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Discussion Starter #1 (Edited)
Engine builders/ machinists could I get a some recommendations or thoughts to my build. My builder is a head Subaru tech at a dealer but rebuilds his sti motors in his sand rails every season and also gets recommendations and tech support from his friend John at Outfront Motorsports known in the sandrail industry to use the Subaru motors. I just dropped my block and whole rotating assembly to my machinist John G. Edwards of Costa Mesa R & D who has experience with Subaru boxer motors. Since I spun a rod bearing, I've been down a couple months. I cannot afford to have multiple builds and need this build to have longevity and reliability. I've been doing alot of research, reading forum threads, talking to different manufacturer's tech support, talking to different engine builders and machinists.

Stock sleeves:
So far I have debated on sleeving but after talking to Cosworth's tech support, decided not to with the track record of sleeving and again with the reconfirmation of this with this thread.

Clearances and crank modifications:
After talking to CP tech support they recommend P/W clearance .003" - .0035". My builder recommends having a .001" rod journal to bearing clearance so I'll be having the machinist check rod clearance before and turn the crank to achieve this. He says taking .001" clearance in the rod journal has fixed the spun rod bearing failures (my machinist concurs with this mod). I am debating on nitride treating the crankshaft. Is this worth while? I have to let the machinist know tomorrow if I want this done.

The way they drive their sandrails sounds way more brutal than an autox session, such as full on 90 degree hand brake turns then full throttle out of it, plus the load that these motors are taking with the paddle wheels and steep grades uphill, with desert conditions at Glamis, not to mention lots of sand.

Addressing oiling issues:

Stock STI oil pickup shortcomings. I'm trying to source the s204 oil pickup, possibly modifying the stock pickup or just get the new Moroso oil pan with new pickup.

My machinist recommended chamfering the oiling holes on the STI crank.
I had the CP pistons skirts and the Cosworth rod and main bearings dry lubricant coated by Polydyn Coatings. Polydyn says it adds .0005" to the skirt.
I bought the 08 sti 11mm oil pump and the jdm 12mm oil pump. Would it be better to port the oil passages and inlet of the 12mm or just run the 11mm with either pump shimmed?
should I port the oil filter inlet on the block?


Driving uses: daily driver, haven't tracked, or drag raced, some spirited canyon driving, but may track in the future
HP expectations: 450-500 whp, the goal is to widen the power band using the new turbo with upgraded cams and valve springs.

Turbo setup: jdm twinscroll headers, up pipe, AVO ts downpipe, vf36 now but will replace with AVO's soon to be released gt3076r twinscroll replacement for jdm twinscroll turbo location/setup.

EM: Hydra 2.5

Build Parts:

used but good condition sti short block casing halves
New STI crankshaft
Manley Turbo Tuff I beam rods
CP Pistons 100mm pistons (crowns ceramic coated and skirts dry lubricant coated by Polydyn coatings)
Cosworth std sized rod and main bearings (also dry lubricant coated)
Cosworth timing belt guide
Cosworth std size head gaskets
ARP head studs
ATI Harmonic balancer main pulley
08 sti 11mm oil pump and jdm 12mm oil pump
Gates blue racing Kevlar reinforced timing belt, accessory belt, and alternator belt
APS side feed fuel rail kit
New oem water pump
New oem oil cooler
Subaru gasket rebuild kit
New STI clutch plate
" " flywheel
" " clutch disc
" " throw out, pilot bearing
New idler pulley
timing belt tensioner?

other possible parts:

272 BC cams, Supertech dual valve springs, retainers
Moroso oil pan, or s204 oil pickup.
 

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He says taking .001" clearance in the rod journal has fixed the spun rod bearing failures (my machinist concurs with this mod).
proper clearance is important. so is oil pressure; 10 psi for every 1000 rpm.

I am debating on nitride treating the crankshaft. Is this worth while? I have to let the machinist know tomorrow if I want this done.
save your money

Stock STI oil pickup shortcomings. I'm trying to source the s204 oil pickup, possibly modifying the stock pickup or just get the new Moroso oil pan with new pickup.
i'm still deciding on one of the high tech oil pans. we're using the stock pickup.

My machinist recommended chamfering the oiling holes on the STI crank.
absolutely not. leave the stock crank alone.

I bought the 08 sti 11mm oil pump and the jdm 12mm oil pump. Would it be better to port the oil passages and inlet of the 12mm or just run the 11mm with either pump shimmed?
should I port the oil filter inlet on the block?
i'd leave the block alone. keep and shim the 08 pump. ditch the 12mm.

