I guess the title tells the story. I'm doing something a little different with my 2.8 heads and need something like a coupling nut with a set screw to lock down the rocker arm. Stock jam nuts definitely won't work. Have any of you seen something like this for the 2.8?
"Normal" nyloc nuts might not last in the engine. Hot Engine Oil can "eat" many plastics. Might not fail outright but nylon and others gets brittle etc and fails for locking the nut.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
There is a very good reason why polylock or nylock nuts are NOT used for retaining rocker arms. You can search high and low and you will not find a set of rocker arms that are sold with this type of nut. Before you consider using nylock nuts to fasten rocker arms you might want to give a long serious thought as to why rocker arms are not sold with this type of nut.
(here's a clue - they will not secure rocker arms in a working engine)
I should have been more specific. I know not to use nylon. I am trying to get a 10MM x 1.25 coupling nut and set screw to lock down my rocker arms, similar to the ones offered everywhere for 1/2 and 7/16th rocker arm studs. I'm trying to adapt the roller rockers from a 3400 to be used on a 2.8 head. I need something other than a jam nut to lock down the rocker. I don't have quite enough threads on the 2.8 stud to use a jam nut. I thought the 60 degree guys might have come up with something.
Polylocks is a brand name for the kind of lock nut the racing cam guys supply for 3/8th and 7/16 studs. It has nothing in common with a nylock nut. I'm not sure why the brand name was ever used because there isn't any plastic in them. If I can't find some i'll go to the steel warehouse and pick up some 4130 hex stock and make some. I don't think it will be hard to find a 10 MM fine thread set screw but the coupling nut just doesn't seem to exist.
Originally posted by woodyhere: I don't have quite enough threads on the 2.8 stud to use a jam nut. I thought the 60 degree guys might have come up with something.
Seems like you need longer rocker studs... or maybe machine down the pedestals on the 3x00 rockers.
Can you post a photo of the issue you're talking about?
- it isn't an issue really. I'm using the 2.8 heads on a 3400 block. I dropped off the 3400 cam to be reground to something a little more performance oriented. I need adjustable rockers. The 3400 rockers are really nice roller rockers and 1.6 ratio. The 3400 beehive valve springs have about 40 more pounds pressure than the 2.8 conical. The 3.4 valves are smaller stemmed and the intake is .040 larger. The right length push rods end being about the length of a 5.0 HO Ford. I drilled the rockers to a few thou over to fit on the 2.8 M10 studs. They won't have the 3400 stand under them. I am using the 2.8 guide plates. Everything mocks up really nice. The only thing I need is M10 x 1.25 coupling nuts to use as posi locks. I'll use set screws to lock them in position once I have the lifters preloaded. I've side stepped buying studs, roller rockers and posi locks. I could just but stuff but where is the fun in that! I was hoping I could sidestep the tedious work of making the coupling nuts. All I can find commercially is coarse thread (1.5) Unless some one knows where to get M10 x 1.25 coupling nuts....I'll be making some.
OK, I was just trying to figure out why you were looking for posi-lock style nuts... i.e. not enough threads for a stock lock-nut, not enough room in the rocker arm for a socket wrench, etc. So I guess it's just personal preference?
I did look around for m10x1.25 coupling nuts, and came up empty-handed.
[This message has been edited by Blacktree (edited 03-12-2016).]
Thanks, it was very nice of you to look. I came up empty handed too. I can't find a stud any longer than the 2.8 with the right threads. With just over .500 of exposed thread there isn't the required .625 the Jam nut needs. The cam is being ground at Berry Cams. The last time I had him grind a cam was over 30 years ago for a 500 inch Cadillac. I did my mock up using the 2.8 block and heads. I'm going to wait until the cam comes back to mock up the 3400 and 2.8 heads together. The combination may require a little tinkering with to get a good contact area on the valve stem. I may be waiting a while. He had a pretty big pile of cams to grind. A tractor pull cam next to the 3400 cam, made the 3400 look like it came out of a Briggs and Stratton!
Just reading your thread brought back memories of an old Pontiac Catilina I had back in the day where the rocker nut would come loose. I ended up using two thinner nuts to jam nut them because two normal thickness nuts didn't leave enough threads on the stud. It worked great for years.
I wish I had room for a simple solution like that. The 3400 rockers are pretty cool but the slot in the rocker is only about 5/8th inch.The coupling nut will need to be turned down to 5/8 dia, so the rocker can have full movement. When I get the bugs worked out this should be a nice way to get good quality 1.6 roller rockers for the 2.8 - 3.4. Ah - the good old days!
Do you think you could maybe file a small flat spot on the stud and then maybe just tack weld the nut to the stud ? That's about the only thing I can think of but would be a pain to remove. Might as well just drill and tap the nuts for a setscrew but maybe file a flat spot where the setscrew ends up.
