HiPo EA81 build questions....domed pistons?

[GeneralDisorder]

ok I have to ask, what if the EA71 pistons went in an EA82? (which started at 9.5:1?)

 

I haven't measured EA82 SPFI pistons, but since the bore/stroke is the same between EA81 and EA82's I would guess that it would effectively do almost nothing. The EA82 SPFI is already 9.5:1 (though carbed EA82's are 9:1).

 

GD

[hatchsub]

Ok noted...either 4wd clutch disk setup or xt6 (ponders if connie still has any Xt6 goodies like that lying around)

[backwoodsboy]

Mmmm... good thread!

 

When I built my brats hi-po EA81 I used an EA82 flywheel, and an xt6 pressure plate with a 4wd clutch disc.

 

I did indeed source a T/O bearing from a nissan 720 pickup to go with the whole setup.

 

Looking back, I probably couldve used the standard t/o bearing, but the nissan bearing was a larger overall diameter and engaged the press plate fingers *better*

 

First, the pistons and head cc's make up the compression. So, SPFI will not guarrantee 9.5/1.

 

The best combination I came up with was;

 

Hydraulic heads(large valve) - blended ports

1600 pistons

Decked .020 - any more and you'll have problems installing the intake

Port matched intake adapter for the Weber

Weber 32/36 with the biggest jets I could find

lightened EA82 flywheel

XT6 clutch assy.

 

 

When I selected pistons for my EA81 last spring, I sourced both the EA71 and the EA82 SPFI.

 

I measured from the piston pin to the top of the piston, and found that the EA82 SPFIs were taller than the EA71s as compared with stock EA81.

 

My afterthought on this is: although the EA82s were taller, they are also dished on top. The EA71s are not.

 

This leads me to agree with Ken that even though I built my motor with EA82 SPFI pistons the EA71s are the compression ratio winners.

Edited April 13, 2010 by Qman

[Qman]

Mmmm... good thread!

 

When I built my brats hi-po EA81 I used an EA82 flywheel, and an xt6 pressure plate with a 4wd clutch disc.

 

I did indeed source a T/O bearing from a nissan 720 pickup to go with the whole setup.

 

Looking back, I probably couldve used the standard t/o bearing, but the nissan bearing was a larger overall diameter and engaged the press plate fingers *better*

 

 

 

When I selected pistons for my EA81 last spring, I sourced both the EA71 and the EA82 SPFI.

 

I measured from the piston pin to the top of the piston, and found that the EA82 SPFIs were taller than the EA71s as compared with stock EA81.

 

My afterthought on this is: although the EA82s were taller, they are also dished on top. The EA71s are not.

 

This leads me to agree with Ken that even though I built my motor with EA82 SPFI pistons the EA71s are the compression ratio winners.

 

The thing that concerns me the most would be the fact that the Nissan TO is further down on the fingers. Which would also mean it would take a bit more force to disengage the disc. With a new clutch cable it probably would never be an issue but... (just thinking outloud again)

[GeneralDisorder]

The thing that concerns me the most would be the fact that the Nissan TO is further down on the fingers. Which would also mean it would take a bit more force to disengage the disc. With a new clutch cable it probably would never be an issue but... (just thinking outloud again)

 

That's true - I haven't compared the EA81 fork to the EA82 fork but if they are the same overall length it shouldn't be any harder than a normal 5 speed clutch..... plus the difference is half the difference of the OD's of the bearings.... so the change in leverage is .1929" .....less than 1/4".

 

I just did a 5 speed into a Brat with a new clutch kit, flywheel cut to XT6 specs, and new cable. The clutch is so increddibly light that even a bit harder would actually be desireable.

 

GD

[Qman]

Sorry, should have been clearer, I meant the fingers on the pressure plate.

[GeneralDisorder]

Sorry, should have been clearer, I meant the fingers on the pressure plate.

