59AB block factory relieved

Walt Dupont--Me.

Walt Dupont--Me.

Well-known member
Talking about these 59 blocks latley. I just had one dropped off in my shop to build for a vintage stock car. It just has 59 on the bell housing, a few smaller casting numbers up above the 59 that has a screw driver head on each end of the no's. I don't think they mean anything. It has the undrilled oil filter bung casting on the back. But the nice thing about it, it's factory relieved. Nice block to build vintage stock car engine. Walt
 
If you read Joe Abbins book, he's a great believer in releivings the block, even on carb engines, He's done alot of dyno testing. Walt
 
We used to have an Army Air military base in my area until around the late 40s and I have flushed a couple of new 59L blocks coated in cosmo that had a light relief out of local garages. I don't know if they were military or not but it's seems strange that they would just be hiding around this area. I built both of them with 4 inch cranks and bored to 3 5/16 and they ran well. I did one of them with Roadrunner blower and it really worked good.
 
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Krylon32 said:
We used to have an Army Air military base in my area until around the late 40s and I have flushed a couple of new 59L blocks coated in cosmo that had a light relief out of local garages. I don't know if they were military or not but it's seems strange that there would they would just be hiding around this area. I built both of them with 4 inch cranks and bored to 3 5/16 and they perormed well.
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From all that I've read, they were designed for heavy trucks (makes sense for military) to lower the compression for the jake brakes. They found that the heat the comprehession brakes generated cracked the valve seats near the relief.

Would be prefect for a light car or hopped up motor though...
 
I think some truck engines were relieved and at lot of engines in the west were used as stationary engines for drilling rigs and some of them were also relieved. G.M.
 
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Thats exactly what I have. The relief has a rough finish maybe done in a horizontal mill in 1 pass. the relief is about .090" deep on cyl 1-4 and .100" on cyl 5-8.
 
This could be a long topic. Yes I understand the reason for the factory relief was for the trucks and commercial engines.
Relieving a Flathead may help if the cylinder head has had the transfer area filed to increase CR. However the flow from the valve wants to go up and not make a hard turn to the cylinder. Using a flow bench I made dozens of tests with varying combustion chamber combination and found that the block relief did not improve flow when the head was relieved.
Now you might ask how do you do that? By removing the lip at the end of transfer area. But remember non of this helps much bellow 4000 RPM and most Bonneviolle engines are NOT relieved. Considering the amount of work it takes to relieve a block right it isn't worth it. Edelebrock makes a low compression head for large displacement and/or blower motors.
 
I have never found any Ford publication discussing the relieved blocks on regular flatheads, but there was a Service Bulletin mention in about '49-50 on the 337 Lincoln type truck blocks. It clearly stated that the engines were being relieved by the factory to address a cracking problem, and gave dimensions of the factory relief cut so that dealers could relieve blocks in trucks sold before the factory began relieving. That is the only Ford mention of relieving I have ever found...I don't believe that the relieved 59 blocks were even identified in the parts books.
 
Flathead folklore...when I was a kid, there was at least one old geezer at every gas station and corner garage with decades of experience fixing flatheads.
I took every opportunity I could get to talk with the ones willing to give me the time.
Several crusty old experts assured me the relieving was an excellent way to ward off the dreaded cracked block...several others warned me to never relieve an engine because it was sure to crack afterwards. Guess we are doomed!
 
Must just be the luck of the draw but I have two 59A motors here, both are factory relieved. My French block is also relieved in a very similar (if not identical way). The French motor was produced specifically for a military truck application, so that makes sense, so may I also assume the other motors probably started out as truck motors?
Mart.
 
First off, I am talking about race engines here. 276 ci or bigger.
A relieved block will make more hp over the whole operating range.
Angle milling the heads keeps the breathing along with raising the compression.
It takes about an hour to relieve a stock non relieved block in a mill.
Starting with a factory relieved one it can be done in 40 minutes.
The original factory relief was broached as evidenced by the machine
marks 90 degrees to the crank.
 
I was not going to enter this discussion but see, now, that I must. There are too many conflicting statements.

After having done several hundred flow tests with about every imaginable combination of port, valve, and relief configuration, I found no evidense that relieving a block will increase power whether it is a race engine or a street engine. The remarkable flow increases, which some claim to see from relieving, just do not exist.

In a "race" configuration the low lift(.050) flow improves, very slightly, with a relief. However, the higher lift flow does not improve. The space opened by the relief will cost more power due to reduced CR and increased residuals than it is worth. With a proper bowl configuration and by increasing valve size the low lift flow is, again, increased. This time by a huge margin. So, use a larger valve and don't waste time milling or grinding a reflief.
 
Barney Navarro felt the same way about relieving the block as Ol' Ron & JWL but if you have one of those old factory relieved blocks, you might as well use it. Many of the aluminum after market heads were made to work with a relief. They may not flow out like the modern science dictates but they will run OK for street. I sure wouldn't set one aside for one with no relief.

A friend of mine was into building small block Fords and he built all of them pretty much the same but he had one that just outperformed the hell out of all the others. He tried to duplicate what made it run the way it did and he never could. Sometimes the science just doesn't explain it all.

Kerby
 
rotorwrench said:
Barney Navarro felt the same way about relieving the block as Ol' Ron & JWL but if you have one of those old factory relieved blocks, you might as well use it. Many of the aluminum after market heads were made to work with a relief. They may not flow out like the modern science dictates but they will run OK for street. I sure wouldn't set one aside for one with no relief.

A friend of mine was into building small block Fords and he built all of them pretty much the same but he had one that just outperformed the hell out of all the others. He tried to duplicate what made it run the way it did and he never could. Sometimes the science just doesn't explain it all.

Kerby
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Kerby:

Well said.

Tim
 
Navarro and also Don Francisco on the no-relief side...
Many pro-relief sources compare flow with aftermarket heads, which typically have a greatly reduced flow area between valve and cylinder in comparison to originals...
I think it would be interesting to compare those opinions agains an unrelieved engine block with the relieving done upstairs in the head...I don't know if any of Abbin's results compare in that direction.
I certainly cannot comment myself as I have no flow bench or any other scientific approach, but JWL and Ron have produced results that seem to agree well with valve seat flow studies published by Yunick and Vizard. The flow coming over the seat can only turn outward slowly, and it seems a stretch that it could turn 90 degrees into a relief area willingly. With a low roof, it would be forced thataway but everything I have read about seat transition seems to indicate that it wants to go UP in that area.
Ron once had pictures of his head work, effectively relieving the roof, online once...anyone have those saved??
 
Porting...early guidebooks show how to port the hell out of the places you can reach easily, like inlet of port, where port is already bigger and more regular that the gnarly bits downstream and of couse the all important transition through the pocket and seats...
I think a lot of current work follows a straight path, right across bottom part of seat and smoothing out the floor up into the lower part of seat by filling it...this agrees with some historical thinkers like Bingelli, with Flatdog (RIP!!) and again tallies with Yunick...Y says it takes a really big bowl in a 350 Chevy to allow the flow to truly turn and flow around the whole valve, implying for us that our bowls are impossibly small for a turn into the valve area...so that linear flow path again seems to sound right.
And...imagine if you COULD turn the flow in a flathead, and get substantial flow most of the way around the valve...what kind of chamber would that need above the valve??!?
 
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