Which rods??

[Steve]

HI,

Was wondering what peoples thoughts were on which way to go with rods. I am aiming around 270 - 300rwkw in an RB25. Do I,

1. Get the stock rods linished, shotpeened and crack tested (UAS have exhange ones for $550),

2. Buy Carillo rods or similar - not too cheap, or

3. Go an RB26 bottom end - if I can find one in decent condition, which I have heard are good for abouts 550bhp?

Any thoughts on cost v's reliability. I am hoping to get away with running about 1.3bar max on a HKS 3037 56T.

Also anyone have any thoughts on what type of pistons I should be looking at? Once again cost vs reliability at up to about 550bhp?

As this sort of power is on the edge of reliability for a stock RB25 setup, I would like to upgrade the internals without paying for a setup that is capable of withstanding huge hp, unless I have no choice.

Cheers for any ideas

Steve

[rev210]

The stock rods are probably fine is crack tested and machined for that sort of power, if the budget doesn't stretch.

You need some good rod bolts and pistons though.

[Merli]

1.3 bar isn't enough.

That HKS GT3037 would be efficient at about 1.5-1.6 bar...

Should be good for around 300rwkw at that boost pressure

Forged pistons, shotpeened/linished rods and ARP rod bolts should be good enough for your application... Only get forged Carillo rods or the like if you're wanting to run high (9000+) redline...

[GTS-t VSPEC]

Steve,

It looks like we are going for a very similar setup, and I'm just planning on doing option 1, I don't plan on pushing hard enough to require different rods, but I have a set of RB26 rods just in case.

See'ya:burnout:

[Steve]

Hi and thanks for your replies. Sounds like the stock rods are the go - will save a few dollars over going carillo or similar, its always nice to save a few dollars.

Merli, with would I have to think about dropping the compression ratio?

Also can anyone suggest what pistons and where to buy them from?

GTS-t VSPEC, so what have you got planned? I would like to hear how others tackle the build up for similar sort of power just to make sure I'm not missing anything. What rear wheel figure are you chasing?

Thanks again

Steve

[GTS-t VSPEC]

Steve,

I am going for Wiseco pistons 8.5:1 compression, no metal headgasket. Port and polish head, balance crank, shotpeen rods.

3037 turbo with 45mm wastegate, custom exhaust manifold, 264 cams, with adjustable cam gears.

The Wiseco pistons are much cheaper than the Jap brands, save more money.

See'ya:burnout:

[Steve]

Hey GTS-t VSPEC, does indeed sound similar to what I am doing. I am thinking a some headwork wouldn't go astray either - help get the turbo on boost a bit quicker. And maybe a 254 inlet or even an RB25DE inlet which is 248 I have been told. Cant rush these things eh. Do you have much idea how much dropping the compression ratio is going to effect spool up and off boost response?

Where would you recommend to pick up some wiseco pistons from - would I be correct that you have already sussed out a reasonable price for them??

Cheers

Steve

[GTS-t VSPEC]

I have a set already, I'll get the contact details for the supplier for you. Headwork will improve spool-up, so will a decent exhaust manifold. I'm trying for no more than 3500rpm as lag.

Don't bother with the RB25DE cam idea, I looked into that already, but 254's would be very good.

See'ya:burnout:

[Steve]

Thanks heaps for that,

Steve

[GTS-t VSPEC]

PM is being sent know.

See'ya:burnout:

[Merli]

Originally posted by Steve

Merli, with would I have to think about dropping the compression ratio?

Steve, forged Wiseco pistons will handle 1.5-1.6 bar boost without breaking a sweat... They're cheap and perfect for you... I'm probably going to use the same pistons.

As for the compression ratio, the rule you should be following is "if at all possible, don't drop the compression ratio".

With good tuning, and keeping detonation at bay, there is absolutely NO reason why you couldn't keep the standard compression ratio.

With your setup, I can see absolutely no reason to drop the compression ratio.

[Steve]

Thanks for the pm GTS-t, replly sent,

thanks Merli, that is what I was thinking, about compression ratio, but its nice to know that it is not unreasonable to achieve the results I want without changing it..Wisecos sound pretty good, quite a cost saving there.

Things starting to take direction

Cheers guys

Steve

[Steve]

Merli,

Can you recommend or even suggest a Wiseco supplier in austalia - I have done a bit of a web search, and I'm not having much luck tracking them down in aus.?

Cheers

Steve

[Merli]

I have a friend who is a distributor for wiseco products...

