Piston Clearance Issue...

[dori34]

Hi guys, in regards to my old thread;

http://www.skylinesaustralia.com/forums/Rb...25-t321488.html

The pistons/crank/rods were dummied up today and have found that the RB26 pistons (using standard ones as dummies), the dome part is hitting the head.

i am using a RB25 NEO head which i believe has a smaller CC compared to R33 RB25 head.

Is it possible to either:

a ) machine a RB26 piston dome flat (will be using ACL pistons, pending budget so will either be forged or cast items)

b ) custom make a piston with either a dished or flat top to suit with RB26DETT/RB25DET compression ratio - 8.5:1 to 9:1 range? (If so, who makes custom pistons and approximately what cost would i be looking at for a set in either 1) forged 2) cast)

c ) custom thick headgasket to help make it clear with RB26DETT off the shelf pistons?

Here what happens when the off the shelf RB26 items are used, you can see where the valves hit.

http://forums.nicoclub.com/rb26-crank-rods...io-t475298.html

Ideally i would like to keep this head and not change to a R33 head which will require rewiring, different injectors,cams etc.

Any help much appreciated.

[aleks]

You can get CP pistons made which take 4-6 weeks. I'm trying to find out if anyone else will aswell.

Speaking to a few machinists/engine builders; getting the combustion cambers machnied and running a thick head gasket (2mm) they were still getting big compression.

The only way to do it properly is to get pistons made.

Edited May 31, 2010 by aleks

[dori34]

whats approximate cost for custom pistons made?

Please let me know if you find any other info. What pistons for what motor are you getting done?

[N1GTR]

Almost any piston company will make custom pistons. Not cheap though and from what ive read you're trying to do all this on a budget.

For a start, there's Mahle, JE, Wiseco, Arias, CP, Cosworth, ACL etc

Id start at ACL then try CP, or if the budget allows about $1700 call Specialized Piston Service in melbourne

[aleks]

Neo engine, same problem as you; no one has off the self pistons except for Jun which would probably be 1900-$2000.

Got quoted $1390+delievery from spool for CPs.

[dori34]

I've checked with ACL, they dont make it anymore.

I will be ringing & emailing a few companies tomorrow and hopefully get something sorted soon so my car and be completed. waiting 4-6 weeks for them to could is very time consuming

If custom pistons is the way to go then thats what ill be doing.

so i assume machining the dome is a no go?

[Adriano]

Is the dome hitting hte head or the valves, you can easily get the pistons flycut to clear the valves

[Simon-S14]

is this a neo only problem? any reason you cant use Rb25 psitons to suit a neo or is there nothing available?

interested as im looking at doing a build down the track.

[dori34]

Is the dome hitting hte head or the valves, you can easily get the pistons flycut to clear the valves

The dome is hitting the head. Will "flycutting" affect the pistons strength/integrity at all? Who can do this sort of service, the bloke machining my block?

is this a neo only problem? any reason you cant use Rb25 psitons to suit a neo or is there nothing available?

interested as im looking at doing a build down the track.

I am using RB26 crank/rod & pistons in a RB25 Neo block.

You can get it to work straight up with a R33 RB25 head as it has a bigger combustion chamber - 63cc compared to 50-51cc.

do any companies make dished pistons for RB26?

hopefully swiper the fox see's this and put some input into this

[TiTAN]

swiper the fox might see it but wont be putting input in.

[rb30dett]

Use pistons for a Neo or mill the crown down

[[200]]

I've checked with ACL, they dont make it anymore.

I will be ringing & emailing a few companies tomorrow and hopefully get something sorted soon so my car and be completed. waiting 4-6 weeks for them to could is very time consuming

If custom pistons is the way to go then thats what ill be doing.

so i assume machining the dome is a no go?

Give quantum racing industries a call up on the south side of Brisbane. They are the main importers and distributors for the CP Piston range.

07 3290 5911

[GTScotT]

Wait, I want to know how that happened.

How long did the motor run for before you found it like that? that looks more like detonation damage than it does valve damage.

Here's what happened last time I saw a piston touch a valve:

And I imagine if the piston was touching the head with the dome that the dome would have damage on it... but from the pic it doesnt seem to have much of a mark on it..

Also, if that was touching, it would have nuked itself within a few seconds of running.. more so that eating abit out of the piston crown.

Would really like to hear more about how that happened.

[dori34]

Titan - why not? i guess this forum is no good for info and input from other members to help others out then.

GtScott - that is not my piston. just some other bloke i found who did the same thing in the us. if you look closely at the picture towards left side of the piston, you can see circle marks from where the valves hit.

200 - i'll be contacting them today. thanks for the details

So from the top of your heads, are there any off the shelf items for rb26 that are dished and not dome?

[aleks]

Forget about rb26 pistons. HIGH COMPRESSION

Lewis engines have Arias pistons for RB25/30 neo heads and engine listed on their site for $1375

Just spoke to quantum racing and they want ~$1520 to get CPs made 4-5 weeks they said.

About to call lewis engines see if they have anything in stock....

Edited May 31, 2010 by aleks

[TiTAN]

why not?

check his user profile if you want to find out.

[STATUS]

Forget about rb26 pistons. HIGH COMPRESSION

Lewis engines have Arias pistons for RB25/30 neo heads and engine listed on their site for $1375

Just spoke to quantum racing and they want ~$1520 to get CPs made 4-5 weeks they said.

About to call lewis engines see if they have anything in stock....

im not a fan of the arias gear, i would spend the dough on CP's or JE for sure.

[dori34]

I emailed rocket industries for Aria items. hoping they may be able to supply a 26 piston with dished head if not then a price on custom units. i'll contact lewis as well unless you beat me to it.

alek- are you doing 26 internals as well or just 25 neo?

would be to use a 25 piston with the 26 rod since the rods are the same?

[J'z-R33]

The dome is hitting the head. Will "flycutting" affect the pistons strength/integrity at all? Who can do this sort of service, the bloke machining my block?

I am using RB26 crank/rod & pistons in a RB25 Neo block.

You can get it to work straight up with a R33 RB25 head as it has a bigger combustion chamber - 63cc compared to 50-51cc.

do any companies make dished pistons for RB26?

hopefully swiper the fox see's this and put some input into this

Doubt it, Admins banned him..

[dori34]

Just spoke to lewis engines, will need a full custom piston from Arias. take about 4-12 weeks and cost around 1870 delivered. they've done this before with their own motors so they know what's involved.