Valve timing. Wrong?

Post by **Axolotl** » Fri Sep 29, 2006 2:23 pm

I've just spent a happy half a day fitting a duplex timing chain kit, and now the engine feels very sluggish. (Won't make 70, have to change down to 3rd for hills that I used to make in top.)

Could I have got the valve timing wrong by one sprocket tooth?

It was basically a case of pull the old sprockets and chain off, and replace the new set without moving the crankshaft or camshaft, and I thought I had the dots lined up when I assembled the sprockets and chain.

I've checked the valve timing according to the book, and it looks like the pulley mark is on TDC with No. 1 inlet valve just starting to open, with the rocker cearance set to 0.024" (per the manual for checking valve timing), but it doesn't give any clue how far out it would be if the chain were one tooth out. Would the engine still run?

Is that check one that it would be very obvious if it were out, or one where it there would only be a fraction of a difference visible?

Post by **kotemaori** » Fri Sep 29, 2006 3:12 pm

sounds from experience the dots werent exactly lined up, pull it off a start again

Post by **Kevin** » Fri Sep 29, 2006 3:39 pm

and I thought I had the dots lined up when I assembled the sprockets and chain.

But were they when you took it off ?
Have you got a timing light to see if things are out.

Post by **Axolotl** » Fri Sep 29, 2006 4:06 pm

I haven't checked the ignition timing, I was thinking that swapping gears would only affect valve timing. Doh! Of course, the distributor is driven off the camshaft, so if that's out, the ignition timing will have changed.

I'll check (Monday now), and see. I think it is as Kotemaori says. Pull it all off and start again...

Post by **bmcecosse** » Fri Sep 29, 2006 9:15 pm

Just a point here - if it's a 1098 engine - on the later Metro engines Rover used exactly the timing and lift of the (1098 engine) AEA 630 camshaft - BUT they timed it forwards by 4 degrees having discovered this gave both better performance and better mpg. So if anyone is looking for a little 'free' power boost - consider buying and fitting a 4 degree offset key for the camshaft!! { Rover did this by making a new camshft - but the effect is the same by using the offset key and a AEA 630}.
In this case - to check the valve timing - remove the rocker cover and crank the engine to tdc on #1 cylinder - the inlet and exhaust valves on whichever cylinder is then NOT on compression (#1 or #4) should be open by exactly the same amount. This is known as the the overlap at TDC - and is a true measure of correct camshaft timing. To measure this you really need a dial gauge - but something (not nearly as good) could maybe be done with a straight edge and feelers from the adjacent valves - or some other datum point. And yes - if the timing is out by one tooth the engine will run very poorly. Your idea of checking the ignition timing will show if there is now a gross error. One tooth is about 15 degrees if I remember correctly.

Post by **rayofleamington** » Fri Sep 29, 2006 9:32 pm

replacing a worn timing chain with a new one will affect the dizzy timing, therefore replacing with an aftermarket duplex kit is going to be at least as significant.
My guess is the dizzy needs moving a bit before you can judge how much the power is affected.
If that fixes it - great! If it doesn't, at least you know you checked it before wading in and stripping things down.