'37 Flathead rebuild questions

[Kurt in NJ]

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

 

[JSeery]

" 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.

 

[cretin]

Did you check if the linebore is straight ??
If it´s off then you get this symptom.

I also thought that this sounded like it could be the line bore. I'm not sure what a good way to check it is. I checked wit a straight edge, and it looks fine, but I'm not sure of a more accurate method.

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

That crossed my mind as well, but its new plastigauge, and isn't hard.

" Third photo is the center main. "

Is it just in the photo that you have the center cap reversed?

Yes, that is just in the photo, that I accidentally reversed it before snapping the photo.

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.

 

[JSeery]

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.

 

[flatheadmurre]

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 doesn´t 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.

 

[JSeery]

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 doesn´t 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.

Take a look at the bearing photos posted, the bearing have high spots on them that are clamping the crank. There is no reason to start checking other stuff until there are good bearings in there. They need to be polished down or replaced.

 

[cretin]

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 doesn´t 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.

Flatheadmurre,
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.

 

[Bored&Stroked]

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

 

[JSeery]

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!

 

[flatheadmurre]

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...

 

[cretin]

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.

 

[JSeery]

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...

Flatheadmurre somehow the rear bearings have creases in them with scuffing on either side of the creases. There are obviously problems with these bearings. I was just suggesting checking with good bearings before investing money and effort in other testing. Your suggestion of checking the fit with the center bearing removed seems like a good approach, but there is no reason for a lot of additional checks until the bearing issue is addressed.

 

[cretin]

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?

 

[Bored&Stroked]

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

 

[Bored&Stroked]

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???).

 

[cretin]

Awesome. Thanks for the info Bored&Stroked!

 

[cretin]

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.

 

[JSeery]

Good to hear!

 

[Bored&Stroked]

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!

 

[cretin]

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!

Thanks! I got most of the main components for this project for a good price, so I decided to put together a budget project. Even though I've already put more money into it then planned or wanted, I'm the type of person the needs to do a job right. My plan was to enjoy the car for a little while, and then sell it to help fund other projects. Even though doing what I have done will cut into my profits, I have piece of mind that everything was gone through, and everything was done right.
That's worth something to me.