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Hasket Sealing On Rb25det Head Rb30 Block

joe blo

By joe blo,
in Engines & Forced Induction

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joe blo Experienced

joe blo

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ive got a r33 rb25det head that i got modded with the vct hole welded up and the new fitting put in at the front. i didnt get any extra welded on where the gasket seals. do most people get that done or leave it as is? i didnt know about iuntill after i had it done.

if i take it back to the shop and get more welded to the area and then resurfaced will it effect the compression or make the valves hit the pistons or anything from being resurfaced too many times or anything?

would it be fine how it is? ive got a rb30 gasket. is that the right one to use?

i had read the guide and printed it out and dropped it off at the machine shop when i got everything recondiotioned but didnt realise about adding extra to where the gasket seals

also. doeas anyone know where to get new tensioners and how much they are? i went to my local nissan-holden parts store and they couldnt get me any.

  • 3 months later...
proengines Rising Star

proengines

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Posted

I weld up the oil feed hole and part of the water hole. Use the rb30 gasket as a template for how much to weld. I have seen one that had nothing welded on the water jacket and did seal, it only had about 1.5mm sealing on one edge though, you're safer to weld it up and shape the hole to suit the gasket.

You shouldn't need to take much off the head face once it's welded, just enough to make it flat where it's been welded.

joe blo Experienced

joe blo

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I weld up the oil feed hole and part of the water hole. Use the rb30 gasket as a template for how much to weld. I have seen one that had nothing welded on the water jacket and did seal, it only had about 1.5mm sealing on one edge though, you're safer to weld it up and shape the hole to suit the gasket.

You shouldn't need to take much off the head face once it's welded, just enough to make it flat where it's been welded.

thanks for the reply. if i get it welded and then resurfaced again how much would it affect the compression ratio? say if it was going to be 8.2:1 if i put it on now what would it be once i get it resurfaced again after getting it welded?

would there be any problems with the squish (whatever that is) or any chance the valves will hit the pistons now? i just dunno how much effect it will have on it when it gets resurfaced coz im not a mechanic and dont know about that sort of technical stuff. or will it only make the slightest difference and its nothing to worry about at all? il be using a standard rb30 nissan headgasket.

proengines Rising Star

proengines

Posted
Posted

Adriano is spot on, the only way to affect squish/quench is by machining the block, using a thinner gasket or using a different piston.

Each cc you remove from the combustion chamber makes just on .1 compression points, for example, going from 62 to 61cc's changes your compression from say 8.2:1 up to 8.3:1.

It takes about .2mm off the head to reduce the chamber by 1cc.

P/v clearance isn't really a problem on RB's unless you are running really big lift, long duration cams.

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