[DeTomaso] 4V heads and roller rockers

[JDeRyke at aol.com]

In a message dated 5/23/09 6:17:21 AM, pantera at fastcat.se writes:

> I have seen an article on internet where they milled the pedestals on 4V 
> heads to accept roller rocker studs, is that a must?
> 
Yes; stock NON-Boss heads have a grooved rocker pedestal that is also 
tapped for too small a thread to fit large rocker studs, and the uncut pedestal 
is too tall as well. It must be cut down to make space for a pushrod guide 
plate that bolts under a pair of rocker studs. Then because the pushrod 
constantly rubs the hardened steel guide plate, hardened pushrods are required. 
Stock pushrods will wear in two. The milling is complex because the rocker 
stud must be tilted in two planes to fit the combustion chambers. Due to the 
cost, its probably not practical to mill open chamber heads which will never 
deliver the power of closed chamber heads. 
But there are options: First, cam grinders and some speed shops sell a 
piloted cutter that indexes into the pedestal's bolt hole and trims the rocker 
pedestals to the proper angles. The device chucks into a hand-held 1/2" drill 
so it can be done in your garage.
Second, Crane Cams (and maybe others) sell a set of special pushrod 
guide-plates with replaceable kevlar grommets, that fit uncut 351-C pedestals, 
guide stock unhardened pushrods and allow roller rockers to fit with no 
machining at all needed, but will not last long with radical cams and heavy valve 
springs 'cause the small stock bolt is used to hold the assembly, rather than 
the much larger stud. Unaltered girdles probably won't fit the Crane 
conversion system, either.

> Is it true that the 4V Boss heads was milled from factory to accept 
> roller rockers studs and girdles?
> 
Yes for the milling but girdles didn't exist in 1969-71. In 1972, Ford 
replaced the Boss 351 with the '351-HO' engine that also used adjustable rockers 
and studs, but with a smog-compliant open combustion chamber. Authentic 
Boss or HO heads are pretty rare but there are many 'clones' for sale and 
they're virtually identical.   In any case, a girdle bolts on with no special 
machining needed. Some girdles will fit under normal cast aluminum valve covers 
while others require special 'tall' covers or stacked cover gaskets. All 
require the sheet metal oil splash guards inside valve covers to be removed. 
Good luck- J Deryke



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