 

I understand what you meant - I'm talking about the ratio of the fork - which is determined by the length from the cable to the pivot ball and from the ball to the contact point on the PP fingers. The ratio is 2:1 on the 5 speed's according to my '85 FSM. The length from the ball to the PP fingers would be reduced by .1929" when using the Nissan T/O vs. the stock 4WD T/O. That would change the ratio...... I would have to take measurements to find out exactly what it would change to, but perhaps it will be easier to just ask backwoodboy how his clutch feels

 

GD

[The Dude Abides]

I dont want to do this but for the sake of knowledge i will ask. Do you guys go for this type of setup so you dont half to mess with the electronics of a ej22. Or possibly to keep the originality of the motor. Because other then those 2 things i cant see why you would work so hard to acheve 100 or so hp when you go ej and get 120 or so with loads more torque. Or do i not know the ultimate advantages of going this route. Because i happen to know of a ea81 and a ej22 in a junkyard. Just asking, dont flame me.

[GeneralDisorder]

Actually - I have given it more thought - and I was wrong in how I was looking at the mechanics of it.

 

The pressure plate fingers themselves are designed to be contacted by the larger 5 speed T/O so the Nissan T/O won't change how the pressure plate feels - actually it's probably still a little small so it will lighten it up just a hair.

 

The other factor is the ratio of the fork. If the 4 speed and 5 speed forks are the same in length and location of the pivot - then the clutch feel will be identical to a 5 speed assuming the pedal lever is basically the same.

 

GD

[Turbone]

I dont want to do this but for the sake of knowledge i will ask. Do you guys go for this type of setup so you dont half to mess with the electronics of a ej22. Or possibly to keep the originality of the motor. Because other then those 2 things i cant see why you would work so hard to acheve 100 or so hp when you go ej and get 120 or so with loads more torque. Or do i not know the ultimate advantages of going this route. Because i happen to know of a ea81 and a ej22 in a junkyard. Just asking, dont flame me.

 

If your a true Subaholic, you will want to keep your old gen car as original as possible. And when you happen to have the opportunity to "show off" and embarrass a new gen owner.......priceless.

Thats one reason I worked so long and hard on my EA82T, to show that average power was achievable, but at a cost.

[mcbrat]

I dont want to do this but for the sake of knowledge i will ask. Do you guys go for this type of setup so you dont half to mess with the electronics of a ej22. Or possibly to keep the originality of the motor. Because other then those 2 things i cant see why you would work so hard to acheve 100 or so hp when you go ej and get 120 or so with loads more torque. Or do i not know the ultimate advantages of going this route. Because i happen to know of a ea81 and a ej22 in a junkyard. Just asking, dont flame me.

 

I can no longer fit an EJ22 into my Red Brat because of the new frame and steering box config... so my final engine mod will be to put SPFI on it...

[hatchsub]

I dont want to do this but for the sake of knowledge i will ask. Do you guys go for this type of setup so you dont half to mess with the electronics of a ej22. Or possibly to keep the originality of the motor. Because other then those 2 things i cant see why you would work so hard to acheve 100 or so hp when you go ej and get 120 or so with loads more torque. Or do i not know the ultimate advantages of going this route. Because i happen to know of a ea81 and a ej22 in a junkyard. Just asking, dont flame me.

 

No flaming necessary lol. I wont speak for other members on here since i dont know the reason that they went the HiPo EA81 route but the reason im doing it is 3 things really...to be different than others who just drop an EJ in, they are way simpler motors, and to keep it looking somewhat original under the hood. I personally love the EA81 and think (the same as others) that it was the best pushrod flat four that subaru made. Yes its true i could get more power by just dropping an EJ under the hood and i have thought about it but whats cooler than blowing the doors off a newer car to have them ask if i swapped an EJ in only to pop the hood and see a single (or possibly dual webers) sitting pretty under there Ive ridden in Backwoodsboys lifted and HiPo'd brat.....hes got 29 inch tires and it put me in the seat more than mine. I cant wait to feel it in a 2wd with stock 13s

[The Dude Abides]

So then i ask this.

