Big Blocks and TH350

smith7629 · 06-03-2007, 09:49 PM

Does anyone have experience with mating a big block, e.g. 454 or 496 to a TH350 transmission? I'm not sure if the bolt patterns are even the same. Currently I have a zz383 small block mated to a Jasper TH350 which has been re-manufactured better than stock and has a stage I performance kit in it. I've been toying with putting a mildly built 454 or 496 in my truck, essentially having the same horsepower as the zz383, but have a smoother running engine because I'd be relying on cubic inches instead of a high lift/duration cam and high compression. I'd hate to swap out the TH350 and sell it because its a great transmission and I haven't had a bit of trouble out of it. I've also put on an aluminum finned, deeper drain pan and a line cooler since new. Being that I'm staying in the same ballpark with torque and horsepower I'm hoping this will work. I don't plan on drag racing or abusing it, I just want a closer to stock engine that will put out the same power, and not have the rough idle.

2002 Caddy · 06-03-2007, 11:06 PM

Ya the SBC and the BBC share the same tranny bolt pattern

Though most will tell you a TH400 is a better pick behind a big block.

**nailhead425** · 06-04-2007, 02:38 AM

Just make sure the converter you use has the large bolt pattern on the mounting tabs, or a dual bolt pattern. The Big-Block flywheel will have a large bolt pattern. Outside of that, it will bolt right up.

smith7629 · 06-04-2007, 07:16 PM

Thanks for the input. Another reason I'd like to keep the TH350 is that I wouldn't have to worry about transmission crossmember, drive shaft or transfer case mods. I'm assuming here that the TH400 has different dimensions than the TH350.

smith7629 · 06-04-2007, 07:18 PM

Also, does the 496 have a different bolt pattern than the 454?

Johnny P · 06-04-2007, 07:44 PM

Quote:

Originally Posted by smith7629

Also, does the 496 have a different bolt pattern than the 454?

No.

All SBC, BBC and Gen. III/IV engines have the same bell housing.

A 496 is a bored/stroked 454.

KingElvis · 08-23-2007, 06:12 PM

Just a thought: the big block will weigh quite a bit more, so maybe an extra leaf is necessary for the axle.

06-03-2007, 09:49 PM	#1 (permalink)
smith7629 3.8 Liter V6 Join Date: Jun 2005 Drives: GMPP ZZ383 Posts: 479	Big Blocks and TH350 Does anyone have experience with mating a big block, e.g. 454 or 496 to a TH350 transmission? I'm not sure if the bolt patterns are even the same. Currently I have a zz383 small block mated to a Jasper TH350 which has been re-manufactured better than stock and has a stage I performance kit in it. I've been toying with putting a mildly built 454 or 496 in my truck, essentially having the same horsepower as the zz383, but have a smoother running engine because I'd be relying on cubic inches instead of a high lift/duration cam and high compression. I'd hate to swap out the TH350 and sell it because its a great transmission and I haven't had a bit of trouble out of it. I've also put on an aluminum finned, deeper drain pan and a line cooler since new. Being that I'm staying in the same ballpark with torque and horsepower I'm hoping this will work. I don't plan on drag racing or abusing it, I just want a closer to stock engine that will put out the same power, and not have the rough idle.

06-03-2007, 11:06 PM	#2 (permalink)
2002 Caddy 6.0 Liter Vortec V8 Join Date: May 2007 Posts: 1,586	Re: Big Blocks and TH350 Ya the SBC and the BBC share the same tranny bolt pattern Though most will tell you a TH400 is a better pick behind a big block.

06-04-2007, 02:38 AM	#3 (permalink)
nailhead425 GMI Staff Member Join Date: Jan 2005 Location: 85541 Drives: '01 Dodge, '88 3/4T Sub, 3-Nailhead Buicks, Monte Posts: 2,360	Re: Big Blocks and TH350 Just make sure the converter you use has the large bolt pattern on the mounting tabs, or a dual bolt pattern. The Big-Block flywheel will have a large bolt pattern. Outside of that, it will bolt right up. __________________ "A foolish consistency is the hobgoblin of little minds."-Ralph Waldo Emerson

06-04-2007, 07:16 PM	#4 (permalink)
smith7629 3.8 Liter V6 Join Date: Jun 2005 Drives: GMPP ZZ383 Posts: 479	Re: Big Blocks and TH350 Thanks for the input. Another reason I'd like to keep the TH350 is that I wouldn't have to worry about transmission crossmember, drive shaft or transfer case mods. I'm assuming here that the TH400 has different dimensions than the TH350.

06-04-2007, 07:18 PM	#5 (permalink)
smith7629 3.8 Liter V6 Join Date: Jun 2005 Drives: GMPP ZZ383 Posts: 479	Re: Big Blocks and TH350 Also, does the 496 have a different bolt pattern than the 454?

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08-23-2007, 06:12 PM	#7 (permalink)
KingElvis 6.0 Liter Vortec V8 Join Date: Feb 2003 Posts: 1,637	Re: Big Blocks and TH350 Just a thought: the big block will weigh quite a bit more, so maybe an extra leaf is necessary for the axle.

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