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Old 05-17-2006, 07:01 PM   #51
Shabib67
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^^Im also interested.
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Old 05-17-2006, 07:32 PM   #52
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On my bench;
EJ205 (stock) heads flow 236.2cfm @ 28.5Ē @.400 lift
96-99 DOHC EJ25 heads flow 231.5cfm @ 28.6Ē @.400 lift

Close but you need to see the whole chart. I have a list of things that I do not like about the 96-99 DOHC EJ25 heads.

SOHC heads have a good low, mid lift numbers and just about the same as the 96-99 DOHC high lift.

Iíve seen some very high numbers from some shops and the only way that I could get numbers up that high would be to remove the sparkplug, think shops donít do this. Or just make intake port volume too large.
On the WRX head you can do some small mods to get your CFM up and keep Port volume reasonable.

I would really like to see the whole graph, not just the high numbers; I was just looking for comparison.

Why we are on this, why not difference from cylinder number 2 and 4, or 1 and 3 exhaust.

If you do not ask questions youíll never know the answer.
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Old 05-17-2006, 07:34 PM   #53
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Quote:
Originally Posted by burnin4
which cams would you suggest for the cobb stg2 block/stg2 head p&p?
The problem is there arent any cams on the market with the correct lobe center for the 2.5L, but if you had the correct cams to produce good power and not lose much bottom end 400L and around 220deg duration @.050" has seen great numbers from my testing (on correct cam blanks).
You will see true billet steel cams available for our porting stages shortly with the correct lobe center.
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Old 05-17-2006, 08:15 PM   #54
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ahh i get ya hooper sorry mate i thought you were on about throat dimentions combustion chambers sizes and squish numbers that kinda thing
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Old 05-17-2006, 09:39 PM   #55
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Quote:
Originally Posted by djviper
ahh i get ya hooper sorry mate i thought you were on about throat dimentions combustion chambers sizes and squish numbers that kinda thing
Itís all good. (That has never come out of my mouth, to old, more like cool or no prob.)
I look at it like this,
You could ask 4 different people to drive to a geographic location, all 4 people will most likely take different routs, but the end result would be the same results.

What does this have to do with us; you could have 4 different heads, from 4 different shops, not even close on certain areas but still end up with the same number. Thatís the game were after right. NUMBERS.

The number that I am talking about is DYNO.
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Old 05-17-2006, 09:56 PM   #56
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Quote:
Originally Posted by BALISTC
I suppose lash caps were an option, but it wasnt too hard to put .01 of an inch of stellite on the tips of the valves whilst the heads were apart

Do the lash caps just sit on top of the valves or are they "glued"? I dunno if I'd want to risk having those if they are just placed on top of the valves, I already broke a shim in the head running too much anti-lag, and I went shimless buckets so I wouldnt have the same problem again...ie, no bits to float around if the antilag held the valves open again!
Sorry I missed this,
Lash caps sit on top of the valves; buckets sit on top of them. Just en ez way if the heads are together on the car. Iíve ran lash caps for 20 years, the only time I lost them was form an over rev with weak springs, NOS, and high boost (well back then high 20lbs). This was with a rocker, not like buckets.

Could you post a picture of your valves with the process that you had done? Iíd like to see how it looks. How tuff is it?
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Old 05-18-2006, 06:54 AM   #57
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No photos, the engine is together now

Applying stellite on valve stem tips is also known as hard facing. Its used in extreme duty applications, where a lot of strength and wear resistance is required IE race engines. My engine builder went with it because not only can a slight amount of clearance be made up with a stellite tip, but its incredibly strong and will never break off or wear out.

They use a plasma transfer arc process to put the stellite on the tip of the valves. Stellite is harder than stainless steel, and harder than inconel.
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Old 05-18-2006, 12:45 PM   #58
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Quote:
Originally Posted by Hopper
When you cut your valves and seats the valve will sink in the head, reducing the valve to bucket to cam clearance. The base circle on the crower with smaller base circle is at .025 smaller than stock.

Cobb does not do there own CNC porting, Mike does it.
I dont think it matters who runs the CNC, Mike at chapman etc. What matters is that the R&D is/was done in house with our hand ported heads and a superflow, spending 3+ years getting things right. Then these ports were digitized to use on the CNC and a few things were refined at this time to thicken up weak areas in the ports.. doing this we did not lose flow, gaining in other areas made up for the changes and then some.

-Jeremy.
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Old 05-18-2006, 03:42 PM   #59
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Here are some pictures of a cutaway Cobb head for development, this is how we know where to thicken up certain areas to keep the port walls strong. These pictures show the porst as they come straight off the CNC and not hand blended yet.





Here is a picture of the USDM AVCS cams that will soon be offered
True Billets the one on top is oxide coated and the bottom is bare.
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Old 05-18-2006, 03:57 PM   #60
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^^Who's the company developing the cam are is it your own cams?
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Old 05-18-2006, 04:17 PM   #61
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Quote:
Originally Posted by Shabib67
^^Who's the company developing the cam are is it your own cams?
Cobb Cams
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Old 05-18-2006, 04:29 PM   #62
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when will the cobb cams be coming out
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Old 05-18-2006, 04:32 PM   #63
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Quote:
Originally Posted by petawabit
Heads ported at DPR racing in Torrance. Dan does fantastic work and is a very knowledgable person. He still needs to add the larger valves as well
What do you think Jeremy? Dan does good work?

