I have a 1970 Olds 442 with a manual transmission. Mine has a brake booster on it, that is about 1 inch from the valve covers . Every where I look a manual transmission doesn't have a brake booster .Could someone let me know what's correct and why the booster is so close to the valve covers .

 

The booster is close because it is a big engine jammed into the same compartment as a normal engine. Love your big engine, and it will love you back.

Manual transmissions are not the same thing as manual brakes. Independent systems. The booster is a vacuum assist for the brakes to help you hammer on them. It does not know, nor care, how the power gets to the wheels through the transmission. The reason manual trans cars often have manual brakes is because both options are cheaper, and are more "race car" oriented. A family man will want an automatic transmission power brake high option car; James Dean will want manual everything.

 

Power brakes were a factory available option on manual transmission cars (except for W-30s due to the low engine vacuum) in 1970. The 11" booster was necessary to provide the needed level of power assist. You only have 14 PSI to work with, and the power booster added force is simply diaphragm area times atmospheric pressure. Smaller aftermarket boosters are available, but simple math tells you that they won't provide the same level of assist. Area goes with radius squared, so a 9" booster provides only 2/3 the assist force of an 11" booster.

Factory big block cars came with valve covers that were notched to provide additional clearance to the booster (and the HVAC box). Aftermarket tall valve covers don't clear. I'm not sure why you're worried about an inch or so of clearance - if the engine moves that much you have a broken motor mount.

 

Thanks for the information ! I'm not worried about it I was just making sure that it was correct . Thanks again !

 

Joe,

To clarify for others, you mean 14psi of atmospheric pressure acting on the pressure side of the diaphragm, not 14" of mercury of vacuum on the vacuum side.

- Eric