bolt-down style roller rockers

Larry Finch did the bolt on Ford Racing M-6564-C351 roller rocker conversion on his car.
http://tinyurl.com/ma835y

Randy Malik at R.M. Competition has fully adjustable bolt-down aluminum
roller rockers manufactured by Harland Sharp to his specs which are dedicated
Ford 351C/351M/400/429/460 rocker dimensions. Randy says they will withstand
spring pressures in excess of 475 pounds open and over 625 pounds open when
using the optional Jesel bolts. These rockers are not the old style flat top
Harland Sharp rockers and are shaped more like the Crane Gold units and are
available in 1.73:1 and 1.8:1 ratios. Rather than mill and drill the 351C
dyno mule open chamber iron heads, I purchased a set. That was several years
back but Randy's email at the time was

rmcomprandy@yahoo.com

IIRC, the Ford Motorsport C351 rockers require shimming for any sort of
adjustment. I have that style on my 5.0L Mustang. They are fine for set
and forget hydraulics but, for a solid lifter cam, you'll want the fully
adjustable variety. Crane made the C351 rockers and I think they were
dropped when Crane went out of business. Crane is back in business but
I don't see them on Summit's site.

Dan Jones

...I Realize I was NOT asked! Buy if I were asked for My 2 cents worth, I would add...

Although I have not seen any reports of the 'Pedestal' Mounting Bolts Snapping Off!
There IS a Huge Difference in Strength Between a 5/16" Hardened 'Grade 10' Allen Bolt and a 7/16" ARP Rocker STUD!! I Have One word for it...SKIMPY! If Your going to go that Route, You might as well leave IN the 'Multi Groove' Valves, as well, for that Class of thinking.
I Imagine 'That'(Pedestal) set-up is fine for 'Mild' Cruzing around the Neighborhood Streets and Highways; BUT! When the Day comes, When You find yourself beside the 'Competition' whom Insists on Challenging the Power of Your Pantera, And You feel the Impulse to Defend the DeTomaso 'Honor'!...I like Knowing I have My 'Mechanical Insurance' in 'Massive Overkill'!

That's just THIS Machinists' Opinion!
Turns out, Most Whom Don't Listen to Me Now...Will Believe Me Later! That's just the way it is! Especially when the Pedestal Kit costs $400.00 and ANY Machine Shop will Mill, Drill and Tap Your Pedestals for a Mere $200.00!!
I'll close with:
The 'Minor Diameter' of that 5/16-18 NC Thread is only .2443"! And the Harder a Steel gets, the Closer it becomes as Brittle as Glass! Before Tempering. If it's even Properly Tempered at All!

As stated or inferred by everyone else the limiting factor in a bolt down rocker arm is the skimpy 5/16" cap screw that holds it to the pedestal. In comparison the adjustable rocker arms that require machining the pedestals use a much more substantial 7/16" cap screw or stud.



The RM Competition rocker arm (pictured above) doesn't use any kind of substantially different fastener to secure it to the pedestal. I don't know of anyone using them. It would be nice to be able to substantiate Mr Malik's claim.

In the good ol' days we limited use of the 5/16" cap screw to the types of spring forces that were common to "hot" hydraulic cams in that era, about 350 pounds over the nose at the most. Any spring force more than that and the recommendation was to use the 7/16" stud type mounting system. I'm not a fan of push rod guided rocker arms however, I never have been.

If your motor's over the nose spring force is 350 pounds or less then its a slam dunk, go for one of the bolt down rocker systems using the oem 5/16" fastener. Or use the stock rocker arm in conjunction with the Crane roller fulcrum kit. If the over the nose spring force is more than 350 pounds my recommendation is to play it safe.

Another adjustable bolt down rocker arm similar to the RM Competition arm is manufactured by Yella Terra, model YT6015. Yella Terra also manufactures a substantially stronger rocker arm of similar design using a 7/16" fastener, model YT6321. Both rocker arms are choice quality stuff, but the YT6015 is limited by that 5/16" cap screw.

You can find pictures of the Yella Terra parts in my 351C technical photo album on FaceBook, see thelink below.
______________________________________

In regards to your motor's compression ratio, its impossible to calculate it exactly without knowing the following information:

(1) deck clearance
(2) head gasket thickness
(3) combustion chamber volume

Assuming those dimensions are nominal your static compression ratio will be one of the following:

(1) Using Australian quench chamber 2V heads - 10.76:1
(2) Using 1970 US 4V heads (D0AE castings) - 10.15:1
(3) Using 1971 US 4V heads (D1AE castings) - 9.82:1

-G

I have 2 sets of 2 bbl. closewd chambered heads. One is Pedistal and the other scrrew in studs with guide Plates and gold roller rockers. The pedistal have Stainless Valves. tHE STUDS HAVE REGULAER VALVES. SOO!, What I`m going to do is Switch Valves ss to the stud heads. Co0ol?. Can I Just Lap them in?? or need to have new Valve angles done? I will use the same springs. They match the cam. Also, Is a 536 lift cam too small for Street?