[Shop-talk] 1965 Mustang Brakes

[bjshov8 at tx.rr.com]

Well pushrods have no direct bearing on the power that an engine makes.  The VALVES are what contribute to the operation of the engine, and when and how far they open.  HOW they open is secondary.  Whether the valve is opened by a pushrod and rocker arm, or an OHC and rocker follower, or an OHC and bucket, the valve just doesn't care.  So you can put the cams wherever you want and they will still work.

There are some implications to the cam position and resulting valvetrain, and they can affect the design of the engine and to some degree its performance.  For instance OHC's are typically assumed to be required for high rpm operation.  They do make it easier for an engine to achieve high rpm's, but pushrod racing engines are easily capable of 8k rpm and more.  If you want higher rpm than that you usually use OHC.  OHC engines can also make it easier to run more than 2 valves per cylinder, or to use combustion chamber layouts that help with breathing, but the Chrysler Hemi is one of the best for breating and it was invented in the 1950's using pushrods.  Pushrod engines can have an advantage in terms of valve lift- the multiplication provided by the rocker arms can give valve lifts of .6" and more, that you can't get with OHC direct-impinging systems.  OHC systems do make the engine larger and more complex, and more expensive.

For almost 20 years I've driven Ford Taurus SHO's, with DOHC 4 valve per cylinder engines.  The engines were great but they needed more cam to really achieve their potential.  My first one developed 73 hp/litre naturally aspirated, which was pretty good for an engine developed in the 1980's.  Now I have a car with the GM LS-2 pushrod V8, 2 valve per cylinder.  It develops 67 hp/litre.  The latest Ford Mustang V8 seems to be a great performing engine.  IIRC it is about 400hp out of 5 liters, which makes 80 hp/litre.  It was probably a challenge to fit that large engine into the Mustang engine compartment.


> > And the new V8s Ford and GM are
> > turning out? Wow! How'd they do that? You're supposed to have to ditch
> > the push rods to make that happen?!