Carb help

[spanky55amg]

Ok... its been...... *sign* 17 years since I have touched a carb. I have been an engine performance tech but its all been mechanical and electronic fuel injection.

So here we go. I have a 84 C10 and everything that I can find on Quads is that it was supposed to have an electronic choke. I was hoping to find a Quad on this truck. It burns RICH all of the time. Idle when cold is rich and even dies. So I was thinking it could have been the choke. Running down the road, this thing burns rich. So Im thinking it needed to be adjusted.

Get it in the garage today and find out that it has a Holley 6210-3, which I have looked up is a 650 double pumper. As per the Holley site, this carb is fine for a 350, and I figure that it should be fine for a 305. Assuming this is a 305. Holley states this is for a divorced choke, and I assume(?) thats what our trucks run. Holley also states this is replacement carb for the Quads....

A. Is this carb too big?
B. Should this carb just be a "plug and play", meaning, everything should work?
C. Do we have a push or pull type choke? -- Im concerned the choke is not working correctly.
D. From the looks of it, all of the emissions have been pulled from the vehicle. It looks like that I will have to make sure all of the vacuum lines are ran correctly. (I cant trust anyone else's work is correct unless I know them. PTSD of working in the shop with crappy techs.) I bring this up because the truck is supposed to have cats but it doesnt and I know that will also make it smell like its burning rich.
E. I do have drivability issues. Dies at idle, it doesnt high idle or doesnt low idle (I cant tell, once again, I think its choke issues and no tach), at partial throttle and get into the throttle (where it should kick down), it will flood and kill the engine. I then have to pull over and try to start it with the throttle all the way down.

Im sure Im missing something. Thanks for the help.

 

[1987 GMC Jimmy]

I think there's a deficit of information here. If you're running a stock 305, I think that carb is too big. If you're running a 350, I think it's more on par. The best way to ID the engine is the casting number on the rear of the block. I understand that's a tough thing to do so my only other suggestion is to check out the casting number on one of the heads and see if they're 305 or 350 and hope someone didn't put 601/416 heads on a 350 to raise the compression ratio. That carb is supposed to be a direct replacement for a divorced choke Quadrajet. I've seen both divorced and electric chokes on squares before so I can't say with any degree of certainty what yours came with. It may help to go through the emissions system like you said and see if lines are cracked up, broken, or altogether missing. Your EGR valve, if you still have it, can be a major vacuum leak, as can your carb base gasket. It just depends on what's there. It sounds to me like the tuning on the carburetor is bad, the jetting maybe off, and if it's a 305, I may switch to something smaller or a Quadrajet.

 

[74 Shortbed]

Double pumper on a dual plane intake on the street is nothing but a big gas guzzler and will never run right, if you're gonna stick with a 4175 you need to get a vacuum secondary, they are a little tricky to tune but they will run nice, and mileage can be close to a Q-Jet just be prepared to do some tuning..

 

[spanky55amg]

so basically take it off and replace it with a Q-jet?

I mean, Im all game for that. I truly am. That's what I know. I dont know Holley.

http://www.nationalcarburetors.com/lookup.aspx?partnum=nd4478

Rochester; Type: M4me; Noncomputerized W/electric Choke; Block Type: V; Liters: 5.7, 5.0; Cylinders: 8; Fuel Delivery Type: CARB; Fuel Delivery Subtype: 4BBL

Has anyone used this company. Im going to check locally at rebuild shops to see if they have one.

 

[spanky55amg]

I think there's a deficit of information here. If you're running a stock 305, I think that carb is too big. If you're running a 350, I think it's more on par. The best way to ID the engine is the casting number on the rear of the block. I understand that's a tough thing to do so my only other suggestion is to check out the casting number on one of the heads and see if they're 305 or 350 and hope someone didn't put 601/416 heads on a 350 to raise the compression ratio. That carb is supposed to be a direct replacement for a divorced choke Quadrajet. I've seen both divorced and electric chokes on squares before so I can't say with any degree of certainty what yours came with. It may help to go through the emissions system like you said and see if lines are cracked up, broken, or altogether missing. Your EGR valve, if you still have it, can be a major vacuum leak, as can your carb base gasket. It just depends on what's there. It sounds to me like the tuning on the carburetor is bad, the jetting maybe off, and if it's a 305, I may switch to something smaller or a Quadrajet.

Im pretty sure its a 305. But, I havent checked the casting number. 84's are electric choke. And Im sure there are probably some vacuum leaks, it is 33 years old. I just have this feeling that this carb is too big. Everyone always wants to put on a double pumper b/c it sounds cool. Ill prob try to adjust this thing out till I can replace it. AC comes first.

