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m50tech 12-04-2008 02:45 PM

lowering compression
 
i have a question if i build a plate out of aluminum just like a head gasket and put a head gasket on both sides of the aluminum plate and place it between the block and the head to lower my compression will it work on a turbo?:idea::idea::idea::idea::idea::confused::con fused::confused:

derkleineman 12-04-2008 10:06 PM

lol i dont think so !

a mls head gasket is about $250 and you can get them in diff. hights
but the best way is to get fordged pistons like i did

m50tech 12-05-2008 12:51 AM

i was also thinking about that spacer just in case the timeing chaine snaps the valves dont hit the pistons and nothing happens to either

NOTORIOUS VR 12-05-2008 08:34 AM

Yes the plate idea would work just fine, although steel might be a better idea. They've been using the plate ideas in Volkswagen's for a long time now. Basically the plate is a copy of the HG, and then there is half of the HG on one side (bottom) and the other half on the other side (top).

Would be far better then an mls I would think, but then again the rules are a little different when you're talking about straight 6's where the head's like to warp and you have sealing issues stock.

SamE30e 12-07-2008 05:00 PM

Like notorious said, steel would def be a better idea because aluminum doesn't hold upto heat as well.

Axxe 12-08-2008 06:23 PM

Bandaid solution. Forged, low comp pistons and a proper rebuild is the only way to do it without going halfass.

Axxe 12-08-2008 06:24 PM

Quote:

Originally Posted by NOTORIOUS VR (Post 1235584)
Yes the plate idea would work just fine, although steel might be a better idea. They've been using the plate ideas in Volkswagen's for a long time now. Basically the plate is a copy of the HG, and then there is half of the HG on one side (bottom) and the other half on the other side (top).

Would be far better then an mls I would think, but then again the rules are a little different when you're talking about straight 6's where the head's like to warp and you have sealing issues stock.

So they split a head gasket in two? That doesn't make any sense at all. The cost of getting a riser machined properly, within spec, would outweigh a set of pistons.

NOTORIOUS VR 12-08-2008 07:10 PM

Quote:

Originally Posted by Axxe (Post 1236699)
So they split a head gasket in two? That doesn't make any sense at all. The cost of getting a riser machined properly, within spec, would outweigh a set of pistons.


Of course it makes sense. On a metal HG, the top and bottom is all you need (its the parts of the HG that actually have the seal) when you're using a metal head spacer like the OP wants to make. The stuff in the middle of the OEM gasket gets replaced by the metal spacer.

And you're right it will be expensive, although you don't know he knows so he might get it done for free or for very little. Although having someone water cut a piece won't be as much as 6 forged pistons. 6 forged pistons are the proper way to do it.

Regardless, it's known that stock internals of an M5x motor will make upwards of 500whp, so if his goals are around that or under it power wise, it's not a bad idea IMO.

m50tech 12-09-2008 02:07 AM

i plan to get the plate cnc machined i am going to make a compression ratio test so that i can set the ratio like at 7 of 8 and in case something was to go wrong nothing happens to the pistons and the valves cuz of the spacer. i do all my work and i have takes apart m50s m20 m10 before nothing new.

NOTORIOUS VR 12-09-2008 01:26 PM

7:1 is too low. Shoot for 8.5:1 or even better 9:1 IMO.

Not sure why you're so concerned about bending valves?

m50tech 12-10-2008 12:22 AM

my friend has a 87 bmw and he was boosting and piston #3 bended the valve and ever since it has never been the same i just dont want to go throught that with my car i rather do my research right

PedroBMW 12-10-2008 07:28 AM

Quote:

Originally Posted by m50tech (Post 1237283)
my friend has a 87 bmw and he was boosting and piston #3 bended the valve and ever since it has never been the same i just dont want to go throught that with my car i rather do my research right

you definitly don't wanna go down to 7:1, your car will be a dog. Piston/valve clearance is not really a very good justification for choosing what compression ratio you want to run. :)

NOTORIOUS VR 12-10-2008 08:51 AM

Quote:

Originally Posted by m50tech (Post 1237283)
my friend has a 87 bmw and he was boosting and piston #3 bended the valve and ever since it has never been the same i just dont want to go throught that with my car i rather do my research right

That has nothing to do with research. And that is a horrible reason to lower the compression of an engine that much.

If everything has been set up correctly, there is no issue with bending valves at all. My friend is making 400RWHP on a stock motor M20. No bent valves.

Just because your friend did something wrong doesn't mean you should sacrifice your build like that and going with such a low CR.

You lower CR to increase detonation resistance under boost. You don't do it to save your valves. If thats why you're doing it, get forged pistons with deep valve reliefs end of story.

SamE30e 01-04-2009 06:52 PM

Quote:

Originally Posted by m50tech (Post 1237283)
my friend has a 87 bmw and he was boosting and piston #3 bended the valve and ever since it has never been the same i just dont want to go throught that with my car i rather do my research right

If you lower the compression too much, you'll have no off boost power.

ACS_DAN 01-04-2009 09:42 PM

^^*Cough* Single turbo Supra's *cough* =p


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