His name is Kristof Kazmer and his email address is: [email protected]

RB25 is RRP$1650... He's quoted me $1550, but I believe GTS-t VSPEC can get them even cheaper. I was actually going to ask him to get me a set of RB26 87mm Wiseco pistons when I had all the other internal parts I needed.

[GTS-t VSPEC]

Merli/Steve,

We bought 5 sets of pistons and as such they gave us a discount, so I payed about $1350 for the set, which is pretty darn good. Chat with the guy and see if he will come to the party, at least $1500.

Hope you manage to score a good deal.

See'ya:burnout:

[Steve]

Thanks heaps for that. Just one more question, if you dont mind, do you know what the bore/piston clearance is on these?

Have been told of a few horror stories of days gone by where clearances required for forged pistons result in excessive blow by and engines not lasting more than 6 months without the need for a rebuild.

I believe the stock gtr pistons are good for upto 550bhp and have a clearance of only 1 thou or there abouts, and still cost considerably less than forged aftermaket items.

Merli, if I remember right, you have been chasing gtr rods and crank for some time - is a decent example or these expensive or difficult to source? Anythings to be aware of when buying them second hand?

Paul, you said you had RB26 rods, any tips from your end regarding sourcing them? Also, will they bolt up to an RB25 crank?

Then I could just get the crank and get some RB26 rods(linished, shot peened), stock gtr pistons. Balance and blue print the lot, and it should be a reasonably tough bottom end with a lowered compression to boot.?

Hope you dont mind me asking, and thanks for your time and replies - most helpful

Cheers

Steve

[Merli]

As far as I can tell, Wiseco have off the shelf pistons and they also are able to make custom requests for customers.

Off the shelf, they stock 86mm (standard bore) and 87mm pistons. I wanted to get the 87mm pistons for two reasons:

1. Juuuuuuuust in case I have any bore damage, and it needs to be machined out a little

2. Then the engine builder is able to control how much clearance there is when putting the engine back together. If you buy the 86mm pistons, you're pretty much at the whim of what Wiseco gives you, and you have to drop it straight in.

I've been chasing RB26 rods and crank for a while because of several reasons:

1. I have nearly bought a few sets from Perth or New Zealand, but I didn't feel comfortable buying second hand bottom end parts without checking them out first, as the smallest warp would render them quite useless. So I've been waiting for a set to come up for sale in Sydney.

2. The R33 and R34 crankshafts have a larger oil pump drive than the R32 crank, and is obviously much newer as well...

If you're going to pay to get your engine stripped, and rebuilt, you might as well do it properly. Forged pistons aren't that big of a cost, and add a LOT of reliability to the engine. Forged rods aren't really that necessary unless you want to rev the tits of the car... GTRs have a redline of 8000rpm, so shotpeened, linished and cracktested RB26 rods should be good for a 9000rpm redline (make sure you upgrade your valvetrain if you want to chase these kinds of revs)

Cheers,

Andrew.

[Steve]

Thanks Andrew,

dont think I need the RB26 bottom end, just thought it might be worth a look in. Spose the thing to do is hold off as long as possible and if some decent RB26 bit become available in time go down that path. Not a biggy either way if the stock rods will hold up ok when linished and shot peened.

Your idea about the oversized pistons is a good one - doesnt cost too much for a rebore, so could just size the bore up for whatever clearence you want. - all sound pretty good.

Dont see the need to go to 9000 redline - just increase engine wear and shorten its life... with the turbo I'm fitting and a bit of headwork it should give me a decently wide powerband - enough to keep me amused for a while anyway. And I want to get the vallve springs upgraded when I do the cams - which will be after the headwork when I know what it is flowing like.

Thanks again for all your help

Steve

[GTS-t VSPEC]

Steve,

I am going the 87mm Wiseco pistons for the reasons suggested by Merli, plus they have a slightly lower compression, no need for a metal headgasket.

I will find out if those RB26 rods are still available, in case anyone is interested, but as you say buying sight unseen is a risk.

For the turbo's we are all using I don't see the need for very high revs, it will be making peak power quite early in the rev range.

See'ya:burnout:

[Steve]

GTS-t VSPEC

Thanks again, that would be great - checking out the rods, looks like I moved to adelaide just a bit too soon. do you have any idea if the RB26 rods will bolt up to the RB25 crank? this would save a bit of stuffing around, but on the other side, it would be easier to get all the prep work out of the way before pulling the motor out - reduced down time = less withdrawls.

A big thanks to you too

Cheers

Steve