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Old Dec 12, 2005 | 02:06 AM
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400M I.D. Question

Hey guys, I looked around and didn't see this question posted so I'll ask it here. I recently came into what I believe is a 400M with C6. This engine/tranny combo came out of a 75' 1 ton so it was someone else's project before it was mine and as such I have no VIN to work from. My question is this: Short of dropping the pan to examine the crank, is there any way of determining that it is a 400 for sure and not a 351? It would be nice to be able to put a date on it as well. It is equipped with a Mallory Unilite point conversion kit so I would imagine it is at least pre 1976. Thanks!
 
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Old Dec 12, 2005 | 02:32 AM
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you sure its even a 335 series?????? how many valve cover bolts?? also there is no 400m but rather a 400
 
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Old Dec 12, 2005 | 11:27 AM
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The 400 wasn't installed in F series until 1977 AFAIK. You probably have a 460 or possibly an FE unless it was swapped in to the truck prior to purchasing. Look at the casting codes on the side of the block near the starter.
 
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Old Dec 12, 2005 | 05:16 PM
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The engine was swapped prior to me coming into it. It's not a 460 or an FE motor because it has a small block C6 on it and the block is just plain visibly smaller. I know the difference between the 351C and 400M was a matter of deck height but the 351W used the same block. I'm trying to find out if there is an external difference between the two. Will the casting # verify the size? Thanks!
 
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Old Dec 12, 2005 | 05:55 PM
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BubbaF250's website will probably help you identify a 335 series engine. The casting number should verify.

http://home.earthlink.net/~bubbaf250/index.html

Also, there should be a 400 stamped in the lifter valley as well, but you would have to pull the intake. Also, C6 trannies have the same bellhousing for the 351M/400/429/460 engines. Then there are the FE engines, which have there own bellhousing pattern, and then the 289, 302, 351W and 351C who have yet another different C6 bellhousing. Are you sure it's not an FE engine? It could be a 332, 352, 360, 390, 406.... Given the year and which truck it is in, I'm betting it is a 360 or 390 FE. But, you'll need to find out for sure. Good luck
 

Last edited by 53fatfndr; Dec 12, 2005 at 06:12 PM.
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Old Dec 12, 2005 | 07:06 PM
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look for an engine build date code near the timing pointer, it's stamped into the front face of the block. also, what is the block cast code near the starter?

dropping the pan is the easiest most sure way to tell what you have, the crankshaft casting code is on the front counterweight. you can clean off the pick-up screen and check if the timing chain could use replacing while your in there.
 
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Old Dec 13, 2005 | 07:48 PM
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Smile

I'm positive it's not an FE motor because the Edelbrock 400 Performer series intake manifold wouldn't be on it if it was. The V is too narrow and it is a small block. I'll take a look at the casting numbers. Thanks for the help guys!
 
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Old Dec 13, 2005 | 09:26 PM
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Originally Posted by Mudflappus
. . . I know the difference between the 351C and 400M was a matter of deck height but the 351W used the same block.
I'm quite sure the 351W and 351M blocks are different.
 
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Old Dec 13, 2005 | 10:15 PM
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From: chicago burbs
correct seventyseven250. the 351M and the 400 use the same identical block, right down to the casting numbers. the 351C is like a short deck M/400 block.
 
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Old Dec 14, 2005 | 09:45 AM
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Well if it's a 351M or 400 then the block is only .010 of an inch shorter than a 460 block and has the same bellhousing bolt pattern. I suppose it's possible that you have one of the rare 400s with the same bellhousing bolt pattern as the 351C but it's unlikely. If it has a Performer 400 intake then it's either a 351M or 400. In that case the only way to tell for sure is to drop the pan and check the casting number on the crank.
 
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Old Dec 17, 2005 | 12:07 AM
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Originally Posted by seventyseven250
I'm quite sure the 351W and 351M blocks are different.
Yes, right you wre but apparently the "C" and "W" keys on my keyboard are not. Sorry for the mix up.
 
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