Erinyes

Engine is a 1965 425 with A heads, 45 degree cam angle. I'm running a mild torque cam with .504 lift, small block Ford Comp Cams High Energy roller rockers with guide plates. Heads have original 3/8" studs.

While checking pushrod length, I discovered that the factory pushrods are 1/4" too short. The originals measure 9.625" long, 5/16" diameter. I need 9.875" length, or the rockers simply bottom out on the studs.

The problem is, I can't find pushrods in that length. Comp Cams have 9.748", nothing longer. Am I going to have to go with custom made pushrods? Any other ideas?

I assume the needed difference in length is due to the differences between the stock cast rockers and the rollers. The guide plates are only .080" thick.

I do wonder if it has to do with the 45 degree cam angle, or the stock studs. I know others have successfully used these rockers, so what is causing the difference in length?

Smitty275

The difference in pushrod length is because of the rockers. Pushrods are available every .050 off the shelf and to exactly what you want if its custom. Are you running 5/16 or 3/8 diameter?

You say you need 9.875 just to get off the bottom of the stud. How does that leave the roller sitting on the valve? Is that long enough to get a decent centered roller pattern with minimal sweep on the valve tip.

Erinyes

I haven't checked every valve, but yes, on the ones I did check the pattern is centered well. I would prefer off the shelf, obviously, but can't find anything longer than 9.75 - Comp Cams 7845.

Special order from Crane looks like B4 style 5/16" ball, but it would be really good if I didn't have to spend that much. At some point, I'd have to seriously consider trying a different rocker.

For instance, would Harland Sharps allow a shorter, standard-sized pushrod? If so, do they make one for 3/8 studs? On their website, I'm only seeing 7/16 for Olds. (I know they're more expensive, but their geometry is apparently a better fit for Olds at higher lift, which would leave me options in the future.)

What I'm really curious about is why I've never seen this issue brought up before. I know people have built 425s using these Ford rockers, but no one that I've seen has mentioned, "Oh, yeah, and I had to order custom length pushrods to make them work."

cutlassefi

Could be you have higher valve tips or different style of Ford rockers. They're not all made with the same cup depth etc. That will skew the outcome as well.

Erinyes

I'm using CompCams 17043 rockers. I positioned one of these next to the stock rocker, and the roller clearly has a higher point for the pushrod to sit. It's not just the cup depth.

However, after a few phone calls, Manton Pushrods will make pushrods for $10.50 apiece. I'm not terribly excited about spending another $180 for 17 pushrods (gotta have a spare; you just never know), but the other alternatives are probably even more costly and pretty much impossible to test without just blindly throwing money at the problem.

Smitty275

I can put you in a set of 5/16 x 9.900 Manley pushrods for $145 & shipping. If you can check to see how that will work with your valve to roller positioning.

I can tell you that the HS 5016 and 5017 rockers will use a much shorter pushrod and give much better geometry throughout the lift range. I have had them made for a 3/8 stud many times. You could also use a 7/16 rocker stud with a 3/8" base stud which would allow you to use a standard rocker without special order.

Erinyes

Smitty,

sent you a pm. Thanks.