Swap - ET2 / A18 / B20A (JDM) / B20A5 / B21A : Head - A20A : Block

[Kabuki]

Well, it turns out the information I got from preludepower was incorrect, the A20 intake manifold does NOT bolt up to the B20A5 head.

Sorry about that, I try to dispel crappy information their, but I have been a little busy as of late. I'm still working on this from my end, but I'm also still waiting for a donor block.

[Kabuki]

Okay, folks... I have an '87 LX coming in for an engine replacement on monday. So I finally will have a bolck to start this project with. I guess I better spend a little time this weekend and tear down the B21A1 that I'm getting the head from. This is the start of probably three long projects*, so we'll see how it goes.

* B21A1/B20A Rebuild for the '88 Lude, A20A/B21A1 for, uh, research, and Probable Turbo for the A20/B21.

[Ichiban]

As far as a 17 tooth crank pulley with a 25mm bore, i can't find anything. most pulleys from the power transmission manufacturers have an even tooth count, so the best i could think of is a 16 or 18 tooth crank pulley and two 32 or 36 tooth cam gears. thoughts?

[baby D]

As far as a 17 tooth crank pulley with a 25mm bore, i can't find anything. most pulleys from the power transmission manufacturers have an even tooth count, so the best i could think of is a 16 or 18 tooth crank pulley and two 32 or 36 tooth cam gears. thoughts?

yeeah as long as they fit in the place as the stock gears it should work, if you get this running could you give me a parts list, and does any one know if we can stroke an a20 to a 4 1/4 stroke, becose thats why im loseing, no torque.

[Ichiban]

change your gearing. trying to make a stroker crank will lead to nothing but problems...could someone with the B21 head post up some specs so i can look for timing gear that will come close to fitting? thanks.

[Kabuki]

I'm looking in to possibility of the B20A3 Crank in the A20 block. Probably the rods too. In which case I may bump it up to the B20A5/B21 crank with the F22 rods. This should give us the extra length of snout that is needed to line up with the head. If it works, it may just be a goo stroker mod for the stock engine too. I've been rather busy at home lately, so I haven't been able to spend much time in the garage with this stuff.

[Ichiban]

....i'm listening..

[Sporno]

so i could get the B20A5 intake manifold , heads, and exhaust manifold and it would bolt on. i need some strait forward answers . does this project actually work?

or is it the B21A1 heads and all ... i need to know what to get

[Ichiban]

you are gonna have to do a lot of reading to even begin to answer that question.

[Kabuki]

Yep, you'll need to read the whole thread. But in a nutshell, no. Not without serious machine work.
The problems to overcome are:
1) The A20A crankshaft snout isn't as long as the B20/21 cams, so the timing belt won't line up.
2) The middle head bolt hole on the intake side is in a slightly different spot, and would need to changed somehow. Part of this issue is that the oil pressure channel runs through this hole near the top.
3) There are two oil drains in the head that need to be plugged, as they have no matching port on the A20 block.

[Ichiban]

Yep, you'll need to read the whole thread. But in a nutshell, no. Not without serious machine work.
The problems to overcome are:
1) The A20A crankshaft snout isn't as long as the B20/21 cams, so the timing belt won't line up.

3) There are two oil drains in the head that need to be plugged, as they have no matching port on the A20 block.

1. Nobody else mentioned the cam/crank pully alignment issue yet? Is this a fact?

3. If the oil drains face the top of the block, won't the head gasket seal it off effectively enough? unless the hole overlaps the edge of the block, only then will oil pour all over the place. Im gonna check the pic's again....

Edit: i see the drainback ports there on the intake side, gofast welded his closed, also the oil drainbacks on the front of the head (exhaust side) need to be modified to keep the oil inside the engine

[Kabuki]

1. Nobody else mentioned the cam/crank pully alignment issue yet? Is this a fact?
3. If the oil drains face the top of the block, won't the head gasket seal it off effectively enough? unless the hole overlaps the edge of the block, only then will oil pour all over the place. Im gonna check the pic's again....
Edit: i see the drainback ports there on the intake side, gofast welded his closed, also the oil drainbacks on the front of the head (exhaust side) need to be modified to keep the oil inside the engine

1) Yeah, they did... back in post #195

[Kabuki]

Okay, I also found that the B series cranks (all of them) have a 55mm main journal, rather than the 50mm journal on the A20 block. So that's not going to work either. Then I was also thinking.... Even if we DID fix that, then the oil pump pulley would no longer be in line. So we'd have to mod that too, or replace it with a dry sump...

[snoopyloopy]

so how does it look now? any more progress?

[Ichiban]

Now that i'm going to school in a machine shop for 9 months I'm gonna make the 17 tooth 25mm ID gear. Who wants to try it?

[Ichiban]

yeah if I can get ahold of a JDM B20A head I'll do it myself

[Kabuki]

Sorry... No progress as of yet. Possibly soon.

[stat1K]

this seems entirely too much work you could just swap one of these motors in for that... but i know that you guys just like tinkering so i'll only add those 2 cents.

[MessyHonda]

this seems entirely too much work you could just swap one of these motors in for that... but i know that you guys just like tinkering so i'll only add those 2 cents.

yeah that is true..you can fit a b18 with just mounts....but the coolness factor of the a20 block and a DOHC head would be pimp...i will die a happy boy if it ever happens..hehe

[Kabuki]

Just having 16 valves and dual cams for boosting with the iron block would be AWESOME.... Be like a DSM engine... :-/

[Sporno]

if we could have DOHC heads that would be great for tuning.. with DOHC u can adjust the cams more than SOHC and valves and cam gears and everything it would make for way more power

[Ichiban]

So, I'm going to school in the machine shop now...and I'm at the top of the class. My instructor is giving me free rein and backing for my final project, and I think this'd be a good one. What do you all think?

[MessyHonda]

So, I'm going to school in the machine shop now...and I'm at the top of the class. My instructor is giving me free rein and backing for my final project, and I think this'd be a good one. What do you all think?

you will be my hero if you ever get it to work...lol

[Legend_master]

you will be my hero if you ever get it to work...lol

[Swap_File]

I finally logged into 3geez after being gone for a few months, and saw a few PMs asking about this project. Here is a quick summary:

Here is what you would need (Mostly from memory):

B21A1 (from 1990 - 91) or B20A5 (from 1988 - 91) head from a Prelude. B21 head lowers compression just a bit, B20 head bumps it up just a bit. B20A5 heads are much more common in the junkyards around here.

Custom lower timing gear (Modify a B20/B21 gear to fit A20 shaft)

Some other timing belt - Unsure of what is needed

Tap and plug the extra oil drain holes in the new head

Redo the one head bolt that does not line up. Probably make the hole in the head a little bigger and oval shaped, and then make a special washer for it.

Redo the oil feed, since the head bolt that doesn't line up is used with the head's oil system.

Upper timing belt pulleys do not quite align with the tensioner and bottom pulley. Probably has to have some shimming done.

You need the B21A1/B20A5 intake.

I remember that the A20 distributor had a different number of teeth than the B20A5/B21A1. You will probably need to switch to one of the OBD1 ECUs to make tuning simpler. Look for the instructions on what distributors fit on the B20A5/B21A1 head on preludepower.com. The ECU swap is a project in itself...

My suggestion: Do the head swap if you are looking for a challenge, if you want cheap power go turbo. I am sure that the head swap could be done, but it will not be easy.

I am currently (slowly) working towards going turbo. College has been keeping me very busy, but I am slowly making progress.