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LT1 M6 to TH350 or 400?

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Old 09-27-2012, 10:43 PM
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Default LT1 M6 to TH350 or 400?

Which should I go for?

How can I tell if I need an external balance flex plate or neutral? It's been years since I had my motor built and I don't remember.

My goal is mid 11s NA and 10s on spray.

Thank you,
Old 09-29-2012, 10:07 PM
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Ok I found out what flex plate I need external balance.
And I am pretty sure 9" tail 27 spline TH350 is easiest to bolt in.

Do I just get any SBC stall converter or does it have to be LT1 specific?
Old 09-30-2012, 10:34 PM
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Any normal bolt pattern converter for a 350/400 will work ... yes a 9" tail is easiest but that is only from the point of view that you can re-use your stock drive shaft... IMO though 9" tail or not I would have a new stronger drive shaft made just for peace of mind ESP when you're trying to run 10's
Old 10-01-2012, 07:50 AM
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Originally Posted by 1slow96z
Any normal bolt pattern converter for a 350/400 will work ... yes a 9" tail is easiest but that is only from the point of view that you can re-use your stock drive shaft... IMO though 9" tail or not I would have a new stronger drive shaft made just for peace of mind ESP when you're trying to run 10's
Thank you! Drive shaft was made and installed when the 12 bolt was put in.

Now I"m waffling between th350 and th400; realistically I'm only ever going to have between 500 and 600HP on the spray (if I'm lucky) and 360-400 on motor. I'm so confused - I don't want to lose ET and waste money on a th400 if I don't have to. I've been googling for days and everyone has an opinion both ways. Heh.
Old 10-01-2012, 11:57 AM
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Its tough the 400 is obv stronger but I've seen people build 350s to be just as strong though
Old 10-01-2012, 12:02 PM
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Originally Posted by Jason94z
Which should I go for?

How can I tell if I need an external balance flex plate or neutral? It's been years since I had my motor built and I don't remember.

My goal is mid 11s NA and 10s on spray.

Thank you,
Your money & all, but why not just get a competition clutch & practice? That M6 isn't stopping you from getting into 11s.
Old 10-01-2012, 12:15 PM
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its true, but suspension set up is far less forgiving with a m6 ... looking at his 60' in his sig the car would proboly do an easy 1.5x and put him right in the 11.6ish area right off the bat... i know exactly why hes doing it because i have almost the same goals ... im shooting for 11.9x's-12.2x's on motor and a 10.9x or better on spray
Old 10-01-2012, 11:06 PM
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Originally Posted by 1slow96z
its true, but suspension set up is far less forgiving with a m6 ... looking at his 60' in his sig the car would proboly do an easy 1.5x and put him right in the 11.6ish area right off the bat... i know exactly why hes doing it because i have almost the same goals ... im shooting for 11.9x's-12.2x's on motor and a 10.9x or better on spray
Thanks you got it.
Broke too many parts with the m6. Clutches are $$ so are output shafts, rear ends, sychros, shift forks etc. etc. An auto will save me lots of $ in the long run. And be consistent. Why fight it?

How do you like your TH350?
Old 10-02-2012, 01:21 PM
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I love my th350 I haven't been able to stop driving the car since I did the swap ... next year I'm going to change valve bodies and put a brake on it
Old 10-03-2012, 06:34 PM
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A mildly built 350 will hold up good.400 is uber strong but 350 will be plenty good if built a little.
Old 10-03-2012, 07:05 PM
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Originally Posted by buddhaz06
A mildly built 350 will hold up good.400 is uber strong but 350 will be plenty good if built a little.
All things being equal how much slower will a Th400 be in my n/a combo?



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