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Discussion Starter #1
Hi, i'm planning on going out and getting a block to start building up a 350 for my 83 el camino. I have the stock LG4 305 right now, i was wondering if anyone might have casting numbers ready that they could list, or anything major that might cause problems during the switch. Also, is it a better idea to get a the TH400 tranny or just rebuild the 350 that i have now? Thanks for the help! :-D
 

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THM350-R3 works for me...

I've got a THM350-R3 behind my 350cid with a 750cfm 4bbl holley.

The THM350 works for me! :)
 

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As a general rule of thumb, once you start making more than 450 ft-lbs of torque at the crank, then you might start to consider changing over to the TH-400. Or if you've got more than 4,000lbs of weight to push around, go with the TH-400. Other than that a TH-350 will work just fine for ya. Hope this helps.

Charles
 

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I have seen the 350th handle some serious power. The 400 uses 20 more horsepower to run over the 350 so keep that in mind.
 

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i would rebuild the th350 instead of going and looking for the th400 and spending money. as far as switching from the 305 to the 350 it is a simple process and you shouldn't have any problems.
 

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I would first consider what you plan on doing to the motor as far as performance modifications are concerned. If you stay under 350 hp a 350THD should survive any punishment you can dish out. Over 350hp and I would go with the 400THD. There are other things to consider though, if you swap to a 400THD, you will need a different trans crossmember, and a shorter driveshaft (added expenses), with a 350THD you won't. If you rebuild the 350THD, most trans shops are going to charge you the same or even more than what it would cost you to buy a TCI Streetfighter trans and they probably won't do as good a job. You should also install a new torque converter with a stall speed based on what your plans for the car are, engine modifications, and your driving habits. Also if you build a 350 motor that does produce some fair amount of torque, you might want to think about replacing the stock rearend with something else (another added major expense), the stock rearend in G-bodies is not a performance friendly rearend, although should be OK if you stay under 350hp and isn't already worn out. Carefully plan everything out well in advance, and then you'll have a better idea what'll it will cost.

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Discussion Starter #7
yeah we're lookin for a different rearend for it right now, trying to either find a good posi unit/axle to fix up or go over to the shop and see what their prices are for 'em. The tranny is starting to slip a little on occasion so i'm thinkin i might as well go for something that a bit stronger anyway. Thanks for the help.
 
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