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'37 Flathead rebuild questions 1 Attachment(s)
I recently got my "37 Flathead back from the machine shop. I'm working on assembly now, and as a Flathead rebuild virgin, I have a few questions.
I wouldn't be surprised if more questions arise in the future, so I thought starting a thread would be a good way to get the answers I need. My first question is about the rear main seal. I'm a little confused. I have the inserts shown in the attached image. Nothing goes on there? I have a fel-pro gasket set for the engine, and it says it includes 2 front crank seals, and 2 rear main seals. I have 2 shorter, wide rope seals, and 2 longer, thinner rope seals. Do the longer thinner ones go in the groove of these inserts? From what I've read it seems that nothing goes in there, that seems weird to me, but I don't know. My gasket set supports a range of engines, so maybe those seals are for a different application? Second question is about connecting rod bearings. Full floating bearings, standard size. My crank was not ground, only the journals polished. I forgot my nice caliper at work, but according to the one I have at home, the rod journals are at 1.985, and the ID of the bearing is 2.003, and the thickness of the bearing measuring 0.11. The books I have say that clearance should be .0017-.0036. But whats annoying is that they don't say what you are supposed to do if you are out of spec. The difference in my measurements comes out to .018. So what is the correct procedure to correct bearing clearance? do I file the edges of the bearing to close it up? or is there more to it then that? I've never dealt with full floating bearings before, and haven't had luck finding the info. |
Re: '37 Flathead rebuild questions If your measurement is correct the rod journals are near .015 undersized
that "rear seal" is for a slinger, it doesn't get anything else, just glued with sealer to the block---or cap styandard rod journal-- 1.998-1,999 standard rod bore-- 2.2195-2.2200 |
Re: '37 Flathead rebuild questions So there is no seal in the rear, just the slinger.
Ok, so Maybe it was ground sometime in the past, so I need bearings for an undersize journal. |
Re: '37 Flathead rebuild questions You got it.
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Re: '37 Flathead rebuild questions You need Plasti-gauge to check bearing clearance....
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Re: '37 Flathead rebuild questions Measure pins with micrometer donīt forget to measure across it from different angles since wear is not even around the pin.
Then measure rods with an inside micrometer to make sure they are not to much out of round. After you got the pin and rod measurements you can deside if youre within specs and what bearings to use. |
Re: '37 Flathead rebuild questions 1 Attachment(s)
Floating bearing are a bit tricky to set up, there is more to it than just measuring them. That is an important place to start, but then you will most likely have to get them into the correct "roundness" for lack of a better word. You might want to get some information on setting up these bearings, Ol'Rons book comes to mind.
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Re: '37 Flathead rebuild questions Ok, well I'm back with a new issue. I didn't get far.
Yesterday, I got my crank back from the machinist, machined to .020 under. Installed the crank, and began torquing the mains downing steps. Started at the center main, then rear, then front main. The first step I went to 55 ft/lbs, and the crank is already harder to spin then it should be. What should I be looking at to fix this? |
Re: '37 Flathead rebuild questions I would definitely get Ron's book for the build but especially for the information on setting up the floating rod bearings. They can be very difficult compared to more common insert bearings. Stay with the pro's here, they steered me through the same build and the problems I came across. Couldn't have succeeded without them. Ol'Ron's book can be ordered from Van Pelt.
http://www.vanpeltsales.com/FH_web/F.../Nostalgia.pdf |
Re: '37 Flathead rebuild questions Could be a problem with the crank grinder or the crank may not be straight. Need to be getting some precise measurements. You do have the main caps in proper order? I don't remember which is which, but one of the front two has offset bolt holes.
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Re: '37 Flathead rebuild questions I do have the main caps in proper order. They are stamped 1-3 from front to rear.
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Re: '37 Flathead rebuild questions Quote:
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Re: '37 Flathead rebuild questions For this kind of problem a bore gauge of some type is mandatory. Even a snap gauge can tell you the clearance. With a light oil the crank should spin. Assembly lub may be alittle slower. I use a resurfaced flywheel to fit the rod bearngs.
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Re: '37 Flathead rebuild questions If the crank has been ground it will be straight.
You can have several problems so some measuring is next. Check the crank diameter and the bore size if that checks out take a straight edge and see if the line bore is off. The bearing inserts could be off specs to. |
Re: '37 Flathead rebuild questions Are the main caps the right way round? They should be tang to tang. The bearing tangs on the cap and block should be on the same side of the crank.
Is everything spotless? And I mean properly spotlessly clean? This includes the back of the bearing shells and the saddle the bearings sit in, not just the bearing surfaces. Martin. |
Re: '37 Flathead rebuild questions Yea, I have the caps tang to tang.
I haven't had the chance to mess with it much. But, I did platigauge it after work today. Got .0015 on all three mains. They are NOS bearings, and had a bit of junk on the back, it's possible that in my haste to get the engine together, and in a hot garage, that I didn't clean them well enough. I'm going to remove the crank, make sure the backs of the bearings are clean, and take some more measurements. Hopefully its an easy fix. |
Re: '37 Flathead rebuild questions 5 Attachment(s)
Ok, got a chance to mess with this again, and this is where I'm at.
I removed all the bearings and made sure all surfaces are clean. Checked all the caps and mains, made sure there were no burs on any edges or anything. Unfortunately, I forgot my good caliper at work, so I didn't get any measurements I trust, but will remeasure if necessary. I put it back together and plastigauged it again. I somehow got .001 clearance this time. I then oiled each main, and torqued caps down one at a time to see if there was one main that was hanging up. I can go to full torque with the center main, and it still spins. It starts getting tight when I start tightening either the front or rear main. I removed the caps after that, and I see some weird wear. There is only a little wear on the center bearings, and the other two are obviously not right. I can feel some small highs where these wear marks are. The first photo is the front main, and the second photo shows the wear mark on the front main. Third photo is the center main. Fourth photo is the rear main, and the fifth is a better photo of the wear on the rear main bearing. Clearly my bearings surfaces are not completely smooth. Is there any way to save them? |
Re: '37 Flathead rebuild questions I cannot offer any real good advice, however, in the first picture, is the bearing shell fitted correctly into the block? The oil hole appears way off.
Those weird marks in the rear main would certainly indicate the back of the shell has some high spots. |
Re: '37 Flathead rebuild questions Quote:
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Re: '37 Flathead rebuild questions Did you check if the linebore is straight ??
If itīs off then you get this symptom. |
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