cam belt replacement

[keen 6]

can someone help with the cam belt replacement procedure for an m40 please and also the way to set up the cam sprocket and time it correctly

[Silver Fox 43]

Hi, if you're just replacing the belt it's fairly straight foward.

It's easiest to remove the fan shroud and fan first, remember fan is anticlock thread. 30mm?

remove the distributor cover, and rotor, 3 x 8mm bolts, 3 x 3mm allen keys

losen the alternator belt and remove fan pulley, 4 x 10mm bolts

remove bottom pulley from front of crank, 6 x 13mm bolts

remove top then bottom front covers, 9 x 10mm bolts

losen cam tensioner, 13 mm nut

remove old belt,

fit new belt without moving cam or crank,

tension belt till you can twist it 90 degrees with your fingers on the tensioner side, and then tighten the tensioner,

Replace is reverse.

You may want to replace the water pump while you have the front off?

Easy eh, just done one today.

Actually had to do the whole headgasket bit as well, but it's going again.

[Greg111 13]

Yes but what's going to stop the camshaft from rocking forward when the belt is removed? Beter to time it up first so if it does move you can just rotate the shaft back to its correct position.

[Silver Fox 43]

OK, it shouldn't move on it's own, but to be safe, set the front crank pulley to TDC, there's an arrow on the block at about 1 o'clock about 15mm from the pulley, rotate the pulley untill the tooth with the small notch on it lines with the arrow, this tooth is the 6th one past the missing teeth on the pulley. The cam sprocket has an arrow also, as well as a notch near the teeth. This should line with the notch in the top of the cam cover housing. If it's pointing to the bottom, rotate the motor thru 360 to get it to the top. At this stage you should find that the square part on the front of the cam just inside the head should be flat across the top, and if you put a straight edge across it and measure down to the side of the head on each side it should be the same. Make sense?

[keen 6]

OK, it shouldn't move on it's own, but to be safe, set the front crank pulley to TDC, there's an arrow on the block at about 1 o'clock about 15mm from the pulley, rotate the pulley untill the tooth with the small notch on it lines with the arrow, this tooth is the 6th one past the missing teeth on the pulley. The cam sprocket has an arrow also, as well as a notch near the teeth. This should line with the notch in the top of the cam cover housing. If it's pointing to the bottom, rotate the motor thru 360 to get it to the top. At this stage you should find that the square part on the front of the cam just inside the head should be flat across the top, and if you put a straight edge across it and measure down to the side of the head on each side it should be the same. Make sense?

I took the head off to be planed due to a blowen head gasket and the machinist took the cam off. and I now see that there is movement of around one tooth when the cam pulley is back on. I thought it would key on tight, but there is this movement of around a tooth which seems to me to be like a vernier pulley but not as sophisticated.There is no doubt that this is made like this but how do you time the cam. just put it in the middle or is there some other way?

[Silver Fox 43]

To do it properly there is a tool to fit over the square section on the cam just in front of the first lobe. This locks the cam in position. Then you put a pin in the block at the bottom back on the passengers side into the flywheel which locks the crank in TDC. I've made up a tool myself, but I believe that if you do as above you can do it successfully.

[keen 6]

Yes it is going to what you have said so far and you are correct it is fairly easy. Where are is the best place to get a cam belt and the best price.also does anyone have a new camshaft seal and a head to block seal on the water side new that they want to sell? ( I'm actully enjoying this and learning at the same time,it is fun)

[keen 6]

To do it properly there is a tool to fit over the square section on the cam just in front of the first lobe. This locks the cam in position. Then you put a pin in the block at the bottom back on the passengers side into the flywheel which locks the crank in TDC. I've made up a tool myself, but I believe that if you do as above you can do it successfully.

OK got that, camshaft locked and crankshaft locked, but the pulley still can move this one tooth either way.Does this not matter? My limited understanding of this is that the camshaft can be altered slightly forward of tdc or back. And can make a cam grind really good or not so good.Am I correct in thinking this? To help my understanding of this I was told to fit vernier pulleys to a twin cam I had so the rolling road guys could adjust the cams to their maximum performance level. Was I being led up the garden path or is that what is happening here? Edited April 6, 2008 by keen

[Silver Fox 43]

You are right, it is for fine tuning, due to changes in timing when you get the head planed etc, also possible slight variations in belt length and wear in the engine. I was told by a wise man that if you lock the cam in place and tension the belt on the right side as you look at it from the front, using the play in the sprocket, then tension the other side using the tensioner, and lock it up you should be right. Am I close Rusty Nuts?

[keen 6]

That is sooo cool I'll let you know how it goes. thankyou for that.