65Mm Pistons - Ie Stock Bore For An New Rb26 Block

[djr81]

Like i said try do it with a set of used rings first. I have a set of detonation damaged SR pistons at home if you want to try, im sure other members have RB sets lying around if you ask.

If your in NSW your welcome to come grab one of my spare pistons and try your luck.

Nah NSW is a bit of a drive from WA. I have the original pistons/rings from my motor so could check those.

But like I said stock rings with forged pistons?

[GTScotT]

Try the original rings in yours and see if they fit.

No issue with stock rings in forged pistons, they are just rings. Usually made from the same material anyway. It's just about fitment.

[Joshbigt62r]

So what size piston rings do you want? Can you list the 3 ring sizes please?

[djr81]

So what size piston rings do you want? Can you list the 3 ring sizes please?

Here:

http://www.aclperfor...rgedPistons.htm

[Ben C34]

...

Edited April 23, 2013 by superben

[Joshbigt62r]

Ok I've just sent a email off to a contact to see what he can do or says. I'm guessing your wanting a thicker top ring to help control your blowby issue? Have you fitted MINES triple flow cam baffles.? They help a lot. You also said you've already done the rear head oil drain and smaller oil restrictor in the block. Do you also have a good catch can setup?

[djr81]

Ok I've just sent a email off to a contact to see what he can do or says. I'm guessing your wanting a thicker top ring to help control your blowby issue? Have you fitted MINES triple flow cam baffles.? They help a lot. You also said you've already done the rear head oil drain and smaller oil restrictor in the block. Do you also have a good catch can setup?

Yes that is why I want the thick top ring. I had a standard motor running 450 horsepowers and it didnt have any issues. After the rebuild it has more issues than Readers Digest. The fundamental difference between a tired stock motor (With no head drain, standard restrictor,no big catch can) and a brand new build forged motor (which over time collected all of the stuff listed below) is in the pistons and more particularly the ring thickness.

I tried JE who do custom rings - just not custom enough.

I have fitted:

A drain from the back of the head.

A small restrictor.

Mines baffles (Which I dont think help anyway).

A Nismo catch can.

Another big catch can with a return to the sump.

A dash fitting in the sump to help vent blowby straight to the catch can.

In getting to that point I have been through umpteen iterations.

Edited April 23, 2013 by djr81

[Joshbigt62r]

So JE won't do you a 1.5mm top ring your saying? With everything you've done it shouldn't be a problem even with a 1.2mm top ring. It sounds like it was possibly screwed together poorly? Slap happy job? Ring gaps all probably not measured or done or who knows? Was the block torque plate honed do you know? Machine work may be not have been done to correct specs? It's hard to say without seeing it if that makes sense. I'd almost think the the problem would lay within how it's been screwed together. Also what oil are you using?

Edited April 23, 2013 by Joshbigt62r

[djr81]

So JE won't do you a 1.5mm top ring your saying?

I asked them for a ring with the same dimensions as the ACL one. They said no. The next step may have to be asking them for a custom piston for a 1.5mm ring of their own dimensions. Is $$$'s, I would guess. They don't do an 86.0mm piston and like alot of people start at 86.5mm.

With everything you've done it shouldn't be a problem even with a 1.2mm top ring. It sounds like it was possibly screwed together poorly? Slap happy job? Ring gaps all probably not measured or done or who knows?

I dont believe it was a slap happy job. In fact quite the opposite given the circumstances I beleive the shop in question tried bloody hard to get it right. Which is perhaps even more of a concern.

Was the block torque plate honed do you know?

Yes, believe so.

Also what oil are you using?

Mineral oil for run in and then Mobil 1.

[GTScotT]

If your willing to go new pistons over and over why not just get a set of oversize pistons and start fresh?

I don't believe in going factory size when building unless its being built with full access to all factory parts. Which means I'd never forge at factory size anyway. I want my machinist to have enough meat to grind so that the quality of the bore is entirely on him.

[djr81]

If your willing to go new pistons over and over why not just get a set of oversize pistons and start fresh?

I don't believe in going factory size when building unless its being built with full access to all factory parts. Which means I'd never forge at factory size anyway. I want my machinist to have enough meat to grind so that the quality of the bore is entirely on him.

I have bought a new N1 block for the new engine build so I am starting fresh. It has bores less than 86mm. So why not use 86mm pistons?

[GTScotT]

Depends how much less they are and if they are less they are. I've just heard too many horror stories where people have built to factory sizes and failed, scares me off i guess. I use what I said above as a rule of thumb when considering a build.

