Pre 1945 Block Cams

[David Lien]

I Have 2 pre 59 AB blocks Numbers (D241. 4. X17) and, #(3223. X3). Both blocks have the round water hole in the middle of the block deck with odd shaped holes at the top and the bottom. Both blocks have 3 and 3/16 Bores one is +.060 and the other is a fresh bore at +.125. Both blocks came to me with a Cam marked 91 A. I have assembled the +.125 block with a reground Esky. 77 B cam that came out of a 1947 59 AB Block.

So How do I determine if my block was built with a 101.5 Degrees of separation (Pre 1945 Block) or if was built with 100 degrees of separation After 1945 Block ???

Also will an earlier block ((101.5 Degrees)) run OK with a 59 AB cam ((100Degrees)) installed.

Also are their any other funny things hooked up to my blocks, that I should know about????

I think I should talk to Pete, however with an entire flock of brains out their, I thought I would try the flock first. thanks up front I will appreciate All the help that I can get. David

[Tim Ayers]

A picture would help, but is the top water hole is a like a squat triangle and the lower is a trapezoid and the bore is for sure 3 3/16", sounds like you have hit the flathead lottery with 99A Mercury blocks. Rumor is they are the thickest of all blocks cast.

Another home test is what's called the pencil test. If a pencil rests on the "ledge" above the cam cavity and where the distributor sits, then it's a safe bet with all of the other indicators that they are 99A blocks. I have a 59L block that passes this test, so it's not fool proof.

If so, then yes, they have the early 101.5 degrees. I'll leave it to others to say if it will make a difference. The 77B is a super tame cam. Some say worse then stock actually.

I'll let the cam experts chime in about that one, but if these blocks are crack free, you did well.
For some reason, these blocks like to crack at one of the center intake valve seats into the bores. Look them over carefully. If pass a visual inspection, have the cleaned, mag'd and pressure tested to be 100% sure they are good.

By chance, does either block have what's referred as a raised intake deck? Meaning the sides where the intake side are lower.

[David Lien]

Below are photos of the 2 blocks, their numbers, and the cam.
Yes they are both raised intake manifold Blocks.

[Tim Ayers]

Originally Posted by David Lien

Below are photos of the 2 blocks, their numbers, and the cam.
Yes they are both raised intake manifold Blocks.

Yep, 99A's.

[Pete]

The early blocks are a POOR choice for any rebuild engine. The valves were closer †o the cylinder bore and that was why they were famous for cracking in that area.
As far as the cam index difference, you will never feel it in the seat of pants. It is barely notable on the dyno.

[flatjack9]

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With a proper cooling system, I wouldn't worry about cracking the block. As Tim said, they are desirable.

[JWL]

The early 3 3/16 blocks from trucks and Mercs are the best for a performance build. Count yourself lucky if you have 2 of them.

[Pete]

In the 50's I had a friend that was in charge of the tear down area in the official Ford rebuild facility of the Northwest. He said 6 out of 10 early flathead blocks they torn down needed crack repair, usually between the valves and cylinder.
That was the primary reason Ford moved the valves farther away from the cylinder in the 59 series blocks.
The early blocks will work fine for stock rebuilds where it is unlikely they will get overheatd.

[rotorwrench]

The early 99 series till 1941 have the core sand removal ports and associated bulges on the pan rails. The 19A block for 41 was changed some with the abbreviated intake deck area and the lack of core sand clean out ports. The 29A engine of 1942 was continued to some degree during the war for some trucks and the T16 Universal carriers so there were surplus engines at one time. Most of that stuff has dried up in this day and age but they still show up now and then.
http://www.robertsarmory.com/T16.htm

There were some 59 series blocks made with no "59" on the half bell but they are not common. They have all the 239 CID 59 series characteristics. The 41A blocks that were made as replacements for the 221 CID blocks during the war, were continued after the war for a time with the 59 marking on many but they have all the 221 characteristics for the smaller pistons.

It has been said that the 99A blocks have the thickest cylinders of all but some folks mention that that changed in either 1941 or 1942. I've not heard of anyone doing a comparison of thickness using ultrasonic devices but it would answer the old question about this. They are still descent blocks but the 59 series with the new valve spacing was also a definite improvement.

[21stud]

Nice blocks! Well, I think for performance build it is best to have valves closer to bore.

[Bored&Stroked]

I've done sonic testing on a brand new "keystone" 41-42 block - it is in my 32 Cabriolet. They are not any thicker than a new 59x 3 3/16 block (which I also happen to have). The old wives tales about the early Merc blocks being thicker - I think they are just that . . . good ole' often repeated stories - passed down through the ages.

I'll take ANY good 3 3/16 block from 39-48 - I think they're all worth using if you find a good one. There - my 3 3/16 cents for the day

[Ronnieroadster]

Originally Posted by 21stud

Nice blocks! Well, I think for performance build it is best to have valves closer to bore.

As Pete noted above. The closer the valve is located to the cylinder bore the easier it is for a crack to materialize. Thus the earlier block is not really a wise choice for a performance build. If or maybe I should write when the engine is built for performance and ends up overheating or goes lean you will now have cracks. With an additional .125 overbore the possibility has now been increased. Care must be taken to keep the engine cool.
Ronnieroadster

[rotorwrench]

All of the flathead V8s will crack in the valve pockets if they get too hot. As mentioned, the chances of that do increase with closer distance to cylinder dimensions and especially if they are rode hard and put away wet. Higher performance generally means higher loading and that all turns into higher temperatures.

Take good care of the engine cooling system and it will take good care of you too.

[Bored&Stroked]

Put some updated water pumps on it (like Skips), run a really good radiator of the right capacity, run thermostats, run anti-freeze and don't overheat the engine. With a good cooling system, it should not run any hotter than a stock engine. My 284 cube flathead runs at 180 . . . and I've sat in traffic for an hour on a hot 90 degree summer day and it never got over 192.

What you don't want to do is overheat the engine, boil it, throw cold water in the already overheated engine block and then wonder why it cracked.