Engine coughing about once every two seconds

[nwxh]

The rattling hasn't gone away, but I think I will take the engine out of the car in a few weeks time.

I tried to do a tune up after the engine was (I think) backfiring going down hill. I've noticed that, at a higher idle, the engine will cough about once every two seconds, which sounds like a burst out the back of the exhaust. Is the exhaust potentially leaking where it connects to the engine?

[bmcecosse]

Could be - is it noisy? Can you feel the hot gas if you put your hand round....obviously this with a cold engine -just started...

[nwxh]

By the manifold? No, but then there's the random heat shield on the left side of the engine under the carb. I could put my hand under.

Otherwise is it just bad tuning? Even using the screwdriver to push the piston up a little, I can't be very precise with the carb adjustment, i.e. can't tell the different between two flats.

[nwxh]

It felt hot, but no gusts so I assume normal. It did feel hotter at the exhaust to manifold"join". The manifold is very rusty, but no point replacing right? How do people get theirs shiny and protected? Wire brush and polish?

Where does the spring for the "choke" usually attach? For mine it's on a heat shield which covers the manifold. I wonder if that's a "hack" for a known a problem...

[nwxh]

Could it be a valve issue too, or would a good compression ratio rule that out?

[The vast minority]

Could it be a valve issue too, or would a good compression ratio rule that out?

Compression ratio is designed in and set and cannot change without mechanical alteration.
Compression can change and does change as things become worn.

Your problem could be anything, make a vid and we can listen to and see the problem.
Al

[bmcecosse]

Measure the compressions by all means - but sounds like Ignition problem to me.

[nwxh]

Not advanced enough? I retsrded it after hearing a quiet rattling up hill in 4th.

[bmcecosse]

You can only try. You need to realise that only tiny adjustments are required....

[nwxh]

You can only try. You need to realise that only tiny adjustments are required....

I find that hard with a 45D admittedly. Have bought a sharpie to see if it helps (drawing a marker line and one every time it peaks before I retard it).

[bmcecosse]

Did the coughing only start when you retarded it ?

[nwxh]

I didn't notice it after immediately after retarding it but it's possible. I've never been quite happy about the ignition timing or carb setting as they seem too vague, especially the carb as there seems to be a long range for which the engine speeds up slightly when the piston is lifted.

[bmcecosse]

That's when you do a plug colour check after a good run !