Identifying a 400 flywheel

[Jimal]

While poking around underneath my recently purchased '65 K10 I discovered that the engine is a 400, not a 350 as the seller indicated. Not the worst thing in the world, but assuming the guy I bought it from didn't know what he had, he probably just reused the flywheel off the 327 he pulled out of the truck (and now sits in my garage).

I'm assuming that the engine came out of the same '75 pickup that a bunch of the upgrades this truck has came from. Should I be able to tell from a visual inspection of the flywheel (without taking things apart) whether the flywheel is correct or not?

[4x4k30]

the quickest way to tell ifs its a 400 look at the harmonic balancer on the front of the engine it will have a good size notch cutout spot on it its a 400.. and if you have automatic the flywheel will have a small weight on it than you can see . the 400 small block is externally balanced . all other small blocks are internally balanced. also look to see if it has 3 freeze plugs on each side some of the 400s did but not all . is one way to tell ifs its a 400 here is a balancer pic for a 400

[Jimal]

Originally Posted by 4x4k30

the quickest way to tell ifs its a 400 look at the harmonic balancer on the front of the engine it will have a good size notch cutout spot on it its a 400.. and if you have automatic the flywheel will have a small weight on it than you can see . the 400 small block is externally balanced . all other small blocks are internally balanced. also look to see if it has 3 freeze plugs on each side some of the 400s did but not all . is one way to tell ifs its a 400 here is a balancer pic for a 400

Oh it's a 400. But what would a 400 manual flywheel look like? An adapter weight is stupid cheap ($13 from Speedway Motors) but I'll also need to purchase a transmission jack if I'm going to have to pull it out in order to install the weight between the flywheel and the crankshaft.

[Jimal]

Okay, I finally got off my lazy arse, crawled under the truck again and looked at the flywheel. Definitely not the right one for the engine. So it looks like I will be pulling the transmission at sometime in the near future. Now, do I go cheap and just install one of those weight adapters, or do I go into "while I'm at it" mode and replace the flywheel, clutch and pressure plate?

[geezer#99]

My advice!!
Redo it while you got it apart.
And if now knowing it's the wrong flywheel then stop running and driving it immediately or you'll be rebuilding that 400 when you hammer the bearings out of the crank.

[Jimal]

Originally Posted by geezer#99

My advice!!
Redo it while you got it apart.
And if now knowing it's the wrong flywheel then stop running and driving it immediately or you'll be rebuilding that 400 when you hammer the bearings out of the crank.

The truck is a ways from driving. At this point I'm loving the divorced transfer case since it seems like it will be relatively easy to get the gearbox out. I'm leaning toward the adapter weight at this point. I'm spending a lot in a short amount of time getting this thing running and driving. If the clutch has some life in it I'll save the money for something else.

[odee]

I would change to the right flywheel. I've seen starter problems happen because of the add on weight.

[Jimal]

Originally Posted by odee

I would change to the right flywheel. I've seen starter problems happen because of the add on weight.

The more I've been thinking about it since I wrote that post, the more I'm leaning toward replacing the flywheel and clutch. The fact that the guy I bought the truck from didn't know what motor he put in makes me suspect of everything. At least the gearbox should be easy to remove because of the divorced transfer case. Right?

[Old Truck Man]

We had a stick shift truck with a 400 small block. And it had a external balanced flywheel. However the flywheel was from a 454. and the engine vibrated. after research ive come to the opinion that no 400 small blocks ever came from the factory with a stick trans. So you only have the choice of a aftermarket stick flywheel. A 454 flywheel will not properly balance on a 400 small block.

[Jimal]

Originally Posted by Old Truck Man

We had a stick shift truck with a 400 small block. And it had a external balanced flywheel. However the flywheel was from a 454. and the engine vibrated. after research ive come to the opinion that no 400 small blocks ever came from the factory with a stick trans. So you only have the choice of a aftermarket stick flywheel. A 454 flywheel will not properly balance on a 400 small block.

Rock Auto and NAPA both show 400 flywheels. I cross-referenced the P/N for the Rock Auto flywheel (3986394) and GM Parts Direct lists it as:

"Outside diameter is 14" for years 1970-80. Crank Flange bolt pattern: 3.58"; clutch dia.: 11"; starter ring gear teeth: 168. For externally balanced 400ci small-block V8 only. Use with balancer P/N 6272225."

Works for me.

[Old Truck Man]

Originally Posted by Jimal

Rock Auto and NAPA both show 400 flywheels. I cross-referenced the P/N for the Rock Auto flywheel (3986394) and GM Parts Direct lists it as:

"Outside diameter is 14" for years 1970-80. Crank Flange bolt pattern: 3.58"; clutch dia.: 11"; starter ring gear teeth: 168. For externally balanced 400ci small-block V8 only. Use with balancer P/N 6272225."

Works for me.

Yes the aftermarket Rock auto or napa flywheel is available for the Small block 400. However its not balanced the same as a 454 big block flywheel. Now I could be wrong however its my opinion that GM never produced a stick flywheel for the small block 400.

[Jimal]

Originally Posted by Old Truck Man

Yes the aftermarket Rock auto or napa flywheel is available for the Small block 400. However its not balanced the same as a 454 big block flywheel. Now I could be wrong however its my opinion that GM never produced a stick flywheel for the small block 400.

It wouldn't be balanced for the 454. The part number is a GM part number, and I've read elsewhere that the 400 was offered with a manual in the 1970 Monte Carlo. They list a bunch of other applications, but as long as it is for a 400 I'm fine. The pictures I've found online have also shown the counterweight.