|
'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.
|
Re: '37 Flathead rebuild questions You need Plasti-gauge to check bearing clearance....
|
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.
|
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.
|
Re: '37 Flathead rebuild questions I do have the main caps in proper order. They are stamped 1-3 from front to rear.
|
Re: '37 Flathead rebuild questions Quote:
|
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.
|
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:
|
Re: '37 Flathead rebuild questions Did you check if the linebore is straight ??
If itīs off then you get this symptom. |
Re: '37 Flathead rebuild questions the marks on the rear bearing--is that where you put the plastigauge, it could be old hard plastigauge making an impression in the bearing
have the crankshaft journals beem measured for taper, out of round---I know from my working at learning to run a cranksahft grinding machine that a setup that works for a modern chevy crank can have taper in the wide bearing surfaces of a flathead crank---it also looks like there is dirt transfer between the cap and the block, perhaps you should clean more |
Re: '37 Flathead rebuild questions " Third photo is the center main. "
Is it just in the photo that you have the center cap reversed? I would take a scotch brite pad to the bearings and really buff them up. This is done by some modern engine builders in race applications. From an engine builder: "I always prep a bearing and have never seen one I'd use right out of the box, but that's just me. Clevites, especially, are rough to say the least. Their coated bearings aren't much better. Uniform surface finish in the direction of rotation is what I'm looking for. I use red or green scotchbrite on the backs of the bearings because I want metal to metal contact for best heat transfer, and white scotchbrite on the surfaces in clean mineral spirits, then sponge-wash and rinse with warm soap and water and blow dry. For me, absolute cleanliness is really important when assembling the bottom end. The green or red, or even gray scotchbrite can embed fine abrasives into the bearing, so I avoid using them on the bearing surface. Shop rags are abrasive, so are brown paper bags." Note: not everyone agrees with this approach, but it has been used by some top race engine builders. |
Re: '37 Flathead rebuild questions Quote:
Quote:
Quote:
I spoke with a few people about this, and they all said that at the tight, you can't trust plastigauge. So I'm going to get a bore gauge, so I can take some accurate measurements, and that it is not problem to carefully take down those highs in the bearings with a little emery cloth. |
Re: '37 Flathead rebuild questions The bearings have problems, need to get that squared away first. The bearing have high spots and with only .001 clearance that will clamp down on the crank. I would not use emory cloth on the bearings becauce of the grit it can leave in the bearing. Use scotch brite.
|
Re: '37 Flathead rebuild questions Fixing the symptoms instead of the source aint the way to go...first find the problem and then deside how to fix it.
If you torque the bearings one at the time do they all turn freely ? If so you doesnīt have a major out of round or bearing clearing issue but some kind of misalinement.. If one of them bind start checking for clearing and out of round there. |
Re: '37 Flathead rebuild questions Quote:
|
Re: '37 Flathead rebuild questions Quote:
I appreciate all input, but I fail to see how I'm fixing the symptoms instead of the source. I clearly have an issue with the bearings, they shouldn't have those high spots. So that is at least one of my problems. I also said I was going to get a bore gauge so that I am able to take all the measurements that I need to. |
Re: '37 Flathead rebuild questions To me, it looks like there is not enough clearance - not exactly sure why. You should get a good quality 2" to 3" barrel mic and measure all the journals . . . and report back to us the precise numbers.
On the main bores, a three-point bore gauge is the way to go, but unless you know somebody who has one, they are super expensive (for one that I would trust - like a Starrett). Also, you need to know that it is correctly calibrated - and know how to use it. The ones I use cost over $1000 . . . not cheap, but necessary. As noted, there can also be a line bore issue - which is hard to check unless you have a precision rule that is 24" in length . . . and are used to doing it. The machine shop should have checked the mains - if not, maybe have them do so. As noted by some, I use ScotchBrite on my flathead bearings - with a bit of solvent. I polish all sides of the bearings. I do not attempt to remove material to "fit" the mains, more along the line of just polishing them a bit. If the crank doesn't easily turn, there is an issue - which shouldn't be solved with Scotchbrite. Are you sure you have the correct bearings for this engine and crank? Once you get to the full-floater rod bearings, you'll need to first mic everything to figure out the clearances. You'll need a 1" barrel mic and something like a piston pin to measure the bearing shell thickness (I use a .750 flathead piston pin - then I do the simple math). You'll also need a precision bore gauge to measure the rod-bore diameter - or have your machine shop give you the numbers (which should be the stock spec). This will tell you if you're in the ball park. Then, you'll need to use a rubber mallet to "tune" their roundness to get them spot on. Also, you'll need to Scotchbrite them on all sides. The process usually takes me about 4 hours to get things exactly right - and I'm not a newbie (so plan accordingly). Also, I frequently have 6 sets of rod bearings and find the "best 4" to work with - as manufacturing differences do exist. Here is a little video I put together last year that describes some of the process for full-floaters - hopefully you'll find some value in it: https://www.youtube.com/watch?v=CyVLsPdbhS8 Best of luck! B&S |
Re: '37 Flathead rebuild questions Guys, take a look at the posted bearing photos. The bearings are the issue, you can see the raised areas and it was stated that you can feel them as well!
