Stock bore forged pistons

[ButikoferSkyline]

I am looking for some info on putting 86mm forged pistons into a stock bore block.

If cylinders look good is it recommended to do this?

[hp44incgtr]

You still gotta send it to the machine shop get hone you could probably put the piston back in the way it is but it's not guaranty the rings gonna seAl property. Either way it's always best to send it to the machine shop get it tested even tho everything's look good doesn't mean everything's fine.

[Skym]

Clean and make sure the deck of the block hasn't got any cracks between the water gallery and I think was head stud hole. If cracked, N1 block is the upgrade.

[_HASEMI_]

Clean and make sure the deck of the block hasn't got any cracks between the water gallery and I think was head stud hole. If cracked, N1 block is the upgrade.

I have a crack between the water gallery and the head stud hole. It is very small and not deep. The machine shop said that it's too small and no deep enough to justify a new block. What is your opinion?

[leung23c]

1. The crack is small now but may grow bigger?

2. A used block isn't expesive?

3. Brand new N1 Block is not exactly expensive

http://www.nengun.com/nismo/rb26dett-n1-block - About $1650 USD. but CAD sucks big time.....

4. You may spend tens of thousands of money into something else of your car and compared to that a replacement block is a no brainer....

5. CAN YOU ALLOW YOURSELF TO DRIVE YOUR GTR KNOWING THE BLOCK GOT A CRACK, NO MATTER HOW SMALL IT IS??????

[Dragon Humper]

Once the crack has started it will never stop, the block is junk.


Jon.

[hp44incgtr]

Also had same issues 3 use block had them the first block every cylinder the second only 2nd and first and block 3 only on the 6 very small crack guy at the machine shop say also it's not an big deal since the crack got no where to go

[hp44incgtr]

This my first block

[hp44incgtr]

And you would never know if you don't cut the deck of the block

[hp44incgtr]

Which most people don't

[Skym]

I have a crack between the water gallery and the head stud hole. It is very small and not deep. The machine shop said that it's too small and no deep enough to justify a new block. What is your opinion?

As far as I know, the stock block cracks due to crank? harmonics, weak engine mounts (Nismo engine mounts are the upgrade), damaged damper or insufficient damper for application, bubbles / hot spots (air separation tank can help to solve this problem) or someone put cold water (flushing the block) through a hot block while changing coolant.

Some brace the bottom of the block with custom CNC mains caps and adaptor plate setup which has worked on higher hp RB30 drag engines to help solve the crank? harmonic problem (similar design to V6 engine block in R35 GTR, V8's, etc). Stock girdle setup has limit's with higher hp engines.

Can buy it here -

http://www.spoolimports.com/spool-billet-main-caps/nissan-rb

You can run a RB30 bottomend with 4wd adaptor plate, custom CNC mains caps, etc if aiming for more hp, torque. A RB30 bottomend with tune to suit restores lower rpm response, torque, hp with bigger intercooler, turbo's.

The Nissan RB30 bottomend is standard in R31 in Japan and Commodore in Australia.

Can buy rebuilt RB30 bottomend here (or maybe a stock unrebuilt short block if you ask) -

http://www.ripsracing.com/catalog/Short-Blocks-37/index.html

N1 block (and N1 head) is said to have bigger water gallery to stop bubbles getting lodged which creates hot spots and overheating. It is a recommended upgrade on any higher hp RB26 rebuild if stock block has cracked.