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Old 08-02-2001, 02:58 PM   #1
8Complex

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Default What I learned about the EJ25 today.

Phase I pistons (MY98) will not swap into a phase II (somewhere in MY99-MY0X) bottom end. The piston is either too long (between wrist pin and top) or the rod is too long in the phase II bottom end.

The piston I swapped in from the MY98 block I had laying around sits .5mm higher then the deck of my phase II block at TDC. I ordered a couple of used MY00 pistons so that I can get my motor back together again.

Also, if you don't know how to tell a phase I bottom emd from a phase II bottom end here is the trick -

A phase I bottom end has 48mm rod journals, and has the thrust bearing for the crank towards the middle.

A phase II bottom end has 52mm rod journals, and has the thrust bearing towards the end of the crank (rear? don't remember).

This has been the first session of Internals 101. Hope you all enjoyed it.
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Old 08-02-2001, 03:00 PM   #2
stimpy
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I wouldn't have thought the MY98 pistons would go in there, but now we know for sure

Are you replacing the rods and pistons from a used motor or just the pistons with your previous rods?

-Jon
www.nothingserious.net
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Old 08-02-2001, 03:49 PM   #3
8Complex

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Pistons with the previous rods. Going to get a hold of a phase II short block and do a little construction, most likely. Either that or I'll get ambitious in the future and I'll rip mine apart again to throw in internals.
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Old 08-02-2001, 05:38 PM   #4
ColinL
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nice to know about the rod journal size. the phase I thrust bearing is on the #3 "main" (there aren't really bearing caps on a flat four) and phase II is on the #5.
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Old 08-02-2001, 09:06 PM   #5
ins8ibl
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Well, here is something interesting, I happen to have a supposed phase II block with '98 DOHC pistons in it. So either it is not a phase II block (although it has the ridges on it where they should be etc.) or the rods are somehow different. Bill Harvey should know about it for sure.
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Old 08-03-2001, 01:13 AM   #6
ColinL
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Trey says he's seen motors like that. He was disappointed that his original theory about the ridges isn't 100% true...
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Old 08-03-2001, 03:47 AM   #7
8Complex

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Yeah, the castings are interchangable between the two for the block, unfortunately. Basically they just used up their inventory of blocks before going with the new casting.

Supposedly - and I don't have the ability to confirm/deny this - the phase I and phase II bottom ends are interchangable within blocks completely. This is particularly interesting to me as I've got a block with a phase I bottom end in it, and if it can be switched, damn right I'm going to do it!
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Old 08-03-2001, 04:33 AM   #8
Scooby South
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So the bigger journals are better/Stronger???? then why aren't more 98's with Turbo's blowing up????
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Old 08-03-2001, 04:43 AM   #9
Eric SS
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swap and N20. gone. : (

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Generally (But i don't know for scoobies) there is a point where the rod bearing journal gets to big. The larger it is, the faster the rod journal I.D. has to travel (Because it has a larger distance to cover) and therefore heats the oil faster and can meltdown faster.. It's complecated but that is the just of it in a nutshell

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Old 08-03-2001, 04:46 AM   #10
Scooby South
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Now that makes sense.....but no one except Andre has Broken a Rod that I know of....Pistons yes...rods or spun Bearings...no
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Old 08-03-2001, 07:41 AM   #11
paultg
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Hey 8,
This maybe a stupid ?, but why are you swaping pistons anyway. Can't you just put the 98 shortblock into your RS as is, and just run your '99-'01 Heads?

I just haven't been reading about this too much, so sorry if you covered it.

Paul G.
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Old 08-03-2001, 08:19 AM   #12
HRE | giulio
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Quote:
Originally posted by Scooby South
So the bigger journals are better/Stronger???? then why aren't more 98's with Turbo's blowing up????
It's the gold rims =)
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Old 08-03-2001, 10:35 AM   #13
ColinL
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dude, you don't see more 98 turbos going up because there weren't that many of them to even be turbocharged!
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Old 08-03-2001, 10:47 AM   #14
8Complex

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paultg - Because it was a "complete" block, so there were a few things missing here and there. I just didn't want to take my chances with it mainly. It had come from a car with a bad case of piston slap originally, so who knows what they did while it was on their shelf waiting to possibly go back on warantee.
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Old 08-05-2001, 10:14 PM   #15
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So your going to use "pistons" from an "incomplete" '98 engine that was pulled at the dealer because of piston slap warranty issue? Can't you just order a new piston from Subaru, or for the really safe, just replace your engine with a new one from subaru, or a used one from a junkyard with low miles.

I just don't understand what you are trying to save by doing this, since it will most likely be "less" stong than the prior engine you destroyed, and you will have to do this all over again?

I guess the "leaning experience" has no price. I hope it works out for you.

Paul G.
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Old 08-06-2001, 01:43 AM   #16
8Complex

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Oh yeah, less strong and less reliable, but I just planned on getting the car running temporarily again while I get and build up a second motor. I was only looking at getting the car to run 2-3 psi for a month or two, realistically, and with low-duty use as well (since I know it's so weak to begin with unless I test it after running and it turns out to be a miracle rebuild or something ).
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