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09-21-2012, 12:52 PM | #1 |
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Location: Larry Young, Tulsa, OK
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Question on engine parts interchangeability
I picked up a free A type engine (1938-41) from a guy that put a crate motor in his car. He told me it had been rebuilt by the PO, but then got stuck. I got the block, crank and valve train. I don't have any of the small journal rods, but I've got plenty of 59AB rods and cranks. Wouldn't it work to put 59AB crank and rods in this block, or is there a compatibility issue I'm not aware of? Is it safe to bore these blocks out to 3 3/16 to get a 239 motor? This will be my first experience with full floating rod bearings, so it should be fun.
Thanks, Larry Young |
09-21-2012, 01:30 PM | #2 |
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Re: Question on engine parts interchangeability
If the block is in fact a 39-41, I believe the 38 blocks had smaller main bearing journals,might want to check this. The 59a crank will work if you bore it to 3 3/16 so the large end of the rod will pass through the bore. You will also need to change to a rope seal in the rear which means you will need to replace the potmetal pieces for ones that will accept a rope seal . The lower one that fits in the main cap has a part number 19B-6336 and is made for this conversion, the number for the upper one in the block is 91A-6335 .
Last edited by Ken/Alabama; 09-21-2012 at 01:45 PM. |
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09-21-2012, 03:29 PM | #3 |
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Re: Question on engine parts interchangeability
Make SURE you sonic test the block at least 4 places each cylinder before you bore it. If you are lucky and have no or not much core shift you could do that. I have a 3 1/16 engine that went out to 3 3/16 and left me with what my machinist thinks is a minimum of .100 left for the cyl walls. You really must sonic test these things because there is no other way of knowing if you will have enough cyl wall left after the procedure. Too thin and you will be out a lot of time and money.
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09-21-2012, 03:39 PM | #4 |
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Re: Question on engine parts interchangeability
One other thing. Properly fitting the floating bearings is a VERY labor intensive job due to rehoning the big end as needed for clearance on the outside surface of the bearing shells. The crank needs to be ground exactly to specs too. Someone with experience with this needs to be involved. You might want to consider 8ba rods, it would probably cost you less by the time you get the engine running.
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09-21-2012, 03:50 PM | #5 |
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Re: Question on engine parts interchangeability
I've never owned a 221 24 stud, but Ron reports they can be assembled with 239 crank and rods with stock bore by assembling from below. He has posted good instructions for dealing with the good bearings. Youl probably also need the late seal holders, as engine likely has slinger type crank.
Yes. 1938 short crank engine is totally different... |
09-21-2012, 04:18 PM | #6 |
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Re: Question on engine parts interchangeability
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Mart. |
09-21-2012, 04:25 PM | #7 |
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Re: Question on engine parts interchangeability
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09-21-2012, 04:30 PM | #8 |
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Re: Question on engine parts interchangeability
Thought so - just checking.
Thanks. Mart. |
09-21-2012, 07:46 PM | #9 |
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Re: Question on engine parts interchangeability
Cartravel.
your 59ab rods will work but if they are used you must have them checked for concentricity and size. Otherwise you will not be able to use them for proper floating bearings fit. You may have to have them reconditioned for proper fit. Maybe Walt will chime in. John |
09-21-2012, 09:01 PM | #10 |
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Re: Question on engine parts interchangeability
Well Larry, you can do all these things above, I've bore many many of these blocks to 3-3/16 with no trouble. As far as fitting the floating bearings, it's not as hard as it sounds, I wish the boys would have asked me the to show them how to fit those floaters when they were up a few weeks ago. BUT, any rod that rides on a floating bearing has to be reconditioned. Those bearings spin in the rods just like they do on the crank. It's alot cheaper to use an 8BA crank and rods, the bearings are alot cheaper than the floaters and there is alot of 8BA cranks kicking around. Walt
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09-21-2012, 10:25 PM | #11 | |
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Re: Question on engine parts interchangeability
Quote:
I did mine with 59AB rods, 4" crank and and floating bearings, book specs work just fine... The part I had trouble with was the shop I used did not quite grasp the importance of a smooth finish on the inside of the big ends of the rods... So, I made a mandrel for the mini lathe from the end of a 4x4 block of wood, used fine emery cloth and then crocus cloth to polish... Did not lose my size by much at all. Karl |
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12-13-2012, 07:11 PM | #12 |
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Re: Question on engine parts interchangeability
I appreciate all the advice on this motor. I am still working on it. It had been stored in a shed and didn't show much rust except for a few of the intake valves. Most of you know that makes valve train removal a bitch. I'm almost there, but have also taken the crank out and collected all my 59ab parts. Last time I took four very stuck 59ab engines apart before I found a useable block. It's too bad people have not taken care of these old engines. The crank out of the "A" motor has the correct mains and rods for a 24 stud 38-41 motor.
When I first posted this message, I didn't understand the part about the rear seal. Now, I see the problem. I assume these conversion parts are available. The "A" motor crank has a groove and what I take to be a scroll seal, but interestingly, one of my 59ab cranks is set up for this, while the other 3 are not. This one crank appears to never have been turned, but one of the rod journals is blue, so it may have had a spun bearing. Is the rope seal better? If not, I could use the crank that is machined for the scroll seal unless the spun bearing makes it unusable. I'm willing to learn how to do floating bearings, so I am planning to use the 59ab rods and crank, but what is you're advice regarding the crank to use? Is the rope seal better? TIA, Larry Young |
12-13-2012, 09:43 PM | #13 |
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Re: Question on engine parts interchangeability
Yes the 8BA crank Is pretty easy and cheep, I have several and you can pick the best one for 100 bucks a nice set of 8BA rods for 150. I know I'm not supased tosell things here but I din't think they should cost any more any place else.
