Titan's high-ratio roller rocker assembly is unique in being the only purpose-built assembly specifically designed for the MGB engine and other than Yella-Terra, the only assembly to offer a full rollerized design. It's safe to say that along with high quality however, comes price and while it is possible to bolt these assemblies up without modification, taking the time to optimize the geometry will ensure you get your full money's worth.
Just as with other brands of roller rocker arms, the original factory rocker shaft height is too low for the new roller tipped design. While Titan has done a good bit of the redesign for you (to the point of making their own pedestals with relocated rocker shaft positioning), they did not change the rocker shaft height to compensate for the roller tip radius. If you want to get a full 1.625:1 delivered ratio at 1/2 to 2/3 the max lift point, you'll have to modify the rocker shaft height yourself.
The roller radius of the Titan rocker arms is .240", so proper rocker shaft height is calculated by adding .240" to the valve tip height and then subtracting 1/2 to 2/3 the cam lift, multiplied by 1.625. The formula is thus:
Rocker Shaft Centerline Height = (Valve Tip Height + Roller Radius) - (1/2 to 2/3 actual valve lift)
Failing to raise the shaft height results in the delivered ratio being much lower than advertised. In our testing, the Titan rocker arm set without correction achieved 1.55:1 delivered ratio at peak valve lift with correspondingly lower ratio numbers at decreased lift (The delivered ratio at the valve seat was literally 1:1). Even with this very poor geometry, noteworthy increases in performance can be had over stock, but nothing like those available with the rocker shaft set to the correct height.
After raising the rocker shaft, standard length pushrods will be too short and because the Titan set has relatively little room for adjustment (compared to stock or other aftermarket brands), nobody will make the mistake of using the adjusters to compensate. The correct adjuster position for a Titan rocker arm will have equal threads showing on both ends of the adjuster. That is, roughly two threads will show above the adjuster nut and two threads will be seen protruding from the underside of the rocker arm.
Once the rocker arm is set correctly, the best way to achieve proper pushrod length is by using an adjustable length checking pushrod. Checking pushrods can be lengthened or shortened as necessary to achieve the correct working length. The adjustable checking pushrod is set to its shortest length on installation and then extended until proper valve lash is obtained. Once the correct length is found, a full set of pushrods can be purchased. The suppliers listed below offer kits and pushrods to any length or size needed.
For more information regarding proper rocker arm setup, click Here.
Correct rocker shaft centerline height for a .256" lobe cam and 1.625:1 ratio Titan rocker arms would be calculated as follows:
Example height of valve tip above rocker pedestal base in cylinder head = 1.625" (will be different for every cylinder head)
Roller tip radius = .240"
One half net valve lift = (.256" / 2) = .128" × 1.625 = .208"
(1.625" + .240") = 1.865"
1.865" - .208" = 1.657"
1.657" is the corrected rocker shaft centerline height above the pedestal base in the cylinder head.
Since the original rocker shaft centerline height = 1.4225"
1.657" - 1.4225" = .2345" rocker pedestal shims required.
Advanced Performance Technology (Shims and Pushrods)
Basil Adams (Shims and Pushrods)
Smith Brothers (pushrods)
Titan Motorsport (rocker arms)
This is what you get straight out of the box from Titan. Their assemblies are very complete and can be bolted on as-is, but not if best performance is desired.
If you find a stiff end rocker like the one shown, holding the assembly by it and lightly tapping the shaft with a soft face mallet will loosen it. (note improper adjuster position)
One way to set proper geometry is with a dial indicator, degree wheel and time. The better method is via the calculations discussed in text. Here we are checking the "out of box" delivered ratio, specifically for this article.
Rocker pedestal shims such as these are used to increase the rocker shaft height (suppliers listed at left).
Titan's offset pedestals are easily seen in this photo...
...and the reason why is seen here. The difference in shaft position of the titan rocker arm is easily seen when compared to stock.
This photo shows a modified set of Titan rockers with pedestal shims welded on. It is not necessary to go to this extreme, but it does assure they will never be lost! (note proper adjuster position)