Packard Forum Index » V-8 (1955-56)

Quote:

All the V8 heads are interchangeable except the spark plugs were changed one time, right?

I have these two junky heads which I'll scrap but perhaps I'll keep the two nicer heads. There is a guy by Ross selling a pair of unpopulated but nice and painted heads for next to nothing LMK if you're interested.

Quote:Yes, No, Maybe.

Yes, either head will bolt on any block.
No, the '55 heads heads have a slightly smaller intake valve, larger combustion chambers for lower compression and the aforementioned shorter spark plug.
The '56 heads (CD) have larger intake valves, smaller and wedge shaped combustion chamber and the 3/4" reach spark plugs.
Always choose the '56 heads unless it's for a correct restoration.

jack vines

Are the 1956 heads also prone to cracks?

Thanks Jack that's good to know. Of course the difference in compression which I forgot to mention, but I forgot the difference in intake valves for the 56.

To clarify Jack's comment, all 56 heads are the same, but the 55's are different for 320 vs. 352 as all 55 engines have the same compression. You can swap the heads on a 55 to the other 55 style to play with the compression, and in fact Packard put 352 heads on the 320 engines sold to Hash to derate the power output.

Jack do you know the effective compression for a 320 with a 56 head? I can only assume a 55 352 will be 9.5, same as 56 352.

Relevant thread:packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=265679