 

ea82 with delta torque cam

 

or

 

ea81 with the setup that mcbrat and hatchsub are going for.

 

I wont ask which is better but which has more hp and torque.

[mcbrat]

So then i ask this.

 

ea82 with delta torque cam

 

or

 

ea81 with the setup that mcbrat and hatchsub are going for.

 

I wont ask which is better but which has more hp and torque.

 

the ea82 is actually wider than the ej22... so there can be some fitment issues there too... plus it's just fun to bash on the ea82....

[GeneralDisorder]

to be different than others who just drop an EJ in, they are way simpler motors, and to keep it looking somewhat original under the hood. I personally love the EA81 and think (the same as others) that it was the best pushrod flat four that subaru made.

 

I agree - I love the EA81. The problem is going to be supporting them - very soon all the parts for them will be obsolete.

 

I have been having a discussion with a couple members about the EA81 oil pumps - it appears that the dealer has zero left in North America at this time. Aftermarket suppliers have them marked as "on order" and it's been that way for a year - at this very moment I cannot get one from ANYONE. I called my local dealer and he put a call in to SOA - the deal with these is that the supply is limited and they only order half a dozen or so at a time. The aftermarket suppliers probably aren't going to have them ever again as Subaru is only working through old stock. I placed an order with my dealer for two just to have them on hand and he says it may take a couple weeks to get them - he is pretty sure that the order will be filled this time - but the demand for them on a national scale is very low - it takes them three to four months to sell the half dozen they order. Very soon there will be no demand to speak of and critical parts like the oil pumps will be discontinued from the system.

 

While I love the EA81, and plan to run a few of mine for several more years - the EJ swap is becoming more attractive all the time.

 

GD

[backwoodsboy]

I JUST checked stock on the oil pumps. THERE HERE!

 

There are 11 in the country as of right now.

 

PART # 15010AA120

 

90 bucks a pop retail.

[Qman]

Actually - I have given it more thought - and I was wrong in how I was looking at the mechanics of it.

 

The pressure plate fingers themselves are designed to be contacted by the larger 5 speed T/O so the Nissan T/O won't change how the pressure plate feels - actually it's probably still a little small so it will lighten it up just a hair.

 

The other factor is the ratio of the fork. If the 4 speed and 5 speed forks are the same in length and location of the pivot - then the clutch feel will be identical to a 5 speed assuming the pedal lever is basically the same.

 

GD

 

The fingers of the pressure plate, not the fork. The fingers of the pressure plate are designed to be pushed from one spot. By using a larger diameter bearing that spot is moved further down the fingers of the pressure plate. Thus, requiring more force on the clutch cable. The design of the pressure plate from the manufacturer will deem how "stiff" it feels. Buy 3 different plates from three different manufacturers and they will all feel different.

Edited April 13, 2010 by Qman

[GeneralDisorder]

The fingers of the pressure plate, not the fork. The fingers of the pressure plate are designed to be pushed from one spot. By using a larger diameter bearing that spot is moved further down the fingers of the pressure plate. Thus, requiring more force on the clutch cable. The design of the pressure plate from the manufacturer will deem how "stiff" it feels. Buy 3 different plates from three different manufacturers and they will all feel different.

 

Right - they do all feel different. But the 5 speed/XT6 pressure plate should already be designed to be pushed from the location of the larger 5 speed T/O bearing. The Nissan bearing just facilitates pushing it from the *same* place but using a 4 speed or 2WD transmission and it's associated T/O bearing holder, etc. All the Nissan T/O is doing is helping to put the contact location on the fingers back where it's supposed to be in the first place.

 

GD

[GeneralDisorder]

I JUST checked stock on the oil pumps. THERE HERE!

 

There are 11 in the country as of right now.

 

PART # 15010AA120

 

90 bucks a pop retail.

 

Sweet! My order will be filled sooner than I thought apparently.

 

Ask for a discount. My dealer always gives me a break - should be able to get them for around $75 each.

