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Old 11-14-2003, 03:16 AM   #1
Kostamojen
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Default Serious hypothetical question: What is needed for EJ20 heads on an EJ18 block?

In all seriousness...

Lets say I can get some WRX heads (which I can) as well as with a turbo kit for my EJ18. I already have an S-AFC on the way for the turbo kit to use with the MAP mod to deal with A:F and whatever, and plan on say a td04 stock WRX turbo combined with a Legacy Turbo water-air intercooler system. Lets presume a wrx fuel pump as well, and since I plan to save a little money with this turbo kit, use a stock wrx uppipe (without the cat) modded to fit with borla headers, and probably a stock wrx downpipe as well modified with whatever exhaust system...

Anyway, the question is, what would be the requirements for the DOHC EJ20 WRX heads to work with the EJ18 block? I know they will bolt up, so thats not an issue, and I presume WRX engine gaskets as well.
But what about injectors/fuel rails and their compatiblity with the Intake manifold? What about dealing with the timing belt? What about actually operating the heads using the EJ18 ECU? What compression would that combo end up running at? (I presume slightly lower than the EJ18 compression of 9.5:1) What other compatibility issues might arrise?

What might help the most would be photos of a wrx block removed from a car... For reference, here is a link to pics of my engine bay:

http://community.webshots.com/album/78362606CUGxjT

But yes, im seriously contiplating this... I just think that the benifits of running those better flowing heads would allow for a greater flexibility and saftey margin running the turbo kit, especially since I found out that the EJ18 heads and the EJ22 heads are identicle in style, all the way down to the camshafts only having a slight elevation difference...

I know, this is somewhat theoretical in terms of that I know of nobody who has done it, but heck if this is all wrong to start with i'd like to know...
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Old 11-14-2003, 03:17 AM   #2
subiekid
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i think someone talked about this in the conversoins forum. might try a search in there.

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Old 11-14-2003, 03:35 AM   #3
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Quote:
Originally posted by subiekid
i think someone talked about this in the conversoins forum. might try a search in there.

Ya, i was one of the first people to bring it up... Ive read the like two posts about it since I was pretty much involved in the discussion Nobody ever came to any conclusions and nothing other than speculation was made...

Im contiplating posting this link there just to get both forums to discuss it thoroughly...
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Old 11-14-2003, 08:25 PM   #4
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Default

if you search on here long enough there was a thread, I believe in conversions, about all the different engine blocks and it had pics of them too. Disassembled If you can find it-it would be a help to you. If all else fails google has yet to fail me. I have pics of my EJ20 before the install. It is the whole engine though.
Take it easy, Micah
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Old 11-15-2003, 03:13 AM   #5
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Are the pics of the engine when its out of the car? I dont care if its the whole engine, that actually would help just the same...

And ya, i have all the disasembled block pics, but nothing in terms of heads... (Exept the EJ18's, i have lots of pics of the EJ18 heads)
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Old 11-15-2003, 11:18 AM   #6
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let me know how that intercooler setup works, im swaying that way for mine.
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Old 11-17-2003, 04:52 AM   #7
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Alrighty, it looks like im DEFINATLY getting the heads... So now, im going to have to get into this even more
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Old 11-17-2003, 12:53 PM   #8
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Are the EJ18 heads DOHC or SOHC? What about direct fire ignition?
If they're DOHC then it should be a pretty simple swap.
If they're SOHC then you're going to run into huge issues. The cam trigger teeth on a SOHC are in compleatly different angles than on DOHC heads, and there is no way your ECU will be able to run them w/ out custom cam pullys.
The direct fire could be another problem, but it would not be a big deal to keep the wasted spark coil your stock engine runs w/ custom wires that reach into the head to the plugs.
The timing belt should not be a big deal either. I belive the WRX idler will fit. I could be wrong, but I'm pretty sure it does.
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Old 11-18-2003, 06:07 AM   #9
Kostamojen
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The EJ18 is SOHC, and as I mentioned before basically identicle to the EJ22T heads (which leads me to believe that the folks who have EJ22T blocks with WRX heads have dealt with these issues)

The ignition design is the same config as the WRX as far as I can tell.

As far as the cam trigger teeth, im not to familiar with this, have any more details in terms of diagrams or photos I can reference?
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Old 11-18-2003, 06:49 AM   #10
Kostamojen
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Ok, just found a little info for compression numbers.

The The Cylinder head volume on the WRX is 49.8cc.

My EJ18 displacement is 1820, with a bore x stroke of 3.46 x 2.95 and a compression ratio of 9.5:1 (this part I knew)
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Old 11-19-2003, 02:59 AM   #11
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Talked some more with folks today.

As for gaskets, I presume the EJ20 gasket would be the gasket to go with?
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Old 01-12-2004, 01:42 AM   #12
Kostamojen
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Just to close this off, the EJ20 heads bold up, the gaskets work great, but the pistons will hit the valves due to the valve reliefs on the EJ18 pistons.

Aftermarket pistons is the only way to do it.
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