Cascade Crew

Quasi-Traction · Posted: Fri Dec 08, 2006 4:57 pm Post subject: Quadrajet woes...

Took apart my extra quadrajet so I could get a feel for how everything goes together and comes apart on it....got a few questions but its definately not as bad as everyone makes them out to be.

Done a TON of research on TGO...and I just have a few questions I couldn't find answers for:

1) the accelerator pump will have a spring that sits inside the carb main body and against the baseplate. Does the color of the spring have effect on the amount of fuel allowed into the jets?

2) The powerpiston and primary rods came out all together. They have a teeny tiny steel retainer that holds them on what looks like a hanger on the top. I left the whole assembly together. If I understand correctly, the rods will have to coordinate with the jet size, right? So if I jet down, I'll need to change the rods too, correct? How can I get them off the hanger wihtout damaging the little retainer for them. (I can provide a picture if what I'm saying doesn't make sense)

3) There is spring under the power piston that was sitting in the carb body when I removed the primary rods and power piston. Does it control the rate in which the primary rods are pulled out? I couldn't tell what the color that spring was. Any reccomendations? I'd like to keep my primaries on the lean side as to maintain decent cruising MPG.

3) I called SMI who makes my carburator in California (who put me on hold for about 2,876,405 minutes!) and spoke with there tech line. They said my primary jets should be .078's!! Seems too big to me. The one I took apart today came off a later 70's truck with a smogger 350 and it had .072's. Should I aim for .070's or .069's to keep it lean? If I go with .070's what primary rods will I need? They were double tapers.

Also there are little steel washers down in where the jets thread in. I couldn't get them out and didn't want to poke around too much and burr the threads. I understand they should be replaced if you do a jet change, is this true?

4) I took the secondary rods out of the one on the car...R hanger with DH rods. I have an L hanger with DV rods and a G hanger with CH Rods. "Damon" on TGO mentioned that I'll want something that pulls the rods out as quickly as possible without any bogging and lower alphebetically hangers pull the rods out faster. Some mentioned the hangers are just stamped at random. I'm considering using the G hanger and keeping the DH rods. Sound alright.

5) I can't figure out how the hell to adjust the float level. I see something that looks like a teeny tiny male double-d end around where the pivot point for the float is. Is this how its adjusted...which way will I want to turn (clock/counterclock?) for raising and lowering the float level.

heh...I guess these things are a little more complex than a standard 4160 holley......

chevymad · Posted: Sat Dec 09, 2006 4:09 pm Post subject:

1: The springs in the accelerator pump have no effect on the amount of fuel squirted. They only change the rate at which the fuel is squirted. If there's any adjustment at all, it will be where the lever connects to the throttle rod. There could be 2 holes there.. but there probably isnt.

2: To jet down you'll probably only want to change the rods to a larger diameter set. There are alot of different shaped rods. If you look at them theres usually a small pointed end, then a tapered area to a larger diameter part of the rod. The size of the small pointed part is the WOT setting of primary rod. The taper and large diameter part are the cruise settings. If you can't get as lean as you want with just rods, THEN you have to change the jets to a smaller set. I would try to find out what rod/jet combo was used on motors your size. Start at that point if you arent allready.

3: The spring determine what vacuum level the power piston starts to move. I wouldnt mess with the spring unless you have a lean bog in the primaries that you can't cover with the accelerator shot.

3.2: As I said above your actual jetting will be determined by the rod/jet combo. So you could have 78s with larger rods in them and be leaner then a 70 with small rod combo. You'll have to find info on the net about what rod/jet combo's came with what. The steel washers sound like the gaskets to me. You could reuse them, not like they'd leak much anyway.

4: I think I used a K hanger with CH rods. Seemed to be successful. WOT afr was 12:1 on the dyno.

5: Float level is adjusted by bending the float itself. Hold the pivot pin firmly seated in the carb, then gently push the needle end of the float down until seated. Now measure the distance from the tip of the float to the gasket surface on the carb. Bend the float up or down till you set it where you want it. That double D shaped adjustment is either the rich or lean stop.. I can't remember which. It limits the travel of the power piston.

The beauty of the qaud is in the rod/jet combinations. You can adjust rates and mixtures at many different points in the power curve. Holley's don't have this adjustment. Only the power valve that opens at a single point in the curve and the ultimate jet size can be changed. This is why the quad's can get alot better mpg then a holley. At least when properly set.

Quasi-Traction · Posted: Sat Dec 09, 2006 6:44 pm Post subject:

Thanks brandon! In case I damage anything does NAPA sell a basic rebuild kit for the Q-jet (is it the Edlebrock brand?) any PN's you know of? I'll need at least a new gasket for where the air horn and main body meet. knowing my luck, I'll end up ripping it getting the old one off.

I decided to go with the L hanger and the DH rods on the secondary side. I'll take it for a spin on the freeway tomorrow and see if anything changed.

Intrestingly enough I couldn't find the weird "z" shaped secodary lockout on the SMI carb. The Q-jet off the truck had it....I'm wondering if I should just rebuild that one and save the SMI one when (and if) I do a head and cam change. Its not like what is in there now will be much over 150-170whp.

I always wondered why the primaries had the dual taper...now it makes sense. I've seen single taper rods...would those be used for a race calibrated carb, where a part throttle or cruise operation would not be necessary?

Any trick to re-seating the needle seat and float?

