7MGTE Rebuild

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Thread: 7MGTE Rebuild

  1. #1
    Your ignorance... mk2racer's Avatar
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    7MGTE Rebuild

    Okay, it's time to rebuild. I've never done a 7mgte before, but here's the story:
    Bought the car, known BHG, possible rod bearing problem. I ran a compression test and got 122psi on all cyl's except 4 and 6; no.4 at 70psi, no.6 at 135psi. The intake mani was already torn apart, so I never heard it run, no idea what noises/etc.

    I pulled and tore down the motor to discover a BHG (as expected), but it was all blown apart at cyl 1 and cyl 4. That confused me with those comp. numbers. Anyway, I pulled the pistons out and the #6 rod bearing was all scratched and scored, the rest looked worn (140k on motor) but in otherwise good shape. The crank at #6 was also all hacked up.

    SO, I found a crank that should be in good shape that I am just going to replace mine with, as opposed to having mine machined. I will be installing new main and rod bearings. I am torn between ACL and Clevite, I've heard good and bad about both, so I don't know which way to go. I can get the ACL's for about $40 cheaper than the Clevites.

    What I don't know is this: I've heard you have to measure the crank with a micrometer and buy accordingly over/under-sized bearings. I saw no option for this with the Clevites or ACL's. Is this only w/ a machined crank? Should I have the new one machined anyway, even if it looks good? About balance issues, should I use the pistons from my motor, or the ones from the motor the new crank is coming out of?

    Anything else I should do/know? Thanks in advance.

    PS- I plan for about 350-400whp when I am done, down the road, so I think stock bottom end and PROPERLY torqued stock HG should be fine for now. Good/bad?

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  3. #2
    SupraForums Member ma71supraturbo's Avatar
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    Finding a good machine shop to help you with the process should be priority number 1. My local machine shop was invaluable in helping me with my rebuild (2nd only to the TSRM)

    But basically, you will take a good set of calipers and measure the diameter of the crankshaft (in multiple locations for each rod journal). The diameter # is important, but so is the variance (if the crankshaft has become slightly ovalized it may need to be reground -- check TSRM for allowable tolerances). You will also want to see the diameter of the cylinder bores, and whether they have become ovalized (there is a better word for this, but im sorry I'm brainfarting and can't remember it). If they are OK, you can just re-ring the pistons (making sure you file the rings to propper gap). If the cylinders aren't round, you'll have to go with a slight overbore and new pistons.

    Since you are going to be rebuilding/machining, I would definitely push for you to get a MHG. I'd consider 350rwhp a good limit for the stock HG (properly torqued). And since you'll have the engine apart, there really is no sense in "saving" $75 on a HKS MHG (over a stocker) when you can rest assured the HKS gasket will hold up to your long-term goals.




    oh, and for bearings I used Clevitte without problems.

  4. #3
    Your ignorance... mk2racer's Avatar
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    Yeah, I should do the MHG, but I figured if I wasn't going to need machining, then why pay to have the block/head surfaced for a MHG if they aren't warped? That will run a bit more than $75. Not that I'm trying to cut corners, but I'm not made of money either. If it needs machine work, I will definitely have the head/block done for MHG as well.

    Glad to hear the Clevite's worked out for you, I'll likey go with them, but was hoping to hear more about the ACL's since they were cheaper. Oh well.

    Also, I noticed that on the no.6 piston, it looks like the side of the top of the piston is chewed up a bit. I don't know wtf happened to this motor, but it isn't looking good. My next question, can I use one of the pistons from the other motor without worring about balance or clearance issues?


    I also found a 7mgte, no head, but supposedly excellent bottom end, for $500. Should I just buy it and throw it in, or would it be more cost effective in the end to rebuild? So far, not taking into account any machine work, I'm at about $625 on stuff I priced out. While it's more, I'd like to have a fresh engine, but who knows how deep into this thing I have to go...
    Any opinions appreciated, thanks again!

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