[rokit]

So, I bought an '83 diesel GMC with no engine, but it had the 700R4 tranny still in it. It definitely had a 6.2 in it previously, though.

In a separate deal, I got a Banks turboed fresh rebuilt 6.2. I dropped the engine in the truck today - lo and behold, the flexplate bolt holes do not line up with the torque converter bolts. The flexplate bolt circle is about 3/8" larger diameter than the TC's.

1) Is the flexplate intended for use with a TH400?
2) Can I simply find a 6.2/700R4 flexplate and swap it in? Are there any balance issues (6.2's are externally balanced right?)?

 

[JTS]

Sounds like it to me. If I remember right the TH-400 flexplate bolt pattern/circle is wider. I just did an engine swap on an 83 4x4 and I had to change the flexplate from a TH-400 to a 700R4. The flexplate goes on only one way and (somebody correct me if I'm wrong) I don't think there will be a problem. My friend just started driving the 83 and he hasn't noticed any issues yet. Hope this helps.

 

[4DR4X4]

I think a new flexplate is fairly cheap thru your local parts store.

 

[D.Camilleri]

Sounds like you have a flex plate for a turbo 400. A new flex plate for a 6.2 with a 700r4 can be bought for around 40.00. The flex plate only goes on one way and will have a heavy counter weight welded on one side. No need to pull the engine either, simply put the tranny and transfercase on a jack, and move the assembly back about 4 inches. This will give you enough room to access the flex plate bolts. Make sure to use loctite on your torque converter bolts to keep them from vibrating loose.

 

[rokit]

Thanks for the replies. I did swap the flexplate last weekend by scooting the tranny aft, and I plan on finishing up and getting running this weekend.

Another question: I was able to turn the engine by hand via the flexplate. I figured that with 22:1 compression and all the glowplugs installed that I shouldn't be able to do that. I bought the engine with the understanding that it has a fresh rebuild. Does this sound fishy to anyone? I am now apprehensive about fresh cylinders/rings...

 

[High Sierra 2500]

Another question: I was able to turn the engine by hand via the flexplate. I figured that with 22:1 compression and all the glowplugs installed that I shouldn't be able to do that. I bought the engine with the understanding that it has a fresh rebuild. Does this sound fishy to anyone? I am now apprehensive about fresh cylinders/rings...

Doesn't really surprise me too much... Most engines are like that. Remember there will always be some compression leakage on any engine when you turn it slowly, mainly because of the piston ring gaps. In addition, a freshly built engine will actually have slightly less compression than one that has been broken in because the piston rings have not had a chance to seat.

 

[rokit]

Yeah, perhaps I'm just nervous. :

I've just seen way too many automotive hack jobs in my life...

 

[High Sierra 2500]

You'll find out when you fire it up, that's for sure... ):h

 

[hexguy]

Yes you flexplate is for the 400 . some had both bolt patterns . Parts stores have new ones around $65.