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Old 06-07-2007, 01:28 PM   #1
womensecks
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Default hybrid 2.5 build

yo guys im a bit new on doing major upgrades to my motor so bear with me on this.

i was wondering if building a 2.5 hybrid motor (ej257 shortblock, WRX heads) will be a reliable setup?

im gonna be running it with a vf34, 565cc pinks, walbro pump, and other support mods tuned on cobb AP protuner.

will this build be as reliable as say ... a stock STi motor?

thanks for the input
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Old 06-07-2007, 01:35 PM   #2
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Stock WRX heads with the STI short block will be reliable as long as you keep the boost down. The compression is raised to over 9:1. Anyone using this combo for AutoX or track use should go with forged pistons to handle the added compression. Cracked pistons are a little bit of an argument on the boards but when they crack you are looking at a motor rebuild. Might be in 2 miles or 20K miles.

To do this build right, you will have to drop some serious coin. 1800 for the short block, 6-700 for forged pistons, 260 for a Cosworth oil pump, 150 for timing belt, since you are in there 270 for timing belt idlers/pulleys, don't forget the Subaru gaskets you will need and other bits for 300 or so. That is just the engine. It would be insane to do all this work and not go over the heads, depending on use/abuse you are looking at 250-500 in parts.

All this an I haven't even mentioned the labor.
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Old 06-07-2007, 02:17 PM   #3
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i see i see..

i also heard that there is a headgasket that can be purchase that will keep the compression close to stock, is this true?

im not planning on running super crazy boost ... im probably gonna be sticking with the VF34 for a while.

most of the other parts i already have sourced, the thing im concerned is if im ready to drop my $ on the shortblock and labor.
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Old 06-07-2007, 02:28 PM   #4
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Well the gasket you are talking about is another contested point on the boards.

I went with Subaru gaskets and forged pistons. Best to have a build that you can reproduce over and over. These thicker gaskets may crush differently from year to year or may not even be available down the road. Suby gaskets will be around a long time. Besides a 9:1 compression engine with a TD04 will make close to 300 FPT at the wheels on 93 octane and at 3000 RPM. Compression is GOOD if the pistons can take it.

A set of CP pistons with rings/piston pins is around $650. If you are going to invest that much into a hybrid build that is nothing. It is the head work that will be the wild card. I am having mine rebuilt by a Suby tech locally.
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Old 06-07-2007, 03:03 PM   #5
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That will be a reliable setup.

I wouldn't waste the money on forged pistons if you are running stock wrx heads. The wrx cams are a huge hinderance in these builds. Power falls dead flat after 4500-5k. Take the money for pistons and spend it on cams, no vf34 setup is going to max out the reliabilty of OEM pistons.
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Old 06-07-2007, 03:42 PM   #6
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Well we have seen 3 cracked piston sets in AZ in recent months. My first statement was it would be reliable if they keep the boost down. Heads can be replaced with ease. Dropping in new pistons later on will take a lot of doing. I still say put them in now and forget about it. Why go through the pain of 2 break in periods.
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Old 06-07-2007, 03:58 PM   #7
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Out of all of the stock piston hybrids I have done for people, I have never seen a cracked piston on a block w/comparibly sized turbo. Hell, my stock internal hybrid saw some boost. My DD 93 map was set for 23.5 psi on a 30r. It ran fine until the car got wrecked .

It is 90% in the tune and 10% assembly.

For a vf34, I honestly wouldn't bother. The potential headaches of a forged motor, outway the need for it in this case. If you are going bigger down the road, or have extra cash for them it won't be a bad idea. It is just in no way a neccessity here.

Extra funds are better spent on cams. I don't see the point in a build that will make 310whp @ 3000rpm, but then 200whp at redline. I have learned this the hard way with these hybrids. Bite the bullet, do larger cams the first time around. :shrugs:
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Old 06-07-2007, 04:23 PM   #8
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Smaller turbo + high compression = massive spool. Quick spool and low end torque.

Power band will be 2500-5500 instead of 3500-6500. Lower RPM = less wear on the power train. I want my power early and I want it strong. Straight line 135+ MPH performance is great if you are running a competition car on the track, but Rally/AutoX/club sport racing needs it down low.

I guess the best advice DrinkAV8 or myself could offer is this. Question what you really want to do with the car in the next 3-5 years. Both of us have differing opinions each back up with our choices for our builds. I will also add that my high compression 2.5L is stuck with AZ/Cali gas which means detonation is a huge risk due to ambient air tems reaching 110-120 degrees.

This is not my car, but this is a stage 2 WRX with a 2.5L swap. He is not running forged pistons, but you can see the torque curve and the power band dropping off around 5500. This is with the stock TD04. To me that is 100x more desirable than a huge snail spooling late.


