Thread: Engine timing not stable.

Probably a worn timing chain, but first check that the centrifugal advance mechanism isn't broken (srings) or ceasing up. I just re-read your post and you say the revs seem constant, check that the outer ring of your crank pulley/dampner isn't loose, the outer ring is vulcanised via a rubber ring to the inside ring of the dampner, they have been known to come loose and eventually fall off, Regards Frank.

Originally Posted by Grimace

Last time I checked the timing I noticed that at idle, the timing was often at the preset 9 degrees but it was very eratic and going up as high as 12 and almost as low as 6 it seemed some times.




p.s. also anyone got a 4 wheel dyno that I can borrow in a week or two

Hi Grimace

Firstly .... forget about the Dyno till you check this first ....

The erratic timing is a "sign" that the cam chain could be (is IMHO) stretched ...
1 ... Take the rocker cover off
2 ... Set the crank to TDC
3 ... Put a socket with a solid breaker bar and stick it on the crank bolt
4 ... Twitch the crank left and right and watch the cam chain take's up slack in conjunction of the movement of the rocker ... If you keep twitching left and right ... You will see how many degrees the cam chain is slack by ... via the timing marker plate at the Harmonic balancer


If not the above ..
The other candidates are the Dizzy or the other gear that you have installed



Hope the check helps


Mike

It could be simply that the tuner has added advance at revs near the idle speed.

For example on the timing matrix of a Unichip ( and I am sure Haltech is the same) , you can add timing at 500RPM intervals, and some tuners will add it at 1000RPM. If the revs momentarily exceed 1000rpm the chip will add whatever is programmed.

If at 250RPM intervals it may be added at 750RPM.

I had a hot starting problem with mine after the most recent tune and had the tuner drop out all added timing and reduction in fuel at idle revs so that it reverted to stock.

Regards Philip A

Originally Posted by PhilipA

It could be simply that the tuner has added advance at revs near the idle speed.

For example on the timing matrix of a Unichip ( and I am sure Haltech is the same) , you can add timing at 500RPM intervals, and some tuners will add it at 1000RPM. If the revs momentarily exceed 1000rpm the chip will add whatever is programmed.

If at 250RPM intervals it may be added at 750RPM.

I had a hot starting problem with mine after the most recent tune and had the tuner drop out all added timing and reduction in fuel at idle revs so that it reverted to stock.

Regards Philip A

Grimace says that the revs aren't changing, with the timing moving between 6 and 12 degrees you would expect revs to rise and fall, so if revs are steady and timing is advancing and retarding a total of 6 degrees without the revs changing, seems strange, I'd be checking the front Dampner, Regards Frank.

I'd go wth either worn Distributor or timing chain at this point.

JC

knackered harmonic balancer

Sorry for the late reply, I actually typed this up while under the influence of my friend bloke in a bottle called Jack.
Then I forgot about it

A bit more info;
-The revs are constant at about 690rpm (a touch low), the revs are not changing and if so it only be a minimal amount.
-The cars starts and runs fine. (starting seems a bit delayed, takes a couple of turns, not instant)
-I already have a complete cam kit and some new heads that are going on the car, was more just curious to learn if this was common and what the main cause was.
-It could be my ****ty timing light

Either way, I will be checking all things mentioned as I begin rebuilding the top end.