Cliff's Quadrajet Parts and Rebuild Kits

General Category => Quadrajet Carb Talk and Tips => Topic started by: Brian B. on November 07, 2021, 02:10:14 PM

Title: #7044270 Idle Tube & Idle Down Channel Restriction Measurements
Post by: Brian B. on November 07, 2021, 02:10:14 PM

Would anyone be able to confirm what the factory measurements for these openings should be? Using numbered drills I've measured the following on mine as close as I could but not certain if these have been altered in the past.

Idle Tube:  .0465"  Drill #56
Idle Channel Down: .052"  Drill #55

Thank you.

Title: Re: #7044270 Idle Tube & Idle Down Channel Restriction Measurements
Post by: Kenth on November 08, 2021, 12:33:42 AM

An original 7044270 has .038" idle tubes and .057" down channel restrictions.

Title: Re: #7044270 Idle Tube & Idle Down Channel Restriction Measurements
Post by: Brian B. on November 08, 2021, 04:21:31 AM

Thank you Kenth.  My engine with no VIN stamping came from the Pontiac Engineering garage during the '74/'75 time period and I now wonder if they may have changed the carb internals. Hmmm.

Title: Re: #7044270 Idle Tube & Idle Down Channel Restriction Measurements
Post by: Brian B. on November 08, 2021, 05:26:01 AM

I could have made an error when measuring too.  If I have the carb apart again this Winter, I will re-measure.

Title: Re: #7044270 Idle Tube & Idle Down Channel Restriction Measurements
Post by: Brian B. on November 16, 2021, 05:53:31 AM

As a follow-up and point of clarity....the idle tube for my carb is .038".  I measured incorrectly the first time and re-checked.  Sorry for any confusion.

Title: Re: #7044270 Idle Tube & Idle Down Channel Restriction Measurements
Post by: Cliff Ruggles on November 17, 2021, 05:12:16 AM

What are you using to "measure" them?

The most accurate will be using a precision numbered bit in a small pin vise.   Be aware that many cheap "import" numbered drill bit sets are not very accurate.  I would verify the size of the bit with a good micrometer and avoid imported bit sets altogether.  Even if they are the correct size they break WAY too easily for my liking.

Best to step up and buy the better USA made sets instead......IMHO.....

Title: Re: #7044270 Idle Tube & Idle Down Channel Restriction Measurements
Post by: Brian B. on November 17, 2021, 06:16:43 AM

I used an imported numbered drill set that I found to not be accurate.  I now check each drill with a two different micrometers.  One of which My Dad, a retired tool designer from International Harvester, gave me. His old school Lufkin No. 1911 Micrometer is dead on and my "go to" device now.

Title: Re: #7044270 Idle Tube & Idle Down Channel Restriction Measurements
Post by: Cliff Ruggles on November 19, 2021, 06:30:42 AM

The Chinese have improved their drill bits considerably over the years, but most are WAY too hard, often not sized correctly and break easily.  We don't see big problems with larger ones, but in the smaller sizes I find them pretty much useless for working on carburetors.  They will break without warning and cause more trouble than what they are worth.  IF you using precision drill bits for this sort of work, "cowboy" up and buy the good stuff and some pin vises to hold them and you'll get better results and sleep better at night!.......FWIW....