Block code
 

I have a dilema !! The engine block code appears to be XZ or possibly X7 but the vin#'s do not jive. Here is the problem. The 2nd owner had the car since the late 70's and her niece had it untill now. They say that the engine was never out of the car !!! This is a 76 Trans am with supposedly a 400. Any ideas as to what I have ???

X7 could be 220 HP 400 from 1978 with 6X (4) heads and a 4bbl carb - auto trans motor.

XZ is the correct code for 1976 400/auto.

You are likely reading the UEN # which is stamped just below the block code.

The partial vin you are looking for is lower down on the same surface,near oil pan close to timing cover.

You will likely have to scrape grease/paint/rust to read it as it is stamped in a smaller font.

It does have 6X heads and is an auto car

Thanks 2 many Ta's all the books I have do not tell me that !! Where did you find that ??

the enginge code X7 is correct for 76 400 auto, very short
production run, casting dates for block , should be after late march.
does your cast date on block predate the car build date?

http://www.wallaceracing.com/engine1.htm

A good place to start.