Carb sizing

[dcreel]

I did do a search all over the net, and found several different opinions on how to measure the size of a carb.

So how do you tell what size carb you have? If you wanted to measure it where would you measure it. I'm trying to use a tape measure (yeah, I know) to figure out the size of a couple of carbs I have. I have heard you measure the carb id where the carb goes into the intake of the engine. I have also heard that you measure the Carb at the filter side where the slide intersects it.

Does anybody know how to do this definitively. Is a micrometer the best way to measure it? I have a PJ carb with some numbers on it but see no correlation with the size.

Help a brother out.:lol:

[juggaloclownz18]

i have been told the I.D. of the intake side, thats what i always measure, with my trusty tape of course, cause it didnt break like my other GDMF over priced tool :mad:

[haggard 2hundie]

hey juggaloclownz18 i got a quick question for ya , what whould you do with a drunken hillbilly ?

[Grizzlypeg]

I'd use an inside caliper and then transfer that into the jaws of a standard caliper or rule. I'm puzzled where the manufacturos measure as well. I'd have thought it would be the minimum diameter of the venturi, as that should be the most restrictive, but industry could pick other measuring points. I'm sure you measure it on the intake side, but where exactly?? Good question.

[dcreel]

I'd use an inside caliper and then transfer that into the jaws of a standard caliper or rule. I'm puzzled where the manufacturos measure as well. I'd have thought it would be the minimum diameter of the venturi, as that should be the most restrictive, but industry could pick other measuring points. I'm sure you measure it on the intake side, but where exactly?? Good question.

I hate to sound like a retard, but I keep misunderstanding intake side.. Is that the intake side of the carb (meaning the side the air filter goes on)? Or the intake side (meaning the side of the carb that goes into the engine's intake)?

I'm leaning towards the intake side meaning the side that the filter goes on. Thanks for any help given guys.

[juggaloclownz18]

Not sure but on blaster forum when i was shopping for a new carb for the old blasty they told me to measure the intake side of the carb (filter side)..... Thats what i always go by, but i cannot promise it to be accurate, just something i was told and go by now..... Better wait for some of the older members to chime in....

[juggaloclownz18]

hey juggaloclownz18 i got a quick question for ya , what whould you do with a drunken hillbilly ?

Id tell em to get the XxXx away from my fridge and go back home, damn neighbors what the hell makes them think they can steal my JD and coke?.... LMAO..... i wont be typing in any lyrics here, too many people might hate on me :w00t:

[Grizzlypeg]

I was thinking intake side as in the side of the carb attached to the intake manifold as opposed to the filter side.

[Slingblade]

Yes, manifold side. Just measure the inside bore on the side toward the engine. I just use a ruler with mm lines and measure across the center. If your measurements are in inches, multiply by 25.4 to get mm. (Example: 1.38 inches,(1 3/8) = 35mm, 1.49 inches (Just under 1 1/2)= 38mm) I was trying to figure this out a while back and found this on another site.

[Vealmonkey]

You measue the round circular area where the slide runs up and down. Most people say measure the intake, which is the side that is after the airfilter as this is easiest to get to since most carbs are mounted up when people measure them. The only reason that you would measure around the outside of the intake side of the carb is if you were trying to find an aftermarket air filter that has to fit around the outside diameter of the intake. The outside diameter of the intake or the outlet side of the carb outside measurement don't have anything to do with how the carb venturi is measured. And if you look, most time the outside diamter on the inlets and outlets of carbs is different anyways. Alot of the outside diameters of modern carbs can be switched around so you can use the same carb on several different machines. Some car carbs even come with replaceable and changeable venturi tubes for tuneability.