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Discussion Starter #1 (Edited)
Hi, I have a crankshaft that was given to me along with some other parts when I bought my Supra. Well the 5mge needs rebuilding, and the crank that was in it is trash. The main journals aren't bad but the rod journals are out of round and too far out of spec (2.019in being the smallest diameter measured) So I thought maybe I can use the other crank. Well.. measuring with my harbor freight caliper I found all the rod journals are between 2.023-2.024in. From what I can find the stock journal size is around 2.046-2.047. This crank probably needs a little machine work done just because it has a little rust on a few journals.. and at roughly 2.0235in they are already a little beyond .50 mm undersize (if my math is right) which the manual says is the max or at least it doesn't list other sizes.

I found some places that sell .75 mm undersized bearings for the 5mge and was wondering if anyone has ever ground their crank down that much? Could I possibly get away with polishing the journals and putting in the .5 mm bearings? I probably won't really push the engine hard, mainly just want to cruise in it.

I've been trying junkyards but Supras and Cressidas just don't seem to ever show up around here. And I don't really want to spend 250-300 dollars on a used crank that I'll have to get machined anyway.

Sorry for the long read. And I appreciate any replies I get. I tried to search but couldn't find anything on the .75 mm bearings other than where to buy them.
 

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I don't think used cranks that don't need machining are that hard to find. Could be the extra one you have is just really high miles or had a rough life. You loose some of the hardening the factory does to the journals when you grind them down. I would recommend going with factory fitted bearings, especially when mixing and matching blocks. The sizes of the bearings they used at the factory are stamped on the underside of the block. I mixed and matched when building my 6mge and I ended up having tolerances outside the range the standard size clevite bearings could account for on a couple journals and my oil control is poor (knocks on startup). Yes you can avoid that problem if you undersize and your machinist is good, but there is some degree of variance in the blocks too and you really need a line bore as well to make them perfect without fitted bearings.

You might want to think about finding a 7mge or 7mgte bottom end. All you need is the block, rods and crank and you can make yourself a 6mge with your remaining 5m parts. Might be easier to find. I used to routinely have to turn down free 7mgte bottom ends they were so common.
 

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Discussion Starter #3
Man I wish I was that lucky. Lol. I'd love to make a 6mge.. I did find an 89 cressida with a 7mge in it. But somebody took the hood off the car and the oil cap was gone so the oil pan had a ton of water in it and everything in there had rust on it. I think I've searched every junkyard within 75 miles over the past 4 months and that cressida is the only thing I've found. Are there any other cars that had the 7m in it other than the MKIII and cressida? Right now I'm kinda just waiting for something to show up in the junkyard or maybe find a good deal on a crank from eBay.
 

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Discussion Starter #4
  • Well I found a decent deal on a crank, rods, and pistons from an 88 cressida. He says the engine ran smooth before disassembly so I guess he's parting everything out, must've been wrecked or something. Not sure why he wouldn't just list the entire engine.. But everything looks good in the pictures, hopefully it is.. I was gonna hold out for some 7mge internals but this popped up and it was hard to pass up.
 

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Hopefully the milage isn't too high.

If you check some local groups with lots of mk3 Supra owners, I beat you won't have a problem finding someone with a 7mgte bottom or complete motor sitting in a corner somewhere. I think there's more 1jz/2jz swapped mk3s left on the road today then ones with 7ms at this point. Same with the cressida guys.
 

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Discussion Starter #6 (Edited)
I did actually find a 7mge on the facebook marketplace for a fair price, but I already got the crank, rods and pistons from the cressida and everything looks great, and the crank is still within spec for standard bearings too. But the #2 cylinder in my block has a .003 taper difference in the top of the cylinder, so I don't think I can use standard sized pistons. Unless the shop can hone that true and leave the cylinder within spec.

I was just gonna get some oversized pistons but that is proving to be very difficult. I can't seem to find anything other than some 1mm oversized pistons on rockauto. And that's too big to me on a block that don't even need .010 of wall taken off. Was trying to find some .020 or .030 pistons.

Where do you guys buy pistons? For cheapish?

Edit As soon as I posted that rockauto showed the .020 over pistons to be in stock. So I got some on the way.
 

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If you can get 1mm over, go for it! Thats only 2 sizes over stock, factory offered 3, and the HKS headgaskets allowed for 4 (2.0mm overbore). Nothing makes real power on an NA motor like displacement and compression!

The machine shop can only clean up the surface for the most part if you are staying with the stock piston diameter. It might be workable, but you will likely burn a small amount of oil like I do.
 
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