 

GD

[Qman]

Right - they do all feel different. But the 5 speed/XT6 pressure plate should already be designed to be pushed from the location of the larger 5 speed T/O bearing. The Nissan bearing just facilitates pushing it from the *same* place but using a 4 speed or 2WD transmission and it's associated T/O bearing holder, etc. All the Nissan T/O is doing is helping to put the contact location on the fingers back where it's supposed to be in the first place.

 

GD

 

That may be correct after all. I always ran the 5sp's behind my hipo builds and never even thought abut having to use a bigger bearing.

[GeneralDisorder]

That may be correct after all. I always ran the 5sp's behind my hipo builds and never even thought abut having to use a bigger bearing.

 

Yeah - I've never had a need to do it either. The 4 speed's suck and I don't own any 2WD's nor would I bother with them in this area of the country. It's mostly acedemic but apparently there are a few folks that can benefit from the information.

 

Now what I would like to know..... because I'm not sure and have never tried it - will the 5 speed/XT6 pressure plate bolt up to the EA81 225mm flywheel if the flywheel is cut to the XT6 step (0.815")? If so that means that with the 4 speed disc, 5 speed/XT6 pressure plate, and Nissan T/O you could just bolt it all up without having to change the flywheel and transfer timing marks....

 

GD

[capn_r]

Yeah - I've never had a need to do it either. The 4 speed's suck and I don't own any 2WD's nor would I bother with them in this area of the country. It's mostly acedemic but apparently there are a few folks that can benefit from the information.

 

Now what I would like to know..... because I'm not sure and have never tried it - will the 5 speed/XT6 pressure plate bolt up to the EA81 225mm flywheel if the flywheel is cut to the XT6 step (0.815")? If so that means that with the 4 speed disc, 5 speed/XT6 pressure plate, and Nissan T/O you could just bolt it all up without having to change the flywheel and transfer timing marks....

 

GD

On my EA81 wagon I machined the step to the XT6 spec and am running an XT6 clutch assembly. I put in a 5 speed but I can't see why the 4 speed 225mm disc and the Nissan release bearing wouldn't work just fine with the four speeed.

[hatchsub]

I JUST checked stock on the oil pumps. THERE HERE!

 

There are 11 in the country as of right now.

 

PART # 15010AA120

 

90 bucks a pop retail.

From the sounds of it i should stock up on a few things. I have a brand new (well 7 years now) water pump on the tried and true hydro that i have in the coupe now but i know that those only have a certain life span. I might want to think about buying two of those and two of the oil pumps while i got the cash cause honestly i dont plan on running another motor anytime soon. I love the simplicity and answering questions like "where are the timing belts?" People on this side of the US are clueless about this car.

[ruparts]

I understand what you meant - I'm talking about the ratio of the fork - which is determined by the length from the cable to the pivot ball and from the ball to the contact point on the PP fingers. The ratio is 2:1 on the 5 speed's according to my '85 FSM. The length from the ball to the PP fingers would be reduced by .1929" when using the Nissan T/O vs. the stock 4WD T/O. That would change the ratio...... I would have to take measurements to find out exactly what it would change to, but perhaps it will be easier to just ask backwoodboy how his clutch feels

 

GD

 

Hi,

I want to comment onthe fork ratio, on ea82 forks the 2wd ratio is 2:1 but the 4x4 fork is 3:1, according to the manual , xt6 too. i have not compared either one to the ea81 forks but 2wd and 4wd are different from each other.

[asis]

Crank and heads - no they won't interchange. Pistons will interchange across all the 92mm bore engines - EA71/EA81/EA82.

 

 

 

GD

 

Just a simple NO eh? Why?

 

81 is just a stroked 71? Not questioning your knowledge, just feel like mine is not being considered and your answer lacks substance.

 

I recall a discussion (more like me listening to you describe, with astounding detail ) about the lineage of subie engines, but I slept since then .

 

I was just curious what the change/improvement/upgrade...? in the block from the EA71 to EA81. I can see reasons for the heads certainly but not sure of the crank...?

Edited April 14, 2010 by asis