Quote:
Originally Posted by Jim Kroeger
Im rebuilding my 1930 Town Sedan motor and am adding a few upgrades such as high compression head, V8 clutch and weighted and balanced crankshaft. I know some install oversized valves and adjustable lifters but is this really necessary? Will I get more horsepower with this addition? What type of machining is involved to intall these bigger valves? Also, I hear others install a touring cam. Will a different cam make standard valves perform better or is it just used when intalling the oversized valves? Finally, are adjustable lifters recommended when using the oversized valves and touring cam or can they be used for the standard setup as well. It seems that valves will need to be reground some day but only after heavy mileage has been incured so why install adjustable lifters? My goal is to be able to drive the freeway at 55-60mph if needed on tours and I will be installing an overdrive in the future to accomplish this. Any ideas? Thanks.
|
I will try to answer your questions based on my engine experience and my dyno tests.
1)
Will I get more horsepower with large valves? Only at higher RPM and then only if you have more carburetion.
2)
What machining is involved? Cut a larger seat in the block and enlarge the passage directly below the valve. Not difficult for an engine shop.
3)
Will a touring cam make standard valves perform better? Yes...the touring cam will provide more lift and typically a different profile or duration. The engine will produce more HP. Touring cams will allow larger intake valves to add a bit more HP...if you have a larger carburetor and intake again most noticed at higher RPM.
4)
Are adjustable lifters recommended when using the oversized valves and touring cam? Yes for the touring cam for the following reason: When using a touring cam the lifter base diameter should be larger than a standard A cam requires. Many lifter bases are about 1.00" Some are close to 1.20" and these larger base diameter lifters are necessary for the higher lift cams. If you use the small base lifters (1" or less) with a higher lift cam, the cam lobe contacts the lifter close to the edge and promotes premature wear. The single-lock lifters manufactured by Colony have the larger diameter. See the photos below:
Lifter pictures: The Colony brand of lifters in single and double lock are shown below. I have purchased the Colony brand from multiple national vendors. The single lock base diameter is about 1.180". The double lock base diameter is slightly under 1" (.998").