Choosing a replacement carburetor

[Ride The Snake!]

Hello all. As you can see I'm quite new to this forum. I've got a '70 GMC C1500 (350 cid with 4 spd manual) that I've had for a little over a year. I've been learning to wrench on it bit by bit, but by no means do I qualify as even a shade tree mechanic. I most recently set about rebuilding the Rochester 2G that came with the thing after it started leaking fuel and later developed a massive vacuum leak. The PO seems to have modified the thing, as it's lacking parts for the choke and has several of the small vacuum tubes on the back side capped off. After rebuilding it myself and finding that it still seems to leak fuel and air, I've decided it might not really be worth my time messing with it any further. The lip on the mating surface between the air horn and fuel bowl was mashed flat in places anyway, so I'm not confident it'll ever form a lasting seal.

Which brings me to my real question--what sort of carburetor is recommended for replacement? I really don't know what--if any--modifications have been done to this motor. From the looks of it, it's had a motor swap. It's clearly a small-block Chevy, but I really only have the seller's word that it's a 350 (I know, I need to look up the engine codes). It wasn't advertised as having any sort of valvetrain upgrades. I don't know what intake manifold it has, just that it worked well with the 2G. When it ran fine, it made plenty of low-end torque. The truck's got a dual exhaust that looks stock save for the mufflers themselves.

I guess I should be looking at something in the 600 cfm range? Any advice beyond that? I know I'm not coming with a great amount of info on my engine, so I expect any advice to be ballpark/guesswork. I'm not trying to make this thing a hot rod, just a street truck with responsive low end and enough balls to get up to 80 mph easily.

I've heard Quadrajets are great if you can get a quality rebuilt/remanufactured one and get it tuned just right. However, at this point I'm not confident in doing that myself, and I honestly would prefer the reliability of a new carb. My dad's got a Q-jet from his '71 Suburban that he tried to rebuild, and eventually got some sort of Edelbrock 4-barrel after being dissatisfied with the Rochester. His motor is tired as **** though.

Apologize for the long, rambling post.

[Ride The Snake!]

I should also add that the mating surface between the top of the block and the throttle body has me concerned. The area between the front two bolt posts has a divot and isn't smooth at all. It almost appears to be a weld line to fix a crack. There is still a lip all the way around the front of the mating surface that IS smooth, but this divot has me concerned. I suppose the old gasket might've been RTV'd in order to make a good seal. After all, it did run fine for the first year I had the truck.

The truck is on the other side of town by my parents' house at the moment, but I'll post a picture of the mating surface when I get the chance.

[Square_78]

I have a 1970 GMC with turbo 350. It has an edelbrock on it and its been a nightmare trying to tune it. Every mechanic I talk to says to throw it away and buy a Holley. I've also read this online a LOT. So yeah, dont buy an edelbrock. When I have funds to upgrade, I am going to buy one of those Holley Demon carbs.

Lonnie

[truckster]

In over 30 years of working on all kinds of cars and trucks I haven't found a carb I like better than the Quadrajet. You can get a professionally remanufactured one for about the price of an Edelbrock 1406 and a new one for a little more. Most distributors will set up the carb with the right jets and needles for you if you tell them your application.

I just pulled the 1406 that came on my Blazer off and gave it to my boy for his Camaro. The Blazer gets a Quadrajet.

[Ride The Snake!]

Thanks for the advice, guys. Yeah, from what most people say either a Holley or a Q-jet seems to be the way to go. I looked up some prices on jetchip.com and I can get a rebuilt Q-jet for about $440. Seems like a lot but I guess it'd be worth it, considering Holley's seem to run around $300-380 depending on what I want. I'd rather get the Q-jet for a bit more money. I'm definitely too nervous to try to rebuild my dad's Q-jet, but I was wondering if I could send it in to Jetchip for them to remanufacture to save some money. You fellas know of any other places that do quality rebuilds of used carbs you can send to them? If not, I might just go ahead and order one of their Q-jets.

Also, I'm wondering if I should get one of their Stage 2 versions designed for use in a modified vehicle, in case I decide to get a more aggressive cam for mine eventually. I wonder if the Stage 2 would still perform well with a stock motor. Of course, I really have no idea if my motor is stock. I bought this truck for $1000 and judging from the completely botched and snipped wiring harness and the way the motor sits in the truck, I believe this truck has had a motor swap at some point. One thing's for sure--it ran strong as hell even with that puny 1 1/4" 2G. So much low-end torque, I could smoke the tires just by mashing the gas in 2nd gear from a dead stop--no need to rev and drop the clutch or use the brakes. My dad's Suburban runs smooth, and he had the entire block rebuilt 10 years ago, but the thing is a total pooch.