 

[74 Shortbed]

so basically take it off and replace it with a Q-jet?

I mean, Im all game for that. I truly am. That's what I know. I dont know Holley.

http://www.nationalcarburetors.com/lookup.aspx?partnum=nd4478

Rochester; Type: M4me; Noncomputerized W/electric Choke; Block Type: V; Liters: 5.7, 5.0; Cylinders: 8; Fuel Delivery Type: CARB; Fuel Delivery Subtype: 4BBL

Has anyone used this company. Im going to check locally at rebuild shops to see if they have one.

In your case I would highly recommend switching to a Q-Jet.

 

[spanky55amg]

Ok... so. I have purchased a rebuilt Q-Jet and I am currently awaiting its arrival.

So I verified that there are 0 emissions on this truck. And the vacuum lines that are there, well, I think a blind man put them on. So one line runs back to this thingie on the firewall behind the passenger valve cover. It looks like it has 2-3 wires coming from it.

There is a pcv valve, no vacuum line on it.

The vacuum line to the choke on the Holley t's off and goes directly to the M/T valve cover.... Im pretty sure the valve cover shouldnt be under constant vacuum like that.

And the last vacuum line goes to the HEI distributor.

Im going to be digging in my GMSB piggy bank here and ask you all for some help with some pictures.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

EDIT: Thank Windows for messing with the orientation of the pics.

 

[kenny78]

The one can with a line on it might be related to a esc distributor. If it's hooked up and you have an extra pigtail coming out of your hei-leave it

I will try to look it up later

The line coming from the tank would have connected to the charcoal canister-which would then connect to emissions controls and a vac. source. The other vac cans with wires are called tip in switches I believe. All are emissions and maybe cruise related.

I'm not familiar with what the scoop thing is the cave cover. If it's not a vent then I would connect the pcv valve up to manifold vac and a breather on the other cover.

 

[75Monza]

Those "scoop things" are old Offenhouser valve cover vents like I used to use on my old 283's and 327's that had the road draft tube and the oil fill in the front of the intake.

 

[75Monza]

The hose going to the right breather should probably go to the pcv valve. Looks like you have an open vacuum line on the top back passenger corner of the carb too. Definitely swap to vacuum secondary, mechanical double pumper works great for wide open drag racing or if you got a mud bogger, but is pretty crappy for running on the street. Could probably find a decent holley 600 vac secondary on craigslist or something, would work just fine for a 305. Just need a vacuum gauge to adjust the air screws, tach to set your idle speed and your good to go.

 

[spanky55amg]

I already have a rebuilt q-jet coming.
I have a cheap tach that Im going to install soon.

Just weird vacuum lines. I do have cruise on the truck, so Im going to try to see if all the pieces are there. I know the accumulator is still on the truck.

Yep, there is an open vacuum line on the top passenger side of the carb. But I think Im dicking around with this double pumper. Ill worry about all the vaccum lines when the q-jet comes in.
I figured Id cap off the vacuum line on the passenger valve cover. Hook up the PCV, distributor, brakes, and cruise if I have the parts.

I cannot get the gas tank to fill up. I thought it was a clogged vent valve, but there is no vent valve. Thats why I was wondering if that hard line by the power steering gear box went to the tank. If so, then that line is probably clogged. I do not want to have to put a tank into this truck till I LSx swap it.

 

[spanky55amg]

So my reman Q-jet comes in today. I need to stock up on some vacuum line...
Dont hate me too much, its been forever since working on older engines, (ducks) what size diameters are vacuum lines. I need to stock up on just about all of it.

 

[75Monza]

Think the sizes on my 86 are 3/16, 1/4 and 3/8, 3/16 being used for carb to plastic tubes,1/4 being to steel tube(i.e,the heat riser,and the vacuum fittings in the manifold),and 3/8 for the pcv,and fuel. I usually get 6-8 feet of each to have laying around. Sometimes best to take a chunk of old with you to parts store, just not a piece that was at a fitting since it will be flared from the fitting and seem larger than actual internal diameter should be.

 

[spanky55amg]

Id love to take old piece in... but the PO dicked this engine up. So I am just trying to make sure its all correct now. So I am just going to get a bunch of it and redo all of it.

 

[75Monza]

Understand your PO pain...we should have a Rant thread just on PO's, lol. Most of the rigs I purchase I end up calling PO's Psychotic Obstructor, since every thing I dig into reveals another fubared installation that is stopping me from reaching my goal.