Build Parts:

used but good condition sti short block casing halves
New STI crankshaft
Manley Turbo Tuff I beam rods
CP Pistons 100mm pistons (crowns ceramic coated and skirts dry lubricant coated by Polydyn coatings)
Cosworth std sized rod and main bearings (also dry lubricant coated)
Cosworth timing belt guide
Cosworth std size head gaskets
the cosworth timing belt guide is unnecessary. phil just had a total catastrophic engine failure with cosworth head gaskets and he won't use them again on his car. the stock head gasket is the way to go.

if you are going to do anything with the timing belt, get an "sti" kevlar belt. stis come stock with the wrx belt, btw.

ARP head studs
ATI Harmonic balancer main pulley
08 sti 11mm oil pump and jdm 12mm oil pump
Gates blue racing Kevlar reinforced timing belt, accessory belt, and alternator belt
APS side feed fuel rail kit
New oem water pump
New oem oil cooler
Subaru gasket rebuild kit
New STI clutch plate
" " flywheel
" " clutch disc
" " throw out, pilot bearing
...not with the power level youre shooting for. the stock clutch will not handle it. go get an act or rps 6 puck. replace the oem flywheel with an oem flywheel if it needs it.

good luck with your build, calisti!
 

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Discussion Starter #3
Thanks, in regard to chamfering the oiling holes on the crank I called the machinist right away to delete this part. I was taken back by your response:
absolutely not. leave the stock crank alone.
Thanks for saving me some $$ on having the crank nitrided. I really don't want to have any issues.
What about the Cosworth head gaskets? Was the failure really due to using them or where there other variables?
 

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Discussion Starter #4 (Edited)
phil just had a total catastrophic engine failure with cosworth head gaskets and he won't use them again on his car. the stock head gasket is the way to go.
I just got off the phone with Eric, an engineer at Cosworth. First I asked if their gaskets were made by Cometic. He says they are not and they are made by themselves. As far as the Cosworth head gaskets are concerned, they have never had a reported failure. After reading that some coatings on the steel gaskets can get scuffed off, I asked him specifically if this were to happen and he says that what people with supposed gasket failures don't take into consideration is that it is critical that the mating surfaces be absolutely be flat. He went on to say that don't trust anyone when it comes to double checking clearances and tolerances. If that was the case, he says car manufacturers such as Toyota, Honda, Nissan would not be using the nitrile rubber coatings on their oem gaskets. I asked if it that was used in the factory Subaru gaskets and he said not on the entire surface, just certain areas. He also said that the machine shops must have the proper tooling to achieve this. So I asked what kind of info I would need to double check with the machine shop. He says the RA (roughness average) needs to be 20 - 30 or better and to have them double check for mating surface flatness.

I also called AR Fabrication regarding the new nuts used on the latest ARP head stud bolts. They said that ARP recommends to torque to 85 ft lbs and then after a break in to re torque again to the same. In their builds they will pull the motor to re torque. But AR Fabrication says to torque to 95 ft lbs where most people will not pay to pull the motor again for the re torquing of the head studs.

I also called ARP tech support to confirm what part number has the new larger nuts and they confirmed that what I have is the right number which is 260-4701. I also asked about torquing the studs to 95 ft lbs and he doesn't recommend doing that. AR Fabrication has a friend working at ARP and also has real world experience with Subaru engine building so I would lean more into his recommendations.


I'm a consumer, not an engine builder, but I'm also the main person most concerned with the build because I want longevity and can't afford multiple engine builds. I don't mean to micro manage my build but after what Eric at Cosworth says to "not trust anyone" and double, triple check flatness and clearances, then I do mean to micromanage my build. A perfect example to this is when I contacted tech support at CP Pistons a day before and got ring gap numbers of 19 for the top ring and 24 for the second when I gave the pressures the turbo I'll be using can be between 24-30 psi. On a gut feeling, I called them again, this time talked to Mike. I told him the numbers the gave me on the last inquiry and asked who gave me those numbers. They were too tight for my application. I couldn't recall but he recalculated them and gave me 25 thousands for the 1st ring and 28 thousands for the 2nd and .15 for the oiling. He says with the tighter gap numbers, I may have had a risk of seizing the piston in the cylinder when the piston expands due to longer heat cycles. He also said that in the honing process due to the top ring's hardness, the cylinders need to have a rough hone. So I had my machinist call Mike to confirm what grit honing stones to use for this hone. So this just tells me to not assume everyone is on the same page as far as synchronizing proper required specs and procedures using their particular product.
 

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Best of luck with your build.

My build (GF8 swap) will come in due time so I'll definitely keep and eye on this thread.
 

