Question on setting float level for a '76 QJet

[wcsinx]

Hmm.. I don't have any source for old carb parts, so I'm stuck with ordering new. Looking at Jegs, they're showing 4 different sizes of 'K' series rods made by JET. 40, 42, 43, and 44

You're saying go with a 48, 49 assuming a 77 jet

77 - 48 = .00284707
77 - 49 = .00277088

Since my jet size is an unknown, I'll order new jets as well. So if I order a 74 jet and the biggest 'K' rod they have (44) that will put me at ...

74 - 44 = .00278031

just a smidge above 2 sizes down from the stock 77 - 51

Is my logic sound? I'm itching to order parts!

Thanks!

 

[010752]

If you have a numbered set of small drill bits, you can insert the shank end into the jet. Use the size smaller than the one that won't go (similar to a Go/No Go gauge) and then mic the shank to find their size.

 

[SmokinBBC]

Check to see if they have your rods at carbs unlimited.

http://www.carburetion.com/quadrajet.asp

 

[wcsinx]

Check to see if they have your rods at carbs unlimited.

http://www.carburetion.com/quadrajet.asp

I did. That place appears to only carry the Edelbrock rods judging by the part numbers, and according to Lars those are all 'M' series. If I can get his blessing on my combo from Jegs, I'll go ahead and place the order.

thanks!

 

[lars]

So if I order a 74 jet and the biggest 'K' rod they have (44) that will put me at ...

74 - 44 = .00278031

just a smidge above 2 sizes down from the stock 77 - 51. Is my logic sound?

No. Unfortunately, your 74/44 jetting combo, although OK for cruise, will put you way too lean at WOT, and the car will run like a New York garbage truck. If you can't find any 48-49K rods, use the stock 51 rods and put in a new set of 77 jets to make sure they're correct. Compensate a little by raising the float level to about .400 and run the APT slightly on the high side (at least .030" on the piston extension). This will make the thing run pretty good.

If you have a numbered set of small drill bits, you can insert the shank end into the jet. Use the size smaller than the one that won't go (similar to a Go/No Go gauge) and then mic the shank to find their size.

Unfortunately, the jet size is not the actual size in thousands of an inch, so you can't determine the actual jet size using a drill - it will only get you close. For example, a #70 jet has a .073" diameter hole in it. You can use drill bits to determine relative sizes (one jet being bigger/smaller than another), but it won't give you an actual true indication of jet size.

Lars

 

[wcsinx]

No. Unfortunately, your 74/44 jetting combo, although OK for cruise, will put you way too lean at WOT, and the car will run like a New York garbage truck. If you can't find any 48-49K rods, use the stock 51 rods and put in a new set of 77 jets to make sure they're correct. Compensate a little by raising the float level to about .400 and run the APT slightly on the high side (at least .030" on the piston extension). This will make the thing run pretty good.

Yeah, I realized that after I posted. Once the rod lifts all the way out at WOT, I'm left with a significantly smaller hole. :banghead:

I shall raise the APT and float a bit more, and see where that gets me. It really is running much better now. I'm just being a perfectionist at this point.

Thanks again, Lars! :drink: