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Old 07-28-2014, 11:23 PM   #1
V8 Sonoma GT
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Default 2.5 with 2.0 heads hybrid build

I know there are a million threads, so thats why searching through them for my exact scenario is about impossible.

I bought a "supposed assembled" 2.0 SB off some "supposed Subu tech". Then I assembled the rest of the motor, buying all Subu parts, and had heads milled/pressure tested.

Went 300 miles, wrist pin slid out, broke piston, gashed the **** out of cylinder wall.

Now I have a line on a 2.5 with STI internals, see http://denver.craigslist.org/pts/4538485106.html

It was assembled by a known/trusted builder.

I know I would have to get all the gaskets, and tuning hardware (how much?) but what else am I looking at needing thats not a fit from a 2.0?

I would like to consider a VF39 or comparable turbo if I can keep the costs low enough...?
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Old 07-29-2014, 07:25 AM   #2
worker0813
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If in fact you do go with that block, do you plan to use your old 2.0 heads? If so, you will want to look into having them cnc chambered and matched to the 2.5. Issues with overlap will occur and cause problems.
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Old 07-29-2014, 11:49 AM   #3
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Pull those pistons out, bore/hone for JE hybrid pistons to drop the cr. Heads don't need cnc. Hand flared works just fine for improved flow into and out of the cylinders.
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Old 07-29-2014, 12:09 PM   #4
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Quote:
Originally Posted by FuJi K View Post
Pull those pistons out, bore/hone for JE hybrid pistons to drop the cr. Heads don't need cnc. Hand flared works just fine for improved flow into and out of the cylinders.
When you say "hand flared" do you mean just removing the sharp edge at a 45 with a die grinder?
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Old 07-29-2014, 12:17 PM   #5
worker0813
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oh...I was just assuming you wanted to do it proper the first time....I guess everyone is not as picky as me LOL. I just like to make sure al cylinders are exactly the same and I have seen the edges left by hand chambering ignite the same way as if nothing is done. Just boils down to how particular you are.
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Old 07-29-2014, 12:24 PM   #6
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You can be as picky as you want to be depending on skill level with a grinder. Check this out

http://forums.nasioc.com/forums/show....php?t=2355816
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Old 07-29-2014, 08:08 PM   #7
worker0813
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Very nice..... That dude has skills lol
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Old 07-29-2014, 08:38 PM   #8
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Quote:
Originally Posted by worker0813 View Post
If in fact you do go with that block, do you plan to use your old 2.0 heads? If so, you will want to look into having them cnc chambered and matched to the 2.5. Issues with overlap will occur and cause problems.
the pistons do have some valve relief to them(from what i remember), is that not sufficient? What exactly needs to be machined? (i used to be a machinist)

are there any other things that will not work directly from the 2.0 motor going onto the 2.5?
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Old 07-29-2014, 08:45 PM   #9
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Old 07-29-2014, 08:52 PM   #10
FuJi K
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Quote:
Originally Posted by beef View Post

When you say "hand flared" do you mean just removing the sharp edge at a 45 with a die grinder?
With the right carbide bit, flare it to 97mm, then round off the edge. Final width will be about 99mm across.


Last edited by FuJi K; 07-31-2014 at 09:23 AM.
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Old 07-29-2014, 09:00 PM   #11
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so let me take this opportunity to tell everyone my goals.

spend less than $2500, which is what i could do a NEW sb with gaskets...

im already $4500 into this now broken again motor

so $1200 on sb, $500 for CNC heads, $300ish for gaskets, tuning hardware...? Tuning? VF39 (down the road)??
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Old 08-03-2014, 10:01 AM   #12
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That may be possible if you buy all used parts and get a really good deal.
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Old 08-03-2014, 11:20 AM   #13
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Quote:
Originally Posted by worker0813 View Post
oh...I was just assuming you wanted to do it proper the first time....I guess everyone is not as picky as me LOL. I just like to make sure al cylinders are exactly the same and I have seen the edges left by hand chambering ignite the same way as if nothing is done. Just boils down to how particular you are.
Have you ran both chamber matched and non-chamber matched heads on a hybrid or are you just regurgitating the theories of others?

