Intermittent, hesitant running

[PhilipB]

Gurus, some advice please..

 

I’ve had problems with uneven running for a while and it’s time to get it sorted properly

 

Running on twin Webbers, rally cam and initially, points distributor

 

Compression very good and very consistent and tappet clearances unaltered. Starts OK and idle speed ok after warming up, running temperature normal

 

Carburettors had been carefully set up and not touched.

 

At first I thought it might be fuel starvation but it’s a new fuel pump and all filters clean with a good supply at the carbs

 

Next step was ignition system

 

Changed, in order, points, condenser, rotor arm, dissy cap, spark plugs, plug leads, coil but with no real improvement. There is no vacuum advance and the springs are still in place with free movement of the weights. Changed to an Accuspark electronic distributor, now with a big improvement but still not quite right. Put a timing light on it to time it and the spark is jumping around, not steady at all.

 

If driven carefully, with careful application of accelerator, it’s capable of pulling strongly with no real issue but it’s as if the timing chain gets a bit of a wobble on and the engine becomes hesitant with no real response to increased throttle opening

 

Conclusion is that the timing chain tensioner is no longer doing its job

 

There are lots of posts re timing chains so was going to The Chain Man for IWIS or similar (there’s still a NOS Reynolds chain on the ‘bay?)

 

What’s the current view on tensioners? Racetorations??

 

Sprockets changed if necessary

 

Recommendations for timing cover oil seal?

 

Before I take the apron off . .

 

Have I missed anything?

 

Phil

[Geko]

"Put a timing light on it to time it and the spark is jumping around, not steady at all" Have a look at the distributor drive gear. It's unlikely that a wobbly timing chain could have that effect.

[peejay4A]

+1 for the above. I think you'd hear the chain moving around if it was having that much effect upon performance.

[Lebro]

Fuel starvation ?

 

Bob.

[ChrisR-4A]

Hi Phil, what do the plugs look like, is one carb flooding.

Is there 12v at the coil, try running a temp feed direct from fuse box or battery.

 

Is the fuel tank venting ok.

 

Is dist correctly engaged, loose or broken key?

 

Has timing wheel on camshaft come loose, is it slotted.

Chris

[Don Elliott]

If it's the timing chain tensioner, the engine will pull properly on acceleration. That's because the load it keeping the timing chain tight on that side.

 

But if you suddenly take your foot off the petrol pedal, and you hear a rattling sound from the front of the engine, then, for a few moments, the timing chain is slack on both sides and the tensioner would need to be changed.

 

You can do this with the engine compartment open and you are working on the carb side of the engine with you ear down to listen for the rattle (looseness).

[iain]

How old is the fuel?

 

Any more than a month or so and i think the consensus on here would be to go and re fill with some good petrol.

 

Certainly mine can run like a bag of horse manure on old fuel.

 

Iain

[Guest]

How old is the fuel?

 

Any more than a month or so and i think the consensus on here would be to go and re fill with some good petrol.

 

Certainly mine can run like a bag of horse manure on old fuel.

 

Iain

^^ this ^^

 

Did you check the LT leads? Contacts et all?

 

Menno