RTH - Crankshaft bearing sizes

[Ziggster]

Spoke with my machinist today, and he mentioned there was a problem with the crankshaft bearings. Here are the particulars:

1. C69 block (supposedly 100 Hp version)
2. Standard crank (90 Hp version) with reground journals, but not sure of size.
3. Company that reground the crank supplied the bearings to match crank

The problem:

1. The crank bearings do not fit the block and main caps. The inside width between the flanges is 0.030" too narrow.
2. Appatently Ford changed the bearing/ block size for 100 Hp rated engines vs. 90 Hp rated engines.
3. They found a set of "correct" bearings in California, but by the time they get here, cost is approx CAN$600!

Has anyone had this issue, and if so, what did you do? Machinist is checking with shops to see if it is "customary" to shave the bearings to fit, but this requires building a fixture on a lathe to turn down the thickness of the flanges.

[GOSFAST]

Originally Posted by Ziggster

Spoke with my machinist today, and he mentioned there was a problem with the crankshaft bearings. Here are the particulars:

1. C69 block (supposedly 100 Hp version)
2. Standard crank (90 Hp version) with reground journals, but not sure of size.
3. Company that reground the crank supplied the bearings to match crank

The problem:

1. The crank bearings do not fit the block and main caps. The inside width between the flanges is 0.030" too narrow.
2. Appatently Ford changed the bearing/ block size for 100 Hp rated engines vs. 90 Hp rated engines.
3. They found a set of "correct" bearings in California, but by the time they get here, cost is approx CAN$600!

Has anyone had this issue, and if so, what did you do? Machinist is checking with shops to see if it is "customary" to shave the bearings to fit, but this requires building a fixture on a lathe to turn down the thickness of the flanges.

Hi "Zigg", the later Flathead's uses a narrower thrust flange but only on the inner rails. The measurement is 2.065" between the flanges on this setup.

On the earlier blocks they were wider, 2.095" between the flanges.

You have the main brg set for an 8BA, it can be machined to fit the early block but it isn't all that easy.

Thanks, Gary in N.Y.

P.S. You are correct, it would take a bit of "fancy" lathe work with a decent fixture. We've done a few here but only when we couldn't get the right part numbers quick enough!

[Ziggster]

Thanks very much Gary. So is what you are saying is that they (crank grinder) got a set of bearings for a 8BA type block instead of bearings for a C69 block, and that should be "common"?

[rotorwrench]

The C69 engine has a rather uncommon bearing type. I guess that was the result of the change over to full insert bearings for the con rods and all. Canada did it first before Ford USA did but then not all Canadian stuff is the same as USA stuff. The bearings are hard to find now days.

[Brian]

Zigg, It'll only be the rear main you need to change. The rear main bearing you require will be #81A- 6331, followed by a letter, which designates the undersize. You'll need to measure your main journal with a micrometer to ascertain what size it's been ground to, and find the appropriate bearing. If you post the measured size, I, or several others on here, can give you the exact part number you'll require.
You'll not need a complete set, so forget about paying $600.00 odd, you'll only need the rear main, and any number of suppliers can provide that.

[leon bee]

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What does "RTH" mean?

[Ziggster]

Thanks again for all the great info, as not much is available on the interweeb. Sorry, on another forum, we used RTH all the time. It means RealTtine Help. I just assumed it was used here as well. The machinist was supposed to have it wrapped up, but then hit this speed bump, and of course everything stopped until he can figure out what needs to be done.
I should have mentioned he has another engine/ block, and it has the same characteristics as mine, so it is not a one-off type scenario. I wish it was this type of detailed info that should be in every flathead engine build book.

[Mart]

FWIW the French motors, though they do have some 8BA characteristics do not use the 8BA rear main. 59A type fit.

Mart.

[Ziggster]

Update: the machinist found the correct bearing at Egge. Some attached pics shaping the difference in rear main bearings. If you look closely you can see the "keyed" section is narrower on the new bearing vs the original. There is a corresponding "notch" in the block.
Original Bearing,

[Ziggster]

New bearing.

[Ziggster]

Block bearing thickness.

[Ziggster]

Bearing comparison. The original bearing has a wider "notch" compared to the new bearing.

[Ziggster]

I forget to mention that the "new" bearing is the incorrect one.

[Bored&Stroked]

He just bought the wrong year bearings . . . nothing special about your situation, you just need the 39-48 style rear main. All he had to do is look at the bearing tang width in the block and cap - to know he had the wrong one.

IMHO: Since he (or the crank grinder) bought the wrong bearings in the first place, he should be the one who is buying the replacement rear main.

To the best of my knowledge, there is no 90HP crankshaft that would have EVER used the bearings the crank grinder supplied . . . so hopefully they're not making some claim along that line. The 49-53 engines all used the 'new' bearing you took pictures of - regardless of displacement or HP ratings.

