[Daves67GTO]

I have a 1966 421 Engine (Casting #9772611 which decodes to late year 421) with 092 heads. Now, here is what I can't figure out...there are 3 letters stamped on the front:

XYH

YH decodes to a 338hp 4bbl automatic car. What is the X for???

Any help is appreciated! Thanks.

David

[Jerry H.]

No one seems quite sure. This seems to be fairly common, and has been discussed on here before. Someone thought at one time the 'x' was for experimental, but I believe that was disproved fairly early on, as these stamping were on the common 421 engines. You might try the 'search' feature and type in 421 and xyh and see if that thread comes up for more info.

[Jerry H.]

Here is the thread I was talking about:

http://216.178.81.108/forums/showthr...&highlight=421

[Barrier Blue]

I had a 421 motor that had the XYH stamping. I always thought that the X was probably put there by a rebuilder, but with others having the same code, I guess that isn't the case.
Jeff

[Daves67GTO]

Thanks for the help! It is a motor that looks to be in pretty good shape. So far, here is what I have found out. It is standard bore, has 4 bolt mains and crank is steel. The XYH code is fairly common and from the casting number it looks like it is a late year 421. Time to get it cleaned up and start putting it back together and get it in a car! Thanks again!

David