Packard Forum Index » V-8 (1955-56)

Should I end up with a Clipper with the 225 HP 320, would I be correct in assuming that boring out to a 352 would be risky at best? Could the 320 heads be run on a 352 block to raise compression or are the ports/Valves less desirable.
Just thinking out loud here, I am not lucky enough to have such a problem at this point. (hey, the year is young!)
Thanks!

Unless the 320 needs a total rebuild including new pistons, I'd leave it a 320. I once rebuilt a very low mileage 320, installed 56 heads on it, and put it into a 56J. That motor ran nice and cool, and got better gas mileage than any 352 I had ever ran.

The power is noticeably less, but unless you are planning on drag racing, that should not be a big deal.

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Dunno why you'd think you'd gain anything by putting heads from a 320 on a 352 block.

If you look at the specs in the shop manual, you'll find the 320 and 352 have same CR, across all lines for 55. Check P/Ns in the parts book, and you'll find that valves and cam are same across all model of a given year.

Although the July, 1955 issue (Vol. 29, No. 7) of the Service Counselor newsletter advised of a running change from machined- to cast-dome cylinder heads for the 320, the text seems to indicate that it does not affect CR or HP.

If you want the performance of a 352, I think it would be cheaper to simply buy a car that came from the factory with a 352.

I've got a NOS 320" short block which needs a good home. If anyone wants a good deal on a new engine, I could freshen it up the bores and ship it at a steal deal.

jack vines

I have a vague memory that Packard used thicker head gaskets on some 320 motors to reduce compression ratio, for Nash and Hudson.

Could it be they used the same head castings but different pistons and gaskets for different motors, to change the compression ratio?

This matter came up over the course of discussion in another thread on V8 Pistons.

The parts book shows alternate pistons in addition to shims for cylinder head and intake manifold for low compression ratio engines. However, the listing for the head shim for 55th Series curiously omits the 5540 chassis, which used the 320 motor. The 320 used the same head as the 55th Series version of the 352 - that is, until a mid-year change to cast-dome heads.

Unless some other factory documentation surfaces, the only other source for further details on low compression equipment might be original engineering drawings.