'86 2.8L V6 - Ext Or Int Balanced?

[EmmJay]

Hey all, just bought my first MJ last weekend and have been glued to ComancheClub for a week straight!  Looks like there is lots of good information here and I look forward to contributing as I learn more about the truck.  My DD is a '97 TJ, but I've had my eye on Comanches for a long time... Picked up a 1986 Custom 2.8L V6, 3-spd auto, 2WD.  Interior and exterior are in excellent shape, and the truck starts and runs decently.  Got an excellent deal on it knowing that it needed a flex plate replacement.

 

My question: I have read that the 2.8's were made both externally and internally balanced, depending on the year.  I've read on some threads that they switched from externally to internally in the middle of the '86 year, while other threads state that internal balancing did not come along until '87 or '88.  Can anyone tell me for sure if there's a definite way to tell if my '86 engine is internally or externally balanced?  I'd like to order the new flex plate ASAP so I can get the work done before it gets too cold outside...

 

Thanks for the help.

[jimoshel]

I've swapped a couple 2.8'S and I don't know how to tell the difference. Mostly I swapped 2.8 from a later year S10 and kept the fly wheel, flex plate with the engine. Never had any problems.

[carnuck]

The flexplate will be weighted on external balanced motor

[EmmJay]

Thanks for the replies.  Yes, I know I can figure it out once I get everything apart, but I'd like to know beforehand so I can order the correct flexplate.  Otherwise I'll probably just order both and return what I don't use.

 

Any other insights on this?  I feel like is a pretty big detail that I'm sure someone knows something about... 

[HOrnbrod]

This might help:

 

http://www.s10forum.com/forum/f106/2-8-internal-or-external-balance-502963/

[carnuck]

The Mopar trans style flexplate has 4 bolts on the converter. The GM ones have 3. Did they use 3 or 4 bolts on the 2.8? I know the AMC 4 cyl 904 flexplate has 4.

[EmmJay]

This might help:

 

http://www.s10forum.com/forum/f106/2-8-internal-or-external-balance-502963/

 

That helps.  I'm feeling pretty confident it's externally balanced.  I'll post here what I find...

[Eagle]

All available information says that the version of the 2.8L used by AMC through 1986 was externally balanced.

[86FUBAR]

My 2.8 was externally ballanced

[carnuck]

Service replacement engines at the tail end of '86 were sometimes internally balanced. I can't find the link on NAXJA anymore.