camshaft replacement

[boxer]

I am replacing the standard us cam with a new 150 bhp cam my querie is every book i read says to set the pistons with no. 1 firing and no. 6 on the rock i checked my cam timing on the existing us cam and the only way all the dots line up is when no.6 is on compression stroke is this unusual .The engine ran perfectely as it is timed at present

[marvmul]

I am replacing the standard us cam with a new 150 bhp cam my querie is every book i read says to set the pistons with no. 1 firing and no. 6 on the rock i checked my cam timing on the existing us cam and the only way all the dots line up is when no.6 is on compression stroke is this unusual .The engine ran perfectely as it is timed at present

The books are correct, but if the camshaft is fitted like on your engine, I think that the oil pump and distributor driving gear should be fitted 180° out, then the timing of the distributor is correct and your engine will run perfectly. So, on your engine, the rotor should point to lead no 6 instead of lead no 1 when the dots on the distribution sprockets line up .

[boxer]

The books are correct, but if the camshaft is fitted like on your engine, I think that the oil pump and distributor driving gear should be fitted 180° out, then the timing of the distributor is correct and your engine will run perfectly. So, on your engine, the rotor should point to lead no 6 instead of lead no 1 when the dots on the distribution sprockets line up .

Thankyou for your reply but what i am not sure of is do i put the new camshaft in the same way or the way the books describe with the dots lining up and firing on no.1

[marvmul]

Thankyou for your reply but what i am not sure of is do i put the new camshaft in the same way or the way the books describe with the dots lining up and firing on no.1

I would do it like described in the books, because when fitting a new camshaft, you have lost the position of the distributor driving gear anyway. It can be difficult to make engage this gear with the drive shaft of the oil pump.

The slot of the oil pump drive shaft should be in a 45° position, pointing to the rear and towards the engine blok, before lowering the gear. You have to take into account that the gear will turn clockwise a bit when it is lowered, because it is engaging with the gear on the camshaft.

[BrianC]

If you do it 'by the book' you should at least save any future owner/mechanic having problems or concerns when fault-finding or tuning.

[Andy Moltu]

If you do it 'by the book' you should at least save any future owner/mechanic having problems or concerns when fault-finding or tuning.

 

That assumes the dots on the crank & cam sprokets are stamped in the same relative position for the different cams (eg USA spec & 150CP cams)

[marvmul]

That assumes the dots on the crank & cam sprokets are stamped in the same relative position for the different cams (eg USA spec & 150CP cams)

That's right, and to be on the safe side, one should always check the valve timing when fitting a

new camshaft. The installation figure (position of the CRANKshaft with maximum opening of the inlet valve no 1) can be calculated from the valve diagram : for most camshafts it's about 104° after TDC : {90° +(degrees ABDC the inlet valve is closing - degrees BTDC the inlet valve is opening)/2}

The distribution chain must be fitted when the crank is at this position and the camshaft in the position with maximum inlet valve no 1 lift.

Alternatively you can check if the valves of cylinder no 6 are both a bit openened evenly when the crank is at TDC and the no 1 cylinder is firing.