Rb26Det Internals in RB25Det

[Trini.Madman]

Hey guys, im just looking for sum information.

I understand the RB26DETT internals fit into the RB25DET Series2 Block.

What i cant seem to figure out is the different Compression Ratios it ends up with?

So what i wana find out is.
If i use RB26DETT crank, rods and pistons in the RB25DET Block, whats the final compression Ratio?

If i use the RB26DETT crank & rods BUT the RB25DET Pistons, (1) will the pistons fit on the 26 rods? & (2) whats the final compression ratio with that combo?

Also, Which pistons will be stronger? The RB25DET Pistons limit the same as the RB26?

[RRRRB]

Hey guys, im just looking for sum information.

I understand the RB26DETT internals fit into the RB25DET Series2 Block.

What i cant seem to figure out is the different Compression Ratios it ends up with?

So what i wana find out is.
If i use RB26DETT crank, rods and pistons in the RB25DET Block, whats the final compression Ratio?

If i use the RB26DETT crank & rods BUT the RB25DET Pistons, (1) will the pistons fit on the 26 rods? & (2) whats the final compression ratio with that combo?

Also, Which pistons will be stronger? The RB25DET Pistons limit the same as the RB26?

The compression ratio should be very close reguardless of the internals, if there is a change it would be very slight.

The RB26 Cylinder head has a larger combustion chamber compared to the RB25 thats why the 2 engines have different compression ratios. So the compression ratio would be the same as the engine the cylinder head came from.

The pistons are not interchangeable by themselves, they will physically fit but the location of the wrist pins are different due to the stroke differences between them. The rods are interchangable but the RB26 rods are stronger.

The 26 pistons are rumored to be stronger.. I have never personally compared them.. however im sure the internet legends have got this one nailed down.

[Darius]

I can chime in on this a little bit since I'm running RB26 rods and pistons on an RB25 crank.

I agree with RRRRB's comments and can add that the RB26 rods are significantly thicker than the RB25 rods. However, I haven't heard of anybody bending rods in an RB25. The RB25 pistons are the weak link. If an RB25 blows up, it is 99% guaranteed to be the ring lands on the pistons letting go. The rings are much smaller and the ring lands are weaker than the RB26 pistons. Not only that, but the RB26 pistons come with internal cooling passages to help draw heat away from the piston via the oil provided by the squirters.

What are your power goals?

[Trini.Madman]

Power Goals?

Honestly i dont have a "number" i am working with. What wanted to do is to turbo charge my RB25DE engine. BUT i didnt wana loose the high compression on the engine. So i was hoping that if i took a 26crank, rods and pistons(8.5 compression ratio) (because they are stronger) and throw it in a RB25 block, i was hoping it would give me back the 10:1 or even more compression ratio than that.

I want to use the stock rb25det turbo unit. Going to put a decently "small" 27" x5.5" x2.5" FMIC with complete 2.5inch piping.

AND... i was thinking to put the RB26DETT intake manifold and ITBs on the RB25 head for ease of piping and the responsiveness of the ITB's.

Now idk what you all will think of the entire build. I also wanted to run a almost "instant spool" LOW boost and i just wanted enough power to have some fun with.

I already have a AEM F/IC 6 to tune with. AND i'll get a UEGO so i can basically tune it myself.

SO after all that information on my total intentions of the build. I was looking for stronger pistons with high compression ratio with stock rb25 head.
Nothing too wild like 12:1 or 13:1. but more like between 9.8:1 to about 10.5:1 CR with a block strong enough to take the 450-500HP the RB26 block takes.

( I really dont want it going BOOM on me )

**ALSO i intend to put OIL SQUIRTERS to use the pistons properly and a oil cooler (duhhh....)

[Darius]

Do you have E85 there?

[Trini.Madman]

got C16 here but i think i can run up to about 5psi on 91octane

[Yellow4g63]

Meth injection will work too.

[Darius]

I would just turbo the RB25DE and run meth injection with mild boost. It will be less expensive and easier than buying all the RB26 components and rebuilding the engine while maintaining the stock compression and responsiveness.

[Trini.Madman]

What about Oil squirters?

I will be putting an oil cooler either way.

AND! my main concern would be what is my power limit? or boost limit?
I really dont wana have a blown piston on my hands or messed up ring glands n stuff

[Darius]

If you are running meth injection on a stock RB25 turbo and have an oil cooler, your pistons should be fine without adding oil squirters. Realize that this isn't going to be as capable as an RB25DET or RB26, so that's why I asked what your power goals were. If you just want it to be super responsive on a smaller turbo, keep the RB25DE. But if you think you're going to want more top end power, you'll need to do engine work at some point. However, there is always a trade off between response and top end power.

[Trini.Madman]

Response is my MAIN goal. Any other things that comes with RESPONSE i'll take but Response.

So run the oil cooler and water meth on 5-6psi boost and i should have a reliable engine? that wont blow a piston/ring?

Thats my other main concern and why i was gona do the 26 pistons & crank

[Trini.Madman]

So i did some MORE digging. Plenty more digging. AND
Apparently, the RB26 pistons are "not stronger" than the 25 pistons...
I also figured out from multiple sites that people said the wrist pin for the rb26 pistons are ***2mm*** higher than that of the rb25
From Wikipedia now, the rb26 crank is 2mm more total stroke so i figured that would mean 1mm extra down and 1mm extra up!

So, now read that over and understand that properly.
Now if all that information is correct, and i use the RB26 Crank and Rods with RB25DET pistons, and this calculator, **http://www.boosttown.com/engine/head_ga ... ulator.php**
The Extra mm upwards shouldnt touch the head or valves of the engine and with a thicker head gasket, i'll get my 2.6L displacement, my HIGH compression engine AND MY ultimately fast spooling RB25det turbo unit on 5psi should be a sick engine with stong enough internals to give me about 300WHP?

[ANVIL]

Im highly considering rb26 crank rods and pistons in my s1 rb25. How much power can be safely made/handle on this setup?

[ANVIL]

Can someone school me on what needs to be done, what prep to take, to run stock rb26 rods/pistons in a rb25?

Whats the opinion on using someone's used rods and pistons who just wanted to upgrade? Do i need to prep anything/replace rings? Do i need the 26 crank?

I want to do this as budget friendly as possible just trying to plan for it. Planning on:

- rb26 rods
- rb26 pistons
- ACL main bearings
- ARP rod bolts
- new oem piston ring sets ?

[RRRRB]

Not much really needs to be done.. It should all bolt in.

You should replace rings and bearings, id polish up the crank and see what kinda shape the cylinders are in to determine if it needs a cleanup hone..

Make sure the rods are sized correctly and check the crank for straightness

You will likely see a little higher compression with an RB25 cylinder head as the combustion chambers are slightly smaller.

If the crank isn't collard have it done, there is no reason a properly prepped stock bottom end RB26 cant make 700whp reliably

[ANVIL]

Anyone have anything for sale to do this?

[ANVIL]

Forged rb25 cp pistons work good with stock 26 rods?

Cant decide if i wanna spend the extra for them. Or just settle for rb26 pistons.

After this block rebuild i dont want to have to tear into it ever again. But if 26 rods and pistons on a 25 crank can do 700hp id rather save the money

[RRRRB]

look at Booztd 3

He was making over 750whp on a stock internal RB26 with small cams, for quite some time now.. he hasnt been on in a while but hes proven it reliable