I've been trying to figure out which heads I have on my 350, but it seems that the casting #s have been ground off on both heads. The only numbers I can find are two small oval stamps on each side on the head, one with "F207" and the other with "21" and then "GM 38" stamped beside the pushrod guides. I checked the front of the heads also for #s but the only thing I could find there was "MRC" and "PHX C" just below that. Is there -any- other way I can figure out which heads these are??

 

Not trying to offend, but you did pull off the valve covers and look, right?

The reason I ask is because you mention every other part of the head except under the valve covers.

 

Eh.. That's where the GM 38 and the F207 121 came from.

 

Most SB chev heads have a identifier cast on the end of the head. What does your identifier look like?

Post a pic if possible. and a pic of the combustion chamber too.

 

F207 = the casting date; the 20th day of the Fth month (the 6th, June) of a year ending in 7

Could be this
14039121...81-86...305..........Truck

But it's hard to say, the dates are out of range.

People grind off casting #s when they're trying to cheat in racing, or screw somebody over in a sale. Not a good sign.

 

If they were cast in a year ending with a 7, I'd say they're from 77, probably about the same year as the block.

I'm not pulling the heads just to find out what the chamber looks like. I tried to get a picture of the front of the head but they all turned out sheetty.

What I can tell you is that the heads have the "right angle" identifier. Mortec says: 3947041....69-70...302/350......"Right angle" casting identifier, 64cc chamber, accessory holes, good HP head ---- 3947041X...69-70...302/350......"Right angle" casting identifier, 64cc chamber, 165cc intake port, accessory holes, good HP head

 

Not sure when it started, but later model heads also have the last 3 digits casted on the bottom of the runner...might be able to get a small inspection mirror under there with a flashlight and see.