7MGTE crank specs

[supraguy31]

Ok All, Ive been fighting a Rod Knock for some time now so I went ahead and tore the motor Down. This is what I noticed on Number 5 Rod

This Pic shows the Difference in size even though they have the same Specs. How does this Happen if they are Exactly the same Size?????? Is this due to the rod being out of Round????

All the other Rod Bearing are fine. Now I understand that there should be a Siver Coating on the Bearing itself but Dam, I think this one is a Little gone. After looking at the Markings on the Bearings, It said that there Bearings are .75 Oversize. Now If Im correct that Means that there was .30 thousands taken off the Crank when It was Turned. am I correct?? and If so, Do you think this is excessive amount. Do I need to get another crank or Since #5 Rod was the only one that showed any wear at all. Just get the #5 Rod checked and if needed Replaced.

Thanks if someone can help.

Robert

 

[supraguy31]

Anyone out there. Dont want this to Happen again.

Robert

 

[figgie]

.035 chewed away the nitriding. need to get the crack journal hard chromed.

 

[supraguy31]

The crank journal looks Exactly like all the other. Nice and Shinny. I cant see any Difference in any of them.

 

[bluepearl]

Bearing size differance by the picture is due to detonation. It's called bearing hammer. You must measure everything, or if you can't, a machine shop can direct you. You cannot guess at these measurements. Measure with inside and outside mikes and a plasti-gauge backup

 

[miggles]

Check to see crank#5 pin hasnt got small hammer marks. I had rodknock in my motor I just built up and I saw these small rectangular marks where the bearing had hit the crank and the insides of the rods. Had to grind .10" and get undersize bearings to suit.

 

[supraguy31]

Well, If that is the case, I guess Im going to have to get another Crank. Im It already has .75 oversize Bearings in it and I was told that was the max that a Crank could be turned.

Robert

 

[IJ.]

SG: When a bearing fails and overheats it loses it's crush (ends pull in towards each other) The difference in size is the actual thickness of the shell this makes the beaing ID match the crank pin = 0.001" ish.

The shell should be a snap fit into it's rod or block (this is part of the crush and why measuring a shell on the bench doesn't really tell you anything)

 

[supraguy31]

Well, After going a Little Farther and Deciding to go ahead and replace the rings also. I have come to the Conclusion that Im totally Screwed.

Lets say 4 of 6 pistons look just like this.......

So in the search for rod bearings, Im also looking for Pistons now. Which would be better. Ross?? JE?? Weisco??

Robert

 

[IJ.]

Using Ross here no problems.