Why use hammer on full floating rod inseerts?
 

Ever wonder why we are told to use a soft hammer to 'adjust' full floating rod bearings? This paper I found in a NOS rod box may explain. (If I can get the photos to post).

Oops. Try again!

Well, can't get the pictures to post, so here's what the paper said: "NOTICE Because of the special alloys used in these full-floating bearings, changes in temperature may cause them to spread at the part lines.
If they have spread, they will bind in the rod. To close the bearings, simply tap them lightly with a rubber or wooden mallet.

DETROIT ALUMINUM & BRASS CORPORATION service division"

So there we have it; straight from the horse's mouth!

Re: Why use hammer on full floating rod inseerts?
 

Yep, sounds funny, but Fitting the floaters is a violent operation.

Re: Why use hammer on full floating rod inseerts?
 

Yep - and it is one of the most common mistakes that "flathead builders" make - they figure as long as they measure shell thickness and do a bit of math, they are good (even if they do that!). They neglect to consider that floaters need to float . . . and in order to do that, they need to be consistently round and also fitted to the rod bores and journals.

If you're running 32 - 48 rods and full-floating bearings and you neglect (or don't know) to do this - then you'll probably ruin some bearings and score your crank and rods. I've seen this countless times - on "just rebuilt" flatheads . . . sometimes from big-name builders.

I remember the first time I heard about guys taking the rubber mallets to bearings - thought "that is crazy" (of course I was about 15). Shortly afterwards, it was my turn to see if my newly bought and expensive (even then) Cadmium Silver "For Truck and Bus" rod bearings would correctly float - about 1/2 of them did . . . the rest got the "treatment". Rubber Mallet, lacquer thinner and ScotchBrite - your full-floater "tools of the trade". LOL

Re: Why use hammer on full floating rod inseerts?
 

Another thing you have to think of is:: Side clearance. for a street engine I run .010/.012 on the bearing aand .006/.919 on the rods. For compition a few tou more. This allows more oil to flow thru the bearing cooling. Also Hi oil pressure can damage them, called flaking.
8 years on a stock car track, is a great learning experience.

Re: Why use hammer on full floating rod inseerts?
 

I agree on the oil pressure. Now I'm somewhat comparing apples to oranges, but I drag race a 289 powered Mercury Cougar and shift around 7400-7600 RPM. The oil pump is a stock replacement with stock pressure. The crank is still standard size and has probably well over a thousand passes in the last 20+ years. Bearings have been changed once. So all the emphasis on high pressure is misplaced. Larger clearances, like you say, allow more flow for cooling but at standard pressure. The "hydrodynamic wedge" within the bearing is what does the lubricating. Besides, it takes horsepower to turn that high pressure pump!

Re: Why use hammer on full floating rod inseerts?
 

I’ve messed with floating bearings. I feel like if the crank journal is round and the connecting rod big end is round that the natural reciprocating motion of the engine running is going to move the bearing shells the way it wants to anyways.

That being said I always check that they float freely in the two rods at the same time and adjust if necessary.

Re: Why use hammer on full floating rod inseerts?
 

I too ruined a set of 020x004 floater way back by just fitting them and then wondered why at 7000 miles some knocked,lucky I had bought two sets,then read up on how to install them,the spare set has been in for 50000 miles no drama.
Lawrie

Re: Why use hammer on full floating rod inseerts?
 

With the floating bearings I made a fixture to hold the crank on the table to fit rod bearings to the crank and the bearings to the rods . This way I can rotate the rods 360 degrees without the pistons in the way. It take time , patience , Rubber hammer , scotch bright . and Lacquer thinner.
Keep the same bearings with the same rods.

Re: Why use hammer on full floating rod inseerts?
 

Another tip: the stock rods big end bore is 2.220, I have this honed out to 2.221/.2215

Re: Why use hammer on full floating rod inseerts?
 

Ron, Do you know if these rods can be resized when they're worn beyond the .008" oversize bearings?

Re: Why use hammer on full floating rod inseerts?
 

Yes - it is a standard machine shop operation . . . as long as the guys doing the work understand that these are BEARING SURFACES -- and they need to hone in a manner that provides a highly polished surface finish. Most guys are used to standard 'insert bearing' rods - they've never worked with full-floaters.

And Ron's idea of opening up the rods just a bit is a good idea - especially for high-performance usage where you want a lot of oil to flow. As we always said "loose is fast!".

Also, the way that you balance these early rods is NOT the same as modern engines - where you have a 'balancing pad' to remove material from. Many shops just grind the bottom of the rod - which weakens it. They need a special fixture that mounts the rod-cap in a lathe - where material is removed in the same manner that Ford did when they balanced sets of rods.

Re: Why use hammer on full floating rod inseerts?
 

I have the caps ground a few thou before re sizing. The shop I used would take them out to a few tents and finish with a white stone which made them looked like they were chrome plated/
. Back in the 60's C&T automotive used the 29a bearings for their OHV strokers. I had one set is a stried "Y" block crank

Re: Why use hammer on full floating rod inseerts?
 

Since resizing requires a slight angle cut on the parting line faces, how is this done with the studs in the way?

Re: Why use hammer on full floating rod inseerts?
 

we only cut the cap, this shortens the length of the rod. only by a few thou.. Not a perfect solution. but it works.

You have to under stand, most of us work on a limited budget. However,even if I had unlimited funds, I enjoy making things and improvising .
Remember, it's the joinery joinery , not the destination.


"joinery" ??????

Re: Why use hammer on full floating rod inseerts?
 

Never having built an engine with full floaters ;
what is the Scotchbright and lacquer thinner for ???

Re: Why use hammer on full floating rod inseerts?
 

Not strictly related to floating bearing, they are used to condition the bearing surface during assembly.

Re: Why use hammer on full floating rod inseerts?
 

There are a couple reasons:

1) Some of these old bearings have coatings and/or may even have a bit of surface oxidation . . . so polishing/cleaning them with ScotchBrite polishes the surfaces and cleans the crap off of them.

2) Then: When it comes to "floating", what is really happening is that we're removing slight bits of material from the inner and outer surfaces . . . the net effect is increasing clearances. It is surely a rough hand-done operation and far from perfect - and I have tended to see more work done on the OD than the ID for fitment. One has to try to apply consistent pressure and hopefully remove material in a manner that is the same over the surface (I know, hard to do). It is no different than hand sanding a paint job for polishing - you learn to not leave "finger marks" and to do it in a manner that is consistent across the surface. (More 'Art and Skill' than science!)

One mistake some make is trying to use ScotchBrite to resolve an issue where a bearing is just plain out of round. If the shell needs a whacking with a rubber mallet to get it concentric - by all means that is the FIRST thing you do.

Only after you see that it consistently touches/mates to the rod-bore, do you then start the ScotchBrite phase. I have frequently used 6 pairs of rod bearings and hand-select/fit them to find the "best four". Just the things you learn to do.

Best of luck!
D

Re: Why use hammer on full floating rod inseerts?
 

I also wash the bearings in soapy water when they are finished. This really cleans them. I also use the scotch bright pads on the modern bearings, I was tough that this gives the oil a better contact surface for break in. Some may disagree here, as I learned this over 50 years ago, and it hard to brake old habits.