gts500

since i didnt get any proper answer to my question at the internal section

i deside to ask here maybe i will get a final answer.

so i have a set of cometic .030 and my mods are DARTS 205 out of the box

and G5x3 with 232-242 not chure plus i did fly cut the pistons and i changed the rod bolts.

so my question is , could i use the gasket as direct replacement without any harasing?and would the piston make a contact with heads if i use it?.

and why too many are afraid to use it ? is it that bad??can someone explain?

please i need a proper answer from expert to shut my mouth up

machinistone

The proper answer is that you always need to measure piston to valve clearance. You cannot assume that because someone else with the same combination was ok, that you will be too.

gts500

well somone told me its not the PTV i should worry about its the piston make a contact with heads?

Old SStroker

Have you measured how far the pistons stick up past the block (out of the hole) or how far they are in the hole at TDC? If not, why not?

I suppose you could put the heads on the block with no gasket and no bolts and turn the engine over with a breaker bar. If the pistons don't hit the head you will have at least the clearance of the compressed Cometic gasket.

If the heads lift, check how much with feeler gages and subtract that from the gasket thickness. Anything less than .030 isn't for the faint of heart.

gts500

you are right . am gonna do that and see what its looks like.

Ryne @ CMS

iTrader: (10)

considering most factory ls1's are around .005"-.008" out of the hole, that would put your piston to head clearance at around .022"-.025" which to me is very risky, if that piston rocks at all at high rpm, it is hitting the head. but measure to make sure.

by the way a g5x3 is a 234-242 xer lobes

ShiznityZ28

iTrader: (11)

I run a 045 gasket and they are near touching at high rpm. but remember on an aluminum motor cold they stick out but warm its close to 0 Deck. Still sounds a little tight for some street-strip stuff.

machinistone

oops - piston to head clearance....either way you need to measure your piston protrusion out of the block, you have aftermarket pistons which may have a compression height that puts them at "0" rather than out of the hole. I would not go below .025" on a street motor with steel rods.

Bo White

iTrader: (59)

Ive ran .024" P/H and its tight, after 6 months of occational driving/street racing there was no carbon buildup at all on the piston were the quinch area is on the head and a few pistons had a shiney spot here and there were they obviously "kissed" the head and the head had the same spots in that area. If the piston is .007" out of the hole at TDC your askin for it...weither or not you get it is all up to Newtons law

gts500

hmmm... getting more complicated, plus am runing 150 shot of juice and shift on 7000.

i think am gonna buy a nother set of .040 but i will measured the clearence first and see, what kind of choise i have here.

PortPros1

You need .038 min piston to head clearance and thats using good parts. You have to measure your deck height, the distance the pistons are in or out of the hole. If your pistons are .010 in the hole and you run a .030 thick gasket your good. But I wouldn't build any street motor tighter than that. You won't gain much and you'll risk a ton.

Think about your rod bearings when your pistons kisses your heads...hmmmm