Just a quickie - I have had to put my Traction project on hold for the past few days (not because of christmas) due to my son's Renault 4L breaking down.

I have fixed most of it (stripped head, cleaned all valves, replaced carb, plugs and cables, sucked out 30 years of coolant sludge...... that is why it was overheating in traffic ) but I am a little stumped on why it is running lumpy now.

I am 99.9% sure I have the spark plug leads matching the haynes manual

But when I pull the lead off each plug this is what happens;

1 - engine revs speed up
2 - engine revs drop near to cut out
3 - engine revs speed up
4 - engine revs drop and cut out

What do you think - possibility of 180 degrees out?? It starts and runs but absolutely no power on the road, timing seems ok with a strobe light - I did reset all the tappets, could I have reset them backwards . A little stumped and fed up with chasing my own arse.....plus I want to get back onto my traction

No, it wouldn't run if plug leads were wrong...

It sounds to me more about air leaking between carb and engine, maybe broken gasket etc. under carburator, and that causes lean mixture...

hmmm, just replaced all the gaskets with new.

Same with the manifold gasket onto the head.

Still stumped

i had a similar problem with my 5HP. The ignition point was too late. Prehaps do a test with a strobe-lamp.

If you pull a lead off and the engine runs the same then the lead is wrong. If it starts to run bad then the lead is at the right place... Is youre camshaft at the good spot. Timing wise????? It must be at the exact right spot timingwise otherwise you can have these symptoms. And as azl57 says is your ignition timing right????? Please check all this when your leads are correct (as you say)..

Is the cam chain drivven????

Yep, chain driven. I have not touched this at all.

I used a stroke and I am 10mm in advance on the timing marker (as per the Haynes Manual)

I tried the leads in the opposite positions and no start at all. In theory I did not touch the cable at all until I changed them and put them in place one by one.

I will have another go.

You said "i stripped the head" are you sure you didn move the chain or put the distributor back with the wrong tooth. Something must have happenn... Is your valve play good??? Can you feel compression on all cilinders????

Head is independent of the chain and the distributor mech.

I set the valves per the book and double checked them when they were warm.

Compression is on average 10 bar on all 4 (it got better after cleaning the valves).

When I put it all back together I had the same fault of the car not starting. I changed the carb for a spare and it started and runs well, but no power at all on the road.

Isn't this a pushrod engine, so it's irrelevant how the cam is driven?
Might be worth checking which direction the pulley rotates...

Just checking Ken. (No not you) Trying to let him solve his own question/problem.. So whats the story bejind the pulley
??