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Old 12-02-2015, 02:30 PM   #1
4eat05
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Default v7 ej207 block us ej205 heads compression?

Hello, Nasioc, I am hoping the geniuses/gurus on here can help me with some possible hybrid build questions.

To start, I have a 2005 Wrx sedan with stock non-avcs Ej205 longblock, stock 4eat and intake, turbo inlet, tmic hoses, uppipe, downpipe, Accessport and stage 2 tune. I am about to hit 150k miles and am starting to plan my "rebuild" but have a few things holding me back right now.

I want to retain my 4eat and a usdm ecu for inspection purposes. Im not that concerned with adding avcs right now. I might look into doing this at a much later point using a usdm 06-07 4eat Wrx ecu, but right now I am just focused on a fresh block and inspected/clean/possibly rebuilt to oem spec ej205 heads.

-I know I could buy a cheap used usdm ej205 block and heads and have them rebuilt to oem specs. Would be fine, let me keep my 4eat and usdm ecu.

-Or, even better IMO, I could buy a brand new ej205 short block straight from Subaru and have my ej205 heads inspected/cleaned/possibly rebuilt to oem spec. Would be better and let me keep my 4eat and usdm ecu.

-OR EVEN BETTER I could track down a brand new v7 ej207 short block and add my inspected/cleaned/possibly rebuilt to oem spec ej205 heads. Would be AWESOME and should allow me to keep my 4eat and usdm ecu. But I have some questions about this one.

What would the compression be using oem v7 ej207 shortblock and oem usdm ej205 heads? Will I have problems with pistons hitting valves due to different piston and combustion chamber designs and volumes? Im sure I will need a new tune but I would like to know the compression and volume difference before I jump in.

I REALLY want the better block, crank, rods and pistons of the v7 ej207 but want to keep my ej205 heads, so please no "whats the point w/o the heads" or "might as well go ej25x" comments. If your reply doesnt apply to ej207 block ej205 heads safe your time by not posting.

Thanks everybody!
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Old 12-02-2015, 03:14 PM   #2
ToneWrx02
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What?

You will gain NOTHING from any sort of building. Why do you want a ej207 block and ej205 heads?

The entire reason why the ej207 is a amazing engine is because of the heads.

If you wamt the easiest thing, get a spare ej205 block, build it with sti rods, manley piston or whatever you want, acl bearing, and call it a day.
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Old 12-02-2015, 04:42 PM   #3
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Yes I know the ej207 heads flow more and thats why most people want to do an ej207 swap, but MY favorite thing about the ej207 is the block, crank, rods, pistons, which is all I want to do right now.
I dont want to do a full ej207 swap, jdm ej205 swap or ej255 swap. All I really want is to refresh my ej205 and figured I might as well get the block, crank, rods and pistons that I want (ej207) while I am at it. I know there will be no power gained without the ej207 avcs heads, but I dont care, I just want the strong, smooth reliable block. I *might* look into better flowing avcs heads at a later point, but not now, I just want info about ej205 heads on ej207 block. No opinions on different heads, port sizes, avcs or different blocks. If I wanted to do full ej207 avcs swap, ej257 avcs swap, ej25/ej20 hybrid I would ask, which Im not. Plus, Im sure the ej207's heads, bigger ports, cams etc will shift my powerband higher up the rpm range which I am not interested in.

The only "swaps/builds" I am considering is;
-HOPEFULLY a new v7 ej207 short block and stock rebuilt oem ej205 heads. or
-new oem ej205 short block and stock rebuilt oem ej205 heads.
-least favorite option is used ej205 short block rebuilt to oem specs
-no head swaps yet, no avcs yet, no 2.2/2.5 swap

All I want is information regarding stock ej205 heads on v7 ej207 shortblock. I do not want opinions about which heads I should use, which block I should use etc.

*Stock jdm v7 Ej207 block with stock usdm 2005 Ej205 heads*
-Will there be piston to valve clearance issuies?
-What will the compression ratio be?
-What will the end cc volume be?
-Has anyone here done this or have links to people who have done this?

Last edited by 4eat05; 12-02-2015 at 07:24 PM.
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Old 12-02-2015, 07:50 PM   #4
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From the one thread I have seen on this, it seems like the v7 ej207 has 8:1cr with 6cc dish pistons and 50cc combustion chambers, and the usdm ej205 has 8:1cr with 12cc dish pistons and 51cc combustion chambers. Is this correct? Or have I been misinformed?

But what exactly does this mean? Should I have no piston to valve clearance issues with us ej205 heads on the ej207 block? What does this do to the compression?
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Old 12-04-2015, 04:02 PM   #5
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Anyone have any info on this? I suppose it would be the same as v7 ej207 pistons in a usdm ej205.

