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L20b pistons hitting head gasket.


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Hello again gang, check this out, l20b 86mm 280z flat top piston ,w58 peanut head, hitting stock felpro gasket fire rings bad! Can't get the gasket even ,this is number 3 of gasket change. I've tried to line up the gasket before and after I put the head back on but the piston end up hitting bad. So my questions are , where to go from here? Will a Nismo 88.5 over sized gasket work for a 86 mm bore? Is there supposed to be more space between the top of the cylinder and the top of the block? Seems the gasket is flattened more than 1.2 mm by the piston hitting it. Does Nismo have a better size gasket? Does anyone? What am I doing wrong? I got 3000 miles out of the first gasket until it blew on number 3 cylinder. It's a fully rebuilt head and bottom end from a reputable California Datsun engine builder. Please help if anyone can . Thanks guys. 38/38 weber, when it runs it runs very good!

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If your using a stock felpro I think it's only a 85mm bore and if your bored out to 86mm your exposing the fire ring which isn't good.... in my opinion the nismo one at 88.5 should be fine to run its plus 2.5mm in diameter..

The stock felpro headgasket covers the l16 and the l20...

L16 stock is 83mm

the l20 is 85mm

Which is a 2mm difference... so..

I am sure other will chime in...

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Hey guys noticed the alignment dowls are missing. Company with the rebuild didn't put them back. I figure that's what's doing it. I'm still going with the oversized nismo gasket. Wondering if the dowls pins are available from anyone? Thanks

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Definitely use the nismo head gasket for the bore size. You are talking about the hollow pins that go in the head bolt holes right?. I believe I got those pins right from nissan....I think you only need 2 and if I remember right I had to buy a 10 pack I should have some extra ones... I can look tonight when I get home from work if you wanna pm me....

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  • 3 weeks later...

Got the plugs. From Nissan , 10 pc package. Seems to of worked .engine sounds great .still have the question about the oblong hole in the back of the head, block, nismo gasket does not have one. What is that hole for? Was I supposed to drill it out? Thanks.

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John 510

I hope it was this one...

Screenshot_20170218-211304_zpsyhi5mj90.p

I think That's from California datsun. The one first talked about in this thread is something different.. I thought I read somewhere those felpro 89mm bore gaskets are an out of production item . I could be wrong but whatever you get from a local parts store is a felpro that fits the l16/l18/l20 that is only up to an 85mm bore....

And datbizz definitely compare the openings on the head and block...

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L20B pistons are 0.45mm below the deck. It's recommended that you not go more than 0.3mm above the deck with the piston to still have some room for rod stretch at extreme RPMs. So if decking, do not remove more than .75mm. 1/3 of a mm protruding piston is ok

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  • 4 weeks later...
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Hey guys noticed the alignment dowls are missing. Company with the rebuild didn't put them back. I figure that's what's doing it. I'm still going with the oversized nismo gasket. Wondering if the dowls pins are available from anyone? Thanks

I was going to ask if you had the dowels in.
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  • 2 weeks later...

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