“……I'm thinking the pushrod holes in the block are not round like in your block picture…..Maybe now is the time to make sure the exhaust pushrods will clear oaky in your block …….”

Cab, frankly if this hadn’t started out as a potential POLY build I probably would not have understood what you are talking about. You are right about the pushrod holes on the late 55 and up HEMI blocks not being round.

My block as an early 55 HEMI block, hence the round holes . From late 1955 on the “HEMI blocks” had drilled/teardrop shaped pushrod holes as shown below.

Y valve Relief 2 by M Patterson, on Flickr



Y Valve relief 1 by M Patterson, on Flickr

Reshaping the pushrod holes was necessary when the blocks were fitted with Poly heads because of the different pushrod angles required for the single rocker-shaft and rockers they used.

1955 was the first year for the Poly engine (in the Windsors and Saratoga wagons) and was a 301CI one year only engine. In 56 Chrysler used the 55 331 CI blocks with Poly heads for the Windsor/Saratoga and in 57 and 58 they based the Windsor and Saratoga Polys on the 354 blocks. By reshaping the holes the blocks could be used with either HEMI or Poly heads. Some of these engines in both Hemi and Poly form also found their way into Dodge trucks (but I’m not real sure on the years or models).

I had been planning on doing the pushrod hole mods to this block for the poly heads until I figured out the 301 Poly heads I have wouldn’t work with the bore size we went with. For now it’s just going together as a HEMI and the factory holes will be fine. As far as building a Poly, I may have a line on a complete 57 354 Poly…….what’s another engine sitting around the shop

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