Bmc timing

[ianmi]

Hi all great forum,

I have a bmc 1.5 engine on my boat which I am reconditioning, I am about to change the timing chain but when I check the orientation before removing it,   it seems the dimples of the camshaft and crankshaft  Aline just after the exhaust valve closes! Is this correct?

the manual just says to Aline the dimples, but I would have thought the dimples should Aline at end of the compression stroke at tdc.

any advice would be greatfully received.

ian

[BEngo]

The dimples are only markers.  So long as the dimples are aligned, it does not matter what the engine position is..

 

If you have the timing diagram and a camshaft protractor you could actually check the dimples are accurately placed but it is highly unlikely that they will be wrong.

 

N

[Tony Brooks]

Never gave it a thought. BMC put the dimples there so as long as they align it should be fine but get the manual so you know where they should be so you don't get one 180 degrees out.

 

As you are altering the camshaft timing (new chain) your major problem will be getting the gauge to set the pump timing pointer but it will probably run if you use the pointer where it is, its just not best practice.

[ianmi]

Hi thanks for the response,

 

so so it does not matter! I wondered if it could be 180 degrees out?

so if the cam and crank are in sync (dimples matched) it’s just the fuel pump which is critical to be a the 5 o clock position when the engine is at 22 degrees btdc?

thanks,

ian

[Tony Brooks]

I THINK, from memory, the dimples on the sprockets should be close to each other, not on the far side of the sprockets but, please check the manual - image below.

 

I don't understand your comment about the fuel pump being at 5 o'clock at 22d BTDC unless you are talking about the master spline on the pump skew gear drive shaft. But unless you have taken the cam shaft out, that should still be in the correct position.

 

If you have taken the pump drive shaft out or taken the cam shaft out, then you will need to set the engine to 22 D BTDC to refit the drive shaft AFTER you have timed the cam shaft.

 

Pump timing is done with a gauge in the pump drive shaft at 22d BTDC, turning the gauge clockwise to take up the backlash in the drive and chain, and then aligning a pointer on the pump hub. The injector pump is fitted so the line on one corner of the pump mounting flange lines up with the pointer.

 

Unless there is a lot of wear in the cam shaft drive or pump drive skew gears, you can usually get away without resetting the pointer in marine use.

 

[ianmi]

Hi Tony,

 

I have removed the injector pump drive spindle, and yes I am referring to the master spline at 5 o clock position. Any idea where I could purchase a gauge to mark the pump timing position?