rod & main nuts

G

Geo. H

Senior Member
I just tore my B engine down for a little maintenance. The hardest part was removing all the cotter pins. Is there something better out there after nearly 80 years?
 
Geo;


Go top Bratton's web page to "Engine" part # 08950.

I have not used these, but have sure thought about it.

Perhaps someone who has used them can chime in on how successful they are.

Dick
 
Hi Geo, Brattons part 08950 is a grade 8 bolt and nut set for the mains. I have kind of wrestled with this question myself, since not only are the cotter pins a pain, frequently when you get the rod or main nuts properly torqued, the castles are right in between the cotter pin holes, resulting in your having to: set them too loose; set them too tight; or, file a bit off the bottom of the nut to make it come out right.
The best cure would be to use a Marsden nut, but they are hard to find in a grade 8 or grade C hardness, which is what you would really need for engine bearings. Marsden nuts have a slotted top which is caved inward creating a self-locking condition. They look reasonably similar to the castelated nuts which were original. Let us know if you find a source for these which would sell in small quantities! Good Luck.
 
I have used the new style main bearing studs and nuts on a couple of engines now, and have been very satisfied, that I do not use the seal washers that are provided.
You may need to obtain a thin wall socket to use on the bolt heads for torquing of the mains. Use a small amount of a polimar sealer under the two bolt heads for the rear main, and the front main for sealing. Use the heavy washers that are provided with the bolts under the nuts. Your modern engine local rebuild shop can provide you with an improved style of nut for the connecting rods. I don't think a person should consider using the nylon insert type of lock-nut, but I did consider using the "Hug Lock" type of nut one time, just out of shear frustration.
 
Rods & mains do not need cotter pins or other devices. I use ARP 12-point nuts on the rods. For mains I ran out of my Cat long-nuts so started using Model A lug nuts that I machine off the taper, and use a hard washer under them. They look cool, have a lot of threads and are of good material. I was a mechanic for a lot of years and never saw a rod nut that had loosened and the cotter pin was holding it on.
 
Jim Brierley said:
Rods & mains do not need cotter pins or other devices. I use ARP 12-point nuts on the rods. For mains I ran out of my Cat long-nuts so started using Model A lug nuts that I machine off the taper, and use a hard washer under them. They look cool, have a lot of threads and are of good material. I was a mechanic for a lot of years and never saw a rod nut that had loosened and the cotter pin was holding it on.
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I was a mechanic for a long time also. I agree the nuts will not come loose if tight to start with. I never seen one come loose either, but I have seen a lot of cotter pins in the oil pan that came out of the rods.
 
I use the Brattons #8950 set sucessfully for the mains. They are a touch longer than stock and have more threads. For rods I got some specialty self locking nuts from Coast Fabrication, what they call Jetnuts, used in racing applications among other things. http://www.coastfab.com/index.html Their catalogue has all kinds of nuts and bolts and the people will talk to you.
 
I wish the front and center mains had used studs with a castle nut on each end. It would make checking and adjusting the mains a lot easier.
 
PC/SR said:
I use the Brattons #8950 set sucessfully for the mains. They are a touch longer than stock and have more threads. For rods I got some specialty self locking nuts from Coast Fabrication, what they call Jetnuts, used in racing applications among other things. http://www.coastfab.com/index.html Their catalogue has all kinds of nuts and bolts and the people will talk to you.
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Thanks! Just ordered a free catalogue!
 
The first model "a" engine I took apart had a strange size of nuts and bolts on the rods. I can not remember but they were like between my 1/2" and 9/16" wrenches. I had my dad's old Ray socket set. The sockets were in thirty seconds .He liked working on Model "a" engines.

I use to be with him when he was working on mom's model "a". He always said they are going to make these again someday. He was kind of right but I do not think he would have bought a Shay.
 
sturgis 39 said:
The first model "a" engine I took apart had a strange size of nuts and bolts on the rods. I can not remember but they were like between my 1/2" and 9/16" wrenches. I had my dad's old Ray socket set. The sockets were in thirty seconds .He liked working on Model "a" engines.

I use to be with him when he was working on mom's model "a". He always said they are going to make these again someday. He was kind of right but I do not think he would have bought a Shay.
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Model A rod nuts were 21/32's. Herm
 
Thanks for all the response, guys. I guess I'll use cotter pins. They're a pain, but they've worked for 80 years.
 
Geo. H & Others - I did a little searching on the internet, and found the following:

http://www.lok-mor.com/mar-loc.html

Notice that they are listed as Grade 8. I am going to send an email to the company asking some questions. I see they accept the usual credit cards; so I guess they sell to whom ever. I will post more info as I find out.

My guess these nuts would be acceptable to use on the A mains and rods without the need for cotter pins.

Are there others of you that can concur and/or verify?
Thanks,
 
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Hi Ron, Yes these would definitely work. They also have a dome-flex in a grade C which would be perfect for engine applications. The $64K question is, will they sell to guys like us in small quantities?
PS The dome-flex will be quite similar in appearance to the original castle nuts.
Merry Christmas, Guys!
 
I've been curious why the A has cotter pins on these yet modern engines don't need them. Whats different? Lock washers?
 
Tom, on my personal engines I make a stud, always put it in the main hole in the valve area and usually in both center mains. They are of 9/16" material with a threaded area that goes into the block an inch or so, the stud continues up at 1/2" diameter and is threaded on top for a nut, this locks it all into place. The bottom is also turned down to 1/2" and threaded to hold the cap on. It is best to do this before babbitt. Yeah, I know that 9/16" is a bit small for the existing 1/2" hole but it works. 5/8" material gets real close to the crank so I don't use it. I start with studs that I bought at a surplus store many years ago. DO NOT USE standard studs without the extension all the way up into the block. A friend of mine did that on his Bonneville engine and the center main web pulled out at about 6,000 rpm and 175 horses on the dyno. That block is now only good for show & tell or the scrap dealer!
 
MrTube said:
I've been curious why the A has cotter pins on these yet modern engines don't need them. Whats different? Lock washers?
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All old engines, Mains and rods used, castle nuts, Lock wires, lock plates, nut, with tin lock nuts like Chevy's ect. Many of the old engines now, have lock washers, as a replacement to keys. The easiest way to solve a lock problem now, if you don't want to use Keys, go to an engine rebuilder of modern engines and get a modern rod, or main lock nut. You have to watch what you buy for lock nuts, at a hardware store as MANY will tear up the threads, on a rod, after years of over torquing. A good Rod, or Main from an engine is very hard, and will laugh at a file. Thanks Herm.
 
Kohnke Rebabbitting said:
All old engines, Mains and rods used, castle nuts, Lock wires, lock plates, nut, with tin lock nuts like Chevy's ect. Many of the old engines now, have lock washers, as a replacement to keys. The easiest way to solve a lock problem now, if you don't want to use Keys, go to an engine rebuilder of modern engines and get a modern rod, or main lock nut. You have to watch what you buy for lock nuts, at a hardware store as MANY will tear up the threads, on a rod, after years of over torquing. A good Rod, or Main from an engine is very hard, and will laugh at a file. Thanks Herm.
Click to expand...

Ahh,

I knew something had to have changed :).

Thanks.
 
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