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dohc swap

 
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Old 07-10-2012, 09:50 PM
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dohc swap

I just got an 89 prelude S. It was advertised as an si so I thought it had the dohc motor. It's got the damn sohc 12 valve carburated engine which I hate. Is there any way I can swap heads for the dohc fuel injected one?? What would it involve? Thanks guys!
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Old 07-10-2012, 10:47 PM
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Re: dohc swap

Welp... How do you buy a car without really test driving it or looking at the engine?

Anyway, you can get a donor Si for parts, but you have to go full circle or the swap will not work at all. Here is a quick parts list, but I know some things are still missing:
- Complete DOHC engine.
- Interior wiring (requires dashboard removal).
- ECU.
- Fuel input lines.
- Fuel return lines.
- Fuel pump.
- Injector resistor.
- Engine wire harness.

Some other stuff. Many people have done the swap, but almost all of them had a donor Si.
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Old 07-10-2012, 10:55 PM
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Re: dohc swap

Damn/: that's a big job man. Maybe ill try and sell this one for an actual si
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Old 07-11-2012, 12:24 AM
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Re: dohc swap

I have one of each...89 Si and an 89 S. Both are 4ws. The S is my winter car and the Si is my toy. Well, it shares that role with my 2010 Camaro SS, lol.

The S is a good car in it's own right. I added a reground camshaft and it really woke this engine up... www.webcamshafts.com. Don't give up on it. It's still a 3rd gen after all.
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Last edited by luzer; 07-11-2012 at 12:26 AM.
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Old 07-11-2012, 01:36 AM
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Re: dohc swap

Don't think the extra head bolts will bolt on to a single cam engine . Sorry.
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Old 07-11-2012, 11:43 AM
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Re: dohc swap

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Originally Posted by Lespaul59 View Post
Don't think the extra head bolts will bolt on to a single cam engine . Sorry.
Actually, the DOHC head will bolt up perfectly. The b20a3 and b20a5/b21a1 blocks are nearly identical.

But the wiring harness, ecu, and fuel system won't support fuel injection and need to be replaced.
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Old 07-11-2012, 05:25 PM
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Re: dohc swap

I'd like to see pics of the car, if it's clean, it might be a keeper.

But I'd say there are many ways you can go with it, just figure out what you want the end result to be, and it will help you determine the path to take.
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Old 07-12-2012, 01:15 AM
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Re: dohc swap

What about the cam sensor at the end of the exhaust cam? Thought the sohc head only came with a distributor at the end. Do they have crank angle sensors near the timing sprocket instead?
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Old 07-12-2012, 01:38 AM
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Re: dohc swap

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Originally Posted by Lespaul59 View Post
What about the cam sensor at the end of the exhaust cam? Thought the sohc head only came with a distributor at the end. Do they have crank angle sensors near the timing sprocket instead?
Think about it, if you swap to the DOHC then you'd have a place for the cyl sensor wouldn't you. Also, part of this swap is the engine bay wiring harness so you'll have a connector to plug it in.
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Old 07-13-2012, 12:50 PM
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Re: dohc swap

Quote:
Originally Posted by Lespaul59 View Post
What about the cam sensor at the end of the exhaust cam? Thought the sohc head only came with a distributor at the end. Do they have crank angle sensors near the timing sprocket instead?
This is kinda why you need a donor car.
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