I just bought a 327/Muncie 4 speed out of a 68 Camaro. The car had 60K miles on it and the Vin # matched the block #. I got to drive it before the engine was pulled and it ran strong. I didn't pay much attention to the heads at the time, but noticed later that the heads had different casting patterns on the ends. I pulled the valve covers off and found the left head is a 3946813 casting and the right one is a 3917293 (This one is original I'm guessing) There are accessory mounting holes on the back of the left head and none at all on the right head. I was planning to pull the heads and swap them so I'd have accessory holes on the front of the right head, but now I'm wondering if I should look for different heads all together? I've got a set of ported 882 heads, but worry about putting fresh heads on a bottom end with 60K on it...What would you do? (Money spent here will slow down my build elsewhere)
If the heads are the same valve sizes,chambers and runners you are fine. The heads are mirror images frt and back so turning them around wont do anything.What you see on the frt of one head is what you see on the rear. Let me check those casting numbers and I can tell you if they are similar in specifications. 3946813 350 69-79 1.94/1.50 3917293 307/327 68-69 1.72/1.50 These are numbers from a cyl head ID guide,so not sure if 100% accurate but unless the valves have been swapped there may be a little difference on the valves.
Fresh heads on a 60k bottom end is not an issue. The pistons can't tell if the valves are new and shiny or not, they just suck and blow whatever the valves will let them...
Tuff call on replacing heads on an engine with numerous miles . In my experience with SBCs "milled" heads production started in 1969 . My '68 camaro with a 327 had non milled heads and my '69 camaro with a 350 had milled heads , the same scenario on my and my friends' chevelles and novas , SO if you do decide to get a set of "other" heads and need the accessory mounts look for 69 and later .
Valve size. ports and shapes are what's need to run a balance..that said, if the engine ran well...why change. PS..ported 882's?...leave'em on the bench
My book said one is 307 and the other 350.As mentioned above they are 1.72s and 1.94s, this will cause problems. the chamber may be the same CCs but will breathe differently. Must have had a problem at some stage, i would pull them, check and replace as required. Good luck. JW
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