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Which engine do I have

Possum

Georgia Chapter member
I wanna know what engine my truck has in it, a 351M or 400 and its buggin me!

My 78 1/2 ton came from the factory with a 351M (accordin to the VIN ID)

I'm not sure if the engine in it now is the origanal, but it is a 351m/400.

All I know that was done to it was it has had an aftermarket camshaft kit installed when the engine was overhauled.

What I want to know is, do yall think someone woulda went through this much trouble with a 351M without putting a 400's crankshaft in it?

How can I tell? Thank yall fer your inputs in advance

P.S. I know I got 400 in my sig, but its just cause thats wut I hope it is
 

Possum

Georgia Chapter member
By the way, the previous owner had all the work done so thats
why how come I dont know what alls done to it.
 

LEB Ben

Arrogant A-hole At-Large
34,919
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IMO...top end work and bolt ons are stupid easy to do, but bottom end work scares me, so I'd say it's definitely possible that the 351M is in fact that. Literally, you can pull the heads one morning, do the work yourself or send it out some place and have them back the next morning...and that is the hardest/longest part of work on the top half. A cam kit, headers, intake, carb can be done in an afternoon and parts would run less than $700.


That being said, take a wooden dowl about 6" long, pull the #1 spark plug, put the stick in, put #1 at TDC, rotate the engine by hand (pull belts off and take plugs out, makes it much easier). Take a look at where the stick stops moving down and starts it's way back up, mark that point on the dowel. Measure that distance, if it's 3.5" you have a 351M, if it's 4" you have a 400.
 

Possum

Georgia Chapter member
Thanks Ben I'll do that, but what did you mean when you said put the #1 plug at TDC?
 

DNFXDLI

The Token Canadian
Staff member
Yes...a nice TMI stroker kit.
 

LEB Ben

Arrogant A-hole At-Large
34,919
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Swapping in a 400 crank strokes it 50 cubes, and should only be a couple hundred dollars.

Can't do crank only. If you change the crank, you also have to change the pistons. The 400 pistons are shorter to allow for the longer stroke. If you change only the crank, then the top of the 351M pistons would be taller than the deck on the block. Just recently did this upgrade myself during a complete rebuild.
 

LEB Ben

Arrogant A-hole At-Large
34,919
1,124
outside your house
Can't do crank only. If you change the crank, you also have to change the pistons. The 400 pistons are shorter to allow for the longer stroke. If you change only the crank, then the top of the 351M pistons would be taller than the deck on the block. Just recently did this upgrade myself during a complete rebuild.

I know this...I was simply letting the guy know he had options.
 

Possum

Georgia Chapter member
Fer a 351 it shore has allota power. Course I'm used to drivin the 4.6


4.6>>:hammer: <<351M
 
I know this...I was simply letting the guy know he had options.

Options without the correct detalis can lead to confusion/problems. I pointed out that changing the crank only was not an option. Incomplete information is bad advise in my opinion. If I had only bought a crank as someone had said, I would have problems when I put it together.
 

LEB Ben

Arrogant A-hole At-Large
34,919
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Options without the correct detalis can lead to confusion/problems. I pointed out that changing the crank only was not an option. Incomplete information is bad advise in my opinion. If I had only bought a crank as someone had said, I would have problems when I put it together.

Kudos to you for being so thorough, I'd imagine most folks would have the capacity to do a little more research or ask more questions when taking something on like this. Also noting he already stated he had no plans of changing his current set up, it wasn't worth the explanation. Other members also suggested stroker kits and running alcohol, care to dissect those posts as well and give an in depth analysis??????
 
If you read back, I did comment on the alcohol. As for stroker kits, well its a kit. I was pointing out that a crank alone was not an option without pistons. As you said "I'd imagine most folks would have the capacity to do a little more research or ask more questions when taking something on like this". I was only providing the additional information that he or anyone else reading the thread would need to know to have the correct information, not the incomplete information you provided.
That being said, I read the same comment you made before I built my 400 a few times on different sites. Thankfully I did a lot more research rather than thinking since I read it in more than one place it must be correct. That was the reason I made my comment that pistons were also required. Hopefully my comment helped someone that is/was doing "a little more research or ask more questions when taking something on like this".
 

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