Rail Rockers on 289 Small Block Heads

[HotRoddin]

Originally posted by sleeperstang
I knew that those were the specs for 1965 289 heads, and I know that it was mid-1966 that Ford went to the Rail-Rocker or self-aligning rockers.

The heads that I have are cast slotted and most of the rocker's are the original or conventional type. My question is....What happens when Rail-rockers are installed? What I'm trying to get at is if what happened to my valve is what generally happens when rail-type rockers are installed instead of the correct self-guiding rockers.

In a nutshell what happened is that I order a 1968 spec 302 block for my 1965 mustang, since I know that that year had the highest compression and those blocks are stronger than newer 302 blocks. My last engine had developed rod knock and I thought that I might as well get a decent cam, so I went with CompCams XE256H.

Later when I build my own engine I'll do a roller cam and all that good stufff.

The reason for my post comes down to......Did the machine shop installing Rail-rockers cause my valve to get stuck, or should I be looking for other possible reasons so that when I go on Saturday to take the engine for them to look at it I have a good load of details where I'm sure it's their fault it failed.

One last note is that this was only the second time I had run the engine, I hadn't even ridden the car with it yet!!!

Thanks for the replies Rev and Shaggy!! And by the way, your posts on the cam thread were awesome, especially the graphs you made Shaggy.

The small block used close tolerance slotted pushrod holes and conventional rockers until May 1966, except the Hi Po heads which kept that configuration for as long as they were built (they never used guide plates). After may 66 Ford went to rail style rockers and big pushrod holes. You're right, you can't put rail rockers on heads with the slotted pushrod holes. Reason being you then have pushrods that can't move and rockers that can't move, so unless you have perfect alignment and zero flex something is likely to bend or wear prematurely. Can't say for sure your problem was caused by incorrect rockers, but I'd say it's sure a possibility.
Using both types of rockers on the same head is truely a rookie mistake that shouldn't have been made, but they took responsibility and thats what matters ... it shows they have integrity.