Ok I have a 91 z28 with a 305 tpi and the previous owner put a different cam in the motor when they rebuilt it. The people obviously didn't know what they were doin when they rebuilt it and when I asked them what kind of cam they put in they said they had no idea except that it was a little bit bigger then stock. After rebuilding the motor myself and getting it running I feel like they put a cam in the car that was meant to be a mild cam for a 350. So while fixing the rocker arm studs that have lifted out of the heads I would go ahead and put in a cam meant for this car. I want to put in just a mild cam for the 305 and was wondering what you guys suggested. Also I was wondering how easy it is to pull out the press in studs and put screw in studs or just go ahead and take them to a machine shop. Thanks

 

wow. the issues just keep getting bigger with that motor!

by the time you replace the heads.. and now the cam you could probably just get another motor... and may as well make it a 350! but if you want to just replace the cam with something mild i think competition cams makes a 268 e for computer controlled cars that is just a little racier sounding than stock but good for vacuum and engine control compatability. i think edlebrock makes a similar unit. and you may want to consider using a kit as the lifters may be damaged or just plain bad if lifter studs are lifting out.

 

Yah I was thinking about maybe replacing the lifters and pushrods because one of the lifters got thrown when the stud raised out. But if that cam is from a 350 then that would explain why the studs are lifting out since it has such a bigger lift on it. I can get all of the studs replaced with screw in studs from a good machine shop for 150 dollars so I think I'll go ahead and do that and while I'm at it check the valves and maybe put in bigger intake valves? And then save up for that vortec setup you were talking about

 

there really isnt a difference between a 350 and 305 cam per se. the real issue is the lift and/ or lobe angle built into the cam. the fact that your lifter studs came out makes me think that either the lift (the amount that the pushrod travels upward toward the lifter) is too high for the stock lifter and head can accommodate or the angle of the lobe is forcing the pushrod too quickly or erratically upwards , possibly from using a flat tappet lifter on a roller cam or something like that.
another option altogether is that the springs in the head may be too stiff for the rocker studs to withstand as they act like a pivot turning the upward motion of the pushrod into the downward motion of the valve. after all, if the irresistible force of the pushrod moving up is unable to move the immovable object of the valve going down something has to give somewhere and that may be the friction force of the press in stud!
with all of these maybe's out there on what you have i'd go with new or fully rebuilt heads as soon as possible. if the rocker studs are screwed in and the same issues exist the give is just going to move somewhere else in the system and that could be even more painful. and i wouldnt bother with the bigger valves right now. that is a lot of expensive machine work with minimal gain. the stock heads have limited potential and it is a lost investment when you do end up getting new heads. if you want some immediate gratification, i'd suggest spending that bigger valve money working on the exhaust flow side first. what is in there has to go out before you can fit in more fuel!

 

Alright thanks for the suggestions. So I'll just get those heads out of there and the machine shop requires everything to be out of the heads so I can make sure all of the seals and everything are good while I'm at it.