1939 A Block vs. 59 AB same dimensions?

[DetroitDesign]

Hello,

I am building an Av8 Model A hot rod and have the opportunity to buy a running complete 1939 “A cast head” Flathead with transmission reasonably. This combination would be useful to me as it would provide me with the dimensions to set up my motor mounts and k member.

My question is: are the front motor Mount locations and motor Mount to bell housing dimensions, and exhaust manifolds, (for steering setup) the same between the 1939 motor and the later 59ab blocks if I wanted to build a more performance oriented 59ab later?

Thanks,

Ian


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[DetroitDesign]

As you can see I am in the very beginning, stock model a frame, I have a stock 1932 K member, the rear is 1936 Banjo with adapter plates for spring over. Any advice on setting up driveshaft length is also appreciated. Thanks


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[DetroitDesign]

This is the 1939 engine I am asking about


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[alchemy]

Yep. Only dimension differences are in the bore, and a very slight valve angle change which many never notice.

 

[rotorwrench]

The 81A block has core sand removal holes on the pan rails with corresponding bulges there in the block. The front of the engine above the timing cover has less slope that the 239 cid types with a pencil thick flat area there. The 221 cid block stayed pretty much the same till 1941 when some casting changes were made to all V8 blocks which deleted the sand removal ports and affected the intake deck shape a bit. The bore wall thickness is limited on the 221 so it can't be bored out near as far as a 239 block.

As was mentioned, the post war engines had a major design change in the valve angles. The 59 series heads will bolt on the prewar engines but the prewar heads have to be modified to fit on the 59 series blocks. It only takes some small cuts in the valve pockets of the chambers to make the early heads work on a later post war engine. Tooling was made for rebuilders to perform this relief work.

The 221 is a good little engine but is a bit limited on how much performace can be squeezed out of it. It can be modified to make a 255 cid engine with stroking and boring but that's about as far as is practicable since there are still a few larger engines out there from the 59 series and 8BA eras of the post war.

 

[Kube]

Hello,

I am building an Av8 Model A hot rod and have the opportunity to buy a running complete 1939 “A cast head” Flathead with transmission reasonably. This combination would be useful to me as it would provide me with the dimensions to set up my motor mounts and k member.

My question is: are the front motor Mount locations and motor Mount to bell housing dimensions, and exhaust manifolds, (for steering setup) the same between the 1939 motor and the later 59ab blocks if I wanted to build a more performance oriented 59ab later?

Thanks,

Ian

Ian, If I understand your question correctly, you only want to use this '39 block and transmission to mock up your chassis for the eventual installation of a 59 series. Correct?
If so, then the answer is yes, outside dimensions, etc. are the same for all practical purposes. The exhaust manifolds are a tad different between the two engines you'd mentioned. You can install the '39 manifolds on the 59 series block if you'd like.

 

[DetroitDesign]

Hi folks, thanks for all detailed information. I would not be investing any machine work into this motor. It is more a nice package for me to mock-up my motor mounts and k member location from. So my question is really about external mounting dimensions and how they compare with the postwar 59a series thanks!


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[Kube]

Hi folks, thanks for all detailed information. I would not be investing any machine work into this motor. It is more a nice package for me to mock-up my motor mounts and k member location from. So my question is really about external mounting dimensions and how they compare with the postwar 59a series thanks!


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See post #6....
By the way, the rear bearing retainer / transmission support is different between '39 and the 42 - 48 transmissions. However, they are interchangeable. Thus, you could mock up to the '39 and later, swap that 39 support out to the later trans.
Or, install the 39 support on the later transmission in the future.

 

[DetroitDesign]

Thanks! Would accessories like the fuel pump and starter interchange onto the 59A?


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[Kube]

Thanks! Would accessories like the fuel pump and starter interchange onto the 59A?


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Pretty much everything will interchange. The fuel pump and starter are for certain direct swaps.

The '39 has the fan mounted on the front of the crankshaft. The later engines have it mounted on the generator (bracket).

 

[36crazy]

Water pumps are the same from 37 to 48 and that is where the motor mounts are so they are identical. The bellhousing, anti chatter rod placement etc are all the same from the 39 motor to the 59a so it is ideal for your use.

