Upgrading 1939 V8 to 1941 specs?

[Tom M]

Can someone please describe the changes made between the 1939 and 1940 V8 that increased the HP rating from 135 to 150 HP?
Is it possible or practical to make these improvements to the 1939 engines without obvious outward changes? I believe the bore and stroke remained the same and I know the later engine had higher compression, it can't be just a matter of different heads could it?
Thanks, --t

[Terry Wenger]

Tom

The difference in horsepower was due to change in the compression ratio. The '39 and '40 heads look the same with one set used on series 50,52,72 and 75 for both years and another set used on the 60S, 61 and 62 for both years. For 1941 another different looking set was used raising the compression ratio to 7.25 to 1 on all series. It is an obvious change to use '41 heads on an earlier car. Milling the original heads would be the answer. I do not know how much.

Terry Wenger

[John Washburn CLC 1067 Sadly deceased.]

Tom,

I believe that you can use the same heads off a LaSalle, smaller bore, and will increase the horsepower.

The later heads have different castings and are easily notices as not original.

The Johnny

[Terry Wenger]

Tom.
As John says , use the LaSalle heads. They were used on the '39-75 and '40-72 and 75 Series cars . They will increase the compression ratio from 6.25 to 6.7 to 1. That raised the horsepower on the 61,62 and 60S cars from 135 to 140 on the 72 and 75.

Terry

[Terry Wenger]

Tom:

I'd better add that '39 and '40 LaSalle heads and '39 and '40 75 and 72 series heads are all the same part number, so either will give you the compression increase.

Terry