Surprisingly I have had a new OEM block with forged internals be PERFECT compression wise with stock sizes (was an SR) but the shop who put that together rushed the rotating assy and it died in many weird and wonderful ways, a few tries over. If its not one issue its another lol.

[djr81]

Depends how much less they are and if they are less they are. I've just heard too many horror stories where people have built to factory sizes and failed, scares me off i guess. I use what I said above as a rule of thumb when considering a build.

Surprisingly I have had a new OEM block with forged internals be PERFECT compression wise with stock sizes (was an SR) but the shop who put that together rushed the rotating assy and it died in many weird and wonderful ways, a few tries over. If its not one issue its another lol.

Well its going to get honed - just to 86.0mm not out 86.5mm. Not going to chuck it together with the finish it has straight from Nissan. Pistons wouldnt fit down the bores anyway.

[GTScotT]

We know this.

My point is factory has many grades of parts, and factory built motors are as good as they are for that reason. I could be wrong and the bores have plenty of room to hone and suit the new pistons, its just something that crosses my mind when considering a build.

Get the block checked by your machinist before going further to make sure he agrees it will suit an 86mm piston of generic type.

[Joshbigt62r]

I must admit I'm with you GTSCOTT on getting the block machined out to 86.5mm. N1 block should be great but yeah I don't know lol. Each to there own I guess. Um what grade oil are you using.?

[tricstar]

I'm surprised this hasn't come up earlier...he said Mobil 1 ? so what 5-40 or 0-40 ??

I tried that on my built engine and blew it all out the back ( or somewhere ? ) at one event..

went back to 15-50 which the builder recommended and no such issues.

[djr81]

I'm surprised this hasn't come up earlier...he said Mobil 1 ? so what 5-40 or 0-40 ??

I tried that on my built engine and blew it all out the back ( or somewhere ? ) at one event..

went back to 15-50 which the builder recommended and no such issues.

5W50 which I have always used. Never had a problem with it.

[tricstar]

I was at the Collie track late last year when you emptied your sump into your catch can and all over the engine bay.. and know how frustrated you are.

In order to eliminate any other contributing factors, and having seen your breathing setup, ( the most hoses, cans, breathers etc,I've ever seen in an engine bay.) especially the sump to can breather? when the track is continuous high speed lefts, the oil is going to run straight up the sump breather on the right side of the sump?

Maybe you can post a pic or diagram of the breather setup, and see what people in the know like Scott etc have to say about it?

just an idea.

[djr81]

I was at the Collie track late last year when you emptied your sump into your catch can and all over the engine bay.. and know how frustrated you are.

In order to eliminate any other contributing factors, and having seen your breathing setup, ( the most hoses, cans, breathers etc,I've ever seen in an engine bay.) especially the sump to can breather? when the track is continuous high speed lefts, the oil is going to run straight up the sump breather on the right side of the sump?

Maybe you can post a pic or diagram of the breather setup, and see what people in the know like Scott etc have to say about it?

just an idea.

And there I was thinking I had done an awesome job of disguising just how monumentally frustrated I am. Other than referring to the car as the Exxon Valdez and carrying on like a pork chop about it all the time, obviously.

Yeah it looks like an octopus orgy. But please understand it started with a couple of vent lines from the breathers in the rocker covers to the catch can and grew from there. To be fair it works at Wanneroo. Just not Collie because there are too many left handers for the content of the catch can to drain back into the sump.

The take off for the vent to the can is well above the oil level so I dont believe it is coming out there. It puked oil before I fitted the vent - at Collie and Wroo. Stopped at Wroo afterwards.

In any case it fills the 2 litre or thereabouts can in two to three warm up laps of a track that is a mile long. The last time there was oil all over the engine bay, on the quarter panel, the side skrits, all over the front suspension, wheel, windscreen and the puddle under the thing was the size of a family pizza. So not a small amount. Catching it with anything smaller than a 44 gallon drum wont work. Sump capacity is only 9 litres so even the P76 boot mod has its limitations.

Anyway none of this is getting me closer to a piston with a 1.5mm top ring. Or a suggestion (Other than somethng with total seal rings) for a piston otherwise.

[GTScotT]

Havent pulled the motor down I wanted to get the parts I needed for a rebuild before doing so. There didnt appear to be a whole lot of point after the leakdown test was done.

Can you tell us a little more about this comment?

I understand that a leak down was done, but the comment of pulling the motor down being pointless based on the results is confusing me.

Did it have pathetic leak down results or was it fine? What's the story?

What others are currently suggesting is that your octo breather pussy party setup may not be helping what you are experiencing.. I think you should rule this out for everyone so that we can continue to try and help. I for one do not want to encourage you to build another motor if you dont need to.