Had a chevy 489 stroker built for my boat in the spring,& now as the season is coming to a end I'm having some valve train issues. I'm running 502 heads with stainless valves & the damn push rod guides broke on 2 exhaust valves. I have no clue what caused this & luckily after removing the head no damage was done to the pistons. I want to know if there are stronger ones or should I buy a different set of heads.

corner cylinders ?

If so are you perfhaps running 1.8 rockers ?

If so, your pushrods are probably running against the cyl head and pushing them away.

It can happen - see it when mocking things up and then grind head for clearance.

High ratio rocker moves pushrod in closer to stud, therefore closer to block and cyl head.

Sometimes pushrod guides need a little clearancing too.

SB it was cylinders 2& 4 but problem was seperate times. They are roller rockers but I believe they are 1.6s. Do you think it would be better to bolt on a set of DART heads.

How much lift is your camshaft and are your springs capable of that lift. You may be a little to close. Or did you over rev and float the valves? Finding the cause is more important that the just the push rod replacement.

Some times the valves can stick in the valve guides (too Hot) and bend things. Are you too lean or have you had cooling problems?