Bearing clearance

The reason I run a Loose (.002+) clearance . is to improve oil flow through the bearing. Bearings need flow to cool the bearing. Heat is the enemy of bearings. tighter clearances, must use a thinner oil to maintain the flow rate, thus 5/20 oil. I love this kind of thread, it makes you think about all the mistakes you made over the past 85 years.
 
Not trying to hi-jack this thread but, I have a large quantity of NOS rod and main bearings that came out of a Ford dealers inventory when they were declared obsolete. There are floaters and later model flathead bearings. How do I find out what they fit? What books or manuals do I need?
 
I've just been through the exercise of fitting full floaters in preparation for reassembly of a 1939 Merc engine (keystone block) and thought others might benefit from what I learned in the process. I started by watching Dale Hay's YouTube video (from 2015) to get an idea of what the 'fit' should look/feel like.

I like Ron Holleran's thoughts on this subject but, never having been able to find any detail regarding the procedure involved, decided I'd write down what I did and the tips I think are pertinent (along with a few photos) in the attached PDF document.

Feel free to weigh in if I'm off base on anything or you can recommend additional tips!

Glen MacDonald
 

Attachments

One additional point regarding use of the outside micrometer in the first step of the procedure - this is simply intended to get you started in the right direction (i.e. determining where to start tapping) or confirm during the process that you aren't going in entirely the wrong direction. In between, you'll mostly be going by feel and the indications witness marks may provide after each set of 'whacks' with the hammer & trial fittings.
 
Very good information! I’m getting ready to rebuild a 59A block and this is going to help greatly.
 
macdonge said:
I like Ron Holleran's thoughts on this subject but, never having been able to find any detail regarding the procedure involved, decided I'd write down what I did and the tips I think are pertinent (along with a few photos) in the attached PDF document.

Glen MacDonald
Click to expand...

I would have to go back and check, but I thought Ron covered the procedure in his book.
 
Yes he did, but this goes into a bit more detail IMO. Both Ron and Glen have helped me understand the full floating bearing in depth.
 
JSeery: While Ron does mention that you need to "use the hammer method" to get the bearings round, there's really no detail on what the method entails. At about $450 a set these days, and never having done this job before, it's darn stressful to learn that you'll actually need to whack them with a bleedin' hammer to get them to fit properly! It's for this reason I thought some people might appreciate more detail.

Cheers!

Glen
 
Yes, knowing how to "hand size" full-floater bearings is a combination of art and science, it isn't that tough if you really think about what you're doing, can correctly measure clearances and keep the end goal in sight --> full floaters . . . must easily float on both bearing surfaces (the crank journal and the rod inside bore). Here is a short little video that might help you a bit.

https://www.youtube.com/watch?v=CyVLsPdbhS8&t=17s
 
The cost and effort of floaters for a moderate flatmotor may not make sense, when 8BA rods and NOS and NORS insert bearings are plentiful, and reasonably priced. Full race, floaters make a lot of sense.
 
Russcc: If all I had to work with was a bare block, I agree with you. In my case, however, I have a perfectly good crank & rod set (original to the engine).


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russcc said:
The cost and effort of floaters for a moderate flatmotor may not make sense, when 8BA rods and NOS and NORS insert bearings are plentiful, and reasonably priced. Full race, floaters make a lot of sense.
Click to expand...

The main reason that I've ran full-floaters for years is that I tend to have my 4.00" Merc cranks offset ground to the 221 Cubic inch 1.997-1.998 rod journal size - to achieve the 4.125 stroke. At this journal size, the only affordable option (before H-beam rods came to town) was to use the 1939-1942 91A or 21A full-floater rods and bearings. The later 1949-1953 rods only come in the larger bearing size - so they won't work in my traditionally built 4 1/8" stroker setups.

Now, when you get to high horsepower blown or Ardun equipped engines, then the good ole' 21A rod can become a weak link . . . so in these cases I'd now run an H-beam rod with modern insert bearings.

If you're thinking of running 49-53 rods and the larger rod journals, then consider buying a new set of 49-53 rods from SoCal. They cost around $275, but aren't a bad deal if you consider the cost of rebuilding old rods and having a NOS set of rods brings some mental comfort! :)
 
Ol' Ron said:
Yes, for floaters, I run about .002 on both the rods and crank. I open the rods to 2.221 and the crank to 1.997. OR find bearings that are .1o8" thick. That's why fitting the bearings are important. Again, I have dozens of used bearigs to choose from
Click to expand...

Hello Ron,

I am just checking my crank and rods. It`s 81A motor. So again about floaters which i have. You say .002 on both ..does it mean .001 between journal OD and bearing ID + .001 between bearing OD and rod ID ?
Or maybe you mean .002 + .002 = .004 total ?

Greetings
 
I'm amazed that I can still read this stuff, and almost understand what we're talking about. Been awhile since I fit a set of bearings, and my new engine has them. Probably have to read this thread a few times so I can figger it out.
Yes the .002" clearance is .001 on each side. Something that wasn'r brought up was rod . Opening up the bearings to allow more oil to pass through, you also have to narrow the bearings and rods as well. .010/,012"is what I use. Again this is old stockcar bS.
Many years ao I built a 296ci engine for Ron Horrell, You don't hear about them much anymore, but they werecheao to build and ran pretty well, Compression was easy to come by. These werrefered to as 3/8X3/8, 3 3/8 bore and 4 18 stroke. after 50k miles It was replaced with a 204 blown engine. I offere to freshen it up but he said it didn't use a drop of oil and had good oil pressure.
Gramps
 
Thank You Ron.
I've made some measurments last evening and some of my rods are pretty loose. I think I need to restore diameter to stock size . Bearings are bronze floaters and are .010 undersize. A little bit frustrating job as I would like to make all by myself... my trust for workshops is very limited.
 
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