1991 Skyline Gtr

[Super_Dude]

the problem is how close you move to the water jackets and what not. That is where block splits.

Why not just grab another block and start from scratch. You could pick up a n1 block, get it machines and fill it with some 86.5mm pistons.

Also, you should do more research on 1mm oversized valves on our car.

[Dakota_gsx]

yeah thats what i though. im just amazed that 1.5mm larger bore makes such a difference in safe and not safe. or what people say so anyways.
does anyone know someone running an 88mm bore?

[gtrjon]

Well like I originally said, I am getting the pistons custom ordered so they will be 87.5mm plus like 4though. I won't be running more than 650 horse to the crank. What would even happen with having too skinny if cylinder walls?

lol what happens when anything gets too skinny? they break! or in the case of cylinder walls they crack. normally caused by detonations.

[Dakota_gsx]

Well like I originally said, I am getting the pistons custom ordered so they will be 87.5mm plus like 4though. I won't be running more than 650 horse to the crank. What would even happen with having too skinny if cylinder walls?

[Super_Dude]

Exploding front diffs is an issue with high power and hard launches. A genuine n1 pump works good. I wouldn't personally run 87.5 or 88 but its personally not a huge deal. Unless your planning on making a crazy amount of power. Hks, apexi and trust used to make 88mm pistons but discontined them a long time ago.

[Bruizer]

87.5mm..i wouldnt want to go over 87mm , the wall are getting a little to thin for comfort after that.

Lots of guys do. It's the same myth/rare occurance of a failed N1 pump or exploding front diff. You'll be fine. 87.5 is the limit though.

[gtrjon]

i havent really heard of anyone running over 87mm. i went with 86.5 just so if i need to i can still bore over one more time and have pistons be readily avaliable since 87mm are pretty easy to get.

[Dakota_gsx]

Yeah my engine builder is saying the same thing. What does everyone else think about that. Are there people running 87.5mm bore or higher without problems?

[DJ]

87.5mm..i wouldnt want to go over 87mm , the wall are getting a little to thin for comfort after that.

[Dakota_gsx]

When they took apart the head, they said they have never seen valve guides in this shitty of shape out of an rb.
There was also so much oil blow by that there is a rubber/silicone like skin on the exhaust ports of the head that didnt come off in their tank. it will come off with a little scrubbing though.


Exhaust valve and Intake valve. (neither valves were cleaned after they were pulled.)

[Dakota_gsx]

So the pistons that were in the engine were a 87.5mm piston. all i can find for these engines are 86.5-87.5. since an 87.5 will not fit anymore, we are going with a custom made piston that will be 87.5mm plus about 5thou. dont know the company name, cant remember, but the guy at the engine shop said they make pistons for top fuel and alcohol dragsters. as well as the fastest evo x uses their pistons.
My valve guides are also done along with three valves. i will be picking up some Ferrea valve guides and oversize valves.

[Dakota_gsx]

Exactly addict. the last thing i wanna be doing is taking this engine out again next year. no way no thanks eff that.
does anyone know what the wiseco pistons are rated at? i wont be pushing anymore than 700bhp.
And since all these internals have been a mystery, we have been trying to figure them all out.
We are pretty sure the crank is Jun, and we are thinking that the rods are Carrillo because the rod bolts were carrillo. but we will never know.

[GTRADDICT]

by budget is whatever itll cost to get the proper parts for this thing. so if getting weisco means there is a chance of them not being enough to handle what im going for, then i will spend more money to get what i need.

Hell Yeah. Do it right or don't do it!

[Dakota_gsx]

by budget is whatever itll cost to get the proper parts for this thing. so if getting weisco means there is a chance of them not being enough to handle what im going for, then i will spend more money to get what i need.

[archaeic_bloke]

whats your budget?

most people rock CP or Weisco, but you can get some crazy good ones from tomei, greddy, Jun etc