The Stovebolt Site Forums The Shop Area Engine Shop 1946 235 crank shaft swap question

Hello, I have a 46 2-ton that I use in my business. It see's about a hundred miles a week and it's time to do an engine rebuild as it is using about as much oil as is it gas. I have been considering swapping in a latter 235 or 261 to get the pressurized rods.

My question is this...

Can I get a crank and rods from a later model 235 and install them into my block? There isn't anything wrong with my block or head and whatever I get I would rebuild. Just thinking a crank and rods would be easier to obtain as far as shipping goes.

Thanks for the help,

I believe the thrust journal in the block needs to be cut down as the thrust journal on the crank is narrower, you have to plug a hole here and there, but other than a couple of minor details you should be just fine. I was going to use the drilled 235 crank in my 216, but as things progressed that didn't happen, if I had known then what I know now I would have went that way. I got a whole lot of information from Gene Beck, and some other fella I can't recall his name at the moment. But yes it is possible.

I have the crank and rods coming from a 1959 235. When I tear into this this winter I guess I will see if they will fit......

The bearing diameters are the same, but as brokenhead mentioned the #3 thrust bearing is narrower on the full pressure crank.
If you can find someone who can cut down the block web to accept the narrower thrust bearing it will work fine.

Gene said all he really does is cut down the thrust journal, and tap and plug the hole where the spigot that feeds the spray nozzles go. That way you get full pressure to the crank, and the oil distributor still only feeds 15 psi to the rocker arms. Be sure to use a '54 or newer oil pump and pickup, as it has a built in relief valve. Now if you want a full flow oil filter then things get a bit more complex, but not much. If you are interested I can run you through it. I really have been meaning to call, but have been just swamped at work. As an aside, even though you are getting the crank and rods as an assembly. Keep in mind that the rod journals are narrower as well on the '54 and beyond. So if you are entertaining any thoughts of using some of those parts from the old engine somewhere along the line, they won't work. This is the simplest way to go about it, but there is a number of variations that can be done. Like using GMC rods for example.....however that presents its own problems.

Would you cut down the block or the crank journal? I guess I will ask the machine shop which one. Seems like it would be better to cut down the block? But easier to cut down the crank.....

The 1954-62 crank uses a narrower thrust bearing so narrowing the block web is what is needed.
The 1954-62 rods will be a direct fit for your 235, I think brokenhead is thinking about his 216 conversion where rods needed do be converted.

I built an old high torque 235, modified for later crank etc, it's not worth all the trouble. Easy way to go is a 54 or later 235 or 261, easy mods to fit your truck.

I was thinking of the pre 54 rods, in his existing engine (his I think is 46, unless the engine isn't original) If you are using the post 54 crank and rods, the conversion would be extremely simple, and since he is most likely having machine work done already, cutting down the thrust journal wouldn't be a whole lot more involved although set up time is somewhat expensive.

Hopefully I will be pulling my engine out in the next few weeks to rebuild. I did get 1959 crank, rods and pistons in. I guess we will see how things measure out...

Hmmmm- - - - -maybe I can see the need for another tooling kit like my crankshaft snout drill jig- - - - -This one would require a bit more machining ability than drilling and tapping a crankshaft, though!
Jerry

Well, I finally have this engine apart and...Well, I can't bring myself to replace the crank or rod's. The bearing's look perfect on both as well as the crank surface. I will take some measurements while I have both cranks side by side, but I believe I will be keeping the babbited rods for now. About the only thing that needs any help are the cylinders. It has 60 over 216 pistons in it to bring it out to a standard bore 235, but the holes are close to 20 over. I think I know where the blow by was coming from.....

And the rods that I got in have 40 over pistons on them so I think I will us these pistons, get a set of rings, freshen up the head and put this thing back together this weekend.

I am curious how this turns out,I have been thinking about converting a 216 or early 235 to full pressure. To some its probably not worth the effort but would be nice to have a original looking motor that has full pressure,I think Jim Carter sold converted shortblocks but has been years since I had a actual catalog.

