I was wondering if the pushrod slots in the L98 cylinder heads changed at all from the earlier models to the later cars. I know that all of the pictures I have seen have the oblong slots even when using self aligning rockers. I was wondering if the shape ever changed to a circle. I was going to get 1.6 ratio pro mags for my stock 91 l98 but I keep reading that it is a crap shoot wether or not you will run into pushrod clearance issues. In one post someone mentioned that the instructions said that elongation was not necessary with the circular hole but was with the oblong. I haven't seen anyone with 91-92 cars mention interference problems so I was wondering if there was a change in the castings. If the slot is oblong for all of the heads I will go with the 1.52 ratio because I don't want to risk running into these problems.

 

I'm not positive, but I believe the '86 L98 (Corvette only) had slotted guides. What casting number are you looking at?

 

I remember reading about this a while back. IIRC, you shoudn't have a problem with interference as long as you're not running a huge amount of lift on your cam. They said the probability of interference increases by using 1.6 ratio rockers, but I think you have to be somewhere over .500 lift at the cam lobe or better to have a problem. You could call a reputable machine shop or maybe one of the tech lines at a cam company, and they could probably tell you for sure. I'm also pretty sure that heads using the circle shaped pushrod hole had to either have factory guideplates or the self-aligning rockers. Otherwise, there'd be no side to side stability for the pushrods.