I am fairly certain it will bolt up and work fine with a tune, but I would really like to know the compression difference, piston deck height if different, piston to valve clearance if different, and combustion chamber cc difference.
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Old 12-04-2015, 06:22 PM   #6
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Having had extensive first hand experience with both the EJ205 and EJ207. Your best option is to buy a brand new OEM EJ205 short block and have your heads inspected. The EJ205 is more than strong enough to make 400whp with a good tune all day long, provided you maintain it properly and have the correct supporting mods.

Here's a link to my old EJ205 setup.

http://forums.nasioc.com/forums/show....php?t=1962172
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Old 12-04-2015, 08:09 PM   #7
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Im aware that the Ej205 should be strong enough for my plans, but I would still like the benefits of the ej207 short block, but dont quite have the information I want before diving into it.
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Old 12-04-2015, 08:13 PM   #8
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Quote:
Originally Posted by 4eat05 View Post
Im aware that the Ej205 should be strong enough for my plans, but I would still like the benefits of the ej207 short block, but dont quite have the information I want before diving into it.
Look, don't waste your money on a mental perception of improvement when there isn't any real world gain. Unless you are planning on making over 450whp, there is zero gain on running the EJ207 v7 SB.

I would suggest spending the extra funds/effort on something that will help your setup across the board. Such as the Tomei baffle (improves windage and stiffens up the bottom end for improved bearing life), 06/07 STI oil pan, external oil cooler, and larger radiator.

Last edited by Fierysun; 12-04-2015 at 08:27 PM.
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Old 12-04-2015, 11:49 PM   #9
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OP, sounds like you have made up your mind and don't want to hear any good advice from anyone. Buy your 207, install it, and notice that nothing has changed.
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Old 12-05-2015, 11:59 AM   #10
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Not surprised there are more posts about changing the subject than staying on subject.
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Old 12-05-2015, 10:01 PM   #11
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Okay want me to simplify this?

Get a EJ207 block, put the ej205 heads on there with ej205 oem gaskets. Tune and you will have no issues.

The only difference in the block is the semi port vs open port.

Internally only difference is the strength of rods, pistons, and depending what ej207 block you buy it might be cross drilled.

So what would i do? Im sure you wont listen or take anybody advice since you already made your mind up, but here I go anyways.

EJ205 block, a JDM V7 crankshaft which can be bought in the US, eagle rods or better, whatever forge pistons from whatever brand *JE, Manley, etc*. Would be so MUCH better and cheaper then buying a new EJ207 block complete which is about 3300 from the UK and that doesnt include shipping, but hey what do i know.
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Old 12-09-2015, 03:29 PM   #12
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Id rather have an unopened oem shortblock than a rebuilt block which is why I like the Ej207, but still dont know what will happen to compression or if the piston will be closer to the valves or combustion chamber volume. which I would really like to know.
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Old 12-09-2015, 08:09 PM   #13
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Quote:
Originally Posted by 4eat05 View Post
Id rather have an unopened oem shortblock than a rebuilt block which is why I like the Ej207, but still dont know what will happen to compression or if the piston will be closer to the valves or combustion chamber volume. which I would really like to know.
Compression will be the same if you get the ej207 gaskets, there will be no difference in stroke bewteen the ej207 and ej205 which means no head issues with valves wtc etc
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Old 12-09-2015, 08:12 PM   #14
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Bore is still 92mm and stroke is still 75mm on all version of the ej20 series. Even on the SOHC versions.
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Old 12-10-2015, 02:36 AM   #15
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Quote:
Originally Posted by 4eat05 View Post
Id rather have an unopened oem shortblock than a rebuilt block which is why I like the Ej207, but still dont know what will happen to compression or if the piston will be closer to the valves or combustion chamber volume. which I would really like to know.
Hence the brand new OEM EJ205 SB from Subaru suggestion. In addition, if you are not doing the EJ207 heads, cams, ecu, and avcs wiring. There is zero reason to even consider the V7 (or any) EJ207 SB if you are not making 450+ whp.

BTW, my EJ205 made 374whp and my EJ207 401whp with full avcs functionally. Zero issues...
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Old 12-10-2015, 09:59 AM   #16
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Quote:
Originally Posted by 4eat05 View Post
Id rather have an unopened oem shortblock than a rebuilt block which is why I like the Ej207, but still dont know what will happen to compression or if the piston will be closer to the valves or combustion chamber volume. which I would really like to know.
I would take it apart, sell the rods /pistons, get aftermarket beefier rods, forged pistons, balanced the rotating assembly and run a 79mm crank.

