I have ran the 1.8 rocker ratio on an otherwise stock motor, in an older jetboat I had, no problem in my motor. I saw a slight power increase to the tune of 100-150 RPM which approximately equated to 20 hp.

Re: Re: 1.8 Rockers on BBC ?
 

My bad, .511" or .512" is correct, not .520".

I'm unclear on your motor. Your builder said your motor did not have adequate clearance to run 1.8s ??

Not enough clearance with a .520-lift cam? That's hard to believe unless I'm missing something.

There would not be a problem with a .512" (or .520") cam, but what we are talking about here is increasing the effective lift of a .483" cam to .512" by changing the rocker arms from a 1.7 ratio to 1.8. This can cause a number of problems with clearance.

1. The 1.8 ratio is achieved by moving the contact point for the pushrod slightly closer to the valve, which means the pushrod may come into contact with the hole in the cylinder head that the pushrod passes through.

2. The pushrods may also be too tight against the guide plates.

3. The rocker arms will not clear stock valve covers.

That said, Rag is the first person I've heard say that he actually had clearance issues. Everyone else I've heard from says it is important to check, but they've never actually had clearance problems (except with the valve covers).

Re: Re: Re: 1.8 Rockers on BBC ?
 

Sorry fellas I lost a "NEED" in there some how must of been in the chat room at the same time and looking for the photo. He does elongate the hole the push rod goes though in a SBC when using 1.6 instead of 1.5. But now I am rambling. I will go fix my post.

Sorry Rag's :( :(

Ah . . . thanks Rag's.