wanted more you would mill the head to reduce cc's of the head creating a smaller combustion chamber and or use a thinner head gasket.

If you went with a piston other than a flat top would'nt you have more issues with piston to valve clearance to deal with?

If the you bought a piston that was .040 taller I don't think anything would change as at bottom dead center the cylinder volume would be still be the same. You would have only moved the piston at TDC .040 closer to the head and at BDC the piston would still be .040 closer to the head. Now I guess the valve timing (duration) as to when the valve closed during the compression stroke would make a variable in this equation but thats where I'm lost

So basicaly I think I have said nothing worhtwhile

 

[woodbutcher]

if you use a domed piston with valve reliefs cut in them yes, you would be changing the compression / cylinder volume. you should be able to do it either way. finding the new pistons that will work may be the problem in the equation but should be doable. make sure you have reliefs for the comp. reliefs.

 

[BillV64117]

Never heard of cutting the bottom of jugs before. Milling heads yes. Replacing pistons is the easiest way to go since they have been engineered for compression & clearances.

 

[Coolbreeze]

You cut the bottom so you don't mess up the fire ring that helps seal the head gasket. Cutting the bottom of the cyln. not only raises the comp., but also tightens up the quench area for a more efficiant burn.I resently did an 04 Mastiff. I took .060" off of his cyln. Yea I pushed the envelope alittle. It runs very crisp.

 

[Coolbreeze]

Taking .050 off puts you at about 10.3:1 comp.

 

[john sachs]

Domed pistons WON'T put you where you need to be, or solve the geometry problem.
John

 

[1mndg]

Doesn't matter where you cut...top, bottom or the heads. You still have to check for valve clearance. All three or should I say four because even if you go with a thinner gasket, you move the valve closer to the piston. All will raise compression and change valve train geometry. It's your call how you want to go and how much you want to spend.

 

[Little-Boo]

What I did was deck the heads 0.030, put the larger valves 2.02 intake and 1.605 Exhaust, to reduec the combustion chamber. I used comatic gaskets 0.010 Base Gasket vs 0.020 stock and 0.030 Head Gasket vs 0.043 stock. My compress went from 9.6 stock to 10.5 which is where I wanted to be and still be able to use pump gas. Runs good Gas mileage suck but it runs good

Carlos