Stock "59 Series" Relieved Blocks?
 

Hi,

The thread, "Re: Building for Torque Porting Question" has me thinking about my 59A block. My block is a 46-48 59 series and it has a stock valve pocket to cylinder relief. I've seen some reference to this being a truck block. Anyone know which series had this relief and what applications?

Glenn

Re: Stock "59 Series" Relieved Blocks?
 

I have a 59 series motor that is factory relieved and I was told that these were used primarily in heavy trucks. Check the bore to insure it is a 3 3/16 block. Mine has a 3 1/16 bore and passes the pencil test which shows it to be a wartime replacement motor. Due to the size of the relief I would imagine that they are lower in compression than a regular 59 series block.

Re: Stock "59 Series" Relieved Blocks?
 

The factory relieved blocks can make good use of the crow foot combustion chambers in many of the aftermarket finned aluminum cylinder heads without dropping the compression. It's usually a good idea to clean up the relief shape for a better match up to the heads. Many of the truck blocks were souped up back in the day since it didn't take as much grinding to make a good relief.

Re: Stock "59 Series" Relieved Blocks?
 

I need to ask, what is the pencil test?

Re: Stock "59 Series" Relieved Blocks?
 

Thanks Stenny,

Mine was a 3 3/16" bore and does not pass the "pencil test". From discussion with Offenhauser tech rep years ago, he said the CR would be .3 less with the stock relief. This reduction is also shown on page #8 of the attached interesting compilation by James Leis.

Re: Stock "59 Series" Relieved Blocks?
 

Somewhere I read that the relief in the 59L truck blocks was to lower their compression to prevent detonation under heavy loads. It would make since. Everything article I read said if you wanted a factory relieved block to go find a 59L. I found a complete 59L engine and when I pulled the heads there was no relief? Just my luck.

When putting high performance finned heads on a flathead the majority of the thicker "race" heads, the ones most people buy, were designed for relieved blocks. The compression ratio that is usually stamped on them is assuming you have already relieved the block. The thinner finned heads, referred to as "street" heads are for engine that have not been relieved.

Re: Stock "59 Series" Relieved Blocks?
 

Early blocks had a "shelf" cast into the block just above the timing cover. Later blocks do not. The pencil test refers to being able to lay a pencil on this shelf.

"All pre WW2 flathead engines, including the 21 stud, will pass the so called "Pencil Test". This pre war blocks have a tiny shelf above the timing cover. The shelf is deep enough to horizontal lay a pencil on it. All post war blocks will fail the pencil test."

Picture from 38 coupes post (the one often referenced for block ID). The test is not about the timing cover holding up the pencil, but the shelf cast into the block.

Re: Stock "59 Series" Relieved Blocks?
 

Yes, Flathead Fever, I have the thick new design Offenhauser 400 heads. With my .080" over and 4" stroke Mercury crank I believe I have a CR of 9.33 as red-box marked on the attached.

Re: Stock "59 Series" Relieved Blocks?
 

Forgot to mention that I also have these numbers on the bell housing,

L8411

Re: Stock "59 Series" Relieved Blocks?
 

Does it also have the large "59" on the bell housing ?

Re: Stock "59 Series" Relieved Blocks?
 

Yes Ken it does have the large "59" too.

Re: Stock "59 Series" Relieved Blocks?
 

My motor is out of a 1946 COE. It has the factory relief and a 59L casting in the bellhousing.

Re: Stock "59 Series" Relieved Blocks?
 

I have a 59L block that is not relieved. Kinda took me by surprise when I pulled the heads.

Re: Stock "59 Series" Relieved Blocks?
 

jrvariel48, nice looking motor.

Does the marking have a large 59 and then below L with numbers or 59L together?

Re: Stock "59 Series" Relieved Blocks?
 

I've built 2 of the 59L relieved blocks, both were new never used blocks. I assume they were military surplus as we had 2 large airbases near here. I found both blocks in old machine shops. I did one with Offy heads and a Roadrunner blower and one with 2 94's and Offy heads. I used 4 inch Merc cranks and bored them to 3 5/16 and did all the other usual stuff. Both ran good and with Walker Z line radiators and 16 inch electric fans ran reasonably cool.

Re: Stock "59 Series" Relieved Blocks?
 

I wonder if the "L" on the 59L blocks stood for lower compression since most of them were factory relieved? Why would they jump from 59A to 59L in the alphabet to designate a different block unless that "L" stood for something? Today the "L" stands for costs "lots" more than the other blocks.

Re: Stock "59 Series" Relieved Blocks?
 

the 99a engine in our 33 is from an old truck and was factory relieved,its a nice engine with .040 over bore and 4in crank, goes great with 75cc chamber cast iron heads,stock 97 carb and 33 manifold.
Lawrie

Re: Stock "59 Series" Relieved Blocks?
 

How far can the 99A block be bored??

Re: Stock "59 Series" Relieved Blocks?
 

Thanks Glenn, I'll see if I can find a picture.

Re: Stock "59 Series" Relieved Blocks?
 

Hope this helps