Decompression Tube Consult
Posted: Mon May 02, 2011 5:49 pm
I'm a bit confused.
I've read that adding a decompression tube with a big bore kit is a good thing to do to help balance out the increased crankshaft pressure to protect the seals.
I understand that one end is connected to the dipstick port, but I'm a bit confused on why some people connect the other end to the valve cover vent? Then I assume plug the displaced tube leading to the intake manifold, which I believe is more of a pollution control element to pull crankcase vapors back in to the engine be burned.
The crankcase and the valve cover are already internally vented to each other via the timing chain through-way. Adding the external circuit seems superfluous. Am I missing something here?
I would think the other end should be open to atmosphere, but then unfiltered air could be pulled into the crankcase, then up through the valve vent into the intake manifold. Granted the cross-sectional area of the decompression tube is significantly smaller than the air-intake c/s area, but some dust and dirt could still be pulled into the combustion chamber. Or would the dust get trapped by being pulled through the oil? Would the air-fuel ratio change enough to require a rejet?
So which, if either, is the right approach?
I've read that adding a decompression tube with a big bore kit is a good thing to do to help balance out the increased crankshaft pressure to protect the seals.
I understand that one end is connected to the dipstick port, but I'm a bit confused on why some people connect the other end to the valve cover vent? Then I assume plug the displaced tube leading to the intake manifold, which I believe is more of a pollution control element to pull crankcase vapors back in to the engine be burned.
The crankcase and the valve cover are already internally vented to each other via the timing chain through-way. Adding the external circuit seems superfluous. Am I missing something here?
I would think the other end should be open to atmosphere, but then unfiltered air could be pulled into the crankcase, then up through the valve vent into the intake manifold. Granted the cross-sectional area of the decompression tube is significantly smaller than the air-intake c/s area, but some dust and dirt could still be pulled into the combustion chamber. Or would the dust get trapped by being pulled through the oil? Would the air-fuel ratio change enough to require a rejet?
So which, if either, is the right approach?