28if mixture

[bison]

Gents,
Here's the story so far. Rene (76 TL) running pretty good, plugs a good colour, but sooty tail pipe, around 45mpg. Opened up the little hole in the manifold where the breather pipe goes in, the one below the carb with the elbow on it, it was blocked. Car instanty runs better (it wasn't that bad before) and fuel consumption much better, pulls up hills with minimum throttle, cruises with a whiff of the throttle pedal. What I'm not sure about is having to unscrew the idle/mixture screw to almost 7 turns out to get a decent tickover, to be honest it was 5 turns out before and hunted a bit. Seems like there's more fuel getting into the inlet side of things than there should be. I've checked float hight, cleaned out the carb, no change. Ignition, timing etc all checked. Starting from cold is instant, but the choke can be shut off withing 100 yards and it runs great, suspicious!. As I said, the car has never run better. Any ideas?.
Alan.

 

[malcolm]

That hose should be blocked :eek: At least a little. There ought to be a restrictor in there that limits the amount of air that can be sucked in after the carb. Hole in the restrictor is about 1mm diameter. Worth checking that's still in place.

Can't explain the improved fuel efficiency or pulling power though. That's weird. Though it's also weird to have the mixture screw out so far - feels like you are compensating for another air leak into the manifold. Possibly where the inlet manifold joins the cylinder head.

 

[bison]

Hi Malcolm,
Interestingly when I cleared the hole in the manifold I took it out to about 1.8mm, I previously made the two little breather plugs with the holes in, the smaller one at 1.5mm, removed them again as they seemed to make the idle rough, but I hadn't taken the mixture screw out to the same extent as I have now. My question is, do all the R4's have this breather restrictor fitted in the pipes?, all the posts I have seen on the subject seem to refer to GTL's.
At lunchtime I'll check the plug colour and refit the small breather, I'll try to locate my old colourtune and dust it off.
Mind you, very soon Rene is going to have a 28mm Mikuni CV carb fitted from a Yamaha Diversion, much better metering of the fuel and flows a lot more air, I'll tell you how I get on with it.
Cheers,
Alan.

 

[AdamWilkes]

hi - reading about Zenith 28if details, from https://www.scribd.com/doc/17158349/renault-4-mentnance-guide , page 229 - restriction 'jets' in the pipe from carb to the intake manifold are set to be 1.3mm.