Hi, I need some help and we all know that this is the best place to find it. I just hauled home a 31 AA truck with the 12 foot bed. As I have been looking it over I see that the motor number is a bit different. It has the star then R F 6851 star. The flat block has not been machined down. So this number has me stumped. Could it be a later production block? Thanks for any help I can get. Scott
Here is a link that may be helpful. If not there is a contact at the bottom of the page where you could email the author.
Best regards, John
Thanks John. I just sent him and e-mail so we wait and see. Scott
Thank you Scott. Please post any results from your inquiry. Regards, John
Is the area where the number smooth or ruff as cast like the rest of the block? I would guess that it's a replacement block that was re-stamped by the builder with their initials and build number.
OK I just got an e-mail back frome Vince, Its a replacement block from Ford. The RF means Richmond. Its a crate motor. LB would mean Long Beach. They made replacement motors from 1930 to 1950? I have not opened it up yet to see if it has counter weights on the crank. But it is in a truck so Iam hoping. Scott
Scott, if it is a Model A motor, it won't have counterweights unless someone added them later. Anything else just contact me and a picture will help.
Uh, James must not have noticed that it's a Replacement Motor, possibly made long after regular A production, and could easily have a counterweighted crank, and the late oil pump with the baffle plate--and even a B camshaft too. Very cool find there Robert!
If you can remove the oil filler pipe, you can look down inside the crankcase to see whether the crank has counterweights. Just turn the crank until you can see the throws through the oil filler tube hole. That will save you the trouble and mess of dropping the pan to get the same information.
The counter weights in question if it is a "B" engine would look like this sample. It is the more desirable crank to have.
The pictured "B" crank is the later design, the third of three: the 1st one in 1932 had no counterweights; the 2nd had smaller counter-weights swedged on; and the 3rd design had the larger counterweights that were cast/forged part of the crank, not swedged on. It's a one-piece crankshaft with weights. I believe this crank came out in late 1933 or early 1934. According to a well-known high performance Model A engine builder in Texas, the second design is the one to use because it is less likely to be cracked than the third version. He says 9 out of 10 later cranks he gets in his shop are cracked, while the ratio is much lower with the swedged-on counter-weights.
Either way, it'd be nice if you discovered your crankshaft has counter-weights.
Hi Marshall, Well I took the cap of the tube but there is a baffle inside so I can not see anything. I will post what I find as I find it. Thanks to all for your help, Scott
That oil filler and breather pipe can be removed. That is what Marshall is suggesting I think. The baffle can also be removed, but I don't think you will see enough without removing the pipe.
Yes. The tube has to be removed from the block in order to see inside the crankcase. Taking off the cap will only reveal the three baffles inside the tube, which block the view inside. Try wiggling the tube back and forth to get it loose. Sometimes they are real bears and can only be removed by driving them out from inside the engine. Maybe you'll get lucky.
I have taken apart hundreds of Model A motors and have never seen a FACTORY counterweighted A crank in any Model A motor. The Model B had a counterweighted crank of 2 different designs but the A never did. Not in regular production or in post production replacements. If anyone ever finds one that can be confirmed as a true Model A factory counterweighted crank I will retract my statement. I don't mean a cut down B crank either.
Ok I have given up on finding a counter weighted crank in my barn find. But will some one tell me if the B crank will drop in and work? Thanks, Scott
The mains need to be cut down to fit in the Model "A" block saddles, but you can retain the rod bearings as is. That's a neat way to go because you gain more babbitt surface area than provided by the Model "A" rods. I seem to recall that you may need to create some bumps in the "A" pan so that the rods don't hit on the sides. Their larger size makes that a possibility. Others who have made this conversion can chime in here. The simplest way around this is to use a Model "B" oil pan with the rear sheet metal housing/shroud removed. Then clearance is assured.
James is right about Model A's not being equipped with counter-weights from the factory. He builds a good engine, so he should know. But the fact that your engine's serial number has been altered by a rebuilder means all bets are off. A "B" crank could have been installed at the time, although the odds are against it. There was an aftermarket engine made in Model "A" and Model "B" forms for industrial use mainly. They are called "diamond" blocks because of the small embossed diamond symbol. The "B" diamond engines definitely had counter-weights on the crankshafts, but I don't recall if the Model "A" diamond engines did or not. Maybe some did, some didn't, depending upon when the engine was built (up to 1943, as I recall). Maybe James can provide the answer to that. These blocks are highly sought by the driving crowd because they are reputedly stronger castings (especially the "B" version), have larger main bearings, the block is re-inforced above the rear main saddle and hardened valves seats were installed from the factory. These engines were mainly used in commercial applications, such as running at low RPMs for days on end pumping oil in panhandle fields or drilling for water wells. I think the diamond symbol is located on the right side, below the valve chamber, towards the front. Once again, though, the odds are against this engine of yours being a diamond block. There were about 5,000,000 Model A's built and who knows how many spare/replacement engines. No one knows how many diamond engines were made by non-Ford suppliers, but the number has to be relatively low. That makes them expensive and desirable.
Ok I think Iam up to speed about " A " cranks and B cranks. So I will not be looking for a counter weighed crank in my A motor. But the good news is after soaking the motor with atf and acetone for 2 days it turns over smoothly. I looked in the chambers after I removed the plugs and it had the color of light charcoal, same as the plugs. I will be busy for the next few days but will get the carb off and cleaned out. The starter will be next. I can almost hear this motor purring. Thanks for the help, Scott
Hi all, OK the pan came off today. And as expected no counterweights. But it is so nice, shiny and clean i could not belive it. The rods are tight. The pistions are shiny as are the cotter pins. So I think I have a very nice motor. Iam going to wash out the pan, the oil pump and rebuild the carb and see what happens. It will take me a while to get this done as I still need to work most of the time. Scott