Thread: Guess on engine based on intake manifold casting number?

Tweet

I have tohis old truck on my property that someone told me had a 454 or a 427 chevy bb in it. As it was a swap and not origional motor i cant look up the records. The engine compartment is cramped and the only numbers i could get were on the intake. The firing order is 18436572, which is standard for all chevy sb and bb engines. the engine casting number is 346260. Jut below that number is a 10 and a OM or MO. Any ideas?

-Nick Meyer

If that's the intake casting number, it's a 1973 - 77 two-barrel intake for a 305 or 350. Do you know the difference between big-block and small block Chevys by how the valve covers and/or exhaust manifolds look?

I can't tell based on the way the manifolds/covers look but it is very obvious that it's a BB. That' the whole reason why I posted here as I was confused. I've had a friend who is a diesel technition and the person that drove it till gas prices made it unbearable to drive tell me that it was a big block, and I have personally looked at it side by side with a smallblock. Believe me, It's big. It is more likely that i got the numbers mixed up as the best method I could find to get the numbers from the back end of the manifold was to make a crayon rubbing of it. The sixes could possible be eights, I am not sure.

The part on the left is right side up and has the best detail. the 10 was directly under it and what appears to be "OM" (bottom left) was right after the 10.

Big block exhaust manifolds have four evenly spaced ports. Small block exhaust manifolds have one on each end, and two very close together in the center.

The number with 8's doesn't fit any manifold I can find.

looks like the "OM" is actually "GM"
That number is a small block intake with a 2bbl carb. 1973-1977 305 OR 350

One thing that identifies a truck big block is the water pump and its huge water neck for the lower hose. All 454 engines were externally balanced so one look at the harmonic balancer gives them away,it's not perfectly roud and square shouldered,it has a scallop in it to offset weight. A 366 is probably the most common truck big block,and I haven't heard much about using them in any performance application. Hope this helps you, Hank

yup look at the exhaust ports/manifolds/headers.
Evenly spaced apart= big block. Like this: I I I I
The two center ones close together=small block. Like this: I II I