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Old 12-07-2017, 12:34 PM   #1
glennpm
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Default 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
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Old 12-07-2017, 01:00 PM   #2
Stenny
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Default 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.
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Old 12-07-2017, 01:07 PM   #3
rotorwrench
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Default 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.
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Old 12-07-2017, 01:10 PM   #4
Tim Ayers
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Default Re: Stock "59 Series" Relieved Blocks?

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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.
I need to ask, what is the pencil test?
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Old 12-07-2017, 01:17 PM   #5
glennpm
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Default 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.
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File Type: pdf Compression Ratios - CR Complete File.pdf (686.1 KB, 48 views)
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Old 12-07-2017, 01:39 PM   #6
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Default Re: Stock "59 Series" Relieved Blocks?

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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.
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Old 12-07-2017, 01:46 PM   #7
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Default Re: Stock "59 Series" Relieved Blocks?

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I need to ask, what is the pencil test?
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.
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Last edited by JSeery; 12-07-2017 at 02:19 PM.
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Old 12-07-2017, 02:53 PM   #8
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Default 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.
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File Type: pdf 59A Compression Ratios - My Ratio .pdf (355.8 KB, 15 views)
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Old 12-07-2017, 03:07 PM   #9
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Default Re: Stock "59 Series" Relieved Blocks?

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

L8411
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Old 12-07-2017, 03:14 PM   #10
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Default Re: Stock "59 Series" Relieved Blocks?

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

L8411
Does it also have the large "59" on the bell housing ?
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Old 12-07-2017, 03:15 PM   #11
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Default Re: Stock "59 Series" Relieved Blocks?

Yes Ken it does have the large "59" too.
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Old 12-07-2017, 05:19 PM   #12
jrvariel48
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Default 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.
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Old 12-07-2017, 05:26 PM   #13
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Default 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.
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Old 12-07-2017, 05:43 PM   #14
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Default 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?
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Old 12-07-2017, 07:45 PM   #15
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Default 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.
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Old 12-07-2017, 08:21 PM   #16
Flathead Fever
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Default 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.
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Old 12-07-2017, 08:23 PM   #17
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Default 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.
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Old 12-07-2017, 08:51 PM   #18
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Default Re: Stock "59 Series" Relieved Blocks?

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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
How far can the 99A block be bored??
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Old 12-07-2017, 09:22 PM   #19
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Default Re: Stock "59 Series" Relieved Blocks?

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jrvariel48, nice looking motor.

Does the marking have a large 59 and then below L with numbers or 59L together?
Thanks Glenn, I'll see if I can find a picture.
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Old 12-07-2017, 09:34 PM   #20
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Default Re: Stock "59 Series" Relieved Blocks?

Hope this helps
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Old 12-07-2017, 09:37 PM   #21
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Default Re: Stock "59 Series" Relieved Blocks?

I opened up an early factory relieved block with a raised intake,no bulges in the pan rail and passes the pencil test. Had Edelbrock heads, Sharp dual intake and an 8BA timing cover. Pistons are marked STD and it’s 3.187. The crank looks 3 3/4 but the cylinders are rusted and I can’t turn it over. It’s not stuck but can’t turn a full rev. Not marked 59.Going to pull it all down this winter........Mark
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Old 12-08-2017, 01:27 AM   #22
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Default Re: Stock "59 Series" Relieved Blocks?

The marking on the blocks are interesting...a lot of the blocks marked with a Y has it sitting upside down...have to wonder if it was done with purpose or not.
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Old 12-08-2017, 02:32 AM   #23
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Default Re: Stock "59 Series" Relieved Blocks?

jrvariel48, That engine you have pictured- have you run it? It appears to have some pistons fitted backwards.
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Old 12-08-2017, 04:34 AM   #24
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Default Re: Stock "59 Series" Relieved Blocks?

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jrvariel48, That engine you have pictured- have you run it? It appears to have some pistons fitted backwards.
Brian, yes it runs great! The motor came out of a 1946 COE dump truck that spent it's entire life on a farm. I'm sure they did their own repairs back in the day, but right now it runs great. I even put a blower on it!!
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Old 12-08-2017, 06:38 AM   #25
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Default Re: Stock "59 Series" Relieved Blocks?

Great, thanks for the picture.
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Old 12-08-2017, 11:09 AM   #26
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Default Re: Stock "59 Series" Relieved Blocks?

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Quote:
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How far can the 99A block be bored??
The 99A blocks in the 1939 & 40 time frame did have some thick cylinder walls but I don't know by how much. A person would still be wise to sonic test before boring to 3 3/8". I know they make pistons up to .2175 OS at Egge but I don't know if they can possibly go out that far without sleaving the block.
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