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hot rodded ea81 is trans. strong enough?

ea81 brat duel range

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14 replies to this topic

#1 ArtRat007

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Posted 05 December 2013 - 03:11 PM

Will my trans. put up with the added power i was thinking of adding?

 

I have a 83 Brat Gl with a mostly stock ea81 minus some emission deletes, an extra ea81 in my garage, and an ea71 next to it.

 

So the plan was and still is at the moment to..

add dual carbs with custom carbon fiber manifold

shave cylinder heads

different cam or cam grind

EA71 pistons

enlarge intake port by a smidge

along with complete new everything i can find

and probably other stuff i cant remember

 

How tough were the 4 speed dual range trans? I think the actual name of the trans was

T81W 4WD

#2 NorthWet

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Posted 05 December 2013 - 06:40 PM

The transmission will be strong enough.  It is unlikely that you will get significant torque increases, and the heads and manifolding limit HP increases.  Neither the engine nor the transmission are overstressed in stock form.



#3 the sucker king

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Posted 05 December 2013 - 06:42 PM

In my opinion you are never going get so much power out of an ea81 that the trans can't handle it. EJ swaps are common and they don't overwealm the EA trans. I would think the axels would be the weekest link anyway. I wouldn't worry about it.



#4 Nate E.

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Posted 05 December 2013 - 11:59 PM

"shave cylinder heads"

 

Don't forget to shorten the pushrods.

 

NE



#5 Turbone

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Posted 06 December 2013 - 02:02 AM

"shave cylinder heads"

 

Don't forget to shorten the pushrods.

 

NE

 

Depending on cam grind, he may not have to.



#6 Nate E.

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Posted 06 December 2013 - 02:09 AM

Smaller base circle but more lift allows for that? Or is it a timing situation?
What about rocker arm geometry?

NE

#7 ArtRat007

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Posted 06 December 2013 - 05:10 AM

Cool thanks guys I hope to have it all hopped up by the summer should be a good project

I was thinking of an EJ swap but decided I'll be doing that to my 86 XT



#8 skishop69

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Posted 07 December 2013 - 05:57 PM

The tranny will take 250hp make before the input shaft goes. As for shaving the heads, you can't. I'm surprised no one else got this. You can have them surfaced, but that's it. Because the intake bolts from head to head, it will no longer fit. You say you are going dual carb. Yes, you could shave them then, but you're going to need custom made pushrods or your lift and geometry will be wrong. NA, dual carbs, the best you can hope for is about 150HP. I would forgo shaving the heads and install EA82 pistons. That will bump you to 9.5:1 compression. I would also loose the dual carb idea and install the EA82 Tbody FI. I've built a lot of high performance engines in my time and put a lot of thought and research into the EA81 build up as I'm starting mine in the next couple of months.



#9 El Presidente

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Posted 07 December 2013 - 07:05 PM

The tranny will take 250hp make before the input shaft goes. As for shaving the heads, you can't. I'm surprised no one else got this. You can have them surfaced, but that's it. Because the intake bolts from head to head, it will no longer fit. You say you are going dual carb. Yes, you could shave them then, but you're going to need custom made pushrods or your lift and geometry will be wrong. NA, dual carbs, the best you can hope for is about 150HP. I would forgo shaving the heads and install EA82 pistons. That will bump you to 9.5:1 compression. I would also loose the dual carb idea and install the EA82 Tbody FI. I've built a lot of high performance engines in my time and put a lot of thought and research into the EA81 build up as I'm starting mine in the next couple of months.

You can shave the heads on an EA81, not an EA82

 

The most you want to take off, running a stock intake, is usually .015-.020(from stock height/head thickness), but the OP is running a custom carbon fiber intake(s). If hes going that far, shortened pushrods isn't a far stretch if he wants to go over .020". You can also correct valve geometry a couple ways including grinding the rocker arms, and shimming the rocker towers.

 

When your not limited by stock intakes, cam and pushrods, the most you usually want to take is .060", but you can take more if you want to push it. 

