Connecting rod

L

LSJUNIPER

Senior Member
Can the studs on the connecting rod be replaced for a 39 flathead? I inadvertently over torqued one nut and the stud broke, yes I feel like a total dumb ars.
Thanks
 
Yup, it is part of the forging. So, will I have to take the crank out to bring it back to the shop to have the new rod sized to the bearings??
 
Could you have it sized to it's companion rod?? Or the one with the broken stud??

How did they size the others??

Mart.
 
NO, at most you need the other rod on that journal (this way the diameter can be matched for floating bearings), the replacement rod should be close in weight too --
 
In my world, I have had rods resized to standard when rebuilding an engine (Aftermarket standard practice) so it's quite likely that a properly rebuild rod will fit the bearing as is...

That being said, Ford did make bearings that were oversize on the outside so that the used rod could be enlarged, rather than the common aftermarket practice of grinding the rod cap to make the hole small enough so that it could be bored- or honed- to standard size...

So, no crank removal.
You may bolt on the replacement rod (Even without piston) as a trial to check bearing fit... Some people use plastigauge. I use brass shim stock (Or tin foil, or paper) to check clearances... It's more accurate, but takes more attention.

Karl
 
Mart, the crank was ground and ballanced. The rods were honed to fit the new bearings. I will have to call the machine shop to double check it's been awhile.
Karl thanks fir the info.
 
LSJUNIPER said:
Mart, the crank was ground and ballanced. The rods were honed to fit the new bearings. I will have to call the machine shop to double check it's been awhile.
Karl thanks fir the info.
Click to expand...


Unlike the cylinder boring operation where the machinist will rightfully insist on having the pistons on hand before the start, the rods are built to a specific size and can be done as a stand alone deal...

Doesn't mean that you don't have to check them.

As you will be looking for one rod, it would be kinda cool to weigh the wrecked one- include the broken part... In hopes the new one will be close.

Karl
 
Just what were you torquing it to? It shouldn't brake at 40 lbs unless it waz defective in the first place.
 
I tourqued it to 90lbs. Had a dyslexic moment. The main bearing are 90lbs not the rods. I should of checked then double checked. Now I have to deal with my own stupidity.........Know what I mean????
 
My balance man keep a record of all the engines he balances and the weight of each part. He can look up an engine he did for me a year ago and tell the weight of the rod, big end small end ect. You should be able to mic the outside of that floating bearing with it on the crank and tell if it std od or .004 - .008 oversize. Did you torque all the rods 90#? Walt
 
Anyone here have a connecting rod I can purchase? Its a 1939 V8 91A. I think it's the 85 hp motor. The connecting rod is 9 inches long and the big end ID is 2.2 ish??
 
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