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Discussion Starter #6
Since I have everything at the machine shop right now, I need to ask them to check the alignment of the block halves with the crank in to see if I need an align hone. I didn't discuss that when I was there. Would it also be beneficial to use ARP main studs? The condition of the mains visually had no damage but I might as well have him check since it's there.
 

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Sound to me like you're doing exactly what a smart enthusiast should do: ask questions, take nothing for granted, and then ask more questions. If more guys on this board would follow your path, there would be far fewer threads about "broken motors." :tup:
 

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Discussion Starter #8
Sound to me like you're doing exactly what a smart enthusiast should do: ask questions, take nothing for granted, and then ask more questions. If more guys on this board would follow your path, there would be far fewer threads about "broken motors." :tup:
Thanks, it's just I can't afford to do this again for awhile.
 

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Have you decided on your P/W clearance? Are you going for the low end (0.003") or the high end (0.0035)?

At 0.003" do you think you will have a lot of piston slap on warmup?

Looks like a very nice build. Will be interesting to see how it turns out.
 

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Have you decided on your P/W clearance? Are you going for the low end (0.003") or the high end (0.0035)?...
There has been a lot of very interesting discussion about this subject over in the built motor section of NASIOC. FWIW, .003' is not low, nor is .0035" high.
 

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Have you decided on your P/W clearance? Are you going for the low end (0.003") or the high end (0.0035)?

At 0.003" do you think you will have a lot of piston slap on warmup?

Looks like a very nice build. Will be interesting to see how it turns out.
im at .0045" and its not that bad on warmup. sure its not silent, but its still quieter than a diesel! :lol:
 

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There has been a lot of very interesting discussion about this subject over in the built motor section of NASIOC. FWIW, .003' is not low, nor is .0035" high.
Yea, I've read that thread as well, i was stating in reference to the P/W clearances he was using, he stated in his first post he would be between 0.003 or 0.0035 as per CP's recomendation. Hence they high and low comments.
 

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Gotcha - I just didn't want some others a little less conversant in this to be confused. The community is learning more about the necessary P-SW clearances with every motor, and the bottom line is we're finding out that the clearance can be taken down significantly tighter than first thought, provided the application and final set-up allow it.
 

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Sorry to take this somewhat off topic, but out of curiosity, in your opinion, what is the "real" low end per se for PTW clearance with forged pistons and a moderate turbo, such as a GT30r or Dom 3? I didn't believe their was ever a consensus among people on nasioc (although its been quite a while since I read that thread, perhapse I missed it).
 

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Discussion Starter #15
Just ordered the BC 272 cams and Supertech dual valve spring kit with ti retainers and alloy seats. I'm not doing any pp or replacing the valves but the machine shop will do a 3 angle valve job.
 

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Jeff Sponaugle opined you should be safe with .0022" with 2618 forged pistons, at or under 400whp, provided the car is not tracked. It's just so damn dependent on use and set-up. Heat is the key...and NOS changes everything.

Personally, I think .0025" is a better (safer) number for the true "lowest end."
 

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I also called AR Fabrication regarding the new nuts used on the latest ARP head stud bolts. They said that ARP recommends to torque to 85 ft lbs and then after a break in to re torque again to the same. In their builds they will pull the motor to re torque. But AR Fabrication says to torque to 95 ft lbs where most people will not pay to pull the motor again for the re torquing of the head studs.

I also called ARP tech support to confirm what part number has the new larger nuts and they confirmed that what I have is the right number which is 260-4701. I also asked about torquing the studs to 95 ft lbs and he doesn't recommend doing that. AR Fabrication has a friend working at ARP and also has real world experience with Subaru engine building so I would lean more into his recommendations.
I had sent an email to ARP about the re-torque after break in for the head studs and they told me it was not necessary. I cant find the email now though. I thought I got a concrete answer from ARP on this, but if AR Fab is saying that ARP is telling them to re-torque after break in, now I dont know what to think again.
 

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Discussion Starter #18
just got my BC 272 cams and Supertech valve spring kit. Now should I replace the valves? What kind of valve job should I be getting? 3 angle, dual radius...
 

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Discussion Starter #19 (Edited)
just got my BC 272 cams and Supertech valve spring kit. Now should I replace the valves? What kind of valve job should I be getting? 3 angle, dual radius...
I took the four 2.5mm allen screws out of the side of both the intake cams. This unblocks the oiling holes to the cams to enable avcs. I thought I wouldn't leave it to chance to have the machine shop forget to do this. BTW, CP recommended between .003" and .0035". I decided to do the .003" p/w clearance since some of the coating will wear off so that should end up somewhere within the range.
 

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wow theres alot of information here...cant wait to read more!

more people should go about building stuff this way instead of just throwing parts in without doing their homework congrats on that!
 
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