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Old 06-08-2007, 05:03 AM   #9
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you guys both seem to really know what you are talking about and have some different views.

but yeah, im not planning on putting a big turbo on this motor ... if anything, the biggest ill go is maybe a td06-18g or maybe 20g? but even that is a far stretch because the vf34 is plenty power for what i like my car to do at the moment so i dont think i will really need forged pistons.

basically my hybrid motor is going to be built w/ the following:

ej257 shortblock
JDM ver8 spec C manifold ( no TGVs )
JDM ver8 STi TMIC

wrx heads
264 crower cams
titanium valve/spring retainers

CUSCO oil catch can
VF34 w/ 565ccPINKS
walbro255LPH

now im wondering what intake setup would be best? stock intake box? cold air intake? short ram intake?

thanks again guys, you ROCK
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Old 06-08-2007, 10:58 AM   #10
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I do not build cars for friends/profit. My knowlege comes from tracking the car and breaking things 8x faster than most folks.

Reliability and Predicatability > minimum cost and max horse power. That being said, the less I spend the more I can race.

Unless you have already bought it, the JDM intake manifold is useless. While my car was pulled apart, we simply removed the TVGs and did some light PnP.

The stock air box is good to about 400 CHP, so your question is based off of what are your plans. I run a stock airbox AND turbo inlet. I tangle with M3s and STIs on the track all the time.

You might want to budget the cost of new exhaust valves. Mine were shot to hell. You may as well replace anything burnt and send the heads out for a PnP to a decent machine shop.

Anything smaller than an 18G will exhibit the same type of power curve like I posted above. The larger you go, the less it drops off at the end BUT the later it spools. When I upgrade I will probably go with a VF22 as they are "cheap" to pick up and will spool well with a 2.5L high compression. I will also mod my injectors instead of paying for a new set of pinks. They will have better flow and be a heck of alot cheaper.
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Old 06-08-2007, 01:54 PM   #11
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yeah i definitely see what you are talking about..

overall im realistically gonna be within the 350+ range ... but probably sub 400hp range.

the manifold i already have from a buddy of mine, so im not gonna complain with that.

i currently have the option of all 3 intakes, either CAI, short ram, or STOCK so im wondering what will be best w/ the VF34 setup.

as said before, im more of a reliability freak as well. i have heard about getting the heads PnP'd ... so i may look into that as well.

so basically ... a hybrid can be successful as long as you know where youre taking it .. i guess this ties back into the 10% build 90% tune deal
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Old 06-10-2007, 02:08 AM   #12
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Have you ever thought to get a set of used STi heads to mate up to the new short block, or locating a long block? Or even going with a JDM set of heads?
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Old 06-10-2007, 03:57 AM   #13
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Quote:
Originally Posted by DrinkAV8 View Post
Out of all of the stock piston hybrids I have done for people, I have never seen a cracked piston on a block w/comparibly sized turbo. Hell, my stock internal hybrid saw some boost. My DD 93 map was set for 23.5 psi on a 30r. It ran fine until the car got wrecked .

It is 90% in the tune and 10% assembly.

For a vf34, I honestly wouldn't bother. The potential headaches of a forged motor, outway the need for it in this case. If you are going bigger down the road, or have extra cash for them it won't be a bad idea. It is just in no way a neccessity here.

Extra funds are better spent on cams. I don't see the point in a build that will make 310whp @ 3000rpm, but then 200whp at redline. I have learned this the hard way with these hybrids. Bite the bullet, do larger cams the first time around. :shrugs:
Best post on this page. A under sized turbo on ej257 block will spool fast but runs out of power fast. I mean really fast. In my oppinion they suck to drive. on/off on/off.

The stock ej257 with WRX heads and STI head gaskets will net you about 8.7:1 compression and is good for lot of boost. Keep it under 25psi and you won't have to worry about it. Yes the WRX cams suck for the ej257 but unless your turbo can feed it it won't matter. On a vf** stock cams are fine. If you put a real turbo on there get cams and you wont regret it. At the power levels you will be at you will never have to worry about the block.

I would say the most important part of the build is tuning. If it is tuned it will last a very very long time. The stock pistons do not just crack! I have seen lots and lots of hybrids and the only ones that fail are the ones that aren't tuned correctly.
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Old 06-10-2007, 04:03 AM   #14
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Quote:
Originally Posted by overlord View Post
Have you ever thought to get a set of used STi heads to mate up to the new short block, or locating a long block? Or even going with a JDM set of heads?
To make USDM STI heads work with a USDM WRX you need to drill and tap a hole for the cam sensor. For this you gain a slightly lower compression and a slightly better cam profile. But the cost of STI heads is generally expensive. For that price you could get aftermarket cams and be much happier with the result. As for JDM heads you would keep you higher compression and get a slightly better cam profile. But again I feel the cost out weighs the means. Besides higher compression is great. Just my oppinion.
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Old 06-10-2007, 05:28 PM   #15
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Quote:
Originally Posted by Brydon View Post
To make USDM STI heads work with a USDM WRX you need to drill and tap a hole for the cam sensor. For this you gain a slightly lower compression and a slightly better cam profile. But the cost of STI heads is generally expensive. For that price you could get aftermarket cams and be much happier with the result. As for JDM heads you would keep you higher compression and get a slightly better cam profile. But again I feel the cost out weighs the means. Besides higher compression is great. Just my oppinion.
Hybrids are always scary. I would always stick with the head and block combo that Subaru designed.

