Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
Lean idle
Sonny:
DCR confounded me too at first. In the book it is noted as Idle Channel Restrictor.
On my Quadrajet the DCR looks like a brass cup pressed into the idle down channel. The cup has a small hole drilled in the bottom. Your logic for opening the restriction to fatten the idle makes sense to me.
Please take my newbie status into account when considering my reply. ;D
53Olds:
Sonny, that clears up the "What is a DCR?" issue perfectly.
I can fit a .039" drill bit into the hole with wiggle room, but a 1/16" (.0625") bit is too large to fit, so I'm not sure I want to just enlarge it without more precise measurements. Recipe One calls for .046", Recipe Two calls for .052-.055", Recipe Three calls for .059-.064".
I'll wait a bit for Cliff to weigh in. I'd hate to open it too far. :-[
Sonny:
Yes wait for input from Cliff!!!!
Also consider checking for obstruction in the orifice at the bottom of the idle tube. Mine had gunk there and after a cleaning the measurement was .006 larger
Cliff Ruggles:
Not sure why you would drill the holes under the mixture screws to .125", that is HUGE and the metric mixture screws may no longer seat. I've built (last time I looked) over 12,900 carburetors since 2003 and have yet to take the holes under the mixture screws past .110", and I keep most down around .090-.096".
Sounds like you need a set of numbered drill bits vs trying to gauge hole sizes without them.
This is exact science, so be precise when drilling items out for improvements.
With a .038" idle tube in that carb you should have PLENTY of idle fuel to the mixture screws with .055-.059" DCR's. This assumes the upper and lower IAB's are still the stock sizes.
I would NOT drill any air bleeds out in that unit, idle or main, they should remain stock to work correctly with the parts I sent.......Cliff
53Olds:
Good news, when actually flipping the carb over to see the idle screw passage while inserting a drill bit, only a 5/64" drill bit extends all the way through. When checking earlier, I was just going by feel, and the larger bit seemed to move on in. My mistake, it doesn't, in fact even a 3/32" bit does not pass through. So, without precise bits in that range, we can at least say the idle screw passage is between .078" and .0938", which seems to fit the recommended range. It might even need to be enlarged further? The idle screw does seat fully when turned in all the way.
I picked up some wire bits last nights, but not a complete set as the only store in that town only sells them individually, it's 75 miles away, and I'd rather get something with a case to keep the bits organized. My eyesight isn't what it used to be, even assuming those tiny bits have sizes stamped on them. I could probably find a more complete set in Billings, but that's 120 miles, and I really hate spending $50 on gas to get a $30 set of drill bits. Mail order would take a week. At any rate, the DCRs are larger than .039" and smaller than .0520". Should I drill them out with a 54 (.055"), 53 (.0595"), or something else?
I haven't done anything to the idle air bleeds, so they are presumably still stock.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version