[jays05]

Originally Posted by all4bspinnin

gotcha, now what kind of displacement increase is a 100mm bore? I plan on doing this...

deburred/shimmed crank (like u said), forged pistons and rods, ARP headstuds... who makes a goodrod bearing? Anything else i should be considering? So dont worry about sleeves since im shooting for around 400-450whp?

i can get rods and pistons at cost price since a good friend of the family works for a major performance distributor. Due to the "hookups" i have im pretty sure i'll be able to put this block together for less than 2500

100mm bore is a 25cc increase, you go from 2457 to 2482cc, plus or minus.

If you are looking to rev to 7500-8000 and make any power up there, you'll need to invest in head work, which could be more expensive than the stroker crank.

[all4bspinnin]

Originally Posted by jays05

100mm bore is a 25cc increase, you go from 2457 to 2482cc, plus or minus.

If you are looking to rev to 7500-8000 and make any power up there, you'll need to invest in head work, which could be more expensive than the stroker crank.

so a bit of portwork and aftermarket valvetrain?

[520]

yah youll need a valvejob and upgraded valvetrain.

clevite makes good bearings.

[jays05]

Clevite changed their rod bearings recently... Ron @ Axis stopped using them from what I read.

My head setup (in sig) worked out to be a bit less than $3k all said and done. Lots of fun, but total overkill for a 400-500whp setup. In retrospect, I miss the massive torque spike @ 5k that the stock cams gave.

[all4bspinnin]

Originally Posted by jays05

Clevite changed their rod bearings recently... Ron @ Axis stopped using them from what I read.

My head setup (in sig) worked out to be a bit less than $3k all said and done. Lots of fun, but total overkill for a 400-500whp setup. In retrospect, I miss the massive torque spike @ 5k that the stock cams gave.

looks like a pretty mean setup... does anyone else make rod bearings? I think im going to stick with the stock cams... they seem to have the best midrange, or should i go with a cam that has a little more top end... personally, i love the midrange


Here's another question... what would happen if i had that built motor installed but was running a vf39 for a month or two... mega instant spool?

[Flycaster]

Originally Posted by jays05

My head setup (in sig) worked out to be a bit less than $3k all said and done. Lots of fun, but total overkill for a 400-500whp setup. In retrospect, I miss the massive torque spike @ 5k that the stock cams gave.

I wish more people would see this and think about it. All you need [and really want] at that power level is the right turbo, supporting parts and tune. Period.

[all4bspinnin]

i guess the first step is to get my hands on a cheap EJ257 block

[PowerLabs]

Originally Posted by crystal_Imprezav

As for bore. If your going to use a new block casting stick with the stock bore of 99.5. The stock bore and hone that comes from the factory will be better than any machine shop can produce. If rebuilding a used block, go with 100 overbore and make sure they are using torque plates on the bore/hone.

Absolutely NOT true.
The stock bore has such low tolerances that Subaru produces TWO pistons for the same engine, to accomodate that.
I bought one subaru STI shortblock that had 3 regular size pistons and one slight oversize one. NEW, FROM THE FACTORY.

Perfectly fine for a street car, which is what STIs are, but don't think for one second that this is about as good as it gets. STIs are mass produced in large numbers as cheaply as possible just like any other factory car. Any machine shop should be able to do *much* better.

And, as was mentioned before, 99%+ of built motors out there run a stock crank. Crawford has spun bone stock engines to 8K with a GT35R attached to it; power drops off dramatically after 7.7K even with a big turbo, but other than that they ran fine. The current power record on a stock block is also well over 600 to the wheels; its all in the tune.

[PowerLabs]

Originally Posted by all4bspinnin

looks like a pretty mean setup... does anyone else make rod bearings? I think im going to stick with the stock cams... they seem to have the best midrange, or should i go with a cam that has a little more top end... personally, i love the midrange


Here's another question... what would happen if i had that built motor installed but was running a vf39 for a month or two... mega instant spool?

Built motors make absolutely zero power more than a stock motor. A 10thousand dollar sleeved, fully forged, counter balanced, nitrided, extra oiling holes, etc etc shortblock will make the same power your factory block makes, but burn more oil and be noisier (particularly at startup when the forged pistons are cold and haven't expanded yet).
ALSO, faced with severe detonation, that fully built 10thousand dollar engine block will be completely destroyed in much the same fashion as a factory engine.

