Valve rockers

[djw090]

A friend of mine is looking to make his own high ratio rocker set to fit to the B series engine in his MGB. The scope for using offset bushes in the standard rockers is limited. So what we are looking for is information about the ratio of rockers from other engines which he could use with custom pedestals and shaft.

Does anyone know of a resourse on the web that details the ratio of various engines valve rockers?

[Moderator]

What a great question!  I don't know the answer to it... but I do know a bunch of MGB racers on this side of the pond are excited about "Chevy Cavalier" 1.6:1 roller rockers as shown and described in this article: http://www.britishracecar.com/AlanTosler-MG-MGB.htm

photo:


caption:
"Fab-Tek roller rockers provide a higher lift ratio (1.6:1) and more stability at high engine speeds.
The rocker arms themselves are actually Chevrolet Cavalier parts. Their use on an MGB requires
machine work on the cylinder head, plus adjustable pushrods, a mounting plate, and an oil spray
bar mounted to the valve cover and fed by a braided hose from the main oil galley, as shown."

[roverman]

David, your  friend wants roller rockers ? Needle pivots ? If so, I would start looking at sbc's with "shaft trunions", and work out from there.Perhaps fab a stud mounting plate for same ? Good Luck, roverman.

[djw090]

The question grew out of a conversation about off set bushes. They only give a small increase in ratio as you are in effect just shortening the push rod side of the rocker. However, that can be improved a bit by modifying the pedestal to increase the length of the hammer side by the same amount. The roller rocker kits available tend to be outside of his budget. So helped by a pint of bitter, we started to consider the use of rockers from another car that had a higher rocker ratio as standard.

Curtis, am I correct to understand from your post that  Chevrolet Cavalier's have roller rockers as standard? You can't see the rollers in that picture, or are they roller bearings rather than roller tips?

A standard ratio or 1.6 would be great. So far we have identified the triumph straight 6 as having 1.5. Standard MGB is 1.426 per the workshop manual but Hi-flow in Australia think they often measure up at 1.327 to 1.367.

[DiDueColpi]

Hi David,
One way that I used to "true up" the ratios on our vintage volvo race engines was to use a larger adjuster screw. Such as the small block chrysler. It has the same configuration but a larger thread @ 3/8 instead of 5/16ths. Simply offset drill the rocker and rethread it to the new 3/8ths by 24 size. If memory serves you could get to nearly 1.7 to 1 and still be ok. The mgb rockers are virtually the same so it should work as well.
Cheers
Fred