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Old 04-11-2019, 02:20 PM   #14
Turbo, what?
klr142's Avatar
Join Date: May 2004
Location: OR

Originally Posted by hessam69 View Post
So who's right?
They both are. It depends on your goals and usage, just like anything else. The more material you have in the head, the stronger it is and better able to deal with heat. The less you have, the weaker it is and less able to absorb/dissipate heat. In a non-turbo application, I don't think the full strength, original head matters. People who aren't in the US who have been modifying these things for years have been shaving 2mm off of them for years and years and years with success. I haven't heard of a car with an issue due to being shaved before, but I don't sit online all day and read about this on forums all over the world.

Originally Posted by VB242 View Post
You can get a Cometic gasket as thick as you need the counter the effects of cutting too much off the head. The last one I ordered was 2.6mm thick.
If your pistons aren't sticking out of the block a ton, that is one way to lower compression but a horrible way to promote good combustion as you want the pistons to be, at most, 1mm/0.040" away from the head surface in a proper build. I would open up the combustion chamber on the cylinder head if compression was too high, well before putting such a thick gasket on it. But, both work and have been done.

Originally Posted by hessam69 View Post
So what happens when I shave my head that much and I use the pinto cam belt but my engine is a B230FB with a round tooth cam belt?
TB089/MD140228 belt.

Originally Posted by NotSoFresh View Post
If you are going to go as far as shaving the head, with the costs and risks involved, might as well just leave the head alone and put in higher comp pistons, and do it the right way.

Or just turn up the boost.
Well, pistons are much more complicated than just yanking the head off for a skim and blend the edge of the chamber so it's not sharp(with at least a 0.5mm bevel preferred). But yes, turning up the boost is the easiest way as long as you're able to deal with the heat and fuel requirements. A thinner headgasket is the best/easiet option, but you will want to have the head resurfaced anyway so you might as well take some off.

Originally Posted by mikep View Post
Machining the deck of the block gives you more bang per thousandth.
Or thin headgasket. On B21 and B23 motors a thinner headgasket still might not be enough to get your pistons within 1mm of the head, though, so those engines commonly need the block's deck surface machined. On B230 engines, the pistons are usually already flush or out of the bore, so you can get the proper piston-head clearance by going to a thinner headgasket.

Originally Posted by Dirty Rick View Post
Exactly! plus you get more squish as the piston gets nearer to the head.

More squish makes more turbulence.

More turbulence makes a more homogenized fuel mixture and helps getting all the fuel lit sooner.

Bumpy pistons get in the way of flame propagation.

So over the course of time it's not so expensive to deck the block.
On a B21/B23.
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