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Converting Poly 270 Engine to Hemi (1955 Dodge)??

From: Tom Siddon
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Date: September 12, 2003


Dear Hank, I just noticed your recent comment on the Forward Look chat-line about the simplicity of converting the Poly-head engine to a Hemi. About a year ago, I bought a 55 Royal 2Dr HT with a Polyhead Red Ram in it. On removing the heads the other day I found that someone had made a locallized repair, using some metallized epoxy under one of the rocker covers. I presume this was to fix a crack around one of the valve stems. This was on a cylinder where there was a very low compression reading (about 50 psi). To get this engine running again, I should probably find a new head for it. HOWEVER: I have already restored another '55 Dodge Royal Lancer with the Super Red Ram Hemi, and still have a lot of engine parts left over from the rebuild, including a spare set of Hemi heads and pushrods. Is the conversion really as simple as bolting on the hemi heads, with the proper push-rods, or do I need to make any otherl changes to the internal engine parts, such as the cam-shaft, lifters, or pistons? (The lower end of the poly-head engine seems to be in pretty decent shape). I have an old set of aluminum pistons from a hemi, which are flat-topped, and they seem to be the same as the ones in the Polyhead engine. Sorry to bother you about this, but I would really like to know what I'm doing before I get too far in to this project. Do you have first-hand experience with such a change-over? If not, are there any books or articles that I could refer to? By the way, could give me any leads on where is the best supply source for mid-50's Mopar engine parts (used or new), including gasket kits, valves, lifters, etc. I will be very grateful for any helpful advice you can give me. Thanks very much for your attention to my request. Yours sincerely. TOM SIDDON


Last changed: July 19, 2018