86mm,86.5 or 87mm ?

[cobrAA]

Would it be possible to know what is the basic guideline when choosing a piston for a rebuilt? How do I know which one I want ? it's only .5mm difference.

On a sidenote, let say I buy a cometic head gasket, can i re-use the same head gasket next summer or I need to buy another one?

Much appreciated!

[gtrjon]

you should always get a new head gasket whenever the head comes off imo. as far as bore + 1 to get a better understanding of picking sizes

[jdms13rhd]

I always bore out to the minimum. Thats 86.5 from a std bore. I say that because if you ever damage your cylinder, There is room for another over bore. Lots of guys bore big to get the "extra displacement". There is no point from that aspect. Your really not going to notice a difference with an extra .5mm.

Head gaskets usually come in even sizes. Ive been using the tomei 87mm's and never have any issues. Also good cuz If I do damage a cyl and go another 2tho over, I can re use the same head gasket.

I've re used metal gaskets once and friends have several times on the same gasket. I've never heard or had problems when re using. I do check the clearance on the decks tho and re surface when needed.

[gtrjon]

with that theory why bore out to 86.5 than over the stock 86? if there is no cylinder damage why not have two extra bores when you need them if that makes any sense? why bore and spend the money on machine shop rather than just getting a hone?

[jdms13rhd]

with that theory why bore out to 86.5 than over the stock 86? if there is no cylinder damage why not have two extra bores when you need them if that makes any sense? why bore and spend the money on machine shop rather than just getting a hone?

Your right, if the cyl is in excellent shape, there really is no need to over bore. Ive only been in that situation once tho. Take the block to a reputable builder/machinist and get an expert opinion before you go and order up a STD size piston. Remember, a bore doesnt cost much. Around $25 a hole is the regular. Nissan has good cylinders out of the box. All the rb30's I've had I could still see the factory cross hatch from the machining process. Looks can be deceivin tho, so get that expert opinion. Once i looked at a block and figured it was perfect. suSre enough, it was far from it.

[derk]

metal head gaskets are meant to be reused, unless it has been damaged.

and dont get a cometic.. cosworth gaskets are way better, and dont cost much more

[gtrjon]

Your right, if the cyl is in excellent shape, there really is no need to over bore. Ive only been in that situation once tho. Take the block to a reputable builder/machinist and get an expert opinion before you go and order up a STD size piston. Remember, a bore doesnt cost much. Around $25 a hole is the regular. Nissan has good cylinders out of the box. All the rb30's I've had I could still see the factory cross hatch from the machining process. Looks can be deceivin tho, so get that expert opinion. Once i looked at a block and figured it was perfect. suSre enough, it was far from it.

sounds like 86.5 is the safest way to go. when your rebuilding your motor spending atleast 3 grand 150 for a bore over should not really be a big concern. thanks for all the info allen

[jdms13rhd]

sounds like 86.5 is the safest way to go. when your rebuilding your motor spending atleast 3 grand 150 for a bore over should not really be a big concern. thanks for all the info allen

Glad I can help if I can.

And on the cometic gasket..... I cant say too much cuz I have never used them before but I have herd stories on them failing and having some issue with a brass or copper o ring or something??? Read up on them before you purchase or I would also recommend the cosworth or tomei gaskets. Tried/tested/proven.

[DarkCaporaL]

You be the judge of which one you want to use:

Cometic < OEM < Cosworth

[cobrAA]

I didn't knew this. glad I did a thread about it! Thanks!

[NerdJuice]

You be the judge of which one you want to use:

Cometic < OEM < Cosworth

where do the super JDM companies fit in? HKS, Tomei, Greddy, etc?

[M13]

Tomei is comparable to Cosworth.

[DarkCaporaL]

Nitto also makes RB26 gaskets, but I think they only make them in 88mm, and they're like double the price of Cosworth.

EDIT: http://www.nitto.com.au/products/gas...=enginegaskets

http://www.rawbrokerage.com/NITTO-Drag-Series-Metal-Head-Gasket-RB26-NIT-MHG-RB26XX.htm

[rbs14]

I run a cosworth and i have no problem !!! I think its well made

[cobrAA]

However, I'm f*cked because they only make 87mm. no standard size.