I have a 73 jet boat with a 455. I will be pulling the heads and timing cover to regasket. I did have engine running but was getting a lill water in oil. Seems this is quite normal for marine 455. when apart I have a set of roller rockers I want to install. Has hyd lifters. First question:


1. The studs will screw into the heads where the solid mounts were without mod correct?
2. would guide plates be required?
3. Would the roller rockers change the pushrod length?
.
I have built sbc's but this is my first time digging into BBO So I'm a newbie any help ia greatly appreciated.

 

Not correct. Olds heads from 1966-1990 used 5/16" bolts to retain the non-adjustable rocker pivots. Unless your roller rocker kit is the Comp Cams kit designed for unmodified Olds heads, the studs will require machining the heads

There needs to be some method to prevent the rocker from spinning on the stud. The stock Olds rockers use the joined trunnions to do this. Unless you adapt the Ford small block pedestal rockers, or get the Harlan Sharp rockers with the pivot trunnions that are joined, you need to run guide plates. Of course, most guide plates require hardened pushrods. Crane makes guide plates for a Mopar Magnum 318 that have plastic inserts to allow un-hardened pushrods. These can be used on the Olds heads with the Comp Cams kit I mentioned above.

Almost always, but the only way to know for sure is to check on the assembled motor.

 

On the water in oil, jet boats often have way too much pressure in the cooling line off the jet pump. Like 60 psi or more. This tends to blow front cover and head gaskets.. Put a ball valve in this line and close it until you just have some movement off 100 on your water temp gauge. You could also hook up a pressure gauge and see what your coolant pressure is and make changes to keep it under 15. Do you have the water exiting to the exhaust or over the side?