Hi all, hope someone can help me with my mystery motor. Recently bought a 51 Chevy and the previous owner told me it had a rebuilt 250 motor and Powerglide trans out of a 76 Nova. The first thing that got me wondering is I found out that 76 Nova's didn't even come with Powerglides that year. Next flag went up when I went to tune up the car and the spark plugs the shop gave me were the smaller 5/8" plugs when the plugs that are in the motor are 13/16". Someone, (of questionable knowledge) who looked at it said it's a 235. the casting number on the block reads 3877178 and the serial number is F0301PX. Is there a sure fire way to figure this out as I am about to buy some Langdon's headers and would love to know what's sitting in that engine compartment!

Just another note...I looked at the casting #'s category to the left and it says it's either a 230 or 250 from a Buick,Olds, Chev, or GMC built sometime between 1962 and 1978. How do I narrow this down? Engine does have a non-integral head if that helps. Thanks in advance.

75-78 newer had the integral head. The 250 did not come about till 67.The 250 will have a dished piston (factory).

Thanks Twisted6, That narrow's it down, but is there any way to tell what it is externally? Don't feel like popping the head off to check on that piston. Lazy you know! Mahalo, Lucky444

F0301PX tells it was assembled in Flint and with a non intergral head the 1 in that sequence makes it a 1971. There were no 230 - 250 in 1961 and in 1981 they had the intergral head. PX is the code that will tell you what trans and other engine options it may have had.

Techno babble aside the easiest way to distinguish the 194, 230, 250, 292 from a 235 or 261 is by the number of bolts on the valve cover. The 194 to 292 all had 7 bolts. A 235 or 261 has 4. Count the holes and order the headers.

Pull a plug out and bring the piston nearing top dead and look in side you can tell if it is dished.

Thanks you guys. I will check the number of holes and pull that plug to check out the piston shape. Sounds like it's a 71 atleast. Much mahalo, Lucky444