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Brat powertrain swaps


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7 replies to this topic

#1 casm

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Posted 19 August 2005 - 06:43 PM

Apologies if this is the wrong forum for this question - obviously, I'm kinda new here so hope I'm getting this right and won't be offended if it needs to be moved :)

Basically, I'm trying to understand the different powertrains that went into various Subarus over the years with an eye towards possibly doing a swap whenever I eventually locate a Brat. From the memories of the '86 I had, a 5-speed is probably going to be first on the shopping list - and I found the guide to swapping one in the USRM; hopefully this will come in handy soon.

What I'm curious about are my drivetrain options. Basically, I'd like an injected engine for some of the steeper trails around here; street performance isn't what I'm after so turbos are pretty much right out. Is the EA82 the injected version of the EA81? I found an early-'90s Legacy sedan in the junkyard with the 5-speed and what I think was this engine, but I'm not sure - all I know is that it was injected and had the 5-speed with dual-range transfer case.

Can anyone point me towards a good comparative guide of the '80s engines in terms of spec, output, and displacement? Also, is there a similar guide to transmission and final drive gearing anywhere? Thanks!

#2 subarubrat

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Posted 19 August 2005 - 07:52 PM

In my opinion, the EA81 is a much more rhobust engine than the EA82. There is a small difference in HP between them, not enough to matter much at trail speed. I would suggest building an EA81 for more HP before swapping to an EA82. If going from an EA series to an EJ series such as the 22 or 25, then you have to consider that you will loose low range because the newer trannys are single range only and that would reduce the benefit of the swap. If you want to go through the trouble of swapping an EJ series engine to your original tranny that would be a solution to many problems with the added complexity of the bellhousing to engine adapter. I love the qualities and tuneability of EFI for sure, all things considered a swap to an EJ22 or EJ25 would be worth the trouble, I would also suggest going to the stronger dual range EA82 tranny that was in the Loyale wagon. It will allow you to keep a low range and add the huge improvement of 5 speeds that combo will enhance the driveability big time.

#3 casm

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Posted 20 August 2005 - 10:53 AM

In my opinion, the EA81 is a much more rhobust engine than the EA82.


Out of curiosity, what make the EA81 hold up better?

There is a small difference in HP between them, not enough to matter much at trail speed. I would suggest building an EA81 for more HP before swapping to an EA82.


I agree with you on small HP differences not mattering at trail speeds, but the main reason I want fuel injection is so that I don't stall out on certain hills. We have a couple around here that will cause carburetted vehicles problems with fuel starvation.

If going from an EA series to an EJ series such as the 22 or 25, then you have to consider that you will loose low range because the newer trannys are single range only and that would reduce the benefit of the swap.


Nope, that's definitely right out. Thanks for the heads-up.

I would also suggest going to the stronger dual range EA82 tranny that was in the Loyale wagon. It will allow you to keep a low range and add the huge improvement of 5 speeds that combo will enhance the driveability big time.


Cool. I'm assuming the tranny more or less swaps straight out between the EA81 and EA82?

#4 Ross

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Posted 20 August 2005 - 06:32 PM

Out of curiosity, what make the EA81 hold up better?


The ea81 is a simpler (OHV as opposed to OHC) engine, no timing belts, less emmision control. Mainly just less to go wrong.

As for fuel starvation, i have had my carb'd (hitachi) ea81 on all sorts of funny angles, never had a prob??

And, yes, the ea82 and ea81 transmissions will swap, with minor alterations only (driveshaft and shift linkage).

#5 subarubrat

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Posted 20 August 2005 - 06:38 PM

The EA81 is a stronger block, simpler design overall, gear driven cam where the EA82 had short lifespan timing belts, great oiling and coolant design where the EA82 had some shortcomings. All things considered the 81 is a damn strong simple pushrod engine. The EA81 was a transitional engine design leading up to the very well designed EJ series. The EA82 5 spd is a great tranny to mate up to the EA81, bolt up job for the most part. You will need to get a rear driveshaft made because the tranny is a different length.


As for an engine solution. I would suggest using your EA81, with EA71 pistons to up the CR. Then drop on the EA82 SPFI manifold and system. It won't be as slick as the MPFI but it is still better than a carb.

#6 Ross

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Posted 21 August 2005 - 02:48 AM

if you prefer, you can use the 3 piece ea82 driveshaft, you just have to weld the center bearing carrier on to the body.

#7 casm

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Posted 21 August 2005 - 11:18 AM

Thanks for the replies - this is all good info. It looks as though the only real major upgrades I'd want to do off the bat is the EA82 5-speed and a set of Peugeot rims and tires - I do enough freeway miles that the higher gearing would be worth it, and I've been into Peugeots for years so actually have a set of 505 alloys in storage.

Is there anything else I might want to consider? How bad are A/C swaps to do into a non-A/C car? We've got plenty of junkyard sedans and wagons with air sitting here, but if I'm going to be realistic about finding a Brat I probably shouldn't rule out non-A/C cars.

#8 MilesFox

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Posted 22 August 2005 - 12:15 AM

i personally would go with the ea82 myself. since you have the parts source and plan to so spfi swap might as well have the motor and all plug and play to it.

spfi on ea82 requires disty mods and

the ea81 carburetor, if not going with the spfi, will bolt onto the ea82 motor(the intake assembly)

the ea82 gets more revs than ea81, the ea82 trasmission is geared appropriately for it. the only modification to make with the ea82 motor is to move the hill holder back a litt,e, and install the motor first, then the distributor so you can clear the master cylinder

relocate the coil to the other side, use ea82 battery cables to relocate the battery to the othe side, if you wish. but you will have to remove the jack mount

make a carrier bearing mount and the ea82 driveshft will be the right length for the tranny and the car going into




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