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Guest Message by DevFuse

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Engine building Q:

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11 replies to this topic

#1 Guest_SOOBME_*

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Posted 05 August 2003 - 01:18 PM

I'm thinking of taking my EA81 w/bad head gas. and puting in the EA71 pistons when I do the H.G.s When I do that, should I use new rings and hone the cyl.s, use the rings from my old EA81 rings, new rings no hone? I don't want to tear into the bottoum end when I do this, trying to keep this on the cheep and eazy side for now. If I like it then I will build it up with new bearing and a better cam later.

#2 Guest_Caboobaroo_*

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Posted 05 August 2003 - 04:17 PM

ok. You should use new rings and bearings... thats a given. As whenever to hone it or not, if the cylinder walls look beat up or they have a ridge around the top, you should get it honed. But if it looks like its fine and doesn't have any ridges or other marks in the cylinder walls, then I think you can get away without honing it. Good luck!!

#3 Guest_GlCraigGT_*

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Posted 05 August 2003 - 04:20 PM

no, you really need to hone the cylinders to get the rings to seat properly

#4 Guest_GeneralDisorder_*

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Posted 05 August 2003 - 05:16 PM

If there is a ridge, then get a ridge reamer and take care of it. Further - when installing new rings you should at least scuff up the surface with a finish hone. This will allow them to wear in quicker.


#5 Guest_x silvershad0w x_*

Guest_x silvershad0w x_*
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Posted 05 August 2003 - 06:13 PM

On my last engine dissasembly, I whent to remove the pistons without tearing into the bottom end, but i didn't have the proper tools. You need a 14mm allen head socket, and one of those nice 3 ft long breaker bars for the front plugs to get access to the piston pins on the front two cylinders. For the rear, pull off the rear bellhousing, and there are two holes in the casting underneath for easy access to the rear wrist pins. You will need a tool, either fabricated or the Subaru factory tool, to get those pins out. I fiddled with what I had around the garage, but no luck, the engine I was tearing down had a lot of carmelized oil on the exposed portion of the wrist pins, so they didn't like to move to easily.

Since I was doing a full teardown, I just split the case, and then removed the rods with the pistons in place.

Never install new rings without honing the cylinders first, if you've never honed before use a bottle brush hone in your drill. The three stone hones are nicer for more control, and it makes it easier to spot out of round cylinders, but this is not something to worry about on the Subaru engines as much as others. It is also very easy to take out too much material with the normal hone.

With the higher compression, and since you are just trying to reach higher HP in general, install a new oil pump if you are past 60,000mi on the old one. While to pressure may still look good, the volume i can guarantee you is down, and the bearings will be taking more of a hit with each power stroke, you want as much oil in there as possible.

Good Luck!

#6 Guest_Caboobaroo_*

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Posted 06 August 2003 - 01:15 AM

ok I went and talked to a guy that I trust with engines and he said to hone it cause the grooves from the hone are what the oil sticks in to help lubricate the cylinder walls so everything runs smoothly

#7 Guest_GeneralDisorder_*

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Posted 06 August 2003 - 01:42 AM

That's some BS - after a few thousand miles there won't be any grooves. The oil had better be on the entire surface too - not just "in the grooves". The grooves simply help the rings to wear to the imperfections of each cylinder. Oil is used precisely because of it's ability to withstand decent amounts of pressure (ie - it won't easiy sqeeze out from between the parts). The rings are designed to leave a thin film of oil on the cylinder walls that actually prevents the rings, and the piston from touching the metal of the bore. The whole thing rides on a cussion of oil. In a perfect world, the parts would NEVER actually touch, and thus there would be no wear at all. Of course this doesn't happen, and they do touch sometimes. This causes the slow wear that you see on any well maintained engine. Smooth is what you want - no grooves please! Like I said - it's a break in thing. Your essencially machining the parts to fit each other perfectly. And I seccond the bottle brush hone - easy to use. Just make sure you make quick up and down movements with it. You want the scoreing it makes to be at a 45 degree angle, sort of like a cross-hatch pattern.


#8 Guest_snotrocket23_*

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Posted 06 August 2003 - 06:20 AM

I'm gonna have to disagree with GeneralDisorder with the honing marks.
If an engine has been well maintained, the crosshatch will still be visible even after over 100,000 miles. Those tiny grooves keep the cylinder lubricated, the rings do a pretty good job of scraping oil off of the cyliner walls.

If there is no crosshatch visible, then consider the cylinders worn. Maybe not so worn that a hone and re-ring wouldn't take care of it, but measureable wear nonetheless.

#9 Guest_ccrinc_*

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Posted 06 August 2003 - 06:59 AM

Good luck on the piston rings...they're getting MUCH harder to get! Specify year, before 1981.
EA71 pistons take different rings than EA81 pistons. And if you've never pulled rings off pistons...when you do, you'll find out, you simply can't use them again.
Besides, not using new rings would make that thing smoke like a chimney, even if they would fit.


#10 Guest_SOOBME_*

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Posted 06 August 2003 - 12:09 PM

Great! Thanks for all the info. and advice:D . The special tool for the rist pins, is that to pull them out, or just to remove the retaners( I don't know what holds them in, snap rings I'm gessing)?

#11 Guest_Adam N.D.J._*

Guest_Adam N.D.J._*
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Posted 06 August 2003 - 05:35 PM

Hey Tony, I got a "special tool" for pulling the wrist pin. The pin has a snap ring that holds it in, then it takes a little effort to get it out of there. Lemme know if ya need to use it. Catch ya Laters.

#12 Guest_NoahDL88_*

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Posted 06 August 2003 - 10:17 PM

Hone the cylinders, even if its just a quick bottle brush hone rough up the cylinders, anyone that tells you otherwise should check their engine manuals. if the cylinder walls are glazed the rings won't seat and you will burn mass oil

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