Weber Jet alert!
 

So check this shit out! I took out my main jets and they say 180 right. That's supposed to be 1.8mm, so I insert my micrometer and they both read 1.63mm. I figure that I'm not useing it right but I drill 'em out to 1.85 according to my micometer. I take my jets to the weber shop and put them on a Weber jet feeler gauge, and it says they're 180's. And that's after I drilled them out. So all this fucking time I've been rollin around with 160 main jets. No wonder it detonated. Also I had ordered 65F9 idle jets that turned out to be 65F8's. And kids the lesson is "never put a jet in your car without sticking a feeler gauge and micrometer in it first!"

It is my understanding that the numbers stamped on the sides of the jets are not necessarily the physical size, but more of a measure of the absolute volume of fluid the jets are capable of flowing.

No it's supposed to be the diamater of the orrifice in 100ths of a mm.

interesting stuff. Could be the reason why I had such weber tuning problems before...

Yes, weber and dellorto have been known to do this. I've had four idle fuel jets that were different size from stamped. Bought a jet feeler gauge for peace of mind.

thats kinda bad then. if it is stamped a size it should be true?

Quality Control.

You are 100% absolutely wrong it's the size...
Spain has no quality control. Weber designed in Italy manufacturered in Spain. Shit they were on strike for 5 years. I bet the shit right before the strike was all crap made by disgruntled employees. Hense all the shit people are getting. LOL!

Where does one find one of these gauge sets?

cbperformance.com

two size ranges, bought both

Thank you Sir.

Thanks for that info, I'd better check all my jets.

Weber Info is important I'm going to bump this thread until it ha 1000 views. I suggest it be archived

top!

A good peice of info.

Rated.

I just found one. My 200 main jet is bigger than my 220. Hhhhmmmm? Thanks Hyper!

Ed

Ed,
Your mail box is full!!!!

Mel, I'll clean it up!

Thanks, Ed

According to books I have read, most recently Weber Carburetors by Pat Braden, the numbers stamped on the side of the jets doesn't necessarily correspond to the actual size of the jet itself.

"Air-correction jets, main jets and idle jets all have numbers expressing their actual flow rates in hundreths of a millimeter. A 115 main jet flows the same amount as a perfect hole 1.15 mm in diameter."

By drilling out the passages for fuel and air, there is no possible way to create a perfect hole. There will always be slight (sometimes not so slight) imperfections. Because of this, and in order to keep jet pairs matched, Weber has stamped the flow rates with respect to a perfect hole. I imagine the engineers at Weber flow test each jet, and compare the numbers they get with theoretical numbers for "perfect holes" attained through thermodynamic laws.

Look at your main jets. You may see that passages are different sizes, but also look at the shapes of the entrance and exit of the jet. I am sure you will find differences there as well. These differences will create turbulence that will certainly cause two jets of different passage size to flow the same amount of fuel.

Sounds like what Holley is doing. They have 2 grades of jets. The higher grade, more expensive ones, are calibrated within a set percentage of the # stamped on them. The standard jets are close to the #, but not as accurate.

Bullshit... Weber sells feeler gauges for drilling out jets. There is no quality control in Spain. Especially for a company that was on strike for 4 years... Your book is wrong. Weber has not changed it's process for 50 years... Why would they. I get my jets from a Ferrari/Lotus/Austin shop they've been doing weber stuff since the 1960's and they're pros I trust their info and they were right. Now my car runs right. Explain why I got 65f8's stamped 65f9. The F size of the idle jets in nonnegotiable. QUALITY CONTROLE DOES NOT EXIST WITH JETS!!! :Kill1:

Having 65f8s stamped as 65f9s is a problem I can see happening. I work in a factory that produces electrical assemblies for aircraft, and I have witnessed with my own eyes, parts that have been mis-stamped. It happens.

As far as Weber not being able to sell properly sized jets, I don't really know what the story is. It seems that a company should be able to check the sizes of their jets, regardless of how poor their quality control is. According to 13BTOY, his 200 was larger than his 220. This is a huge deviance in size. I fail to believe that Weber is so bad in QC that they couldn't find this problem before the jet shipped out.

If Weber is so poor at quality control, then why do you trust their feeler guages? Are they not inspected by the same people, or what?

I am just restating what I have read on several occasions. I feel this is a possible answer to the mis-sized jet problem.

Its a bad batch of jets. I never seen this issue with the older ones. But who am I to say since I been drilling them out to match my application instead of buying new ones.