I have a 1989 Si, with my *second* B20A5 engine. The first one "blew"
the #4 cylinder rod bearing at 178,000 miles. Not bad since it's my
daily and also my autocross-er!

What I would like to do is to rebuild the first engine, and am wondering
if it would be better to build it with OEM parts, or, try to convert it
to a B21A3 (90-91 Si Engine - I think).

So, are there any *major* differences in the block? I found out that
both use the same crank. Also, any place I can send out the throttle
body to be rebuild with a larger bore?

Thanks!

 

unless there is a different motor that i haven't heard of yet, you are looking for b21a1 motor parts. that motor is from the 90-91 si with the 2.1 (2.0.5) motor. that motor is definately better and faster than the b20a5 motor. the crank is the same, but the 2.1 has an 83mm bore instead of 81mm. the heads have slight differences in camshaft size and the intake and headers are different. the b20 motor has 135 hp and 127 ft lbs tq while the 2.1 has 140 hp and 135 ft lbs. if you can find a b21 motor or a jdm spec b20 motor (with 143 hp) they are both direct bolt ins and worth it if you are looking to put in a new motor. you can probably get a motor from the junkyard or something like that for 500 bucks. your 2.0 wiring harness will work as a direct bolt up to the 2.1 as well. you won't need the computer or any wiring. when i swapped in the 2.1 into my 89 si i noticed a big difference.

 

What you need to find is this:
http://www.honda.co.jp/HOT/ModelData...1/20si_sy.html
(Run the site through a translator calle "Babelfish" found on AltaVista's search engines)

It is a B20A w/ 160ps (~158hp) that was found only in the latter 2g Preludes. If only I could find one...

David

 

i'd stick with the B20 and turbocharge it. unlike the B21, B20 has iron sleeved block and can take boost pretty well if rods and bearings and strenghtened.
just my $.02

 

A few questions reguarding 3rd Gen Prelude engine swaps.

I have a 91 Si with the B21A1 engine and with about 115 000 miles on it, I threw a rod bearing a few weeks ago and need some help.

I really don't want to go with another B21A1 cause of the oil burning issue so I have decided to go with a B20.

Anyhow I found a low mileage (50 000 mile) B20A from this engine guy for $450 bucks. He said its a JDM engine with more power than a B21A1. Is this true or false? Is a B20A a JDM motor with over 140 hp? Torque?

Also what about installation? How hard is it to do? Do I just need the engine itself, or do I need the tranny, ECU, wiring harness etc etc?

Also does the fact that the motor is from an a automatic Prelude make a difference?

Anyways if you guys could help me out that would be great

Thanks a bunch

Evan

 

Good idea about the turbo, but that would kick me out of
my class in autocross. Staying with a 3rd gen engine
allows me to stay.

 

then you're better off with a B21. more torque and more hp.

 

like i said the jdm and the usdm are direct bolt ups. the jdm b20a has 143 hp with about the same torque. the usdm b21 has 140 hp and 135 ft lbs tq. so yes, the jdm b20 has 3 hp more. you can use the same computer and wiring harness for both motors. i believe even the jdm motor can use the same 2.0/2.1 usdm harness. i know you can use the computer and mounts and everything else. the intake manifold and exhaust header/manifold will bolt directly up. the transmissions are all the same bolt pattern so they will all bolt up. i have a b21 from an automatic that i put the 2.0 manual tranny on in my car. everything is pretty much interchangable. the complete swap (taking the old motor out and putting the new one in, hooking everything up and filling everything up) is a long days project, but i got it done in one day. you shouldn't have any problems.

 

Any "gotchas" when installing the B21A into my '89? I was planning upon using
the exisitng wire harness and such. My current tranny should bolt right up to this engine, shouldn't it? Thanks for your input!!!

 

Or , of course , a UK B20A7 with 150 bhp & 133 lb/ft torque .

 

you won't have any problems putting the 89 2.0 tranny to the b21a motor. the only difference in the wiring is where it attaches to the b21 intake manifold. other than that, everything is a direct bolt up. the manifolds, both intake and exhaust, are interchangable from the 2.1 and 2.0. the only thing you have to make sure you use from the same motor is the manifold and the egr tube. the 2.1 manifold comes out a little farther, so the egr tube is longer. other than that, if you use the 2.0 manifold, use the 2.0 egr tube. both bolt up the same way, just one is longer.