|
Re: '37 Flathead rebuild questions I see that they been scuffing but if each bearing individually torqued moves freely but not when all 3 are torqued down i would say size is not the only issue.
At least center torqued spun freely so may want to take center bearing out and torque front and rear to see if they alone moves ok.. Sorry cretin if i sounded harsh just want you to find the issue before starting to grind on bearings... |
Re: '37 Flathead rebuild questions No worries, it didn't sound harsh. I'm not sanding on the bearings yet. I want to check everything I can and have as much info as possible before doing anything. I think the bearings are a problem, but may not be my only problem. removing the center and seeing how it spins is a good idea, I'll try that while I'm waiting for my bore gauge to show up.
I appreciate the advice. |
Re: '37 Flathead rebuild questions 1 Attachment(s)
Quote:
|
Re: '37 Flathead rebuild questions Ok guys, sorry I've been gone, but I hadn't had the opportunity to mess with the engine. I finally did. I needed to order a few things from Van Pelt, so while I was at it, I got another set of bearings from him. So, my plan being to test everything out with bearings that didn't have these highs on them. I decided to not switch the center main bearings, since they spun fine at torque.
Unfortunately, of the other two I was only able to replace the front main, as the rear main didn't fit. I have not brought that up to Van Pelt yet, I'm not sure where the issue is there. I was really hoping to replace the rear main, as that was the worse of the highs on the bearing, but it didn't work out. So, I took some scotchbrite to the highs on the bearing, and reinstalled everything and began torquing the caps down. Seemed a bit better, but not good enough. So, I took the center bearing out, installed the crank, and torqued the front and rear bearings down. It spun better after that, but I wanted to make sure that wasn't because of taking care of the highs on the bearings. So, next step, was I reinstalled the center bearing, and began tightening down the front and rear caps, without the center cap. It was still tight, so It seems obvious to me that the bearings were only one problem, and Im going to need a line bore. So, it's back to the machine shop for me. So, I also have a question about the rod bearings. I have info about it, and I've read advice about it, and watched Bored&stroked's video. All that references non-flanged bearings. I have flanged bearings, so I assume that the process is the same, just with the added steps of unbolting a re-torquing the rod clamp every time you need to check the fit. Is this correct? |
Re: '37 Flathead rebuild questions On the flanged bearings . . . yep, just takes longer! Kind of a pain in the rear, but a necessary step. Who knows, you may get lucky and find them concentric out of the box. :)
Also, once you think you're done with them in the rod vice, then put the set on the crank journal with a single rod (torque to spec) and make sure you can easily turn the bearings on the journal and that the rod can slide back and forth (as with only one on the crank, there is room on the pin to do this). This makes sure that it truly "floats" on both sides. B&S |
Re: '37 Flathead rebuild questions On the line bore - have the shop setup the block to remove the LEAST amount possible on the block side. Some places don't like doing this - but you want to keep the cam-to-crank centerlines as close as possible to stock . . . or you can get cam gear interference/wear with the crank gear. It is hard to find undersize cam gears these days (at least I haven't seen many???).
|
Re: '37 Flathead rebuild questions Awesome. Thanks for the info Bored&Stroked!
|
Re: '37 Flathead rebuild questions So, I thought I'd give you guys an update.
I dropped my block off at the machinist on tues to get the mains line honed. Picked the block up Friday, I just installed my crank and torqued the mains down, and she spins beautifully. So, finally on to the next stage of assembly. |
Re: '37 Flathead rebuild questions Good to hear!
|
Re: '37 Flathead rebuild questions Awesome news! Thank gosh that you didn't just throw it together and "run it" . . . you found an issue, took the time to research it a bit and have resolved it. Having the patience and time to do the job right - so important. Great Job by you!
|
Re: '37 Flathead rebuild questions Quote:
That's worth something to me. |
| All times are GMT -5. The time now is 12:20 PM. |
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2026, vBulletin Solutions Inc.