I think whatever you do, have them flow tested to make sure they flow evenly. You don't need a lean outlier.
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Old 05-18-2006, 04:38 PM   #64
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Quote:
Originally Posted by Jeremy@Cobb
The problem is there arent any cams on the market with the correct lobe center for the 2.5L, but if you had the correct cams to produce good power and not lose much bottom end 400L and around 220deg duration @.050" has seen great numbers from my testing (on correct cam blanks).
You will see true billet steel cams available for our porting stages shortly with the correct lobe center.
What do you the right LSA is? I agree with ya. The LSA on my cams is too narrow for forced indcution.
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Old 05-18-2006, 06:34 PM   #65
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Digitizers are just a copy machine, if you have a bad port and digitize it then cnc machine it, you still have a bad port. You cannot just port a head and flow test it, see big numbers and think youíll make big power, itís not that EZ.

Thanks Jeremy for the pictures.

I was a little surprised on the intake ports; I thought they would have looked like, the bottom of a cretin sail boat, or maybe the picture is a little deceiving?
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Old 05-18-2006, 07:16 PM   #66
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Quote:
Originally Posted by Hopper
Digitizers are just a copy machine, if you have a bad port and digitize it then cnc machine it, you still have a bad port. You cannot just port a head and flow test it, see big numbers and think youíll make big power, itís not that EZ.

Thanks Jeremy for the pictures.

I was a little surprised on the intake ports; I thought they would have looked like, the bottom of a cretin sail boat, or maybe the picture is a little deceiving?
You bring up a very good point. Starting with a good port you repeatedly get a good port.

You and I both know flow is not the only thing looked at
-flow
-intake to exhaust flow ratio
-port velocity
-The whole flow chart not just a peak number
-etc. etc.
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Old 05-19-2006, 11:04 AM   #67
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Quote:
Originally Posted by Jeremy@Cobb
Here are some pictures of a cutaway Cobb head for development, this is how we know where to thicken up certain areas to keep the port walls strong. These pictures show the porst as they come straight off the CNC and not hand blended yet.
Wow, those are some nice pics. Is this an STI head or a WRX head? There are many who believe the added quench of the WRX head on a 2.5L block is the ticket to bigger power from a 2.5. Is this your opinion also, or are you going with a re-port of the STi head?
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Old 06-19-2006, 06:59 AM   #68
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some flow data from the UK on the JDM spec c heads,

http://www.litchfieldimports.co.uk/subaru_06specc.asp

from MY03 to my06 all JDM engines (sti and spec c) use the same heads and cams.
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Old 06-19-2006, 01:00 PM   #69
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Quote:
Originally Posted by Jeremy@Cobb
I will take detailed pictures of the ports, when I get back from the Wicked Big Subaru Meet. You would be surprised what a 5 axis CNC can do along with the small bits.

Jeremy.
yup...it will blow your mind!!! I love 5-axis cnc's!!!

now if I could only afford one
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Old 06-19-2006, 01:01 PM   #70
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Quote:
Originally Posted by Jeremy@Cobb
You are exactly right.. looking at a flow chart you are comparing flow vs lift. On our subaru heads (unported or ported) after a certain lift, larger cams will not gain any power but gradually move the powerband towards the right.

-Jeremy.
thank you discharge coefficients and fluiddynamics...the bigger the bore the better the flow and less energy is lost in the flow

so long as you don't make it so big...then you lose your velocity and kill your combustion as nothing swirls/crowns when entering the cylinder...
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Old 03-18-2011, 10:31 AM   #71
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Bump this up.

It seems everyone in here is pushing way more than my goal of anywhere between 275-325wtq. Utilizing stock cams, and a new valve train(current gear has over 200k on it) is it even worth a pnp job?

I have no plans of ever shooting over the 350wtq mark. Ever.
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Old 03-18-2011, 11:01 AM   #72
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I would say no need to PnP. Others may say do a mild PnP while its out.
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Old 03-18-2011, 12:48 PM   #73
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Wow, this is an old one. A bunch has changed since this thread was started, probably the biggest thing being Chapman's company didn't make it through the recession and went out of business. It's a shame because they did really nice work.
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Old 03-18-2011, 07:23 PM   #74
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Quote:
Originally Posted by Psychoreo View Post
Bump this up.

It seems everyone in here is pushing way more than my goal of anywhere between 275-325wtq. Utilizing stock cams, and a new valve train(current gear has over 200k on it) is it even worth a pnp job?

I have no plans of ever shooting over the 350wtq mark. Ever.
You can get 350wtrq without a PnP job. That's turbo characteristic and what size turbo on your engine setup. A Simple 16G-sized will do right around there just fine.
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