15hp increase from 1940 to 1941 346 flathead. How?

[Percy]

Hello All,

Just curious where the 15hp increase came from. For 1940 I'm showing 135hp and then for 1941 I see 150hp. Does anyone know what changed on the engine for this increase?

I've heard that 1948 346 heads had slightly higher compression than other previous heads, maybe this is the case for 1941 versus 1940?

Thanks,
Percy

[Steve Passmore]

The biggest factor I have found is they shaved away a lot more metal around the inlet valves making better flow. Unfortunately. there's not enough casting there and they crack.

[Bob Hoffmann CLC#96]

The Buick Road Master & Century had 150 HP & Cadillac not to be out done.

[Tom Boehm]

In 1940 series 60s and 62 had a compression ratio of 6.25:1    and 135 horsepower.
In 1940 series 72 and 75  had a compression ratio of 6.70:1    and 140 horsepower.
in 1941 all series had a compression ratio of 7.25:1                and 150 horsepower.

It seems a change in compression ratio upped the horsepower. Displacement and carburetor were the same. Do any of you guys out there who know more about 1941s know of any other changes?

[Steve Passmore]

This ratio thing has been very curious to me over the years Tom because at one time I had a cylinder head off every year from 1937 through to 1947 on the shelf. With a straight edge and a vernier gauge, I studied every single one for size and depth of combustion chamber and they are all identical down to the last one-thousandth of an inch.
I have never understood that???

[Brad Ipsen CLC #737]

The 1940 higher compression was achieved by putting the LaSalle head (322) on the 346 engine.  These heads are stamped with compression ratio and engine cubic inches.  There must have been some difference.

[Steve Passmore]

The 1940 higher compression was achieved by putting the LaSalle head (322) on the 346 engine.  These heads are stamped with compression ratio and engine cubic inches.  There must have been some difference.

One would think so Brad which is what I was specifically looking for. To confess though, I did not have a LaSalle head here.

[suchan]

The 1941 Buick Century/RM/Limited had 165 HP with dual carburetion.

The Buick Road Master & Century had 150 HP & Cadillac not to be out done.