"spun" camshaft issue.
#1
11-03-2016, 09:01 PM
"spun" camshaft issue.
I have read many posts about this subject.
Many of the reply's I have read tell about the repair but I have not seen anything written about the cause.
Anything that comes loose or breaks does so when an external force of some kind is applied to that part. In this case, the cause is from the harmful harmonics that are transmitted up from the crankshaft via the timing chains and into the valve train. Some camshafts designs certainly induce further harmonics into the Valve train, if not break parts. So choose camshafts carefully too.
These vibrations are so high in frequency range, they cause everything to shake at very high speed. Parts bolted together can come loose, parts that are pressed together with interference are easily prone to failure.
Locking the sleeve to the camshaft may stop the sleeve from coming loose, but it doesn't stop the vibrations. The cam timing is now under threat and the performance of the engine will suffer. This is horsepower lost not made.
Yes, the sleeves have to be pressed into the camshafts but do not think you have the problem solved. Go deeper, take care of the cause and not just the result. Look for companies that offer a solution to this problem and ask them for their advice.
Many of the reply's I have read tell about the repair but I have not seen anything written about the cause.
Anything that comes loose or breaks does so when an external force of some kind is applied to that part. In this case, the cause is from the harmful harmonics that are transmitted up from the crankshaft via the timing chains and into the valve train. Some camshafts designs certainly induce further harmonics into the Valve train, if not break parts. So choose camshafts carefully too.
These vibrations are so high in frequency range, they cause everything to shake at very high speed. Parts bolted together can come loose, parts that are pressed together with interference are easily prone to failure.
Locking the sleeve to the camshaft may stop the sleeve from coming loose, but it doesn't stop the vibrations. The cam timing is now under threat and the performance of the engine will suffer. This is horsepower lost not made.
Yes, the sleeves have to be pressed into the camshafts but do not think you have the problem solved. Go deeper, take care of the cause and not just the result. Look for companies that offer a solution to this problem and ask them for their advice.
#2
03-06-2017, 07:24 PM
Though there may be some substance to your description of engine harmonics causing spun camshafts, I think the cause could be much more rudimentary. The sleeve that is a press fit into the camshaft has a tolerance on its diameter. So does the bore in the camshaft into which the sleeve fits.
It's more plausible to think that the slippage of these sleeves may occur if the tolerance buildup is to great, producing a loose fit. In other words, if the outside diameter of the sleeve is on the minimum side of its tolerance limit while the inside diameter of the bore in the camshaft is on the maximum side of its tolerance, the press fit of the sleeve into the camshaft bore may be very close to being loose. With the engine up to temperature, the thermal expansion of the camshaft may be such to render the press fit "looser" allowing the sleeve to rotate in the camshaft bore.
If the sleeve is a loose fit, then thermal expansion cycling could eventually lead to a sleeve "spinning" in the camshaft, known as a "spun" camshaft.
If the above argument is probable, then pinning the sleeve to the camshaft is a good fix.
It's more plausible to think that the slippage of these sleeves may occur if the tolerance buildup is to great, producing a loose fit. In other words, if the outside diameter of the sleeve is on the minimum side of its tolerance limit while the inside diameter of the bore in the camshaft is on the maximum side of its tolerance, the press fit of the sleeve into the camshaft bore may be very close to being loose. With the engine up to temperature, the thermal expansion of the camshaft may be such to render the press fit "looser" allowing the sleeve to rotate in the camshaft bore.
If the sleeve is a loose fit, then thermal expansion cycling could eventually lead to a sleeve "spinning" in the camshaft, known as a "spun" camshaft.
If the above argument is probable, then pinning the sleeve to the camshaft is a good fix.