Twin H head bolt size

ArtS

Hi There: Can one determine the size of head bolts (7/16 or 1/2) just by measuring the span of the bolt head (11/16 or 3/4)? I can pull the bolt but just changed the anti-freeze so I'd prefer not to do this right now. The reason behind my question is that I've got a 53 Hornet. I believe the block to be original, 7/16 bolts, since serial numbers on car and block match. But the block is painted red, not gold. Also the cast iron head is stamped 309121 that COULD mean it comes from a 56 motor. My Hudson parts books for 52 and 53 don't show this number. If from a 56, then the head is made for 1/2 bolts. Either the mounting of this head and gasket is spot on (no leaks seen) or the 53 block was machined to accept 1/2 bolts. Any comments here would be greatly appreciated. Thanks much. ArtS

hudsontech

Easiest way, and surest, is to buy 1 each 7/16th nut and 1 each 1/2" nut and try them.



Hudsonly,

Alex B

ArtS

Thanks, Alex and Ken for the info. My hex heads measure out as 3/4 in. suggesting that the block has been modified to accept 1/2 in. head bolts. I'll pull a bolt to confirm next time I drain the anti-freeze. ArtS