Factory mismatch

[BelvedereII]

I recently purchased a 1975 2bbl 400 out of a Plymouth Fury and have taken it down to major components. Removing the heads, I found a 452 on the driver's side and a 975 on the passenger side!!
Both sat on what looked like factory original steel head gaskets, the intake valley gasket had two "packages" of foil-wrapped insulation pinned under the intake manifold, it all looked like it was from the original build.
Date cast into the motor is 4-15-75, maybe someone wasn't happy with paying their taxes that day and took parts from two bins? Never heard the motor run, but the guy who pulled the motor said he drove it onto the trailer.

I plan on storing this for a future buildup into a 451 or 470, is there any reason to keep the crank, pistons and rods?

B II

[passing you]

975=75'
452=76'
same head really, go with the 440 rods.

[cudachris]

one thing that comes to my mind when somenone mentions 2 different head castings on one block, make sure both use the same kind of spark plug, there are 2 different kinds of seats like ball and flat shape if i remember correctly.
kind regards
chris

[BelvedereII]

PY, nope they are the same length, way under 75 feet each!!

I read the resources as well, they are indeed supposed to fall under '75 and '76 productions but they wound up on a motor built in April 1975. I phoned Muscle Motors, Eric told me they'd run into mismatched parts on motors before, no big deal at that.

CC, same plugs in each hole. The heads really do look the same except for casting numbers. They'll sit on a shelf for now.

Crank, rods, pistons all in the trash. All of it looked very clean, not much of a ridge at the top of the cylinders, just a coating of what looks and smells like ash baked into the whole top end of the motor. I understand certain oils can leave certain types of deposits, but this looks like a burnt on coating throughout the lifter valley and coating everything under the valve covers. No gelled gunk on any of it, though. Oil drained out black, of course.

Quiet idle in the back of the garage for now.

B II

[dtpolk]

I've seen this on a number of older Mopars. Often an owner will replace a single head (probably to save bucks over a full set) if it's bad and he/she may not be able to find an exact replacement.

[BelvedereII]

DT, I expect that happens as well, from time to time.

B II

[Dart 65]

I have taken apart several 360s and have found two different part numbers on the rods, so it's not unheard of at all.

Chrysler, being the smallest of the Big Three, had to be the most frugal of the bunch and use what they had on hand a lot.