The coupling nut is just a long nut. The set screw screws into the end of the coupling nut until it hits the end of the rocker arm stud. The nut is then locked in place at the height needed to get the proper preload on the lifter.
Since you'll probably be making your own "posi-locks", maybe you could find some properly sized tube stock, tap it for m10x1.25, then cut a couple flats on one end so you can get a wrench on it. But I guess if you have a lathe, turning the flats off the bottom of a coupling nut might be easier.
In any case, best of luck. And please post photos.
I will have to get photos posted. I have had a lot of trouble in the past. I was stupid enough to use, Photo bucket, a provider than posts everything on the internet. I had check valve proto-type for carbs to prevent gas spills from the vents in roll overs. Within a year the big guys developed and marketed the same. They even lobbied to made it mandatory for racing.
I might have to go to round stock. I'm not sure I can get 4130 or 4330 in hex stock. I'll get pictures posted somehow and if things work like I hope they will, I can make extra locks for people that need them. The large trunnon 3400 rockers are really easy to find in the u-pull it or Rock auto. I'm going to check with some of the machine shops that have screw machines. It's a perfect job for them and would require a minimum of programming time. I do have to be sure with some testing before I get to that point. The car the 3400/2.8 is going into is a 84 cheepy that I am putting all the high option stuff from a 85 GT rust bucket. I may have to build a test stand to run the engine on because the car is a long ways from actually being a car. I have a nice 87GT and would like to have a nice 85GT.
- it isn't an issue really. I'm using the 2.8 heads on a 3400 block. I dropped off the 3400 cam to be reground to something a little more performance oriented. I need adjustable rockers. The 3400 rockers are really nice roller rockers and 1.6 ratio. The 3400 beehive valve springs have about 40 more pounds pressure than the 2.8 conical. The 3.4 valves are smaller stemmed and the intake is .040 larger. The right length push rods end being about the length of a 5.0 HO Ford. I drilled the rockers to a few thou over to fit on the 2.8 M10 studs. They won't have the 3400 stand under them. I am using the 2.8 guide plates. Everything mocks up really nice. The only thing I need is M10 x 1.25 coupling nuts to use as posi locks. I'll use set screws to lock them in position once I have the lifters preloaded. I've side stepped buying studs, roller rockers and posi locks. I could just but stuff but where is the fun in that! I was hoping I could sidestep the tedious work of making the coupling nuts. All I can find commercially is coarse thread (1.5) Unless some one knows where to get M10 x 1.25 coupling nuts....I'll be making some.
Thanks, Woody
You're going through all this trouble, just have the heads machined for 3/8" screw-in studs which will be better in the long run.
Just follow the links above. Yes I read your post where you stated "I could just buy stuff but what's the fun in that?" The fun is that the problem is solved probably cheaper and with a huge time savings over trying to custom build a solution. There is a solution available - problem solved.
[This message has been edited by lateFormula (edited 03-13-2016).]
10 MM is .010 larger than 3/8 inch. Machine the heads? You see a problem where one doesn't exist. The 10MM studs are fine. Your problem is you can't or don't make your own stuff. You see making some poly locks as a big project, which I think is just another little job. I was just having a discussion. I had hoped someone might have some metric engine building experience and have a source for the lock nuts. The 3400 rockers can be reamed for 3/8 studs because they have a .340 bolt hole. It's just as easy to go another .010 and use the studs that are already there. What seems to be such a difficult job for you is an easy one f or me. Just make some poly locks. If other folks could just use some 10MM poly locks to use 3400 1.6 rockers on their 2.8 to 3.4 it's an inexpensive upgrade.
10 MM is .010 larger than 3/8 inch. Machine the heads? You see a problem where one doesn't exist. The 10MM studs are fine. Your problem is you can't or don't make your own stuff. You see making some poly locks as a big project, which I think is just another little job. I was just having a discussion. I had hoped someone might have some metric engine building experience and have a source for the lock nuts. The 3400 rockers can be reamed for 3/8 studs because they have a .340 bolt hole. It's just as easy to go another .010 and use the studs that are already there. What seems to be such a difficult job for you is an easy one f or me. Just make some poly locks. If other folks could just use some 10MM poly locks to use 3400 1.6 rockers on their 2.8 to 3.4 it's an inexpensive upgrade.
I've been racing almost my whole life.
Let me know how this works out for you and how long it takes to get this thing going.
I can't thank you enough for finding the nuts and set screws for me. I searched using every description I could think of and came up empty handed. I'm going to order a bunch of both. I did order the 4130 steel this AM for making nuts. I'm still going to make the nuts. I will have a friend do a hardness test on the galvanized nuts that I'll order from the sites you found for me. I'm sure the galvanized will do the job just fine. It might be different if a person was using killer valve springs like in a SC situation. Then the chrome-moly might be needed.
