crank tolorance

4

4ford

Senior Member
I have a 59AB the crank main bearings come out to .004 .005 .006 .004 is the rear looks like the book says .005 is ok..

I am installing new rings one peace valve guides new valves. cam looks ok crank is on the edge free floating rod bearings. so if I get the crank turned and install new bearings (main) and new rod bearings do I have to put new rods in because of the free floating bearings?? or just all new bearings. then a new cam also??

please advise...

thank you mike
 
This is too complicated to address with out more information. You have to mike the crank and rods to come up with the clearance ans .005" Is too much main clearance. With out going into detail the cost of new floating bearings and rods would be very expensive and might not be needed. Only a reliable machine shop fermilar with flatheads can tell you.
Might be cheaper to put in an 8BA crank and rods.
 
Ron.
so if I need to replace the rod bearings I need new rods because the over size bearings won't work with the rods in the motor now?
 
To answer your specific questions:

When you turn a 59AB crank rod journals (with full-floater rod bearings), the new bearings will typically be for STD ROD IDs and the new (under-size) crank pin. The full-floater bearings could be ordered with undersize values for a turned crank, a STD rod bore, or an oversize rod bore. Finding bearings for oversize rod bores can be a real *****. :)

What I normally would do is this (with full-floater rods):
1) Have them checked by a competent machine shop that understands flatheads and full-floater bearings/rods.
2) Determine if the rods need to be rebuilt or not. Rebuilding full-floater rods and buying new bearings can easily cost $500+ (and that is assuming they know how to do it!).

When the rods are rebuilt, they will normally bring them back to STD, so you'd be looking for 59AB style rod bearings, with an undersize crank (like .010) and STD rod bores. These typically run somewhere around $150 - 200 a set.

Now it is decision time: If you're going to need the rods rebuilt, it may actually be cheaper to go to a later style crankshaft, with new rods and insert style bearings, than rebuilding your 59AB crank and 29A rods.

You can put a 49-53 Ford crankshaft (same 3 3/4 stroke) or pay more to get a 49-53 Merc crankshaft (4" stroker) and then run the later rods with more modern style insert bearings.

Since you're investing in regrinding the crank, rebuilding the rods, etc - you might just decide on the 49-53 rotating assembly route, potentially with more cubes in the motor if you go to the Merc Crank. This is a bit easier system to setup - as you don't have to 'hand fit' the full-floater rod bearings . . . which most machine shops do not know or care to do.

Note: If you decide to run a 4" stroke Merc Crank (you can buy them new from Eagle, SCAT, etc), you must have the CORRECT pistons to match the longer stroke! All this stuff is easily purchased from a variety of vendors.

If you need more help, just ask!

B&S
 
ok thanks,
so this motor has been bored .030 already not buy me. the main bearings and crank don't have any marks on them. the crank for the rods have a slight marking. so do I just put it back together and drive it only putting 500 miles if that a year. any idea the cost to do what your thinking with the new crank and rods and pistons. looking at the complete rotating assembly 1,699
 
When you started this thread, you posted some bearing clearances. I wasn't quite sure what were rods, what were mains, etc.. How did you arrive at those clearances in the first place - with some good micrometers? The numbers were obviously too big and I have my doubts that they're actually those sizes (especially the mains). Maybe recheck them?

You might want to post some quality photos of the rod journals and associated bearings. I'd love to see what you're looking at. When correctly setup, the full-floater bearings would last a LONG time. The problem is that a lot of folks didn't know how to set them up, or had incorrect clearances, etc..

Take some pictures of the rods and their bearing IDs

Maybe we can save you a few $$$

B&S
 
here is the rod bearings and the crank I used a plastigage in the center of the rod bearing it says CB-10G 010
 
Ok, I have not messed with floating bearing much, but wouldn't you have to check with plastigage (if that was what you were going to use) on both sides of the bearing at the same time (crank side and rod side or crank side and main cap side).
 
I don't see pictures? In case you are not sure what floaters are think of it this way. The bearing (floaters) are sized so that when assembled you would have .001 between the rod inside diameter and the outside of the bearing and .001 between the outside of the crank journal and the inside of the bearing. Think three concentric circles.
 
You need to measure the ID of the rod's big end, the diameter of the pin and the thickness of the bearing. This will tell you the clearance. Ol Ron covers this in his book.
 
Not to add to the confusion, I was in the automotive machining business for a bit- ten years, spread out over a bit more time than that. And, more recently messing around with a couple of flat heads. I have not seen a set of Ford flat head rods that were not egg shape on the big end, - .003 to .005- by the time the rest of the engine was run out... And thusly needing rebuilding.
 
I was looking on ebay and seen floater bearings that said two different sizes.. one for the crank and the other for the rods is there such a thing and wouldn't it work for my application? or keeping the the parts that I have just won't work?
 
You will need to figure out the crank diameters first and see if it is within tolerance. Also need to check the rods. This requires some fairly good measuring instruments or a machine shop to check. This is just to check the components, then you have to use the techniques described by Ron and other to determine required bearing sizes. But, the components have to be within specifications first.
 
4ford said:
I was looking on ebay and seen floater bearings that said two different sizes.. one for the crank and the other for the rods is there such a thing and wouldn't it work for my application? or keeping the the parts that I have just won't work?
Click to expand...

There are two different sized floater bearings. One for the early engines with a 1.999 journal and one for the 59A engine with a 2.139 journal.
 
If you are running about 500 mi/year, and if it was running ok before you took it apart, then why are we/you worrying any of this? Put it together & be happy. Odds are, used rod bearings are probably ok. Crank is probably ok. If rod big end needs attention, do it. If main inserts are worn bad, change them. If main inserts are only .001 out of spec, forget it. As the others have posted, I'd go for some 'competent' measurements, first (forget about plastigage-useless). For 500 mi/yr, I'd be thinking in terms of OLD flatheads, how rebuilders did it in the 30's - 50's. And, NOT in terms of how modern machinists / builders want to do it today. If you want 'modern', well, I'm sure you could accomodate.
For the record, my 36 LB, in a 34 car, has rods & mains that are in excess of .001 out of tolerence. No problem. And, I've taken it on a few multi-hundred-mile trips. No knocks, no bad happenings. It will probably only last for the rest of my life. It's just an old Ford, not expected to go 30K per year, like my wifes modern car.
My opinion...
 
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