ON the early blocks, sometimes the rear main cap had the rope seal machined into the cap. Reds has a kit to modify the cap for a rope seal. Using *ba rods on the 59 crank is not recomended but many people have done it for a street engine. This is because the side clearance allows the oil to lubricate both bearings. |
10-28-2014, 07:33 PM | #14 |
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Re: Question on engine parts interchangeability
It's hard to believe this rebuild is still going on, but I thought I would bring it up to date. I put some of this info in another post, but thought it might be better to put it with the previous discussion.
I was originally hoping this would be an economy rebuild to get a ’40 pickup back on the road. I got this “A” motor for free from a guy that went for a SBC in his ‘38. He said the engine had been rebuilt, but then it got stuck. He gave me the block with the crank and valve train, but no rods or pistons. I have a bunch of 59AB parts and one that was supposedly “recently rebuilt”. I thought I would combine the pistons, rods, crank and rod bearings from the 59AB with the A motor. I was hoping to use the valve train from the A motor too, but some were stuck, so that didn’t work out. After making all the measurements, I decided I could not reuse the rod bearings from the "recently rebuilt" 59AB either. So, I bit the bullet and I had the mains and crank pins ground to 0.020 under and the rods resized back to stock (they showed only 0.001 wear). Then, I discovered that the block had already been bored 1/8” and the cylinder walls were too thin (probably why it got stuck). This economy rebuild got more expensive, since we had to sleeve every cylinder. It went to 1/8” + 0.030 over, the size of the pistons from the 59AB. After all the machine work, it sat for a while, but I eventually got back to it. The crank went in with no trouble. Then I had trouble with the cam installation. I should have started with the cam. This is the second time I have found new cam bearings that were too small for an original worn cam. I know it is not wise to hone Babbitt bearings, since abrasive particles can get embedded, but with my back against the wall, I used a brake cylinder hone to enlarge the cam bearings enough to install the cam. I don’t know if anyone sells cam bearings of the correct size. The crank went back in with no problem. A check with plastigage showed a clearance of 0.0015 to 0.002 and the end float was about 0.005, so it looked good. Then, I moved to the rods. I was expecting this to be an ordeal. I am using some NOS copper/bronze rod bearings I found on ebay. From measurements (of limited accuracy), I got a clearance of about 0.002. I bolted the rods onto the crank pins. They seem to turn fine with slight drag on both the ID and OD, so I think I'm good. Now, for rings, pistons, valves and lifters. Larry Young |
10-28-2014, 07:35 PM | #15 |
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Re: Question on engine parts interchangeability
I am using standard 4 ring pistons in this rebuild. Is there a front and back on these pistons and rods? They seem to be the same either way, but I thought i should check.
Thanks, Larry Young |
10-28-2014, 10:19 PM | #16 |
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Re: Question on engine parts interchangeability
If the pistons are directional, there will be a mark on the piston dome which would go forward. The rods are usually installed with the number of the rod toward the outside of the block for that row of cylinders.
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10-29-2014, 05:50 PM | #17 |
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Re: Question on engine parts interchangeability
These pistons are standard 4 ring type like I've taken out of almost every 59ab engine I've taken apart and look like those shown in Mac's catalog. There are no markings, so they are apparently not directional.
I ran into a problem with the rings. The pistons are grooved for 3/32, 3/32, 5/32 and 5/32 rings. I bought some 0.030 over Grant rings from one of the vendors. They appear to be for 3/32, 3/32, 3/16 and 3/16. Does someone make the correct rings or should I consider machining a wider groove? Also, the instruction said "do not file moly rings". These had no end gap without filing, so what do they expect me to do? I'm trying not to be a pest. I spent a couple of hours searching the archives, but could not find answers to these questions. |
10-29-2014, 06:51 PM | #18 |
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Re: Question on engine parts interchangeability
I feel bad about all the wrong stuff you got for engine. They have .010 cam bearings for cam journal that need grinding to .010 under. Sound like you got those bearings. If your engine has been bored .030 over 3-3/16 and you got .030 rings they should have at least .012 end gap. If you got zero end gap you got the wrong rigs. Personly I don't like Grant rings I use Hastings. I would have used the 8BA crank and rods, the rod will go down that hole. The aluminum upper real seal retaine from a 59 block will fit in the A engine, You'll have to get the seal retainer for the cap from Job Lot or Red's, a lot of places have that special retainer for installing a later crank in an A block. Walt
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10-29-2014, 08:58 PM | #19 |
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Re: Question on engine parts interchangeability
One of Ford's advantages was interchangeable parts between models, but it is also a trap for the uninitiated. The best reference is probably the "green bible", the huge parts list for the Model A days thru the flathead V8's. Parts that look the same are often are not for a variety of reasons. Thankfully, most genuine Ford parts contain numbers so they can be identified with the book.
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10-29-2014, 10:07 PM | #20 |
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Re: Question on engine parts interchangeability
The rings are the only problem. What are the standard groove widths for the oil control rings? 5/32 or 3/16? Everything else appears to be good.
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