Claying pistons for clearance

[digger]

Standard, the better squish more than offsets the slight increase in CR

[zaq123]

quick update:

Pistons are 10:1 advertized. I got VR test gasket (+0.3 oversized) and used 2mm solder wire. My P dome to H clearances are in mm...

cyl1 - 1.33 cyl2-1.30 cyl3-1.26 cyl4-1.25 cyl5-1.19 cyl6-1.21

Mahle recommended clearance for steel rods 0.04" or 1.02mm. I'm using H beam forged 4340 rods

I already have STD size OEM gasket but it will reduce recommended clearance to 0.035" on cyl5 with my setup. I haven't checked P to V yet (waiting on the TB parts) but IE/Mahle pockets look deep (I will obviously verify the exact P to V clearance).
Putting P to V clearance aside at this moment.....would you guys recommend to run +0.3 heads gasket with or go with STD one? This build should be capable to run on pump premium gas.

no need to torque the hell out of it IMO but if you have an old set of bolts and cheap HG then go right ahead, i would use a VR gasket or similar of the same thickness. i usually order a VR topend gasket kit and an OE HG gasket (better quality) so there is a spare HG left over anyway

[digger]

no need to torque the hell out of it IMO but if you have an old set of bolts and cheap HG then go right ahead, i would use a VR gasket or similar of the same thickness. i usually order a VR topend gasket kit and an OE HG gasket (better quality) so there is a spare HG left over anyway

[zaq123]

was it indention of just discoloration / deposits?

It possibly was a discoloration......the head was skimmed and for some reason I remember indentations around HG rings....Maybe it was the deck....the deck definitely had some electrolysis pitting/corrosion around the rings before it was resurfaced.

I don't have old HG. So you guys recommend to torque new cheap HG all the way with old bolts to clay it properly?

[TobyB]

The only time I've seen a head deformed by the gasket is the
2002 'cutting ring' gasket- it has a ridge in the head side that's
designed to o- ring itself into the head material.
And even that made a gouge not much over.005" deep.

Other than that, a flat gasket just won't hurt the head surface...

...and I just use an old gasket, too. Snugged, but not torqued.

t

[digger]

was it indention of just discoloration / deposits?

[zaq123]

my m20 head had clearly visible and tangible marks in it from HG. Maybe I'm too ocd. I can see spacer not marring the head but OEM head gasket isn't all metal

[e30davie]

Yah ive never seen a "dents" from the rings on any head i've removed, bmw or otherwise.

[nando]

I don't think there's enough clamping force on the head bolts to "dent" the head around the compression ring.

[digger]

I laser cut a gasket from 2mm aluminium sheet. It's just a fancy spacer, itvwont Marr the head not that i noticed the stock gasket did. I use it as reference to work out how thick of a mls ( not cheap) I need

[zaq123]

Interesting conundrum. What do you mean by "marring the head"?

If you get the cheapest gasket you can find that is the same thickness as the one you intend to use, then just re-use any old bolts for the test that would have to give you a pretty good indication? Sure you arent supposed to re-use head bolts for running, but i reckon they would be fine for the test.

or find a second hand used gasket that is hanging in someones garage. I tend to hang my old head gaskets in the garage, dunno why...

typically, when you tighten the head, gasket's metal rings dig into softer aluminum surface of the head, slightly marring it. If I'll use new gasket, it won't give actual compressed height since it's not compressed till the final torque is applied.
I can just assemble it with new gasket and subtract uncompressed height from the final measurements. I just wanted to know if there are any tricks/ideas from experienced folks who've done it a few times.

[e30davie]

Interesting conundrum. What do you mean by "marring the head"?

If you get the cheapest gasket you can find that is the same thickness as the one you intend to use, then just re-use any old bolts for the test that would have to give you a pretty good indication? Sure you arent supposed to re-use head bolts for running, but i reckon they would be fine for the test.

or find a second hand used gasket that is hanging in someones garage. I tend to hang my old head gaskets in the garage, dunno why...

[zaq123]

any suggestions?

[zaq123]

my old head gasket got bent and all out of shape. Any reliable way to use anything else/cheap new head gasket to get P/H and P/V clearances?
If new cheap HG is the only way....how should I do it without torquing the bolts all the way? I would like to avoid marring the head too much while compressing the test gasket to its final thickness.

IMO you dont normally need a very accurate measurement with clay for P to V as most people arent trying to optimise it , rather just check there is enough so clay is good enough.... with squish clay is likely not going to be accurate enough if youre trying to get it accurate within 0.05-0.10mm or so on a performance engine its easy to squish it a bit much with verniers or not enough...

[TobyB]

It takes a lot of force to bend a valve,

See, this is the difference between an occasional mechanic and a pro-
I just don't do it enough to have a good sense of how tough they are.

And yeah, I cussed when I went to cc it and it leaked...

thanks- I learned something today!

t