Difference between JDM A20 and USDM A20

[zerotap]

OK here is the situation. My car was produced in Japan, sold in Hawaii and was driven there by the same owner from 88 to 03. From there it was sold in washington to two other people with less than 7 thousand miles between those two. From this information I am assuming it is a USDM A20 engine in the car however, I would be curious to know if it could possibly be a JDM A20 engine. Is there a way I can tell by reading the engine number as shown in the Hayes book, if so how. LoL I suppose I should mention that my car is an 88 3g Hatchback. :)
My next question is what is the performance difference between a JDM A20 engine and a USDM A20 engine. My engine is carbed so I know that will have different performance from a EFI but I want to know if USDM and JDM carbed engines have same horsepower, torque etc.
The reason for asking this is because I plan on buying an engine from the yard to tear apart and study. I want to thoroughly understand the internals and how it is put together before I start messing with the engine currently in my car down the road for overhaul and repair.
In the future after I study the engine I plan on putting together a high performance engine. I have seen Sean put together some engines capable of handling up to 400hp and I plan on something similar though I probably won't do N2O and turbo will be two or three years in the future due to expenses, I just want the engine able to handle the power. I know I will need to upgrade other components i.e. fuel pump etc but that will be part of the project.
I just would like to know the differences, if any, between the blocks as far as performance is concerned. I am only concerned with similar performances between JDM carbed A20's and USDM carbed A20's not difference between EFI and Carbed. I couldn't find any sticky's posted that explained the differences between the engines so any info would be appreciated. I don't need a whole book written just a short explanation if there are any major differences and if there are a ton maybe giving me some direction on where to go to do some reading. Thanks guys.

[accelerator]

Good timely post. I am doing a motor swap on my 87 Lxi, using a JDM A20. I looked high and low for an JDM A20 here in Southern California and finally found this one with 28k miles on it. The pad only says A20, not A20A3 like my U.S. Version. My new engine is a carb version, but my connection says that the JDM cam will work with my EFI. He says that the smog restrictions are much less restrictive in Japan than here in the U.S., and the cam may be the same or possibly bigger than my Lxi version. I would like to know if this is true. I figure the only way to get a true answer is to tap the minds of the experts on this site.

[k-roy]

From all I have read and seen (I allmost baught a JDM A20) the JDM A20 is Identical. The differance is in the emissions systems and the block code, the JDM will be just plain A20, not A20** like yours.
Sure it may have a slightly differant cam or compression but that would be about it.
Honda never really did much with the A20 other than mass producing it, thats why they made the B20A.
But like most good Honda's us North Americans got screw out of the good motor, dual pot calipers, digital dash, Aerodeck package and a few other goodies.

[RobT5580]

The JDM EFI version the only differences i noticed when i got my JDM A20 was the thermostat housing had one less sensor, i used the USDM intake manifold and exhaust manifold. I dont recall anything else but i did the swap a few years ago.

[Ravenix]

why go for an a20 when you can get a jdm a18? its got a lil ectra power than the a20 and the engine is just about identical bolts right in and fits all the usdm intake and junk

[carotman]

why go for an a20 when you can get a jdm a18? its got a lil ectra power than the a20 and the engine is just about identical bolts right in and fits all the usdm intake and junk


The A18 has more power because it's got 2 carbs..... just get a better carb for the A20 and you'll pass any A18

[zerotap]

Would love to do a B20 swap but I am not sure if it'll hook up to my automatic transmission. If it will I may do that cuz it has more horsepower to start with and my goal is to have 200hp without turbo or N2O but set up the block, cam, pistons etc to handle up to 400hp or more. I know I read some sticky's on this I'll have to go back and see if they give a list of engines that'll hook right up to my tranny or with very little modification needed.

[RobT5580]

Your automatic wont fit for sure but you are lucky in the fact that most come with a automatic and you can probably get spares for dirt cheap. On the other hand i dont think the auto will handle the abuse of hard driving like that so you would probably go through a few.

[b20aTURBO]

I have b20's with automatics now comes complete

[zerotap]

Can yoo give me some more info on your B20. Thanks.
I have b20's with automatics now comes complete

[b20aTURBO]

B20a motor's 88-89 Black top
Come with auto tranny Intermediate Shaft (rare rear tranny mount)
comes with Distrib, alternator power steering pump some I can get with the AC if you want very clean motors less then 30,000 on them you can ask some of the guys on here that have bought from me how clean the motors are

[zerotap]

B20a motor's 88-89 Black top
Come with auto tranny Intermediate Shaft (rare rear tranny mount)
comes with Distrib, alternator power steering pump some I can get with the AC if you want very clean motors less then 30,000 on them you can ask some of the guys on here that have bought from me how clean the motors are
Damn sounds like a good deal, too bad I am not gonna be ready till next year at minimum. This year is study, research, and learn everything I can by getting a junked motor with everything on it and tearing it apart and going over it. Next year I'll be ready to put a new hight performance engine together. If you are still on the board by then I'll get back to you. Right now just getting info together and soon focus on learning different components of the engine when I get one in next couple of months.

[BootMachine]

I own a few USDM A20's and A18 and ONE JDM-A20.

Here is what I have noticed is diff:

- wiring harness goes over the OTHER "shoulder" of the engine
- fuel rail has a bowl at the bottom and LOOKS like it will hold more fuel (On the JDM) although if it does...its not much...we are talking like 3 eye droppers worth here
- Pulleys on the JDM engine have holes drilled in them including the crank pully. The USDM crank pully is solid and heavy!

Cam gears are the same size, pistons are the same, cams LOOK the same although I WILL measure the lobe width on both USDM and JDM and post the results.

Thats all I know for now. I have yet to determine the compression ratio of the USDM engine OR the JDM engine. I bet there is a SLIGHT diff. though!

But then again.....perhaps not!

As I learn more I will keep everyone updated!

I PLAN (and am 1/2 way done) building up a JUSDM engine using the JDM bottom end and cam and a USDM head and intake manifold.

[zerotap]

Yeah I want to do something similar. JDM bottom end for performance and USDM top end cuz of that stupid emmissions crap. Otherwise I'd go all JDM. Let me know how it goes. I think I want to see how far I can push a standard A20 block. If I can get 150-180 with no turbo or n2o I'll be happy with that for a daily driver.
I own a few USDM A20's and A18 and ONE JDM-A20.

Here is what I have noticed is diff:

- wiring harness goes over the OTHER "shoulder" of the engine
- fuel rail has a bowl at the bottom and LOOKS like it will hold more fuel (On the JDM) although if it does...its not much...we are talking like 3 eye droppers worth here
- Pulleys on the JDM engine have holes drilled in them including the crank pully. The USDM crank pully is solid and heavy!

Cam gears are the same size, pistons are the same, cams LOOK the same although I WILL measure the lobe width on both USDM and JDM and post the results.

Thats all I know for now. I have yet to determine the compression ratio of the USDM engine OR the JDM engine. I bet there is a SLIGHT diff. though!

But then again.....perhaps not!

As I learn more I will keep everyone updated!

I PLAN (and am 1/2 way done) building up a JUSDM engine using the JDM bottom end and cam and a USDM head and intake manifold.