Quadrajet Overhaul
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,404
Likes: 418
From: Chester Virginia
Quadrajet Overhaul
I have just starting overhauling my quadrajet carb. Should I replace the primary jets and metering rods or just reuse the existing ones? The carb has 100,000 miles on it and it is 28 years old. Just wondering if the minor wear on the rods and jets could make a difference? I do not want a new/rebuilt carb. I am trying to kept the Vette original when possible and practical.
Roger
Roger
Racer
Joined: Oct 2001
Posts: 274
Likes: 2
From: Pampa Tx
Re: Quadrajet Overhaul (RMS73)
Should be fine unless someone has been messing with it. If you aren't familiar with Qjets, be sure to read Lars Qjet tuning paper to get the top performance out of it.
Phlash 72 BB Roadster :seeya
Phlash 72 BB Roadster :seeya
Le Mans Master
Joined: Sep 2000
Posts: 6,036
Likes: 2
From: Westfield Indiana
Cruise-In III Veteran
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Cruise-In V Veteran
Re: Quadrajet Overhaul (Phlash)
Another good resource for Q-jets is the book 'Rochester Carburetors' by Doug Roe. I bought my copy at the local bookstore. Lars is a great resource, but I try to find out as much as possible on my own and ask questions only when necessary.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Quadrajet Overhaul (RMS73)
Roger -
I've never seen jets or rods suffer any wear whatsoever. There is slight movement between the two parts (jets and rods) during normal operation of the power piston, but there is no load or force on the parts. I've measured tons of jets and rods over the years, and I've never seen jetting parts with any wear. Providing the parts are the right size and free from obvious damage, re-use what you have.
But this brings up an interesting point. These old carbs have almost always been messed with over the years. Be sure you check the correct jetting/rod combo for your carb number before you assume that what's in it is correct. The carbs I receive for rebuilding are most often not jetted correctly for the carb number or vehicle application. Getting the jetting back to its correct, stock spec is a great place to start for a good carb tune.
If you need any of the specs or any help during your setup, don't hesitate to ask.
I've never seen jets or rods suffer any wear whatsoever. There is slight movement between the two parts (jets and rods) during normal operation of the power piston, but there is no load or force on the parts. I've measured tons of jets and rods over the years, and I've never seen jetting parts with any wear. Providing the parts are the right size and free from obvious damage, re-use what you have.
But this brings up an interesting point. These old carbs have almost always been messed with over the years. Be sure you check the correct jetting/rod combo for your carb number before you assume that what's in it is correct. The carbs I receive for rebuilding are most often not jetted correctly for the carb number or vehicle application. Getting the jetting back to its correct, stock spec is a great place to start for a good carb tune.
If you need any of the specs or any help during your setup, don't hesitate to ask.
Melting Slicks
Joined: Aug 2001
Posts: 2,833
Likes: 15
From: Southeast La
Re: Quadrajet Overhaul (RMS73)
RMS73,
Unless you have one of my old race Qjets....it probably has the same jets and rods it came from the factory with. ;)
I used to drill my own jets to try and optimize fuel flow, particularly the secondaries and especially with N2O. I have also 'modified' metering rods (I found it easier to taper and file my own rods than to scour junk yards looking for spare rods and jets) to get a desired point difference in the rod and the jet orifice. :jester Financial deprivation sometimes leads to extraordinary creativity.
Unless you have one of my old race Qjets....it probably has the same jets and rods it came from the factory with. ;)
I used to drill my own jets to try and optimize fuel flow, particularly the secondaries and especially with N2O. I have also 'modified' metering rods (I found it easier to taper and file my own rods than to scour junk yards looking for spare rods and jets) to get a desired point difference in the rod and the jet orifice. :jester Financial deprivation sometimes leads to extraordinary creativity.