From every indication I see it looks like you would need the crank and rods and machine the block to accept a narrower thrust main bearing. Block off the oil feed going to rod dipping tray ( that's the best name I could come up with) and put things back together. I guess you could remove the "rod dipping tray" but I don't think it would hurt anything if left in.

I can't bring myself to do this conversion to my engine. It's in too good of shape!

If I can ever find a early 235 I have a 56 235 that can donate the crank and rods,right now I am in the hiding all the modifications and making it look somewhat original phase but if I could ever find a good running 303 or 324 Olds and hydramatic then keeping it powered by a six goes out the window very quickly..

Jeff, when you make that swap, be sure to look for the adapter that moves the starter to the passenger's side of the block. That was the big problem when putting an Olds engine in an early Ford frame- - - -starter/steering gear interference, and I'm pretty sure it would be worse on a stovebolt. Those adapters were made by a company called "Trans-Dapt", and I think they're still in business. Whether they would still have a bellhousing adapter in stock 50-something years later would be the 64-dollar question!
Jerry

I forgot about the starter issues so maybe a 331 caddy would be better as I doubt those adapters are still being made.

back to the original question. I don't know for sure how much a machine shop would charge to cut the journal in the block, (Jerry would be able to give you a round figure probably) The fella that did some of my machine work said he has done it a few times, but that the set up time is the most expensive part, as he was using a line boring machine. One heads up if you do it this way, that would be a perfect time to have the rear cap machined for a full circle lip seal. This however would preclude the use of shims, requiring you to be sure the crank is ground to produce the proper clearances. As you will no longer have any adjustment. I do however know how much it cost to drill a crank. Crower cams, crankshaft division did mine for $180, shipping was about $75 each way. Many people think this is a waste of time and money, but any good hobby is supposed to be a waste of time and money. That is why we work.... But anyway, I have gathered a rather sizable amount of information regarding this matter, I will post some stuff on the tech tips one of these days when I have some spare time. (yeah, right) but if you are even casually interested, you can PM me.

I have talked a local machine shop about this and he thinks he should be able to do it so if I ever come up with a early 235 it might happen.

It wouldn't be terribly difficult to design a fixture that bolts into the main bearing web in question that would guide a flycutter to do the narrowing procedure, but unless there's a lot of demand for the tool, it would take a long time to recoup the cost of making it. It would be fairly simple to fabricate- - - -something that holds 3 or 4 replaceable carbide cutters and some sort of depth-of-cut jackscrew to control how much material gets removed. The tooling could be driven by a variable-speed 1/2" capacity drill motor.
Jerry

How true, the measure of a real hotrodder is spending a minimum of 2-3 times more on a car or truck than you could ever possibly expect to get back out of it!(LOL)
Drilling the original crank is going to be the cheapest alternative, and for what Crower charges to do it is very reasonable, plus it eliminates having to further modify the thrust surface in the block to accept the later style crank. Then you can toss the babbited rods in favor of the GMC rods if you want to further upgrade the engine. With the stock early crank, they are a direct swap and don't require any mods to use them, just get the correct piston. Its a rather easy mod to perform.

Hmm... I agree drilling the original crank would be the way to go. I didn't think it would be that cheap. i will probably go this route id I ever pull the engine back down for rebuild.

I did get the valves and the seats ground last night. So the head is ready to go back on. I ended up shooting a nail through one of my fingers Sunday night so my progress is going to be a little slower than I would like.

I am going to see if anyone locally can drill the crank,it seems way less work they trying to fit a later 235 crank. If I cant find a early 235 I might try it with 216.

"Danger, Will Robinson!" Unless somebody has a lot of experience doing the drilling, they're just about guaranteed to ruin a couple of cranks getting the hang of it. It's going to be a LONG hole at an oddball angle that has to come out exactly right on the first try. Then they've got to do it five more times, with a zero margin for error.

I'd go with the place that's been successful, even if it involves some shipping cost rather than rolling the dice with somebody who "thinks" they can do it!
Jerry

I know of a couple machine shops that have been around since the 50s so it does not hurt to ask.