The cam sensor is an easy add on, and as far as cost goes you could get a set of STi heads for 1k, That way you wouldn't need any cams, no head work etc. Then sell the old WRX heads and make up some of the cost.

I am doing the STi longblock swap, much better than these hybrids. Then if you eventually want to use AVCS you can use it.
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Old 06-11-2007, 01:40 PM   #16
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OK guys, I may be running a TD04, but the OP has a VF34. Not exactly earth shattering, but not exactly a tiny turbo either.
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Old 06-11-2007, 02:42 PM   #17
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Default hybryd

in the engine ej22 i can use only the block to built a engine of 1.8 on a sub impreza 94 awd, i have a damage block and i have the rest, intake etc, i can replace the block for the block ej22, and add turbo of 8 lbs?
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Old 06-11-2007, 02:54 PM   #18
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Default hybrid swap

Ok
I have done this swap on my previous 02 wrx. I put a sti block with wrx heads. cometic heads gasket, vf39 stock wrx heads, air intake, sti pinks, gm boost solenoid with the restrictor pill removed, hex bellmouth downpipe, perrin headers and a acessport.

The car was very quick. But if I had it to do over again. I would of PnP my heads and put bigger cams in it. Your heads can flow the same and the non avcs cams are alot cheaper.

NOTE* You need to run a oil line to on of the two heads from the extra oil port in the middle of the ej257 block. I learn this the hard way. The added pressure blew my cam seals twice until I uncapped it and ran a line to the valve cover.
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Old 06-11-2007, 04:09 PM   #19
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thanks again all for the input.

when my block is apart im thinkin of doin a PnP since it's already off. as for cams, crower 264s will fill that in.

looks like im gonna follow through with it... longblock isnt very price reasonable at the moment and plus i dont care much for AVCS.
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Old 06-11-2007, 04:30 PM   #20
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A complete set of STi heads sold yesterday on ebay for less than 500.00,
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=009&sspagename=STRK%3AME WA%3AIT&viewitem=&item=190119610900&rd=1,1

Tell me that is not a reasonable price. The last I checked the cams were 800+ alone, with the spring kit, PnP, etc you will be spending much more than it would cost for STi heads.

In any case good luck with the build, I am curious to see what you will put down.

Last edited by overlord; 06-11-2007 at 04:31 PM. Reason: spelling
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Old 06-12-2007, 01:19 PM   #21
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good information everyone...you have opened my eyes to what i want to do for my motor.
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Old 06-12-2007, 09:44 PM   #22
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I have a vw van with a 02 wrx motor in it.I cooked the 2.0wrx motor,so I bought a ej257 short block.I am using the ej207 heads.What head gaskets should I use,and what other items do I need to watch for?I will be running the stock turbo,and stock boost.
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Old 06-14-2007, 04:47 PM   #23
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now i'm planning on a 20g setup for my future hybrid plans. Lately i've been reading on how much of a good idea replacing the cams are and valve springs etc. In doing that obviously you're looking for more power, and in saying that i would think replacing the bearings would be an equally good idea. I've seen a lot of posts with spun bearings, even after hybrid builds. Thats holding me back from getting the cams. am i wrong? would the stock block internals be ok for say 22-25 psi with cams?
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Old 06-17-2007, 04:24 PM   #24
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a nationwide website that people look at 24 hours a day and nobody's answered my question. Someone answer me now.
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Old 06-17-2007, 05:19 PM   #25
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Honestly your not gonna get much of an answer by being rude. But yes if you have the money then take the block apart and put new bearings in it and if you have the money right now do the cams and valves but for that price you might as well buy the sti heads and have the avcs. However its kindof hard to convert it. But its all about the money honestly me myself I just bought the sti block ported and poilished the wrx heads 660cc injectors, hks 3in downpipe,catless up, external wastegate, ported stock turbo, boost controler, lc1 and enginuity. I would of put forged pistons and ripped apart the block but im out of money at this point lol. I needed my car and couldnt wait that long and i figure it blows it blows thats when ill rip it apart and dothe cams and pistons ect.
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