Classic Australian Wooden Power Boat Association

hey guys, im about half way thru building a 202 blue motor with nine port head with roller rockers and solid cam.
at the moment the boat has a cast inlet/exhuast manifold by rolco., obviously the manifold wont flow enough either way so im hopeing to run a four barrel holley or some triples..

does anyone have a holden 6 or similar with triples on it????

the thing i want to know is, will the angle of the engine being mid mount upset the carbys???? if they wont work i'll run a four barrel with a wedge.

any one got any advice??

brian

Hi Brian,
it depends on which end you're driving from, as to what you can find in the way of manifolds. If you want to run a separate inlet to the water cooled exhaust, most car style manifolds are angled to run with the flywheel end lower and that stuffs up the angles if you want to run off the front of the crank. At least with the SU style you can make your own manifold pretty easy.

Alan.

hey alan,
the engine will be running a dog clutch off the crank,

i was going to go with some triples but setting up manifold and linkages was going to be a pain in the arse. im pretty set on a single four barrel manifold now. i'll buy a wedge or make one if i cant buy one to suit.

the engine will also be running some custom headers to run the manifold.

fingers crossed it should go ok when its done. it is meant to be a social engine but seems to be getting abit carried away now

brian

Hi Brian

A question from a novice, what is the effect of fitting roller rockers?

Joe

less friction

I've had this discussion before with a mate who spent about 15 grand on a 351 engine. My thoughts are the rollers will last longer because of the area instead of coming in contact with the same point every revolution, so therefore it is an endurance issue, but what would I know I'm not a mechanic. Is there a roller at the point the valve gets pushed

Jeff

Jeff there has been a roller at the valve end and the pivot point on every set I ever had - you can also obtain them at different ratios eg 1,5 or 1.6 to 1 - much smoother running but more maintenance regarding clearances so they dont hammer the roller bearing to pieces

The reason roller rockers are used is to stop the top of the valve from being pulled from side to side by the rocker arm. A rollerless rocker arm has an amount of friction when it contacts the end of the valve stem, as the rocker arm moves through an arc it tries to move the end of the valve stem through the same arc, thus causing wear on the end of the valve stem as well as the sides of the valve stem and the valve guide. All of these actions cause friction in the valve train, less friction in any part of the engine means more horsepower at the end of the crankshaft. Not to mention that less load in the valve train means a lot less load on camshaft lobes etc. The more efficient you can make the valve train the more you can make it rev.

Spook

Very well explained Bob, I now fully understand how it works particularily the side thrust. Next question is what is the difference in power gain between conventional and roller.

Jeff

Jeff,
The two main reasons that rollers should be used is for their ultimate strength at sustained high RPM and the ability to handle higher valve lifts than stamped OE rockers. The problem in measuring the power gain is, you can't use big cams for big power with standard rockers, and as the friction is reduced as a percentage (and a small one at that) you can't measure it at higher power outputs to get an accurate look at the difference.

Alan.