Boss 351 Roller cam ?

[Boss 351 cobra]

I have a Boss 351, With solid lifters. I need to know what has to be done to engine to put in hydraulic roller lifters and cam. Is it worth the time and money. What kind of HP can I expect .

[trularin]

Other than block oiling problems, it will certainly add some zip.

Why are you doing it?

[Daniel Jones]

> I have a Boss 351, with solid lifters. I need to know what has to be done
> to engine to put in hydraulic roller lifters and cam.

It depends upon the type of conversion kit and cam core material.
Some hydraulic roller retrofit kits use standard Ford hydraulic
roller lifters and a spider that screws into the block to hold the
lifters in place (roller lifters must not be allowed to rotate).
A reduced base circle cam must be used with this sort of kit.
Other kits like those from Crane use a link bar between the lifters
and can use a standard base circle cam. Crane's hydraulic rollers
are made from 8620 steel and require a compatible steel or bronze
distributor gear. Other's like Comp lists their hydraulic roller cams
and certain street solid roller profiles as being compatible with OEM
cast iron cam gears. Their -8 part number hydraulic and street roller
cam cores are austempered ductile iron. A surface treatment hardens
the cam lobes so they can run a roller lifter. He also said either a
cast iron or cast steel distributor gear is compatible with the -8 cores.
Not compatible are machined steel gears like the Crane 351C part which
is made of 8620 steel, the same as a solid roller cam core. He said
the OEM and Ford Motorsport steel gears are cast steel and would work
fine with their street rollers but not their race rollers. Unfortunaely,
Ford doesn't make one for a 351C. Solid roller cams are usually ground
on 8620 billet cores and require bronze distributor gears which wear
rapidly.

Mallory makes a special gear for their distributors that is made for
"austempered ductile iron billets" and "proferal billet" cams that is
supposed to be compatible with the Comp austempered iron cam cores.
As I understand it, the gear is heat-treated for compatibility.
Also Comp has recently introduced a polymer plastic gear but I think
they are only currently available for the SBF and SBC.

You'll also need shorter pushrods due to the taller lifters.

Crane makes a 8620 steel gear

Compared to a solid flat tappet cam of similar specs, a hydraulic roller
will typically float the valves at a lower RPM, given the smae spring
pressure and will be limited to the maximum spring pressure and RPM.
Comp also makes some interesting beehive springs with nickel-sized
retainers which help offset the wieght of the heavy Cleveland valves
and are said to be worth 400 RPM.

> Is it worth the time and money.

It depends upon what you are interested in. The biggest advantage of
a hydraulic roller cam is that the cam and lifter tend to last forever.
Drawbacks include cost, potential gear problems, and RPM limitation.

> What kind of HP can I expect.

It depends upon the particular cam's specs and the rest of the engine.
In many cases there may be no HP increase over a solid flat tappet.

Dan Jones

[ENTDOC]

I have a 351c and I put in the crane kit during the rebuild;it is very simple.I went with the bronze dist. gear.Hot Rod magazine did a nice story on the roller cam and concluded that more usable HP was generally obtained with one, since the lobe profiles can be more efficient. The rollers are heavier and tend to float at high rpm's but probably not much of an issue for the daily driver. chuck