Need EA81 build advice - Breaking the ridge and honing a cylinders at home and compression ?'s

[El Presidente]

The HG blew on my '82 EA81 and I'm seriously considering dropping in some EA82 SPFI pistons to bump the compression while its apart. The EA81 is in a 90 loyale with the 90 SPFI system on it, so I think it would be perfect for the setup. I'm also mulling over taking some more off the heads to get the compression a little higher. With SPFI pistons I'm hearing it will be about 9.1-9.2/1...how high can I go on 87 octane?...maybe spfi pistons and .010" off the heads....or leave the heads alone?...I know one guy I wheel with has .020-.025" off the heads and ea71 pistons and he needs mid grade at a minimum. I'm not looking to go crazy, I just figure...why I have it apart...why not..

 

I'm not going EJ in this car yet..

 

I've never considered putting new pistons in a motor without boring over and getting brand new pistions/rings/etc., but having been around subarus awhile, I've learned you can get away with alot. What exactly can I get away with? can I use old pistons? Assuming I get new pistons and rings(stock sized), do all I need to do is grab a glaze hone and a ridge breaker  from oriellys and drop them right in??

 

I used to be an auto machinist so it was always drilled into my head to "do it right" and not half-rump roast it, but since then I've learned there's a lot of grey area in between. Im also tight on cash...

 

Josh

[Crazyeights]

I've built LOTS of EA81's. Just break the glaze on the cylinders with a ball hone (if even that) and install your used SPFi pistons with new rings. Don't worry about a ridge, with the cylinders on the side like they are they almost don't wear at all. I always tend to run premium in my custom builds because I like to push the timing a little more advanced than stock. Either .010 or .020 from the heads will be fine but the valve train geometry is very finicky on these engines.  My advice is to run the stock cam especially if your running SPFI or you could end up with unwanted noise or incurable low end drive-ability issues.

Edited July 14, 2013 by Crazyeights

[El Presidente]

Ok thanks.

 

If I don't break the ridge at the top, won't the #1 compression ring break when the piston comes to full stroke considering the SPFI pistons are taller? Are the ring lands in the same location?

 

I've still got the EA82 that came in the car, its got something like 258K on it...do you think the pistons are too far gone to reuse in an EA81? Its hard to find an EA82 under 200k anymore.. I was thinking of fixing the EA82 motor I have and putting it in another car to flip, but if it will work for what I'm doing, I'll just yank it apart and scrap the rest.

 

Josh

[Crazyeights]

Go ahead and use the 200k pistons. Measure the diameter at the skirt to make sure they aren't too badly collapsed. As long as they aren't "creamed" they will be fine. I have torn down MANY EA's and EJ's and I've never had to cut the ridge on one yet simply because there isn't any. Remember this isn't an "inline or V" configuration engine. Upper cylinder wear in N/A Subaru engines is usually very minimal. Thompson-Engines on Ebay has a really good price on ITM piston and ring sets for the older Subarus. For about $150.00 you can replace them all if you are worried. That is the way I went on my last couple of builds and it worked out very well. The EA82 I just finished has about 5k on it now and it's bone dry underneath and runs like a watch.

Edited July 14, 2013 by Crazyeights

[Idasho]

Im running a set of ITM SPFI pistons and rings in my fresh high compression EA81.  Also purchased from Thompson from ebay.   Ive got about 4k on the motor now, and so far so good.   They seem to be a high quality, inexpensive route to go.