Hi,
I need some help regarding my SC engine (616/16). So far I haven't been able to find the nominal value of the clearance between the top of the cam and the bottom of the rod when they cross each other (in the case of an SC crankshaft and a standard camshaft).
What is the acceptable and reliable minimum value for the clearance specially when considering a new camshaft (Neutek SX-1) ?
Thank you and best regards
Herve
Rods and camshaft
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Re: Rods and camshaft
Herve
That issue should never be a problem unless something is amiss. If you are using different cams/timing or Carrilo/Crower rods then you have to be the "engine builder" and create the clearance you can live with by the best means available.
Bonne Chance
jacques
That issue should never be a problem unless something is amiss. If you are using different cams/timing or Carrilo/Crower rods then you have to be the "engine builder" and create the clearance you can live with by the best means available.
Bonne Chance
jacques
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Re: Rods and camshaft
Herve,
How lucky do you feel? How high are you going to rev the engine? How stiff is the crank; is it cut undersize? All the racers run that clearance very close but probably no less than .020"/.50mm and they do so with the highest quality parts available. The cam grinders change, reduce, the base circle dimension to get more lift on the hotter cams without having the lobes crash into the rods. This of course creates less surface area for the tappets to work against per rotation therefore shortening cam life. Add to that the fact that more aggressive cams require stiffer springs to control the more lively valve action and long term reliability goes away fast. That means that the cam grinders make the cam as big(base circle) as possible without hitting the rods. This means that every different cam grind will be ground on a different base circle so that the lobe barely misses the rods. Stock cams have lots of room. Carillo rods have bolts that poke out of the threaded holes and it is common to have to grind part of the bolt off while the bolt is torqued into the correct position. Sometimes the rod itself is ground slightly. These are some of the reasons that serious race engines are expensive. They are assembled and taken apart many times before everything is fitted correctly.
How lucky do you feel? How high are you going to rev the engine? How stiff is the crank; is it cut undersize? All the racers run that clearance very close but probably no less than .020"/.50mm and they do so with the highest quality parts available. The cam grinders change, reduce, the base circle dimension to get more lift on the hotter cams without having the lobes crash into the rods. This of course creates less surface area for the tappets to work against per rotation therefore shortening cam life. Add to that the fact that more aggressive cams require stiffer springs to control the more lively valve action and long term reliability goes away fast. That means that the cam grinders make the cam as big(base circle) as possible without hitting the rods. This means that every different cam grind will be ground on a different base circle so that the lobe barely misses the rods. Stock cams have lots of room. Carillo rods have bolts that poke out of the threaded holes and it is common to have to grind part of the bolt off while the bolt is torqued into the correct position. Sometimes the rod itself is ground slightly. These are some of the reasons that serious race engines are expensive. They are assembled and taken apart many times before everything is fitted correctly.
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