I came across this info and I am NOT a Q jet expert so what do you think about this info? Is it the real deal or is it bad information? Maybe someone Like Cliff R will chime in.... http://www.florida4x4.com/tech/quadrajet/qtune.pdf http://www.florida4x4.com/tech/quadrajet/qjtshoot.pdf
BUMP!! I saw that article a few months ago. I thought it was one of the best articles I've found on Q-jet tuning. Lots of good, basic info and very useful tips for those of us without a dynometer in the garage!:TU:
I don't think the carb. number decoding is accurate. If that is wrong, who can tell about the other technical info. That being said, it looks pretty accurate to me.
I thought he presented a lot of good information from a hands-on poiint of view. I might have worded some things differently but his information for the most part looked accurate. Definitely worth the read.
The first article #6 said the idle fuel ratio should be corrected by main jet and rods. Actually the idle restriction tubes, down channel and air bleeds should be altered to correct the mixture along with the needle screw passages and needle settings. Cliff Ruggles book covers this quite well; with pictures. Overall there is great info in those two articles. I copied them way back when and have reviewed them at times. Other things mentioned........... The 74 & older metering rods are mostly B rods with .026 tips The 75 and up metering rods are shorter and come in K rods with .026 tips or M rods with .036 tips. This info is RARE INDEED, yet a mistake will throw you off 4 jet sizes at wide open throttle. Generally use big tips with big jets .077-.079; and small tips with small jets .069-.075 I use the area charts as shown in the above article and know how to match rods to get any flow I want. eg .073 with K OR .077 with M is the same at WOT. (THE .040 THRU .054 NUMBERS ARE FOR FINE TUNING CRUISE: ABOVE THE TIPS OF THE RODS) Flow area charts may not be completely perfect in real life but you'll be a damed site closer than no game plan ( or explaination, or instructions, etc) at all! Also 750 cfm carbs usually jet 2 or 3 jet sizes smaller than 800 carbs in the primaries; so be carefull of that.
The later carbs were also delivered with "P", "L" and a rare rod used mostly in very late Motor Home units. The "P"'s and "L"'s are .026" tips, P's taper .010" on the upper section, L's about .002-.003", but have a long smooth taper down to the .026" tips. I use and prefer the "L" rods as they are smooth taper, not "stepped" like the other varieties. They provide a smoother/cleaner fuel curve and transition. I don't use "K" rods as they simply don't have near enough range of adjustment with the APT system. "M" rods are used and designed for the later model single main airbleed units, but can be used in older APT models by upping the jet size some. I didn't read the info, not much time and it required some sort of download onto my already over-loaded/outdated computer!.....Cliff
Cliff, I have never seen an "L" rod. Do you stock them? I have never seen the complete story on primary rods. Our two posts above is probably the closest anyone can get to the full story on that subject. I'm glad you jumped in here Cliff. It is a learning experence every time! Thanks.
"Cliff, I have never seen an "L" rod. Do you stock them?" Yes, we stock a 44L metering rod, for the later carburetors. It can also be used in early units, we have jets with a shorter distance to the orifice to compensate for the rods being a tad shorter. It's just too expensive to have dozens of different numbers made. Most companies woln't even talk to you unless you are talking a minimum order of 10,000 pieces, some want that much a month to set-up and make parts for you....Cliff