I've run a multitude of hydrid combos and between the last two, one with UN-matched heads and ones with full cnc jobs, I saw now difference in knock sensitivity at all and they both made decent power.

Fuji knows his ****, Micah aka HomemadeWrx knows his ****, I've been building these things since 2004 so I think I know small amounts of ****. With that being said, there is more than one way to skin a cat and if they achieve the same results, one is not more right than the others.
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Old 08-05-2014, 09:39 AM   #14
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Yeah from all my research and the first hand experiences of others that I have run across it seems that both set-ups can be reliable if done right and tuned by someone that knows what they're doing.

I chose to go the chamber matching by hand route because I was confident I could get them right or darn close and I wanted to run 4032 pistons not hybrid pistons and or thick headgasket. Now my car is still in the build stage so maybe I don't have ground to stand on here, but my heads came out great haha...

OP I think you could stay in budget, but I would probably be leaning towards the hybrid piston route if I were you. For around the same $500 dollars that the CNC work is going to cost you to chamber match the cylinders, you can get JE hybrid pistons and have the peace of mind of forged pistons and eliminate the "weak" STI pistons.

Like Fuji said, hone and drop in JE's. He technically said bore/hone but as far as I know JE only makes 99.5mm bore hybrid pistons so maybe just a small typo on his part. All you should need is a good hone job on the cylinders and you can drop in these pistons.

https://www.flatironstuning.com/p-22...j20-heads.aspx

With that set-up of forged pistons and stock S20 WRX heads you will be able to push 300-400whp with supporting mods and a good tune. There are guys making well into the 300's whp and wtq on a VF39 and E85 with the exact setup you would have.

As far as the budget is concerned it really depends on the price of the shortblock you got and if you are handy enough to rip it apart and drop pistons in after a good hone job from the machinist. If you are you will save a lot of money. Lets say for example sake $1200 SB, $600 pistons, used VF39 $350, tune $400, machine shop hone $200. Thats $2750 if you can do all the other work on your own. Prices are more reference than exact but you get what I'm saying.

That being said, that price can balloon quickly. For starters while you have the block apart I would do bearings and check clearances. Others will say if the block is split you're dumb not to do rods.....etc.

Either way good luck and enjoy the build.

Last edited by 00rs-jshol; 08-05-2014 at 09:50 AM.
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Old 08-05-2014, 02:01 PM   #15
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Nice answer...... Makes a lot of sense...
Let me re phrase what I said...
I personally worry too much and have OCD. I know without a doubt that my skills are not up to par to attempt to do this by hand. Even if I could, I would worry constantly that I didn't get it right ..lol...So if you can do this by hand, I say do it and save some money to put toward another area.
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Old 08-20-2014, 11:28 PM   #16
Prorex1911
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I am currently in the process of the same build. Going on 3yrs now... But that's another time.. I recently heard this hybrid create too much pressure and blow head gaskets or bend valves. Any thoughts or knowledge of this? Or is that only if not matched?

I hope your build goes well, not like mine taking forever. ��
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Old 08-21-2014, 03:57 AM   #17
kellygnsd
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Of all my builds , the hybrid build with un-modified chambers lasted longer than any if the rest. 400/375 for about 45k miles and the only reason that came to an end was due to a fire caused by a power steering line failure.
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Old 08-21-2014, 07:30 AM   #18
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I really wish people would get off the "heads need cc chambers matched" bandwagon. That's the biggest pile of horse**** on this site. I think that got started when a shop owner bought a cnc machine and needed to pay for it by spreading misinformation about hybrid engines and why they tuned like **** back when people first started building them.

Back then it was either drop 400+ to machine out combustion chambers to 57cc vs 100 bucks extra to order custom dish pistons. You wouldn't believe the sheeple that bought into that notion and dropped 400 bucks on machining. Since JE started offering the hybrid pistons you don't need to pay the extra 100 bucks for custom dish pistons, they are offered at regular price right off the shelf.

You always won't the smallest combustion chamber possible for numerous reasons other than compression ratio.
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