Where/how to find STOCK jet/metering rod and idle tube specs for a particular combo, i.e., 78 camaro with 305, 65 vette with 427 etc.?
To double check the gear ratio. I blocked one tire and turned the other tire ten times and counted 15.25 turns of the drive shaft. I multiplied 15.25 x 2 tires = 30.5 divided by 10 tire revolutions = 3:05 gear ratio . Is there such a ratio?
My memory tells me these carbs were known for their tendency to drip fuel from lead plugs on the bottom. This fuel went into the intake and was not seen from the outside. There used to be a hard rubber plug available which installed between the carb and the mounting gasket. Hope this helps.
What is that all about???? You said you have an open rearend...no posi. Block 1 wheel. Turn the unblocked wheel precisely TWO rotations...while counting the rotations of the driveshaft. Mark the shaft and the tire with chalk or whatever so you can be exact. If the driveshaft turns 3 exact turns you have 3 to 1 ratio. A bit more than 3 exact turns...3.08. Almost 3.5 turns...3.43 gears. Just over 4 turns...4.10-4.11 ratio. I have a headache just READING what you did! LoL
I would definetly check the rear end ratio. When I built my convertible 455 400TH Q-jet (the carb that was on the engine) my rear end was a 256. I didn't give it thought, but my mileage was terrible, and the car wouldn't get out of its own way. A few years ago I changed gears to a 308, performance and milage both picked up. The Q-jet is a very good carb.
fwiw I have 3.08 gears in my Suburban that gets pretty good mileage with a Qjet....I don't go into overdrive unless I'm going 55 or faster.
OK...but it would scare the crap out of anyone else attempting to check a ratio without disassembly! Absolutely no need to go thru such a complicated procedure...
It's a simple procedure, you just turn wheels some known number of turns, count pinion turns, and divide one number by the other (with a factor of two, or not, depending).
Why are you supporting his complicated way of doing it? You need to do excess math to make it work! The way I suggested (the most common way!)...you can do it in your head at the junkyard or out in the treeline for that matter. His way, despite all the extra effort, still only came out somewhat close to correct...and its hardly practical. Ya got me baffled....
I don't care how you do it, or how he does it, whatever way a guy can come up with the answer is fine. There are lots of ways to figure out gear ratios. They're mostly all correct. And, finding new ways to do things usually teaches me something I didn't know already.
Very true. I just like to see simple things kept simple so people won't shy away from trying it themselves. Its reasonable to assume that a lot of people reading the HAMB are new to the hobby and somewhat unsure about how to do stuff others might find really simple. Anyway...its all good! I think we need to get back to Carbs...we're working at the wrong end!
If you haven't already, I'd run the numbers on the carb to confirm what it came off. There is a number stamped on the drivers side of the carb - google it and you should be able to find out what carb you have. The thing about q-jets is that they are full of tiny fuel & air passages that were machined to a specific size based on engine requirements. So if someone has stuck a q-jet from a 454 powered Chevy truck on you 307 it's going to be hard to get it tuned right either for power or economy. If that turns out to be the case, I'd take Squirrels advice and look for a different q-jet. There were about a gajillion late 70's Chevy's with 305 4bbl engines so finding one shouldn't be too tough.
3.08 gear ratio and overdrive from the 200r4 is a bad combination. You will never get any fuel milage if it goes into overdrive. Try driving around with the overdrive unhooked. The later q-jets form the 80's were all 800 cfm, they did this for emissions. These are far better carbs then the early ones. Rochester redesigned a lot of the internals by the end of the run. I have a complete Rochester listing with all the spec's you will need if you get the number off the side. Joe
Joe H, here is the carb number 17057213 AWP. From what I can find from the internet, it is from a GM truck 1972-1979 V8.
Weren't the 80's Q-Jets designed as feed back carbs with an electric connection to pulse the metering rod? Friend had an OT Pontiac with the feed back style carb. Just trying to remember. -Dave
Most of the 80s Qjets were computer controlled, but not on larger trucks. That 70s truck Qjet is probably just fine for your application...assuming it's in good condition, meaning no one has #%&@#'d it up over the years.
actually they came with a 2GC , all the ones I run across in the past were, ( my 72 caprice had one ) unless I known it to be changed out to a 4 bbl and most of those were hollied , few guys I know would run a truck quadra manifold . GV ( vacuum assist divorced choke ) were the manifold spring thermostat , GC ( Carb mounted choke stat) with the vacuum heater pipe and later they electric choked them which is now the 2GE . and all chevys up till 73-74ish were small bores and bolt pattern compaired to the BOP models this is how the carb place taught us counter rats to identify them . ( 2 G was manual choke small bore )
thats a 1977 HD 350 truck carb with #64 jets on the primary side ( runs a little rich ) you might want to try the # 60 jets the last q jet that Gm offered was on the 1995 454 Kodiaks and school bus chassis and they were non electric , the feedbacks ( dancing needle, half squirt pump carbs ) were on the small blocks
otto if you want to buy jets and parts for the unit try this place . http://quadrajetparts.com/ been buying stuff from them for a while ..
I am doing as suggested. The previous owner told me he tuned up the truck 6k miles ago so I just checked to see if it is within specs. The dwell was at 34 degrees so I brought that to 30 degrees. The timing is correct at 2 degrees BTDC. I also adjusted the TV cable per instructions from a transmission site. My only question is, before I adjusted the TV cable, the slider was sticking out about 1/4 to 3/8" now the slider is not sticking out at all. I adjusted the cable by depressing the adjuster tab, pushed the slider all the way back in, released the adjuster tab and moved the throttle linkage to wide open and released.
The TV cable should be taut with the pedal at full throttle. Also, the pivot points need to be correct, if it's a factory type setup with the right bracket and cable and carb, it should be right. pictures help! The initial timing setting depends on the distributor, so make sure you know what distributor you have, and that the advance is working properly. I like to check the advance at higher rpm, too. Should go up to about 34 with the vaccum advance disconnected, and revved up to 3000 rpm.
Jim (Squirrel) what should go up to 34 at 3000 RPM? The TV cable is taught at full throttle and has a little play at idle. Attached is a picture(I hope)
Since the timing plate does not go to 34 degrees, I am assuming you need one of the timing lights that you dial in, to check timing at 34 degrees. If so, I do not have one of those.
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