Do carb jets usually MEASURE bigger than stated size?

[Glade]

Ordered some 182.5 air correctors. I really need 180 but these are pretty cheap and I understand that air correctors generally go in steps of 20.

Out of curiosity I popped them on an optical CMM...

They measure 1.864, 1.856, 1.862, 1.852 So are up to 0.039mm oversize.

40 microns, not much really?

I guess they used a 1.82 ish drill and these are what you get.

I assume that this is fairly normal variation?

[fatjon]

1.825mm diameter = 2.615 sq mm area
1.864mm diameter 2.728 sq mm area

= +4.3%

So I would say it's within a reasonable tolerance given the tiny sizes the manufacturer is having to work with. Not sure I could do better with my black and decker.

[Pumaracing]

I've never seen one where the next size up drill bit would go through. Usually they're within a thou of nominal size. I wonder if your measuring machine really took the actual size. Try fitting a 1.825mm and 1.85mm drill bit through them if you have such to hand.

[Glade]

I don't have those drill bits to hand... but the CMM is a good one in the lab at work, calibrated, serviced etc.

They aren't original dellorto parts. Have worked with brass orifices used in v.accurate pressure regulators before and understand some variation due to tool wear, jigging etc is not surprising.

Just wondered if jets usually had a big tolerance so when the book says 180, it may well be more so the system is sort of accounts for it.

[PeterBurgess]

Over the last few years we have had many, many instances of replacement jets, needles and carb components not measuring what they are said to be. Worst case was emulsion tubes in a pair of brand new webers too short and wouldnt pick up fuel, four old tubes and we were away. I always check the jests are near enough what they say before I change anything. It is not unusual to have a range of too small to too large! I suspect it is the source of manufacture of the parts

Peter

[Glade]

Idle jets i needed arrived today... 55's.

Measure 0.57
Ah well... that's what you get for buying cheap!

[one eyed mick]

Buy undersize jets and correct size drill and you can have what you want ,weber used to offer jet reamers too or if to big solder them up and redrill [ I 've never done any of this but am told its done!!!]

[PeterBurgess]

Hi Mick, I trust you are well?

When jets are too large we solder them then re drill to the size we want to try. Some folk have called this in the past saying it is inaccurate, but, when the car leaves it is with jets suited to the application. Some folk rush out and buy new jets but it is an eye opener to those folk when they measure the 'new' 'proper' jets and find them different sizes to each other and from the size stamped

Peter