I have a 390fe engine. It flattened its cam and had coolant leak that was coming out of the breather and dripping down the valve cover if the engine was running. So I ordered a cam, lifters new valve springs and all the gaskets for the engine. While I was cleaning the heads up I noticed they have two completely different casting numbers.
The passenger side is:
C2SE 8090
and the driver side head is:
C3AE 6090C
from what I can see online and I’m not saying that it has to be right is one of my heads is a 390 head and the other is a 406 head. My question is how did this work wouldn’t one side have a completely different compression ratio not to mention other problems? Would I be better off to get another set of heads?
thanks.

Driver side


Passenger side

 

Cc the chambers and check the valve sizes and port sizes

 

I would say yes, get a matching pair, or match one new head up to one of the other ones (of your choice), but like somethingclever said, you can at least CC the heads and look at the combustion chambers for shape and plug angle.
Have you searched out each number and that's how you got the compression ratios? They may be different just due to a difference in engine stroke, or deck height, or piston design, or whatever. So Cc'ing is the only way to know for sure.
However, if they look different, then there's no way they should be working together on the same engine. Someone did a valve job or something in it's past and swapped in a head mistakenly.

I found the same thing on my brother's '66 Corvette 327 many years ago. Both heads were different part numbers for the same engine series (327ci - 300HP) and would have been found in Corvettes of only slightly different build months. It's possible they were in the bins at the same time even, but they were not the same exactly.
Good enough that the engine ran passably well, but any imperfections could have been a result of the two different types. So I found a matching head for one of them and used the pair. Still have the old "wrong" head 35 years later too! I'm really bad about selling stuff on....

Good luck. Hopefully it works, or getting a new one is a quick-n-easy fix. But personally I'd want the part numbers to match.

Paul

 

According to my Robert Winkleman High Performance Parts Identifier book;

C2SE-A is a 62-63 390 6v 390 HP head, 66-69cc, 2.02/1.55 valves, 1.34x1.93 intake port, 1.28x1.84 exhaust port, 6v or 4v w/ flat top pistons

C3AE-C is a late 63 406 6v head, 57-61cc, 2.09/1.66 valves, 1.34x2.34 intake port, 1.28x1.84 exhaust port, and has machined spring cup seats.

I'd try to come up with a pair of heads, D2TE-AA, C6AE-R or C8AE-H are all pretty common and good heads (D2TE's have induction hardened seats for unleaded) and relatively cheap.
Then clean up your heads and throw them up on a FE or Galaxie page for someone looking for a single and flip them. OOORRR try to find your own matching pair for each and build some cool engines.

 

Thank you for all your answers. I’m going to be getting a matching set. And replacing these ones so I’m glad I noticed and asked before putting it all back together. Thank you.