Technical Tell Me All You Know About a Ford Flathead Relieved Block!

I have one of these blocks. Someone correct me if I'm wrong, but I believe the relief was referred to as a "Fire Slot". As Alchemy said, It was used in 41 large commercial trucks. It's purpose was to provide va***e? for a very early power brake system. But then again, I'm 78 years old and my memory is fading fast and I could be just full of ****. I got this block long ago as a gift from a local guy who was liquidating a collection of parts when the owner died. Not likely I'll ever use it, and someone else will have to liquidate it when I'm gone.

 

Somewhere I read yrs ago, that the ~'41 truck blocks were factory "relieved" due to problems w/cracks in that area. So a small shallow relief stopped that, due to, it was claimed, a difference in casting wall/deck thickness, & abuse that the trucks received from the lead-footed drivers - ie: "never lift 'till she blows"... Don't know since I wasn't there then, but also got told similar ~ 50+ yrs ago by an old machineshop owner, who told me the factory relief was *not* for performance, so quit looking for something "not" special. Who knows... ???
<shrug> ???
Marcus...

 

Except that I’ve never seen, and the OP’s isn’t either, a prewar factory relieved block. It’s a post war 59A block, so it can’t be a 1941.

 

I have two C69A blocks. Both were truck engines or industrial engines. Both have the large oval cleanout in the pan. One is relieved and the other is not relieved. Weird?

 

Mine too !

 

I must correct myself on my previous reply. Alchemy did NOT say 41 commercial trucks. They could have ben 39 or 40. As previous replys have stated they were used in Ford fire trucks.

 

Alchemy, you're probably right, I don't remember the exact yrs. Could've been pre, mid or post-war yrs, idk? Once the factory was setup for that machining operation on that line, it probably kept going, 'till someone at ford was able to prove it wasn't needed, then dropped to save a few cents in mfgr costs, IDK??? Those weren't the point of the convo, it was the factory relief. Which was a thin-shallow straight-edged cut that wasn't at all much like the hotrodders hopup technique, since the days of Ed Winfield & probably older. I lost my interest in ford v8 minutiae ~35+ yrs ago. Flathead stuff in general, & hopups, oh yeah, you bet, ford-detail-specific, no. No biggee. Happy to be corrected. Correct info is always best. .
Marcus...

 

Just because I’ve never seen it doesn’t mean it’s not out there. My wife tells me every day that I don’t pay attention. I hope some HAMBers will post more minutiae pics of the oddities, as well as the regular stuff. We gotta build our knowledge banks.

 

I have a merc engine with factory reliefs that came out of a 41 merc. Nearest i can tell it's a pre war block. Unfortunately it's buried in a container. So no proof

 

During the time I have been messing with Ford flathead V-8 engine blocks I have seen relived factory blocks with a bore size of 3- 1/16 which places them at least from 1939. From 1939 all the way to 1948 factory relived blocks were produced as others have written for commercial application's. The 59A version blocks with a factory relief I have seen and owned at times could have additional letter designations these letters L , Z and Y.

The relief originally from the factory may have been added to help REDUCE the cracks that develop under extreme use from the cylinder bore edge to the valve seat. Its been my experience the relive will help reduce cracking in an extreme environment that being well over five times the originally horsepower burning gasoline. Any block relief will enhance overall power output for a hoped up flathead V-8.

If one looks at the Harley factory teams KR flathead engine designs developed well after the Ford flathead was long out of production. Those engine's had a relief the reason because it works.
Ronnieroadster