1972 and 1970 chrysler 55hp powerhead interchangeable?

[HootTruman]

Hello all, I have a 1973 Chrysler 55 hp longshaft motor that will not run and I have a 1970 Chrysler 55 hp shortshaft that runs very well. Rather than swapping parts and hope I can get the "newer" motor running, can I change the entire powerhead and use the 1970? If I am looking at this correctly, I believe it will work. the changes in the 1973 still have the bolt holes for the electric choke location on the 1970 shortshaft. Any assistance in this matter, including a part number for the powerhead gasket would be extremely appreciated! I have ordered a Chrysler Service manual for my 1973, but thanks to USPS and its current issues, It is still in transit for the last month!

Thanks again,

Tim

 

[Nordin]

Yes you can swap the 1973 power head with the 1970 it will fit.
One thing that can be different is the route of the unburned air/fuel mixture.
Both has the recircle system with the check valve in the "dog bone" at the star side.
But at the early engines there was two hoses at intake manifold that got connected to a T-fitting and then routed down to a barb fitting down in the midleg.
The later had a hose from the "dog bone" to the # 2 cylinder intake port cover and one hose from #1 cylinder intake port at top of the power head just under the flywheel down to the lower part of the crank case at port side.
I think this change was done somewhere in 1972-1974 but not exactly sure when.

 

[HootTruman]

Thank you very much! I have ordered both gaskets that I need as well as another factory service manual. I ordered a manual a month ago but the post office fiasco has struck again! This at least gives me time to work on a few other things with my New project. I am the proud owner of a 1972 starcraft jetstream.