Inliners International Forums General Discussion Hi Performance GMC casting number location

Where are the casting numbers at on the GMC inline6? I found a 52 or 53 duce and a half with a GMC 6 in it And the oil filter covers up the serial number. Whats the chance that it is a 302?

I'm not a GMC person, hope someone jumps in here; but ive seen the 248/270/302 stamped on the machined flat where the distributar sits. You might also check the various leads from websites and listed casting #'s on the blue sidebar at the left of this page. If not repost in the engine section of the bulleten board.

Thanks for the reply Old Newby. I went back and looked at it some more I think its a 302 the number your talking about is covered up mostly by the oil filter. The guy said $200 and I pull it if its not what I want just leave it at no cost.

The ser. no. starts w/ the displacement
(302xxxxx) and is stamped at the rear of the machined pad behind the distributor, nowhere near the distr?

Thanks Ed the oil filter on this motor is behind the distributor and covers up the first part of the ser. no. But after looking on the internet I found some pics of a motor and the casting number is on the drivers side lower middle part of the block. Is $200 a good price for a military 302? And what is the difference from a military and none military motor?

I think the main diffferences are cosmetic, i.e., waterproof ignition w/ aircraft type plugs, etc., giant generator and regulator(24V.)
Some had larger, deeper oil pans, some drove hydramatic transmissions, some had 2bbl. carbs.

I think any 302 is worth $200., you get the head with the large intake passages, etc., and the large bore. All the military stuff comes off easily. Make sure and replace the harmonic balancer w/ a modern one fron a 292 Chevy, 2 groove is OK, 3 groove is better.

Also if memory serves me, the military block has no provision for a mechanical fuel pump & uses electric pump?

Thanks Ed Pruss and Old Newby for the help. I'm new to GMC's and did not know to use a 292 balancer. Is it a direct replacement or do you have to modify it? Any other tips that I should know about? I want to put it in a 1953 GMC 3/4 ton.

I just got a two pulley one and I have to turn off .125" off the engine side I think, it has been a while since I measured it. Someone said on the 3 pulley one you need a small spacer, which they made from a piece off their old one.

Make sure you make it square so the balancer doesn't wobble. You can get rebuilt water pumps w/ the correct .375" pulley from Carquest and others. Ask for one for a early '60's 270 PU.