[Bored&Stroked]

Originally Posted by rotorwrench

The C69 engine has a rather uncommon bearing type. I guess that was the result of the change over to full insert bearings for the con rods and all. Canada did it first before Ford USA did but then not all Canadian stuff is the same as USA stuff. The bearings are hard to find now days.

I believe this is true on only the RODS . . . not the mains.

[Brian]

B&S has it correct....

[Ziggster]

Originally Posted by Bored&Stroked

He just bought the wrong year bearings . . . nothing special about your situation, you just need the 39-48 style rear main. All he had to do is look at the bearing tang width in the block and cap - to know he had the wrong one.

IMHO: Since he (or the crank grinder) bought the wrong bearings in the first place, he should be the one who is buying the replacement rear main.

To the best of my knowledge, there is no 90HP crankshaft that would have EVER used the bearings the crank grinder supplied . . . so hopefully they're not making some claim along that line. The 49-53 engines all used the 'new' bearing you took pictures of - regardless of displacement or HP ratings.

This makes more sense, since I mentioned that he already stated the other C59/69? engine was the same, but he stated it had a "100 Hp" crank meaning it had an additional oil passage gallery. He also mentioned that the 100 Hp cranks used the older style "spinning" con rod bearings if I understood him correctly. I find all this a bit confusing as he also mentioned the "relieved" blocks were referred to as "flatheads" and the "non-relieved" blocks were referred to as "L" heads. My block has the "factory" relief cut into the block, whereas another C59/69/59A block he had did not, as well as another 8BA block he had. I can't remember if the other "100 Hp" block had the factory relief. Is there a definitive flathead engine rebuilding book that goes into this detail ?

[Brian]

ANY valve in block engine, relieved or not, can be called a flathead, an L head or a sidevalve, all terms relate to the valve in block design.

Some FORD flathead 100 HP blocks were relieved, some weren't. Nothing definitive....
Canadian C69A blocks, as well as SOME other Canadian 85 and 100 HP blocks, used a double drilled throw crankshaft and lock in shell bearings in the rods. The American engines ran exclusively full floaters until the 8BA came out, when they went to lock in 'shell bearings'. The 8BA style of rod bearings/rods, differs from the original lock in bearings/rods used in Canadian pre 8BA assemblies.
As the original Canadian lock in bearings are now next to impossible to find, simply use the regular full floaters. They will directly fit.

[Ziggster]

Much appreciated. I think he was saying something to that effect. Figures it would take a Kiwi to educate a Canadian about a C69 engine. So what differentiates the different engines - 85 vs 90 vs 100?

[Brian]

Us Kiwi's got our Ford products from Canada- British Commonwealth...hence my familiarity with Canadian engines

The 85-90 HP engines are the 221's 3 1/16 bore x 3 3/4 stroke
100 HP engines are the 239's 3 3/16 bore x 3 3/4 stroke.

[Bored&Stroked]

Hey Ziggster . . . there is a lot to know about the various years of flathead designs (Ford and Mercury) as well as the various crankshafts that were used.

If you captured what he was saying correctly (about the 100 HP cranks), then he isn't correct on that either. There were 100 HP engines that used full-floating bearings that had 1 oil hole in the rod journals and there are also later 100 HP engines that used tanged (non-floating) rod bearings in some Canadian variants as well as later 49-53 Ford engines.

Also, his statements about "relieved blocks" is completely incorrect . . . the term "flathead" has nothing to do with relieved or non-relieved blocks. The term 'L-Head' is just another term for an engine with the valves in the block . . . AKA a "flathead".

Hopefully he knows these engines well enough to do the correct machine and assembly work - as some of his statements/claims make me a bit nervous.

[rotorwrench]

Relieved blocks generally found their way into trucks. It was a way of reducing compression without modification to the heads. In later years they just made heads to do the job.

The first 239 was the 99A and it was 95 horse power. After the war, all the 239 engines were 100 horse power. The G model 6 was 90 horse power.

I knew something about the C69 was different but I wasn't sure whether it was the rod or main bearings. Some folks just replace the crank with an 8BA type to repair them and use bearings that are more easily available. You guys are right about the mains. The rule of thumb on mains is stick with the block characteristics to choose the mains. The French SUMB engine is half 8BA series (front) and half 59 series (rear) so it figures it would use the 59 series type mains but it was late enough to use the 8BA type crankshaft.

[Ziggster]

Thanks guys. I really appreciate all the feedback. Yes, my block was used as an industrial engine and had a heavy duty truck oil pan and trans attached, so I'm guessing it was a "truck" application. I never really thought about relieved blocks having less compression, but I'm guessing the supposed increased airflow made up for any power losses due to the reduced C.R. For me it's not about power so much, but just knowing what it what. It's the engineer in me.