Think I'll get hold of a hard copy then. It's nice and easy to understand. Anyone got a copy they want to get rid of?
That's the only bit I did know how to do, I think. I set mine at dead level by bending the metal bit a tad - 10mm from memory. When they were set up on the rolling road it ran like dream - got over 60hp at the wheels out of a 1584cc type 1 (OK so it might have a few internal tweeks). The problems started when the idle jets got muck in them. I've lost count of how many times I've had the idle jets out (only accessed via the top on these ones, which is a pita) or even stripped and rebuilt the carbs. It seems that although I didn't change any settings that eventually they go out of whack. What I want to learn is how to keep them perfectly balanced and what kit I need to buy. Presumably some sort of gas analyser for starters. Oh and the book of course.
I assume the Webers are the same as Dells - the air intakes for the idles are down a hole. That gets bunged up and your idle goes up the swannee. Or maybe the inlet’s on the side of the holder - can’t remember. You can get kits that, I think - can’t recall exactly how they work - relocate or raise the intakes, and you bung up the original hole with a small ball bearing. Worth a look? Not to be confused with the extended idle jet holders (which I’ve got on mine).
Now you see why I need the book. You might as well have told me to replace the 7 degree pinion shaft flange.
Well, obviously you’d start with the flange, but I’d go for 10 degrees... Idle jet bungage is a well known prob. What state are your air filters in?
K&Ns cleaned and oiled and I have the K&N hairnet thingies that go over the filter. Outside of that is a home-made stainless steel 3/4 shroud to protect them from the crud coming off the tyres. I've only done 2000 miles since the build and must've done the carbs every 500 miles.
A friend came round with one of those but we didn't sort it it. We the all 4 idle screws out about 1 and a bit turns, which is how it came back from the rolling road a year or so ago. Apparently he's now got them at 2 or 3 turns. No idea what could have changed to cause that.
There is a significant difference in the idle jet position early to late IDF. Early carbs have the idle jet in the top adjacent to the main jet stack; late carbs have the idle jet in the side of the carb. Early idle jets have a chamfered seat to form a seal, late jets have an ‘o’ ring. AFAIK there are no modification kits to relocate the intakes, but I could be wrong as I’ve never looked. IMO 40’s are too big for a 1584cc (unless it’s a racing engine build for maximum bhp at high revs), especially if the normal 30 vents are still fitted – fuel metering and tuning will be difficult.
You're right for a stock engine I'm sure but this one's in my buggy and is far from stock. When set up they do run very well. I think the chokes are 32s in fact. It is a high revving engine that was built to Formula Super V spec by a guy called Andy Storer back in the 80s.
Well the buggy came home and he didn't need to nick the bus carbs, which is a relief. He found that it was running too lean which I don't understand. All four idle mixture screws were on one and a bit turns out, as he had set them on the rolling road about a year and a half ago. Now the left carb has to be 4 turns out on each and the right carb is 5 turns on each. What could have changed to make this difference? The idle jets are the same ones & nothing has changed apart from stripping the carbs and rebuilding multiple times. He was baffled too.
Yes, because of the way the book is written there is that lot written about the IDF, a bit on progressives because they have so many features, some history and tables of random data that are useful in the 1980s when your scrapped Ford Cortina would give you a free progressive Weber for instance. And diagrams of several now rare carburettors. I started reading the book again and I finally get the progressive power valve (just when you get it jetted right, a power valve opens up at high rpm when airflow speed is high and pours petrol in an extra fixed main jet for instance. Which makes 5 jets in one carb.)
Fuel pressure dropping away? Dirt again ?. Theres a reason people persist with strange things like single centremount IDFs : one barrel left, one barrel right, to do with dirt on buggies.
Fuel pressure is good I think. I really believe it's congealed ethanol residue in the idle circuits. Can anyone recommend a petrol additive that will help dissolve it? I'm going to try using "Super" grade petrol for a while as well.
I’ve run E5 and E10 through my IDF’s for the last 8 years and have never used an additive. I don’t think Ethanol is your problem – unless there has been water leaking into the tank.
You were probably sensible and used yours continually. I on the other hand left mine sitting for 6 months and not for the first time! I think this is a problem that has built up. I ordered some Seafoam SF16 to give it a try. I'll let you know if it works.
