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Guest Message by DevFuse
 

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Honestly, who has measured/compared EA71, EA81, EA82 SPFI pistons?


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7 replies to this topic

#1 RavenTBK

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Posted 18 October 2006 - 01:43 PM

Anybody actually physically measured the dimensions of the EA71, EA81, and EA82 SPFI pistons?

I've called up CCR to actually get the ball rolling on my replacement motor (with swapped pistons to bump up compression), and heard some other things. And taking into consideration that wives tales are spread frequently on message boards as facts, I just wanted to ask for some hard confirmations.

Here's what I've read/heard/studied on multiple boards (not just USMB), and am now wanting confirmation on:

* compression can be bumped to ~9.5:1 by using 82SPFI pistons in the EA81.

* ~9.0:1 is possible by using 1600 (EA71) pistons in the EA81.

* EA82 SPFI pistons are a more desireable swap as the oil ring lands are stronger than those on EA71 pistons.

* EA82 pistons have weaker oil ring lands than EA81 pistons

* EA71, and EA82 SPFI pistons are 100% swappable into the EA81.

* EA82 pistons are prone to cracking, as their overall construction is not on par with the EA71/EA81.

Here's some threads about piston swaps that has gotten me to the confused point I am at now.
http://www.ultimates...ead.php?t=65756
http://www.ultimates...ead.php?t=65720
http://www.ultimates...ead.php?t=63761
http://www.ultimates...ead.php?t=42164
And this one has a post from ShawnW that goes against all the others (1600 pistons yield 9.5?):
http://www.ultimates...ead.php?t=39966


I'd rather not hear speculation, just hard facts, preferably by firsthand experience.

Thx. :burnout:

#2 carfreak85

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Posted 18 October 2006 - 01:46 PM

I'll let you know at the end of the quarter when I'm finished building my picante off-road motor. I'm going to be using EA71 pistions in an EA81, and some other goodies.

#3 GeneralDisorder

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Posted 18 October 2006 - 02:56 PM

I measured it, and from the wrist pin to the piston top, the EA71 piston is right around .008" - .010" taller. It's not much really at all. If you shave the heads the full .020" (or even .025", and enlarge the manifold holes) you can get it up to around 9.3:1 by my calculations....

I'm using them in the engine I'm building right now, but in the future I would use the SPFI pistons. The EA71 pistons have very thin ring lands, and the SPFI are much easier to get, and provide higher comp.

GD

#4 GeneralDisorder

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Posted 18 October 2006 - 08:08 PM

As to the rest of your questions (about durability, etc), I know of at least three EA81's with cams and EA71 pistons that don't have any trouble at all. CCR has no qualms about installing them upon request, and if there were any known problems with the ring lands when used in Hi-Po EA81's I'm sure they wouldn't be willing to install them.

I wouldn't worry about the ring lands unless you are planning to run forced induction or very high RPM. The EA71 pistons seem to do fine with 100+ HP. I'm running a torque cam so I don't anticipate high-rpm loads, and I already bought a set of chrom rings for mine. Otherwise I would use the EA82 pistons just because of the higher comp.

If you want THE BEST pistons, I've heard amazing things about the RAM performance sets. But at $120 each, I think I'll pass....

That info that shawn posted..... not sure where he got that, but he may have done his calculations thinking the EA81 was 9:1, when it's actually 8.7:1 stock. If you take the numbers I listed, and factor in taking 25 - 30 thou off the heads as well, that's maybe a .040" difference in chamber volume... which IIRC worked out to less than 9.5:1, but more than 9:1.... FWIW.

GD

#5 RavenTBK

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Posted 20 October 2006 - 03:39 PM

Thanks for the info GD.

The reasoning behind these questions is just to confirm all that I've read. I'm wanting to get a fresh motor from CCR, and as expected, they had no issues with doing EA71 pistons in a fresh EA81 block, however, they are difficult to find, causing a build time of 2+ weeks. Now, when I mentioned SPFI pistons for the increased compression and them being easier to find, the conversation went south.. seems as though they've never heard of that swap, and they seemed rather timid about getting it done. Emily said they'd call me back on it a couple days ago.. *shrugs*

Its not like I'm calling them up wasting their time "window shopping".. I'm actually wanting to get something moving, and wanted to arm myself with the correct information before I call them back again.

The final goals with this (although irrevalent at this stage) is an EA81 that I can do a bi-fuel propane swap on. High enough compression to make the propane more efficient, but not so high that I cant run it on pump gas if I needed to. And since I have no real knowledge of doing an internal buildup myself, I'd just as soon pay CCR to build a good motor and swap it in myself.

Hehe... my current motor is still hanging by a chain from a tree in my backyard.:dead:

#6 GeneralDisorder

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Posted 20 October 2006 - 03:49 PM

The SPFI pistons really aren't all that different. EA81 and EA82 both have the same bore and stroke. The SPFI pistons have "dimples" where the valves sit.... but that's really only so the EA82 doesn't bend valves if the timing belt breaks. The EA81 being gear driven wouldn't have this problem anyway. Shouldn't be any different than using EA71 pistons.... there were some JDM EA63's?? that were designated "HC" for high compression, and already had 9.5:1 running with a carb. But I think that was before leaded fuel went away :mad:.

GD

#7 Urabus-84HBDR

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Posted 06 November 2006 - 10:52 AM

if oyu want i can get all the specs for any of the subaru pistons or motor for that matter... any of it... my bro is in a machining class and we are going to be rebuilding an ea81 with the ea71 pistons and some other goodies, weber carb, dual exhaust, and some other secret stuff.... lol. let me kno i can get the info if you want! laters.


Anybody actually physically measured the dimensions of the EA71, EA81, and EA82 SPFI pistons?

I've called up CCR to actually get the ball rolling on my replacement motor (with swapped pistons to bump up compression), and heard some other things. And taking into consideration that wives tales are spread frequently on message boards as facts, I just wanted to ask for some hard confirmations.

Here's what I've read/heard/studied on multiple boards (not just USMB), and am now wanting confirmation on:

* compression can be bumped to ~9.5:1 by using 82SPFI pistons in the EA81.

* ~9.0:1 is possible by using 1600 (EA71) pistons in the EA81.

* EA82 SPFI pistons are a more desireable swap as the oil ring lands are stronger than those on EA71 pistons.

* EA82 pistons have weaker oil ring lands than EA81 pistons

* EA71, and EA82 SPFI pistons are 100% swappable into the EA81.

* EA82 pistons are prone to cracking, as their overall construction is not on par with the EA71/EA81.

Here's some threads about piston swaps that has gotten me to the confused point I am at now.
http://www.ultimates...ead.php?t=65756
http://www.ultimates...ead.php?t=65720
http://www.ultimates...ead.php?t=63761
http://www.ultimates...ead.php?t=42164
And this one has a post from ShawnW that goes against all the others (1600 pistons yield 9.5?):
http://www.ultimates...ead.php?t=39966


I'd rather not hear speculation, just hard facts, preferably by firsthand experience.

Thx. :burnout:



#8 RavenTBK

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Posted 07 November 2006 - 10:39 PM

if oyu want i can get all the specs for any of the subaru pistons or motor for that matter... any of it... my bro is in a machining class and we are going to be rebuilding an ea81 with the ea71 pistons and some other goodies, weber carb, dual exhaust, and some other secret stuff.... lol. let me kno i can get the info if you want! laters.

Absolutely! Grab any/all info you can and post up. The more info thats on the board the better it is. We all know what fits, but a little more detail on measurements and stuff would be excellent.




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