But. ..... that's just me.
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Old 12-10-2015, 01:30 PM   #17
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heres what i did on my 205 beater car. I bought good condition ej207 pistons and sti take off rods . All the 257 guys going for big power scrap them and go to aftermarket rods. Having a crossdrilled 04 2L crank already, its the same recipe for a 207 bottom end without the semi-closed case. It gave me the same peace of mind for my 205 without breaking the bank.

that said, i wish my budget had been bigger to just do a full 207 swap. My "refreshed" motor doesnt give me much more power, if anything it doesnt blow smoke anymore due to new rings and a hone.
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Old 12-10-2015, 02:58 PM   #18
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Quote:
Originally Posted by El Guapo View Post
heres what i did on my 205 beater car. I bought good condition ej207 pistons and sti take off rods . All the 257 guys going for big power scrap them and go to aftermarket rods. Having a crossdrilled 04 2L crank already, its the same recipe for a 207 bottom end without the semi-closed case. It gave me the same peace of mind for my 205 without breaking the bank.

that said, i wish my budget had been bigger to just do a full 207 swap. My "refreshed" motor doesnt give me much more power, if anything it doesnt blow smoke anymore due to new rings and a hone.

Do you know if and/or how your compression changed using 207 pistons and 205 heads?

I know all the ej20's have the same bore and stroke, but im pretty sure they have different dished pistons and different head cc volumes.
I know the ej205 heads would bolt up to the ej207 block and run with no problems, I just really want the know if the compression changes or combustion chamber volume changes before I do it.
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Old 12-10-2015, 05:16 PM   #19
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Quote:
Originally Posted by 4eat05 View Post
Do you know if and/or how your compression changed using 207 pistons and 205 heads?

I know all the ej20's have the same bore and stroke, but im pretty sure they have different dished pistons and different head cc volumes.
I know the ej205 heads would bolt up to the ej207 block and run with no problems, I just really want the know if the compression changes or combustion chamber volume changes before I do it.
Not really, i left all that up to the tuner. I assume he started safe by backing off all the timing when he started and slowly added it in as he saw fit.
On this forum some people go out of the way to get high compression pistons. I highly doubt using the 207 pistons are as aggressively high compression that what these guys are putting in their cars.
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Old 12-29-2015, 02:24 AM   #20
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Quote:
Originally Posted by El Guapo View Post
Not really, i left all that up to the tuner. I assume he started safe by backing off all the timing when he started and slowly added it in as he saw fit.
On this forum some people go out of the way to get high compression pistons. I highly doubt using the 207 pistons are as aggressively high compression that what these guys are putting in their cars.
Which ej207 pistons did you put in your ej205?

I'd still really like to know the compression, piston to valve clearance, and combustion chamber cc difference using a v7 ej207 shortblock and usdm ej205 heads or v7 ej207 pistons in a usdm ej205.
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Old 01-22-2016, 10:02 PM   #21
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I am looking to do the same thing. If it does work, Swapping an ej207 block should be way easier and more cost/time efficient than building any block from the ground up and will handle more power than a stock ej205 reliably. I don't care about AVCS and I certainly have no interest in trying to use JDM ECU just to make it work then being impossible to inspect my car.

Last edited by xisb4u; 01-23-2016 at 05:07 PM.
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Old 01-24-2016, 11:23 PM   #22
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Quote:
Originally Posted by xisb4u View Post
I am looking to do the same thing. If it does work, Swapping an ej207 block should be way easier and more cost/time efficient than building any block from the ground up and will handle more power than a stock ej205 reliably. I don't care about AVCS and I certainly have no interest in trying to use JDM ECU just to make it work then being impossible to inspect my car.
If you can source a new EJ207 block for the price of a EJ205 block new then please let me know! The blocks go for what $3200-3500? Plus shipping from EU?

Good luck!
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Old 02-07-2016, 06:33 PM   #23
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Ej207 is a better block out of the factory so you get what you pay for, plus most of the time you are getting an entire longblock as opposed to spending $2000 just for the rebuild kit for an ej205 not to mention labor and down time. If you ask me $3500 or even $4000 is perfectly reasonable for an ej207 long block. Unless you are building the block and doing it all yourself, you will almost never save money by rebuilding and it will be more work and down time. Getting an ej207 longblock, pulling everything off and dropping it in would take only a couple days and wouldn't cost much, if any more than a rebuild or replacement of the EJ205.
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Old 02-08-2016, 04:36 AM   #24
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$3500-4000 for a LONG BLOCK used is perfectly reasonable.

Im talking about just the block itself, that means you would still need to invest in gasket kit, headstuds, assembly if you can do it yourself, etc otherstuff +new ej207 short block which would be $3500-4000

At that point i rather just buy a built block which would be cheaper!

https://revworksinc.3dcartstores.com...ck_p_3435.html

Hell thats the strocker engine so its slightly more money.

At this point I think people just want a EJ207 short block to say JDMTiGhT YO.
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