L20b/z20 block head gasket .030 over

[sick620]

Just got my .030 over z20 short block (720) back from the machine shop.

 

with a new std bore l20b head gasket it is very close to the cylinder bore .. like it might fit pretty much exactly on the edge of the wall too close to call if it’s in the cylinder very slightly or not…

 

reading on here some people say a stock head gasket size should fit all the way up to .40 over … my pistons seem to not come out of bore at all .. sorry no pic of gasket on there but I can get one.

Edited April 21, 2022 by sick620

[datzenmike]

The Z20 pistons stop about 0.3mm below the deck. That's 0.011".  Only engines that I know that rises above the deck is the L16 and the late Z22 used in the S110 200sx. It's 0.1 and 0.15mm or 0.004" and 0.0059".  That's alright, there is a 1.2mm gasket thickness between the block and the head.

[sick620]

13 minutes ago, datzenmike said:

The Z20 pistons stop about 0.3mm below the deck. That's 0.011".  Only engines that I know that rises above the deck is the L16 and the late Z22 used in the S110 200sx. It's 0.1 and 0.15mm or 0.004" and 0.0059".  That's alright, there is a 1.2mm gasket thickness between the block and the head.

The question im wondering is if the head gasket for a 85mm std bore l20b/z20 will work with myh motor bored 30 over. 

[datzenmike]

30 over? like 0.030"??? that's only 0.015" removed from the cylinder walls. About 4 sheets of newsprint thick. The 'fire ring' shouldn't protrude into the combustion chamber. It survives because it's protected/cooled by the head and the block. Should be ok.

[sick620]

6 minutes ago, datzenmike said:

30 over? like 0.030"??? that's only 0.015" removed from the cylinder walls. About 4 sheets of newsprint thick. The 'fire ring' shouldn't protrude into the combustion chamber. It survives because it's protected/cooled by the head and the block. Should be ok.

Yes correct .030 over … I was concerned because the gasket sitting on the block the “fire ring” is extremely close to coming over into the bore… it is right on the edge scary close..

[banzai510(hainz)]

Mike I told him if possible find a 87mm bore gasket. (I have some for the L20 I got from Australia) Durapro brand Made in Japan.

 

I guess depends on the brand of gasket.

Z22 gasket????

Edited April 21, 2022 by banzai510(hainz)

[datzenmike]

Z series gasket for Z22 (87mm) or Z24 (89mm) will work but the coolant holes are differently placed. L series has more flow on the manifold side because hot exhaust are beside the intakes so need more cooling. Z are cross flow so more evenly spaced. Just cut the front timing chain area off and graft an old L series front on... it only seals fumes and oil spray anyway.

 

I looked at an L28 (also 87mm) but the oil hole is in the wrong place... it would be a mess.

 

I put a U67 L head on a Z24 block using a Z24 gasket and comparing it to an old L series gasket. There was a hole on the L block that's not there on the Z. I think I got it matched pretty well.

 

The hole on the left doesn't exist on the Z24 block so to get coolant into the L head I cut a groove across.  The Z24 also doesn't have that bulge so I JB welded it slightly to prevent coolant sneaking out through the thin part of the Z24 head gasket. 

 

 

 

By adding a little JB weld here I was able to use a Z24 HG on an L head without grafting the L front around the timing chain. Can't use the two front 10mm bolts but... shrug

[Stoffregen Motorsports]

13 hours ago, sick620 said:

The question im wondering is if the head gasket for a 85mm std bore l20b/z20 will work with myh motor bored 30 over. 

Yes. "Stock" head gaskets will work to .040" over, and slightly more.

[metalmonkey47]

You should just snag a NISMO head gasket, PN 11044-A7651. It has an 88.5mm bore.

That's what I used on my LZ after having issues with other stock replacement gaskets.

EDIT: That might be tough to get. They're out of production and the distribution centers show ZERO in stock.

Edited April 21, 2022 by metalmonkey47

[datzenmike]

Measure diameter of the old gasket. If more than 85.764mm or 3.379" should be good.

[sick620]

I ended up just using the normal 85mm l20b gasket.. It was close but a few people have said its good up to .040 over so I'll just have faith that is the case. 

 

engine is almost together. Head in place and I got it timed today and front cover on..

 

regarding cam timing, I timed it in the 1 position on the sprocket, that put the little v in the sprocket pretty much exactly dead center on the mark that is behind the sprocket. I read online now that l20b is supposed to be on 2 position, but 1 position was exactly lined up. I really don't want to take it all apart do you think the 1 setting will be fine?  Yes bright links were in correct spots, block was at TDC and cam dowel was at 12oclock, im sure its timed good I'm just worried its going to be 4 degrees too advanced in the 1 position. 

[datzenmike]

V should be below the horizontal etched line on the cam thrust plate above it... or just slightly to the right as viewed from the front. It's good. This is the defining position for stock cam timing and how you get it doesn't matter. Cam tower shims or advancing the cam to the next hole will move it to the right. There used to be head head gasket shims too.