hi to all,
got a few questions for all u techies out there,
i m going to rebuild my tired old 2wd sapphire cos engine.i ve managed to get old of some cheap 0.5 oversized mahle pistons that have done very little miles. the problem is that they ve been skimmed 1.5 mm (compared with standard deck height pistons).this will make the squish clearance massive.what i want to know is that if i get the block decked 1.5mm to get the correct squish gap back will it work? obviously i would have to get the pistons machined to the same spec as standard to get correct comp ratio etc but this is nt a problem.i ve read that skimming pistons on a turbo engine to lower comp ratio is quite common but i think this method is cheap and nasty and will drastically alter the squish clearance which is a very important characteristic of an engine.basically will this work? will it lower the cc s of the engine? etc etc .
any info would be great.
thanks

 

anyone got an answer for this ?

 

Have you not found out in the last 2 years?

Sorry I don't know the answer.......

 

Unfortunately it would not be that simple. The squish area of the head is not an exact shape (cylinder) all the way up to the valves - whereas the piston is perfectly cylindrical. So, a 1.5mm slice of the top of the piston wont be the same as removing a 1.5mm slice of the squish area of the head.

I guess in theory you could probably do some volume based calculations and make it work.....but imo, get some new pistons and be certain it will work. It would be a lot of work to have some disapointment at the end of it all.


Matt

 

I think u have read it wrong mate, I m not touching the head ,it s the block I was talking about.

 

then yes im guessin it would be fine, why has it taken 2 years to repost the original question BTW

 

projects been on hold for a while buddy.

 

It's a bloody good way to bodge a engine.

Mark

 

Ah yeah. haha. um, i guess in theory then yes - but its not a route i would personally go down.

 

Whys it a bodge then ?