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  #1  
Old 06-01-2001, 08:44 AM
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Default 400 sbc identification

sorry about all the posts guys, but i want to make sure this is a good deal, not like the parents will like another broken vehicle in the yard...
but anyhow, is there any specific markings to let you know that the block is a 400 sbc? any markings that are easy to find? just want to make sure i don't get screwed and it is only a 350 or a 305...
also, any way to tell between a th350 & a th400 tranny?
thanks all

Craig

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  #2  
Old 06-01-2001, 09:28 AM
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Default Re: 400 sbc identification

If I remember right, a 400sb has 2 freeze plugs whereas a 350 has 3. Maybe it the other way. Someone correct me if I'm wrong please. Also, a 400 is externally balanced whereas a 350 is internally balanced so you can look there too. to tell the difference between a TH350 and TH400 you can look at the pan. The pan of a 350 is more square with a corner cut off. Look here for some info like that:

http://www.off-road.com/chevy/f-faqs.html

Anyways, hope this helps and I hope my memory is correct for you. I'm sure someone else here knows it better thatn I do though.


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Old 06-01-2001, 11:09 AM
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Default Re: 400 sbc identification

<font color=purple>From the drivetrain you described on the S-10 board, that's definitely gonna be a TH350 tranny ('79 Blazer with Auto/203).</font color=purple>

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Old 06-01-2001, 11:20 AM
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Default Re: 400 sbc identification

The quickest way to tell a SB 400 from other SB's is the size of the harmonic balancer.The 400 crank uses a larger one due to the external balance. (Unless someone has already made a 383 out of the 350 block) If the motor is disassembled, and/or heads are off, then check for the steam holes on the deck. The 2 vs. 3 freeze plugs doesent always hold true. I have both 2 and 3 freeze plug 400 blocks. The trans is best identified by the shape of the pan. A Chiltons or Motor manual will show you what to look for.

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Old 06-01-2001, 02:30 PM
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Default Re: 400 sbc identification

LMC catalogs alos show how to identify transmission types.


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Old 06-01-2001, 05:05 PM
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Default Re: 400 sbc identification

I always thought that 305=green 400=blue 454=red. But then I've seen some blue 350's so I dunno. Isn't there some kind of color code?

77 Chevy heavy half, fulltime 4X4, np203, TH400, 400ci., Edelbrock 650cfm carb w/electronic choke.
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Old 06-01-2001, 05:15 PM
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Default Re: 400 sbc identification

Get the casting numbers on the upper left rear of the block. Post it here someone will tell you if you have a 400. if you have the heads off you can look for steam holes in the block and heads and measure the bore. they should be larger than 4 inches.

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Old 06-01-2001, 05:41 PM
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Default Re: 400 sbc identification

There is no color codes, the core plugs don't tell either. Nor does the size of the balancer. Many 350s also came with the 8 inch balancer. But the 400 balancer does have a notch part way around it for the external balance.
As for the trans, vacuum mod pointing to the rear T350 pointing to the side T400.

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Old 06-01-2001, 05:48 PM
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Default Re: 400 sbc identification

A Th350 will have the kick down cable attached the carb.
The TH400 has a switch by the throttle pedal to kick it down.

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Old 06-01-2001, 08:06 PM
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Default Re: 400 sbc identification

One way to identify the SBC 400 is by the crankshaft. All SBC 400 cranks will have a small 3/8" dowell in the flywheel / flexplate bolt pattern, all other SBC cranks do not have the dowell.
dave

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