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

[kitto]

People have answered your question.

I have CP pistons so id like to know what happened.

This forum is about helping people. You asked a question that has been answered and we're asking a reasonable one back.

Is that not fair?

[GTScotT]

Real street performance do wiseco's for a good price. But any search on ebay or google would have revealed that.

Correct me if Im wrong but arent RB25 and RB26 pistons interchangeable?

[djr81]

It is probably not unreasonable to ask but nevertheless I don't want to put it on a thread on an internet forum. Sorry.

To reiterate it is not a CP piston issue so stop worrying about your motor.

[djr81]

Real street performance do wiseco's for a good price. But any search on ebay or google would have revealed that.

Correct me if Im wrong but arent RB25 and RB26 pistons interchangeable?

I wanted to get some comment from the real world rather than google as the stock size is the least common of the sizes and I increasingly find that what a lot of vendors list and what they actually have are two different things.

[kitto]

So if its not a CP piston issue then buy CPs... Problem solved.

Most manufacturer website lists every single piston they make in a cstalogue.

[djr81]

Different pistons have different attributes. EG compare ring thicknesses between Tomei (1.25 upper and lower), CP 1.25 & 1.5 and ACL 1.5mm. Cant find a number for HKS.

I was trying to get an idea of what i could get as my first couple tries gave me squat. Anyway the ACL looks to be worth further investigation.

Just because you build one motor one way doesn't mean you necessarily want to do the next exactly the same.

Edited January 4, 2013 by djr81

[JustinP]

Correct me if Im wrong but arent RB25 and RB26 pistons interchangeable?

RB25 Neo pistons are different.

[brenton21]

Correct me if Im wrong but arent RB25 and RB26 pistons interchangeable?

Wouldn't they have different compression heights due to the slight difference in stroke?

[GTR81]

Different pistons have different attributes. EG compare ring thicknesses between Tomei (1.25 upper and lower), CP 1.25 & 1.5 and ACL 1.5mm. Cant find a number for HKS.

I was trying to get an idea of what i could get as my first couple tries gave me squat. Anyway the ACL looks to be worth further investigation.

Just because you build one motor one way doesn't mean you necessarily want to do the next exactly the same.

HKS 86mm pistons are 1mm top ring and 1.25mm bottom if that's any help

[r33_racer]

You could just get some pistons made how you want. It's usually no more then normal in terms of price, just a bit of a wait.

[djr81]

After a great deal of messing about - the ACL piston is a no go. I actually had the things but for whatever reason the top piston ring came with far too much end gap. ACL no longer make the rings and could not change them. Nor could anyone else supply a ring to fit the piston.

So in the absence of a 1.5mm top ring does anyone have an opinion on the 1.25 vs 1.0mm?

[Joshbigt62r]

What's the reasoning behind the ring end gaps being no good?

Unless your really aiming for a rb power record what's wrong with JE PISTONS, CP, NITTO, MAHLE ect. Many many many people with rb engines making over 1000hp with these. So just go with a set of JE/NITTO SLUGS. problem solved mate. I've always ran JE's in my rb engine with no problems.

[djr81]

What's the reasoning behind the ring end gaps being no good?

Unless your really aiming for a rb power record what's wrong with JE PISTONS, CP, NITTO, MAHLE ect. Many many many people with rb engines making over 1000hp with these. So just go with a set of JE/NITTO SLUGS. problem solved mate. I've always ran JE's in my rb engine with no problems.

The concern is I had an engine built last time. By a workshop who claimed a reputation for building track motors. (And no I dont want to talk about who it was). Unfortunately things didnt go well and I need to rebuild the rebuilt motor. It has CP pistons and enough blow by that I cannot run it at my local track. Basically I am trying to find a recommendation for a piston that reliably produces single digit blowby numbers and therefore will allow me to do more than one lap at a time without the motor puking its oil out the breather. And yes I read all the threads on the subject and have done the mods listed in there.

The difficulty is trying to differentiate the motors used on the road (because mine would be fine if it was just used on the road) and those used on the track.

I had hoped the 1.5mm ACL top ring would be a large part of the answer. Unfortunately when we got the top ring and stuffed it into the (unhoned) N1 block the end gap was already 22 thou. Or in other words too big.

