Engine Vibration

[Dave-R]

I have noticed the left mixture screw does not make much difference to the tick over if screwed right in, but does get unhappy if wound right out thou. The only thing I have not changed is the ignition module now.

Usually a sign you either have a fuel leak from the carb into the engine OR don't have enough initial timing so you have the throttle open too much to get the correct idle speed.

[Wolfman]

I have noticed the left mixture screw does not make much difference to the tick over if screwed right in, but does get unhappy if wound right out thou. The only thing I have not changed is the ignition module now.

Usually a sign you either have a fuel leak from the carb into the engine OR don't have enough initial timing so you have the throttle open too much to get the correct idle speed.

When it stops raining I will see what timing it has, Can't remember off the top of my head it's probably been 10 years since it was timed up.

[Wolfman]

Okay I spent some time on this today. The timing has been set at 8* for as long as I can remember, so I tried taking it up to 14* to see and it was not bad seemed crisp on throttle response too but did not like the vacuum pipe plugged in. I then dropped it to 12* and still not happy, so now I am back where I started at 8* As it seems happiest there If I was doing it right I think total timing was 38* . As I have no idea what was done to the engine before me. I will have to wait for the Module to come to do much more in case it is messing up results. Also there is definitely a ticking coming from 1 cylinder and when cold it is very noisy and takes ages to quieten down a bit.

[Dave-R]

Okay I spent some time on this today. The timing has been set at 8* for as long as I can remember, so I tried taking it up to 14* to see and it was not bad seemed crisp on throttle response too but did not like the vacuum pipe plugged in. I then dropped it to 12* and still not happy, so now I am back where I started at 8* As it seems happiest there If I was doing it right I think total timing was 38* . As I have no idea what was done to the engine before me. I will have to wait for the Module to come to do much more in case it is messing up results. Also there is definitely a ticking coming from 1 cylinder and when cold it is very noisy and takes ages to quieten down a bit.

You don't have enough initial timing to be running on the carb idle system at idle.

Get a vacuum gauge to measure manifold vacuum.

Set the total @ 3000rpm to 34 degrees with the vacuum line off the distributor and plugged.

Then reconnect the vacuum line to MANIFOLD vacuum - NOT the port that feeds from above the throttle blades.

Starting with the idle mixture screws 1.5 turns out, get the idle speed set to around 800-850 rpm. Make a note of the vacuum reading. Use a T-piece in the distributor line if needed.

Turn each idle mixture screw IN by a quarter turn.

If idle speed and vacuum go UP turn the screws in more.

If idle speed and vacuum go DOWN turn the idle mixture screws OUT.

The idea is to turn the screws a quarter turn together in and out to find the position where idle speed and manifold vacuum are only JUST at a maximum.

Then reset the idle speed to around 800 rpm and do the process again to check you have the screws out JUST enough to give you max rpm and vacuum.

[Wolfman]

I have followed the instructions to the letter this afternoon Dave. Luckily my balancer is marked up as needed which helped. I also have a Vacuum gauge fitted all the time as my good old Dad did but not a rev counter . Anyway I have about 18 bar vacuum on tick over too. So I will have to wait for the module to try and sort the fluffiness/missing thing going on, checked coil and module voltage and that is stable too. :-

[Wolfman]

Update I have now fitted the module too and she is running a lot better. I still have the vibration so today the misses kept the revs up and I had a feel around to try to narrow down the area, It seemed to be around the rear gearbox area. So I removed the bolt from trans crossmember to rear rubber mount and lo and behold the vibration was a hell lot less, So do I have a bad new rear mount?. Trouble is where do I get a good quality one from to cure this?.

[Pete]

Poly Trans mounts are by far and the best, but - you have guessed it - they are the most expensive and you have to use the housing from your old mount to retro-fit it in...

[Wolfman]

Poly Trans mounts are by far and the best, but - you have guessed it - they are the most expensive and you have to use the housing from your old mount to retro-fit it in...

Would poly bushes transmit vibration too? that is why I had bought a standard one. Frying pan into fire comes to mind. I might try to get another brand to see if it is different.

[Dave999]

i used a standard rubbery one about ten years ago...
the metal parts were rusty in the packing so i de rusted and painted the whole shooting match in the smooth hammerite i had left over from when i did my armrest cusions

i apply paint like the evarge joe applies marmalade i.e not a skill i have tuned in any great way .. but seesm to have helped here

bit daft for rubber but hey i was in a hurry.... seems to have inadvertantly kept the rear main seal oil leak off the rubber i.e it has not turned to mush, yet

Dave