Thanks once again brandon for all the help and knowledge. Its been a great help.

chevymad · Posted: Sat Dec 09, 2006 7:13 pm Post subject:

Napa sells a kit for it. You'll need the # that runs vertically on the drivers side of the carb. Usually either starts with a 7 or a 17.. like 8 or 10 digits. There are many many different quadrajet kits out there.

That lockout bar is only to keep you out of the 4 barrels until the choke is completly warmed up. Sometimes the thing can get sticky and stop you from using the 4 barrels at all.. so many people remove it.

GM used both kinds of rods in different years. No idea what their reasoning was. It could be that emissions caused them to make some changes. I believe the quad started in 67. So it had over a 20 year run. They still used a version of it on 91 caddy's with the 307 olds.

Reseating? Not sure what your talking about there. It seats itself. Just screw the seat down tight then install the float/needle.

Quasi-Traction · Posted: Mon Dec 11, 2006 2:27 pm Post subject:

Ok, took it for a spin yesterday with the new secondary hangar and rods.

Seems to react nearly the same, secondaries open, no bogging. No idea what changes if any to the Air/fuel mixture With the secondaries open. Still very rich at idle but gets a little leaner when the car is running at normal temp. I think I need a new anti-stall dashpot solenoid for it. When you throttle it hard and come off it quick the motor will sometimes stall out. Anything else it might be?

Also got rid of my electric fan, its now got a pulley driven.

*sigh*.....I should have just gotten an Edlebrock 600.... Why me why me?

I keep trying to tell myself this is a learning process and i just have to be patient.

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

Twilightoptics · Posted: Mon Dec 11, 2006 4:20 pm Post subject:

83Z28BlackBetty · Posted: Mon Dec 11, 2006 5:02 pm Post subject:

Yeah for carb problems! im glad to see someone else working with a carb, too much talk about tpi, turbo rams, and injector-itis blah... Laughing

Hope all is working out well. I'm going to be going through the exact same problems in about a week when i get home for christmas break so i'll need your new found knowledge and expertice Smile

I get to tear into my carb and figure out why it is running so rich and boggs down when i punch it. have a few ideas but more on that next week.
GOOD LUCK CHRIS!
~JAKE

chevymad · Posted: Mon Dec 11, 2006 7:43 pm Post subject:

Idle mixture has nothing at all to do with the primary jetting. The idle jets have their own fuel source and passages. BTW is this a CCC carb or not? Makes a big difference on how to change the idle mix. If its not a ccc carb then turning the screws at the base in will lean out the mixture. You are actually not metering fuel with these screws but a fuel/air foam mix. By changing the air bleed size you can regulate the mix of the foam. That isnt something i've had to do though. I've actually had to drill my idle jets out larger to get more fuel in. Makes me wonder what else you might have going on with yours.

If this is a ccc carb there are some special tools you need to set all the mixture settings correctly. There's a whole process to it and you actually adjust the carb with a dwell meter attached. It's kind of like tuning a tpi you try to adjust the mixture till you center it in the ecm's range.

Quasi-Traction · Posted: Tue Dec 12, 2006 9:14 pm Post subject:

Paul--- Not much room to adjust on the primary side other than a rod/jet change which I think is part of the problem. I think those .078's are just too big for it. I even tried the mixture screws fully seated and it'll only idle for a few seconds and die because its not gettting enough fuel. Seems to favor about a turn and 3/4 out from seated for the leanest mixture possible to keep it idling. I'm not sure if any choke adjustment would do any good but I don't really think so. Choke is set the way the 305 it was on favored it.

Brandon---I have Three Quadrajets: a CCC Q-jet, that was orginally on The car as I got it from Bobby, Smogger one I pulled from the truck in the JY, and the SMI calibrated Q-jet. SMI carb that is on the car is a Non-computer version. A couple big differences i noticed B/t the CCC and the non-CCC were on the primary side. They had a different design for the power piston and the jets were less like jets in the CCC carb and more like tubes. The primary rods also had springs on them on the CCC carb and the non-CC didn't. Everything else seemed to be about the same.

I think your intial suggestion was right and I'll have to go with the Rod/jet change on my primary side. I'll really have to get it up on the dyno to find out how the mixture is on the secondary side...or put in a wideband O2.

Jake---Thanks for the kind words man! Do you have a Quadrajet on your car? I've learned quite a bit about these carburators in the last week or two and I can do basic adjustments/tuning. You can probably use this posting to answer quite a bit of your questions if you tear into it in depth. If its an Edlebrock/Carter it should be fairly easy to tune, they're pretty forgiving. Holley's are pretty simple too, but I've heard will never be as economical as a spreadbore design. Good luck! Let us know how it goes!

83Z28BlackBetty · Posted: Wed Dec 13, 2006 1:27 am Post subject:

Thanks, its a holley of some sort, i havent looked into it properly. what is the best way of figuring out what kind BTW. what numbers should i look for?
~JAKE

blue89 · Posted: Wed Dec 13, 2006 8:07 am Post subject:

I have a PDF scan from the book "How to build horsepower Vol 2" sitting in my Documents folder. Chapter 8 is "Performance Mods for the Q jets". It might help if you want to read it. My dad redid his using this chapter. 10 pages, 5Mbyte. You want? I can send it when I get home tonight.

Quasi-Traction · Posted: Wed Dec 13, 2006 10:41 am Post subject:

sure, I'll take it. I'm always willing to learn more.

I'm not sure if the PM's will support it, so send it to TheKobaltDuck@msn.com