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djw090
David Witham
Warwick UK
(115 posts)

Registered:
06/12/2008 11:20AM

Main British Car:
MGB 1974 and MG ZT 160 turbo 2005

Valve rockers
Posted by: djw090
Date: September 28, 2010 07:24AM

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
Curtis Jacobson
Portland Oregon
(4576 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Valve rockers
Posted by: Moderator
Date: September 28, 2010 11:52AM

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: [www.britishracecar.com]

photo:
http://www.britishracecar.com/AlanTosler-MGB/AlanTosler-MGB-CH.jpg

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
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Valve rockers
Posted by: roverman
Date: September 28, 2010 09:03PM

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
David Witham
Warwick UK
(115 posts)

Registered:
06/12/2008 11:20AM

Main British Car:
MGB 1974 and MG ZT 160 turbo 2005

Re: Valve rockers
Posted by: djw090
Date: September 29, 2010 03:21AM

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
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Valve rockers
Posted by: DiDueColpi
Date: September 29, 2010 06:24PM

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


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