240/300 rocker arm conversion? newbie question

[Anonymous]

Hi all, I did a search and did not find anything on this topic. I am looking to install a full roller rocker arm set up (shaft and rocker tips) on a later model 250 head I am putting on my 65 200 block. There seems to be some sort of supply backlog in terms of the ones available from Australia. I note that Crane has a full roller shaft-mounted rocker set up for the 240-300. I expect that the mounting bolts are larger diameter and maybe the blocks are taller. However, I don't know about the length of the shaft. Is it possible to machine the 300 rocker arm set up to fit on a 250 head? I figure enlarging and tapping the holes for the mounting bolts and possibly machining down the height. HOwever, I don't know if length will be a problem, or even whether the geometry of the rocker arms would be appropriate. I assume that the 300 shaft is a larger diameter than the 200/250 so that I could not simply strip the rockers off the 300 shaft and reinstall on the 200/250 shaft.

If this conversion is not possible, does any one know of a source, other than FordSixParts, for a full roller rocker arm set up for the 200/250 head?

Thanks.

BTW - I had the head Extrude Honed. I should be getting it back next week with a full documentation of flow numbers before and after, broken down by cylinder. They did the job with the port divider in place and gasket matched the exhaust ports to the header flange. They are talking around a 20-30% increase in flow, compared to stock 250. That should be a lot more than the stock 200! Got to wake up the cam and carb to take advantage of it.

 

[80broncoman]

240 and 300 engines have never had a shaft rocker arms. They mount on a stud much like a small block 289 or 302 ford.
The rockers that crane sells for the 300s are stud mount rockers

 

[addo]

There are some geometry issues which bear consideration with rocker arm swaps. Put generally, anything too far from original won't be clever. The roller rockers (and roller tipped) avoid tip issues with the roller aspect, and the ratio change is quite small.

You can prepare the head for the roller rockers, by tapping a thread in the well under the last pedestal, and fitting oil-through lifters. I personally have not used oil-through lifters with non-oiling pushrods, but see no problems doing so. Then when they arrive, you should only need to change the rocker arms and pushrods, and wind a 1/8 NPT plug into the tapped thread.

It almost goes without saying that the steeper ratio of the new rockers encourages a new timing set...

Regards, Adam.