Sorry if I sound cranky but this is doing my head in.

[GTScotT]

22 isn't too big but once you hone the shit its going to open up.

I wouldn't be afraid to run 22 and 26 thou ring gaps (top and bottom). I am running 18 and 22 on my street motor which is tighter than.... I won't say.

[djr81]

Well the ring gap claimed for my CP piston install is/was 19 thou. And its looser than...... I won't say.

But yes the 22 thou number is already larger than what I wanted to run and the bores are in the 85.7 to 85.8mm range. So yeah add about 10 thou to 22 and I dunno you get next weeks winning lotto numbers.

Edited April 22, 2013 by djr81

[GTScotT]

Well that's just shit. Did you pull the motor down and check the gaps to be the said 19 thou? Definitely the rings which are letting the oil through? Take the manifolds off and see what the valves look like. If the inlet valves are soaked it would indicate its coming from higher above. Not assuming you don't know your stuff, just trying to be helpful.

FYI I have a set of SR pistons at home which appear to have a 1.5mm ring from standard. 86mm bore, stock Nissan item. Want me to get a caliper on it on the weekend? I could send you the set and you could get your ACLs checked to make sure they will accept the ring. If anything they may need a minor rework.

[djr81]

Well that's just shit. Did you pull the motor down and check the gaps to be the said 19 thou? Definitely the rings which are letting the oil through? Take the manifolds off and see what the valves look like. If the inlet valves are soaked it would indicate its coming from higher above. Not assuming you don't know your stuff, just trying to be helpful.

FYI I have a set of SR pistons at home which appear to have a 1.5mm ring from standard. 86mm bore, stock Nissan item. Want me to get a caliper on it on the weekend? I could send you the set and you could get your ACLs checked to make sure they will accept the ring. If anything they may need a minor rework.

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. The engine isnt burning oil just puking it.

As for pistons, the ACL stuff is here:

http://www.aclperformance.com.au/NissanRB26DETTForgedPistons.htm

Ring part number is C1686 (As per RB30)

SR20 is here:

http://www.aclperformance.com.au/NissanSR20DETForgedPistons.htm

Part number is: C1834

There may be a 1 in a thousand chance that ACL have a couple sets of SR20 rings left. They dont have any C1686 unfortunately.

To be clear the rings you have a re ACL items? If so and you could check their end gap that would be awesome.

[GTScotT]

No mate, I'm saying I have a set of stock SR20 pistons at home (used) which have rings that appear to be 1.5mm thick.

What I am suggesting is that you try put the stock SR20 ring on your piston and if it works then order a set of stock SR20 rings for your ACL RB30 pistons. I am suggesting this because you said ACL rings are not available, and they are 1.5mm thick for an 86mm bore, and other brands are thinner IE 1mm or 1.25mm..

So in theory if the OEM SR rings are 1.5mm thick, and they fit on your ACL pistons without fouling the piston itself, you will be able to buy a set of SR compression rings which should have gaps tight enough for you to work with.

Let me know if were on the same page.

[djr81]

No mate, I'm saying I have a set of stock SR20 pistons at home (used) which have rings that appear to be 1.5mm thick.

What I am suggesting is that you try put the stock SR20 ring on your piston and if it works then order a set of stock SR20 rings for your ACL RB30 pistons. I am suggesting this because you said ACL rings are not available, and they are 1.5mm thick for an 86mm bore, and other brands are thinner IE 1mm or 1.25mm..

So in theory if the OEM SR rings are 1.5mm thick, and they fit on your ACL pistons without fouling the piston itself, you will be able to buy a set of SR compression rings which should have gaps tight enough for you to work with.

Let me know if were on the same page.

I see what you are saying. I could try a set of Nissan rings for an RB26 - not sure what they have available or how they match up with forged pistons. Has anyone tried this?

[GTScotT]

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.

hey are a simple thing. Has width and depth like what it says on the ACL site. If the width is right, and the depth is the same as or slightly less it will be fine. I would just make sure you use the ACL oil control ring.

Also, is it both your top and bottom comp rings that are too large or just the top?