Cam timing - I've completely lost it...

[Griff]

I'm in need of some help...!! Having probably missed the glaringly obvious, I'm struggling to get the cam timing back to a basic (safe) starting point following an engine stripdown.

 

It's a K-series Roadsport A with verniers that lack any obvious marks except "I" and "E" for inlet and exhaust. The head's just been skimmed so I guess this might have a minor effect when I eventually get to the point of refining timing using Dave Andrew's method.

 

Currently the crank is at what's described in the Haynes manual as 90 deg BTDC with the pulley notch in line with the cam cover marking a little clockwise from the TDC mark (more or less as 12 o'clock). Here I start getting confused because it looks to me like this mark is about 30 deg after TDC . Anyhow, drinking straws down the plugholes tell me pistons are about midway up the bore. Rotating the crank pulley clockwise (viewed from the front of the engine) and pistons 2 & 3 drop, pistons 1 & 4 are rising.

 

My main question is without any other reference points how do I get the cams to the right starting position?

 

Also, should I reset the the verniers to their midway markings now, or maybe advance the exhaust, retard the inlet a little to begin with to be extra safe (DVA suggests 10 degrees).

 

Goal is to be back on the road for New Years Day, but the clock is ticking and other chores are piling up. Any useful pointers really appreciated.

 

Cheers

Mike

 

 

[Englishmaninwales]

Griff

You must use the timing mark on the front rim of the pulley, align it with the cam cover mark at 12 oclock. This will be 90 BTDC.

 

Safe starting point is the inlet retarded 10 deg and the exh advanced 10 deg.

 

Malcolm

Edit to add: You will need to transfer the timing marks from the std pullies to the verniers, this is detailed on Dave 's web page.

 

Edited by - Englishmaninwales on 27 Dec 2007 16:52:11

[Griff]

I should have said, I don't have the standard pulleys so can't transfer those marks over. Have had a close look but can't spot any markings on the end of the camshaft either. Maybe I should try to borrow some standard pulleys - anyone near Cirencester got a pair???

Cheers!

[Casbar]

I think I've got a pair, but live in Salisbury, so there might be someone nearer

[Ivaan]

Griff,

 

Have you removed the cams from the head, or just taken off the cam belt?

 

Clive

[Peter Carmichael]

There is a simple way to eyeball the settings into the right alignment.

 

Starting from your 90 BTDC, set the cams so that the inlet cam lobes on #1 are ~45 degrees away from opening the inlet follower. Set the exhaust cam so that it is about 45 degrees away from closing the exhaust.

 

After tensioning the belt and removing the cam locking tool, very carefully rotate the crank towards TDC, being prepared to stop at any point if there is mechanical contact. If (using the straw) when you get to TDC, the inlet is slightly open and the exhaust is slightly open, then you are there. If either cam is not open, return the timign to 90BTDC (turn the crank anti-clockwise) and try moving the offending cam a tooth.

 

You need to be really careful setting the cambelt back on the pulleys exactly the same after each change in timing otherwise you could get mechanical contact from moving too far. Mark the pulleys (even if just temporarily) and you should be able to see the relative position from your marks after each time you loosen/adjust/tension the cambelt.

 

The main thing to help you get out of your current predicament is to look at getting the cam lobes 45 (actual) degrees away from their respective intended positions at TDC while you're setting them up at 90 BTDC. The inlte lobe (on #1) will be pointing up away from the follower at 45 degrees (towarsd the centreline of the engine). The exhaust cam lobe on #1 will be just after full lift.

[Griff]

Thanks for the tips. I'll give these a go and gingerly rotate the engine by hand to check nothing interferes. Am hoping to lay my hands on some standard pulleys later today to double check before the engine goes back in.

 

Cheers *thumbup*