anyone running a mild hyd roller cam set up using stock 5/16” size rocker studs??

My build is near-stock street motor anticipating < 5500 rpm cruiser.

I’m wondering if i could sneak in just enough spring rate without modifying heads for larger rocker studs.

 

Depends on your open spring pressure. Check with your rocker manufacturer.

 

It’s the stud that has the limitation way more than the rocker. They don’t recommend anymore than 340# open

 

Red car has a little HR in it, iirc it has the “conversion” studs - 5/16” in head with 3/8” upper for rocker.

Cam is Engle, specs roughly .510ish, 250/265ish, 204/212ish @ .050. Everything is “ish” since I built it in ‘08-‘09 and car is a year round, every day driver with appx 100k on the engine, the details have become foggy.

 

Would be nice if the 5/16 conversion studs had a longer thread engagement into the heads. The studs i bought (comp cam) only thread into heads about .520” but the heads ate threaded about 1” deep.

if the studs had more length of 5/16 threads on them, seems it would greatly increase pull-out resistance.

At any rate, i’d like to hear testimony of anyone running small mild hyd roller using 5/16 conversion studs.

 

bccan...thanks for reply. Couple questions for you. Do you recall specs on valve springs in red car ? What is generally max RPM that car sees ?

 

That blue car is a very nice combination!

 

When thread engagement is 1.5x the bolt diameter (in this case, 0.469" is 1.5x), more engagement isn't going to help anything. You can get away with as low as 1x, but 1.5x is definitely plenty. They don't fail from pulling out of the head, they just break. With the small cross-section, 5/16" is not very rigid or strong in bending, especially using it like a stud.

Your best bet is to use the Harland Sharp bolt-on minishaft rockers. They can be used with a mild hydraulic roller... keep the lift relatively low (maximum 0.530-0.540" at the valve) because the rocker geometry isn't correct, they are really Ford rocker bodies. You'll want to shim the bases (or buy the taller pedestals they sell) to optimize valve contact sweep the best you can.

 

^^^THIS. Even assuming the lowest possible shear strength for cast iron, the tear-out load at that 5/16" stud is still more than an order of magnitude higher than the load from the rocker. The problem is bending (and eventually breakage) of the stud where that 5/16" section transitions to the larger diameter. Stud bending causes unwanted motion in the valvetrain, which negates the action of the cam.

 

However the HS pedestal setup has the same spring limitation as a plain stud, approx 340#.
You could also use the more popular 7/16 stud rockers via Cranes 7/16x5/16 stud and build your own roller rocker setup.

 

These replies pretty much sum up what you need to know and why.
.....Just my two cents worth.

 

Thanks! Like Dustin Hoffman, it’s an “ excellent driver.”

I will see if I can figure out what’s in there.

 

Valve Springs from head rebuild this past spring listing below. Brought about by broken #3 intake spring and somehow the filled exhaust crossover melted out on that head. Not sure which was the chicken or the egg. He drove it for days.

I never heard of this brand but do have some level of trust for the machine shop. I just hope they don’t give him or nearby motorists cancer.(Fig 2)

Cam card in Fig 3 to clarify all those “ish” specs. Upon review I was at least in the ball park.

 

I really appreciate you digging up that info. I’ve been pouring though spring specs trying to land on a configuration that will let me run confidently run hyd roller with 5/16 studs.

Since engine is numbers matching 400G in 442, i plan to keep revs below 5200. Your set up gives me hope i can run low lift hyd roller to keep open spring rate in ballpark of 290-310