 

[Flathead Fever]

All the '39 to '48 blocks, with their water pumps and transmission bolted up on are the same length. I just had a friend build a 1931 AV8. One book said to use a 1932 wishbone, so I found him a nice one and I bought it for $300.00 and he paid me back. But then he found the book was wrong, a 1932 wishbone was way too long. A 1933-1934 wishbone was the perfect length (shorter than a '32). They sell for around $300.00, a lot cheaper than a '32 wishbone. He sold the 1932 for $600.00 and made enough profit to pay for a '34 wishbone. I just bought two nice straight, rust pit free '33-'34 wishbones for $450.00 for the pair. I stuck a wanted ad on Craigslist, because I needed one for my '34 pickup and ended up with two. I'm keeping the second one just in case I ever build an AV8.

If you assemble a spring, axle and a 1934 wishbone, bolt it to the Model A front crossmember. Then use the 1934 wishbones' ball to locate the narrowed 1932 K-member it could not have worked out any better on my friend's '31 Roadster. The '34 wishbone was just like it was made for putting a V8 in a Model A. One-inch shorter or longer and it would not have worked. You will end up with just enough firewall clearance at the rear of the engine, and the radiator clearance in the front will be just enough to run the shortest factory generator mounted fan which I "think" was the '37-'39 fans. You will need to attach motor mount pads to the frames' side rails for the water pumps' motor mount arms. If you mount them too high, the back of the intake could hit the firewall. Do not weld or drill holes in anything until you have it all temporarily assembled to check clearances; body mounted on the frame with radiator and fan in place.

Don't take anybody's word on this stuff until you have done your own measurements and confirmed what others have told you is correct. Especially if I told you!

 

[Flathead Fever]

As you can see I am in the very beginning, stock model a frame, I have a stock 1932 K member, the rear is 1936 Banjo with adapter plates for spring over. Any advice on setting up driveshaft length is also appreciated. Thanks


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See how you rear shackles are straight. That will not allow the spring to move. When it's done and all the weight is on them the shackles need to pe pointing down at around a 45 degree angle so the spring can grow longer when you hit bumps. If the shackles are straight the spring has nowhere to go. You might need a longer main leaf. You'll have to see where the shackles end up when all the weight is on them.

 

[Pete]

See how you rear shackles are straight. That will not allow the spring to move. When it's done and all the weight is on them the shackles need to pe pointing down at around a 45 degree angle so the spring can grow longer when you hit bumps. If the shackles are straight the spring has nowhere to go. You might need a longer main leaf. You'll have to see where the shackles end up when all the weight is on them.

If the spring has an arch in it, it will get longer between eyes as it is pushed down. His shackles will probably end up around 45 degrees. The angle depends on the weight.

 

[rotorwrench]

There is a lot of interchangability in all the flathead 221/239/255 engines. Any engine with the 1937 through 1948 water pumps is the easiest fit in the 1928/29 model A types since there is little room from radiator to fire wall. Running a 1932 type k-member will require the 1932 type rear engine mount to fit that type cross member. The transmission will have to have the rear trans bearing retainer from 1932 thru 1936 plus the disk plate to use the 1932 rear mount. The 33 thru 36 used a different mount but the retainer is basically the same. This stuff will let you mock the frame up for a conventional AV8. The body or at least a cowl will need to be there for clearance checks. A radiator would be good too. The 59A configuration isn't that much different than the 81A but the front pulley has to fit in there. In 1939 they changed to the long crankshaft snout to do the fan on the crankshaft gig. The snout on the 59 series crank is the same and so it the 8BA. There may be some clearance issues on the front cross member but that can genrally be overcome by trimming the rear wall of the member down a bit. The 1932 wishbone will work for the 32 K-member but the Model A or 33/34 types can be lengthened to work as well.

The fit in a model A is tight but it can be done. The early short snout cranks actually fit the best but most folks want more cubic inches than what was available in those early engines. The long snout crank can be cut down to the earlier dimesion to use the early type pulley. The possibilities are nearly endless. The HAMB has many different builds.

You will need the get the engine & transmission set in stone before you can measure out and trim the torque tube. The hollow tube drive shaft is favored over the solid shaft since the system is shortened a good bit. Dick Spadaro, God rest him, used to make a nice drive shaft kit but a person can still make one from the front section of the mid 30s hollow drive shafts to build one up.

 

[DetroitDesign]

Thanks to all, this is great information. In regards the spring shackles I believe once the wheels are on to support the axle and there is some weight on the chassis the shackle will rotate up into that 45 degrees orientation. Thanks for the feedback on the wishbones too, I will likely start with one of those two options, mock it up and if it isn’t lining up, ill sell one bone, I’ll switch to the other or go to split bones, depending on how things line up in my case. Noted that mock up / trying it is king. Thanks!


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