 

Josh



#10 moosens

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Posted 08 December 2013 - 02:25 AM

You do you own mold making , vacuum bagging ,and cooking?

#11 ArtRat007

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Posted 08 December 2013 - 06:05 PM

yeah thanks for the advice dudes but i dont have EA82 parts hanging around so i wont be using them. I do have ea71 pistons which are taller than EA81 pistons  so thats what i'll be using(I need to check my facts on that) anyways i'm planning on documenting all of my building projects will post in the summertime when i get around to them. As far as carbon fiber mold making and all that stuff goes I do that and for this application should be as easy as a cat's rump roast im going to use carbon fiber tubing.

 

Also i have a question about geometry of the pushrod, cam, rocker assembly I've never done one of these im not a pro mechanic so be nice. can a person not grind the cam so the pushrods are short at that point? and then shave the heads to close up the gap between pushrods and rockers while gaining compression?



#12 El Presidente

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Posted 08 December 2013 - 07:26 PM

You could grind the cam to fit milled heads using the stock size pushrods, but you'll lose valve lift, which negates the point of what your doing. If you put in ea71 or ea82 pistons and take .015 off the heads, you can get away with using stock pushrods. You'll just need to run a tighter valve lash. Last ea81 I had, I took .020 off the heads on stock pushrods and I ran my valves at .006" intake and .008" exhaust. It ran great!

 

Josh



#13 ArtRat007

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Posted 09 December 2013 - 07:31 PM

You could grind the cam to fit milled heads using the stock size pushrods, but you'll lose valve lift, which negates the point of what your doing. If you put in ea71 or ea82 pistons and take .015 off the heads, you can get away with using stock pushrods. You'll just need to run a tighter valve lash. Last ea81 I had, I took .020 off the heads on stock pushrods and I ran my valves at .006" intake and .008" exhaust. It ran great!

 

Josh

Break it down for me I'm new to life. So your saying if i want to shave the heads and grind cam I should get custom pushrods or I'm not going to have enough valve lift to make the shave/grind add power and not just backfire alot? and, I know, I know I need to do more learnings on this subject.



#14 El Presidente

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Posted 09 December 2013 - 10:38 PM

Ok, heres the deal.

 

You can take this project as far as you want to go couple hundred to a couple thousand, but heres what you can get away with. You can take up to .020" off the heads and use the stock cam and stock pushrods. You'll have issues of valve ticking, so you'll need to tighten up the valve clearance to stop this. It will not backfire, you'll have more compression which equates to more low end torque. You'll have the same lift, but the valve train geometry will be off. Running custom pushrods anytime you adjust head thickness, or deck height will hep things run better, but its not critical at .020".

 

First thing decide what you want to do with this motor. If you run ea82/ea71 pistons and take .020" off the heads, you may be stuck with running premium fuel to stop detonation, but it will sound like a chainsaw and tear up the road. If you want something a little more than stock for the road, just put ea82/ea71 pistons in and run a stock ea82 efi setup on it. If you want an animal(a little one), take .060 off the heads, run a custom intake, custom pushrods be stuck with aviation fuel and only get 100-130hp. 

 

Add up how much your preferred option costs and compare it to an ej swap. An EJ18 puts out 110hp stock is the easiest EJ to install. Search around and decide what you want. Theres tons of EA81 build threads and tons of EJ18 swap threads.

 

Josh



#15 ArtRat007

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Posted 09 December 2013 - 11:09 PM

Awesome thanks for being so helpful I think i still want to stick with the EA stuff cause i have all that already and it didnt cost me a thing

Do you mean it will sound like a chainsaw cause valve noise? I dont think that will bother me much but there was a guy on a thread somewhere that somehow fit little springs on the push rod side of the rocker, or so was stated... putting slight pressure on the rods(dont ask me how it was never elaborated) and from what was posted in that thread his soob didnt make much noise at all, but then again i dont know what kinda setup he had besides it being a modified ea81 and not saying i would try that just throwing it out there since on the topic







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