Broken exhaust rocker studs on afr 185 heads???

[Dan Gray]

i installed AFR 185 heads on the engine about 6 months ago. When i installed the heads i used an adjustable pushrod to check pushrod length to place the roller rockers in the right place on the valve. I got a pushrod that was .100 longer. i asked around and that seemed to be the going rate of what everyone was using. But i noticed that to get the right rocker placement and preload on the lifter, the jam nut for the rocker arms only screws on to the rocker stud about 4 to 5 turns. That seemed odd to me.

About two months later one of the exhaust jam nuts falls off at the race track. I install it back on and drive it home. I adjusted all the rockers again. well it lasted 4 months until last night when in the same night i broke 2 exhaust rocker studs off just under the jam nut. So now i know something is wrong!

Are my pushrods too long? Are the rocker studs are too short??? Why is it only the Exhaust studs breaking? Has anyone run into this problem?

I do spin this engine just over 6000RPM, and am now wondering if the studs are Flexing? Will I need a rocker arm stud girdle to help with flex?

Thanks
Dan

 

[Markus]

Hello Dan,

i think the studs are too short. I use on my AFR 185 the
Comp pro magnum 1.6. My studs were also too short.
I take a set of ARP 134-7104 with 1.895 inch length.
I believe the AFR studs have 1.750 inch. AFR say AFR´s #9409 ?? Particularly with the pro magnums.

What rockers did you use ?


Markus

 

[Markus]

Hello Dan,

i contacted AFR. They confirmed my assumption.
The ARP 134-7104 are the correct studs.

Markus

 

[Dan Gray]

Yes, i'm running those pro magnam rockers. I guess the trunion is too thick for the stock AFR studs. Thanks for all the help. Im going to double check the pushrod length again just to make sure and then order those ARP studs up.

Thanks

Dan