which way is it balanced? LT1

My machinist told me when he was building my LT1 383 that stock, an LT1 is sort of a hybrid...internal front/external rear was the way he explained it. If you are going with all new stuff (crank, rods, pistons, flywheel) you could balance it internally, just like any other non-400 block SBC. Since I was using a stock type T56 flywheel, I got a special crank made specifically for an LT1 (Eagle lists a different part # for that reason), to avoid using lots of mallory to rebalance. So, to sort of answer your question, you should use a similarly weighted flexplate with a stock rotating assembly. The late style stock flexplates will accept a TH350 or TH2004r, and I'm pretty sure you can use one with a TH400 also.
 
All 87+ 1pc main seal roller motors have that, it has to do with the crank flange. On the 1 pc main seal motors the flange is just a round machined end where the seal goes over and as we all know, perfect round without additional weight or holes but evenly spaced bolt holes has no counterweighting properties. The older cranks do.

hppp_0704_02_z+third_gen_pontiac_firebird_engine_build+crank.jpg


You can see it in that pic. The absence of that counterweight pad makes for the need for that neutral balance pad on the flywheels & flexplates.
 
TT...trying to understand. The newer crank, having no additional wieght to balance the back end of the crank is the reason they put a flexplate with a welded on weight to "counter" that lack of balancing? If so, then would putting a "non weighted" flexplate on it not throw it out of balance? Wouldn't I need the larger 14" 168 tooth flexplate with the same weight welded to it? (To counter the lack of rear weight on the crank like they did at the factory?)
 
Jclgodale3 said:
TT...trying to understand. The newer crank, having no additional wieght to balance the back end of the crank is the reason they put a flexplate with a welded on weight to "counter" that lack of balancing?
Click to expand...
Correct.
It is not so much a "lack of balancing", as it is GM's chosen way of balancing the 1 pce engines

Jclgodale3 said:
If so, then would putting a "non weighted" flexplate on it not throw it out of balance?
Click to expand...
Correct

Jclgodale3 said:
Wouldn't I need the larger 14" 168 tooth flexplate with the same weight welded to it?
Click to expand...
Correct
If you have made no internal changes to the engine , then you need a stock 1 pce seal ext balance flexplate in the size of your choice with the 11.5" convertor pattern.
 
Last edited:
vetteoz said:
Jclgodale3 said:
TT...trying to understand. The newer crank, having no additional wieght to balance the back end of the crank is the reason they put a flexplate with a welded on weight to "counter" that lack of balancing?
Click to expand...
Correct.
It is not so much a "lack of balancing", as it is GM's chosen way of balancing the 1 pce engines

Jclgodale3 said:
If so, then would putting a "non weighted" flexplate on it not throw it out of balance?
Click to expand...
Correct

Jclgodale3 said:
Wouldn't I need the larger 14" 168 tooth flexplate with the same weight welded to it?
Click to expand...
Correct
If you have made no internal changes to the engine , then you need a stock 1 pce seal ext balance flexplate in the size of your choice with the 11.5" convertor pattern.
Click to expand...
Whew! I need to quit second guessing myself because that is the flywheel that just arrived! 168 tooth for a 1 piece rear seal, with a weight welded on it that will bolt to my Turbo 400 converter...:cussing:
 
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