The point of a built motor is that it will withstand more power, more reliably. Forged pistons will take a little bit of det before they go, and other forged components will take higher power levels without breaking, but the power does NOT come from building the engine, it comes from what is attached to it and how it is tuned, and similarly, reliability will only come from an engine that is tuned properly and does not detonate.

Now, answering your question, Calico, Clevite, and Cosworth all make race bearings. My forged motor ran:
Calico Bearings: These are steel, moly coated. There is a thread on NASIOC where a WRX drag car lost the wastegate hose, boost spiked well in the high 30s, low 40s of PSI, detonated the pistons and rods into small pieces, and when it was taken apart, the bearings were in perfect condition. These are the ones to get, in my opinion.
ARP Head Studs: 180thousand PSI tensile strength cro-moly steel. The best there are.
Wiseco Forged Pistons: Lightest forged pistons out there.
Factory STI head Gaskets: 3-Layer Stainless steel; Crawford uses them on 700+HP builds.
Shimmed oil pump: Bumped up my oil pressure about 15-20PSI higher.
Power Enterprises Kevlar Timing belt: I had a belt go lose before, so didn't want to take chances this time.

It ran great; 8100RPM redline at 20PSI boost. Then I did a top speed run on the car, hit 177MPH, saw 1680F EGTs and melted piston number 1 right off. The engine was completely destroyed. All the best parts in the world still won't help a crappy tune or an unforseen event

As far as the heads, again, Crawford states that they run bone stock blocks to 8K. They told me that at 7.7K there is a large drop in the powerband that mostly goes alway when the valvesprings are shimmed, making them assume that this is caused by the onset of valve float.
My next engine will be similar to my last one:
ARP head studs, Calico race bearings, Forged Pistons (probably Wiseco again), Stock gaskets, Kevlar Timing Belt (Prob. Power Enterprises again), and, this time, stiffer valve springs. The springs alone will prevent valve float. Your cams and heads won't allow much power to be made at high revs, but with a big enough turbo you can benefit from a higher redline.

[crystal_Imprezav]

The whole point of buying a new block is to know the exact bore size of the casting. As I thought most would know it is a common knowledge that if stuffing forged pistons into a new casting, you are suppose to take a look at the 'A' or 'B' markings on the pistons in the block. With those specs, you can easily call up you desired piston manufactorers and give them those numbers and have them send you the correct parts for you application. Again, still going to be a way more precise bore/hone than any shop can do.

[all4bspinnin]

Originally Posted by crystal_Imprezav

The whole point of buying a new block is to know the exact bore size of the casting. As I thought most would know it is a common knowledge that if stuffing forged pistons into a new casting, you are suppose to take a look at the 'A' or 'B' markings on the pistons in the block. With those specs, you can easily call up you desired piston manufactorers and give them those numbers and have them send you the correct parts for you application. Again, still going to be a way more precise bore/hone than any shop can do.

So your saying, i'll have to have pistons custom made for the build? I cant buy some premade to a specifc bore piston?

[modaddict]

Powerlabs has some Great points and I agree with most of it.

I do believe that the factory can bore/hone an engine better than any aftermaket machinist can. this is because the factory uses much better tooling. that's usually the bottom line.

[all4bspinnin]

i agree to, however since we arent going have the hookups with Fuji Heavy Industries... can we just have the block honed/sleeved... that would work fine for my goal..?

[Neanderthal Racing]

Originally Posted by PowerLabs

Absolutely NOT true.
The stock bore has such low tolerances that Subaru produces TWO pistons for the same engine, to accomodate that.

this is very interesting as i have never heard that before. while i'm done with all controversy with respect to my former shortblock, if true, this would explain a lot.

as far as the rest of the discussion goes, i have a stock crank in my cobb pro stage1 "big bore" 2.6L motor. do i look worried? (isfh)

[Flycaster]

Yep, the "A" and "B" cylinder sizes are true - you can see the markings right on the block. Subaru shoots for a .0004", with a supposed accepted tolerance of .0000" to .0009". The reason for this discrepancy is tool wear.

IMO, if you measure each cylinder and match the larger pistons to the larger bores, you're gonna be close enough since every piston has slight variations too.