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Old 03-31-2005, 09:40 PM   #1
bongchild
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Impreza GC8 Some questions about putting different heads on EJ18 block

Hey guys,

I did a search on this and found some useful info, but there are still some holes in my knowledge.

What I'm thinking of doing is taking my EJ18 block and putting either EJ22 or N/A EJ20 heads on it. As far as I know:

stroke for all 3 engines is 75mm and rod length is the same, so the bore is the only difference. Therefore, I can use the same rods and crank. EJ18 rods and crank are forged like the early type-RA engine and therefore will be able to handle high rpm's/boost.

Different bore means I'll need the pistons from the donor engine. I'll also need the cams, valves, lifters, and exhaust headers since the heads will have a different design. This also means the coolant and oil passages may need to be altered. Intake manifolds are the same so i can use the same fuel injectors.

Physical dimensions are the same so the oil, water, and a/c pumps can be transferred. I can also transfer my lightened pullies over.

So, how far on/off track am I here?? Is there anything else I need to take into consideration? And don't tell me to do a turbo swap/buy another car/forget about it like u do to everyone else.
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Last edited by bongchild; 04-01-2005 at 11:23 PM.
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Old 03-31-2005, 09:58 PM   #2
Storm
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If you're only changing heads, you don't need to change pistons too. Use the complete head and don't worry about what cams etc. to put in them.

Is this going to be a FI motor or NA? That may help choosing parts or a path to follow.

Jay Storm
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Old 03-31-2005, 10:50 PM   #3
bongchild
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Oh, im gonna stay NA.
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Old 04-01-2005, 01:15 PM   #4
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This will lower your compression ratio won't it? What would be the advantage unless you want to go turbo? I think what you want to do is put your 1.8 heads on a 2.2 block.
John
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Old 04-01-2005, 07:35 PM   #5
bongchild
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OK, that's one of the things I wasn't sure about. How would I raise the CR in ths case? Pistons? Thin headgasket? rods?
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Old 04-01-2005, 09:02 PM   #6
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Dont mess with an EJ18. I cant think of one reason to put any money in a 1.8 block. You will lose power by bolting a 2.0 or 2.2 head on a 1.8 not that it has any to begin with.
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Old 04-01-2005, 10:07 PM   #7
bongchild
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Yeah, that seems to be the consensus. I was just going over it in my head as an option for my build-up. Looks like the best thing to do is just swap in another engine. That or slap a turbo on if i change the heads.

But still, for the sake of my own knowledge how accurate is my info?

Last edited by bongchild; 04-01-2005 at 10:20 PM.
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Old 04-02-2005, 10:57 AM   #8
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Look in the N/A forum for the "High Compression Frankenstien" thread. Probably the best info for what you are thinking of..
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Old 04-02-2005, 01:31 PM   #9
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boost the ej18, its great at that sort of thing.
also the bores will be different if you use different heads, which means that the quench areas at the edges of the combustion chamber will be shaped improperly. it would be best to get them machined to the correct shape, but many people just ignore that.
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