Back in the 50's nobody even considered drilling a stovebolt crankshaft for full-pressure oiling. Splash lube was just the way it was done. 50-something years later, it's still the best way to lubricate the connecting rods on those particular engines. Drilling a crankshaft that was intended to be a solid piece of metal might be possible, but there needs to be some reason to do it other than "just because I can"! I'd much rather concentrate on getting the clearances right so the engine can run just like untold millions of others have done since the 1920's.
Jerry

I am with Jerry on this. It is not the dipper oiling system that killed the rods in these engines, it was the HEAVY cast iron pistons. If rebuilt with aluminum pistons there are no bottom end concerns.

nope Jerry, I need no more reason than that. I do know that at least California Bill was drilling cranks in the 50's unless his book is pure fabrication. Although there is one caveat, he said it was only necessary if you were running it over 5000 rpms. I however just wanted to. And you will play He## finding someone locally, all the shops around here told me flat out it couldn't be done, if you look at the rod throws, there is a large hole running right through the center that leaves a rather small amount of metal to try and hit. That is why you would want to send it to crower, they have a CNC program they built for Gene Beck, Gene told me they told HIM, the programmer dude didn't have anything to do, so he built a program. There is however a rather important item to look out for, make sure you mark/tell them where exactly to drill the holes to lineup with the grooves in the mains, otherwise they just go to the center, (keep in mind they don't have any references other than what you tell them) whilst the grooves in the journals of the first and last bearing aren't IN the center. Which presents you with rather sticky situation. Whatever the case, if you decide to go full pressure PM me I may be able to help you avoid a couple of pitfalls.

Your correct brokenhead, the GMC rod conversion was done on the babbited cranks for many many years before the full pressure Stovebolt's even came along in 1953, and you can't do the GMC rod conversion without having oil holes in the crank to oil the rod bearings. Guy's and hotrodders back then were true doers, not followers like some are today, and most were machinists or had buddies that were. There is also a new Stovebolt performance book series fixing to be printed that shows how to do a GMC rod conversion in the later full pressure Stovebolt's.

This is all great info guys. Thanks for chiming in. I would also like to add that the babbited rods are 1.470" wide and the inserted ones are 1.245". So if it is your plan to run an inserted bearing rod on a drilled crank it may get trickier....

I do know that my engine has been down before. I do not know if it has had new rod bearings pored in. The bearings are in great shape, still have the shim in between the rod and cap. I have not measured the clearance yet, but I will this weekend when it goes back together.

Back in the days before Plastigauge we used a piece of shim stock between the rod cap and the crankshaft to check oil clearance. With a piece of .002" shim about 1/4" wide and 3/4" long between the crankshaft and the cap, remove shims until you get a firm drag when the crankshaft is moved back and forth by grabbing the flywheel. When the crank turns freely with a .001" shim, and drags or locks up with a .002", the clearance is right. This procedure is a lot faster than fumbling around with Plastigauge. Just remember to remove the check shim before moving on to the next rod!
Jerry

Yes that's right, you have to use the correct Stovebolt rods for the crankshaft being used, they do not interchange between the babbit crank or full pressure crank because of the width difference. But when performing the GMC rod swap, the GMC rod is a direct bolt-in for the babbited Stovebolt crank, as they are the same width. But to install them on the later full pressure crankshafts, they have to be narrowed, but that is easily done.
So if your going to drill the babbited crankshaft rod journals for modern oiling, then you can perform the GMC rod swap in that engine, otherwise the babbited rods are the only choice you have to use in that engine.

the only real issue with GMC rod swaps is you have to get custom pistons made, as they are longer and have larger pins. The pistons aren't cheap, probably around $600 for a set W/ pins and rings. possibly a bit more. Ross and venolia will make custom pistons for certain, and there are probably more. It is all about what you want. But I do know it isn't any more expensive than a big hot rod motorcycle, or a boat.

Well back in the day before custom pistons were available, the guys would use and modify the GMC pistons, since one of those engines already has the same bore size as the 235 Stovebolt's and already had the GMC pin size, so going custom isn't necessary but is an option is someone wants to. But without divulging too much info that is in the Stovebolt Performance book I mentioned earlier, it show's and explains how all the swapping is done without breaking the bank.