G'day all,
Whilst installing a metal timing gear (from JP Engineering) in a mates FE today we discovered some interesting differences and possible anomolies.
1. The position of the dot on the steel camshaft gear was one tooth out with respect to the keyway from the original fibre gear. Can anyone provide any explanations?
I don't understand why it would be different unless it was incorrectly marked. Having it a tooth out would either advance or retard the camshaft, depending on which way the dot has been marked. Some gears have what they call a multi fit sprocket. These have about 6 keyways cut into them so that the cam can be advanced or retarded, depending on the use of the engine. However to have it one tooth out would be too much. Contact JP and ask them if they have had a batch that has been incorrectly marked, or seek further advice from them.
2. In the original GMH FE manual it says to line up the two dots before sliding the camshaft into position. Once the helical effect of the gear takes effect this means that the two dots will be one tooth apart once the camshaft is 'home.'
?
This is not ,meant to be the case. when the camshaft is installed the dots need to be together. Adjust the gear so that when the gear is installed the dots match.
3. Should the dots line up before or after installation, both on the metal gear and the fibre one also, given the difference I pointed out earlier.
Dots must line up.
Can someone explain to me in simple terms how to degree in a camshaft also?
Not really. not a simple job. However this is how it is done. Assuming you have a known cam profile (for example a 30/70) where the intake opens 30 degrees before TDC and the intake closes 70 degrees after bottom dead centre, the following needs to be done to degree a cam in.
First locate TDC, then fit a degree wheel to the crank securely to ensure that it does not move while the cam is degree'd in. then using 2 dial guages, (one for inlet one for exhaust) look at the cam manufacturers cam card. This should state at what degrees the cam will open @.050" lift. rotate the crank, (with cam installed in engine) to ensure that the cam profile matches manufactures card.
Degreeing a cam in is done to ensure that the camshaft profile metches the camshaft manufacturers stated claims on the card, it also ensures that all parts of the valve train have been manufatured correctly. ie dots are in place in relation to keyways etc...
In the event that you were to install a camshaft and were to degree the cam in and find that the camshaft was correct but the degrees were wrong due to a possible mismatch of crank or cam timing gears or the position in which the keyway had been cut, it gives you the point to work back from, basically a chance to work out which item is incorrect or faulty. It becomes a process of elimination to ensure that the engine will operate that way that it should.
I hope that this helps