[69GWC]

Never had a good Q jet before and could not make my self buy one..lol
Allways had good luck with holley carb and I have a 670 Street Avenger on right now and it worked great right out of the box.
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[Shyguy]

My son likes Edlebrocks, but they do have some special needs. A pressure regulator and a phenolic spacer under them to provide reliable service.

My brother swears by Holleys.

Both are mechanics.

I had Q-jet on a stock 350 in a '72 GMC and it worked real well even after I rebuilt it, that was way back in the 1980's.

I think if you get a professionally built and setup Q-jet you will be satisfied because it should give you better mpg using the primaries and plenty of power when you kick in the secondaries.

I am sure many others will give you their opinion of what works best for them and their application.

[geezer#99]

First take a pic of your motor for us.
Since you really don't have a clue about carbs, intakes etc just figure how to fix what you got.
If you can't get the 2gc rebuilt and running how will you ever get any new carb and intake installed and running.
JMHO

[Z10]

I have a Edlebrock on my 350 ZZ4 crate in my 69 Camaro and it runs fine. Well, maybe a bit rich, but it get's about 17mpg on the highway. Been on the car for 10 years.

[custom1970]

I had my old Holley re-built and re-anodized by these guys http://www.carburetorusa.com/
It took a while and they have very specific instructions on their web-site. Think it's a small shop, but the guy I spoke to was very nice. I also had a problem with the secondaries sticking and had to send it back, but they took care of it at no charge. I'll ad that it did look almost like new when i got it back.

oh, I'm also not a fan of Edelbrocks, bought one to use while the Holley was being re-built and i couldn't ever get it to run worth a dam...

[truckster]

Summit Racing has remanufactured Quadrajets starting at about $270. They'll set them up for your application:

http://www.summitracing.com/search/P...t&autoview=SKU

[Ride The Snake!]

The carb isn't even a 2GC, it's just a 2G. It looked like some of the choke parts were missing, such as any linkage that might go towards the dashboard to operate it from the cabin. The shaft on which the choke plate sits seemed slightly bent at the passenger end, allowing air to pass through it. A gasket was supposed to go on there, but whatever component existed for it to mate to outside the air horn was also missing.

None of these missing parts are included in a rebuild kit, of course. Now I'm just thinking I'm not comfortable using a bastardized carburetor in the long-term.

I DID get the truck to start, but it was running wicked lean and obviously had a massive vacuum leak somehow. I'm thinking it's the bolts that were used on the back of the fuel bowl-to-throttle plate mounting surface. The ones used by the PO didn't extend all the way through into the top of the fuel bowl and lacked nuts. I tried reusing them unwittingly after the rebuild, and I think this might be a major source of vacuum leak. One has to wonder how the thing ever ran at all.

I'll try to post pics tomorrow. By the time I can get to the rig tonight, the light will be too low to get good photos.

[LEEVON]

Originally Posted by truckster

Summit Racing has remanufactured Quadrajets starting at about $270. They'll set them up for your application:

http://www.summitracing.com/search/P...t&autoview=SKU

This right here. I'm on my 4th install...love 'em.

[geezer#99]

That's why I asked for pics. Some of the things you describe don't effect how it runs. Like the choke plate gasket.
With a pic we could point out your problems.
Just trying to help.

[Ride The Snake!]

I understand the need for pictures, and I really appreciate all the responses so far. I checked my copy of the lousy Haynes manual and in the picture the intake mating surface with the carburetor does have the roughly-machined divot I mentioned earlier, so that gives me a sigh of relief that there wasn't some sort of welding job done. The book also informed me that I should've RTV'd the throttle body to intake gasket--something I neglected to do. I also did a rush job of cleaning the intake surface. That, coupled with the wrong bolts used for the fuel bowl to air horn connection may be the source of my vacuum leak.

I yanked the carb off yesterday and I think I'll try to remedy these issues before I finally decide to replace the carburetor. Down the road I definitely see it as a necessity, particularly if I ever decide to modify the motor.

Of course, a lot must be done before that. I plan to pull the valve covers and do a valve inspection and try to get a baseline on the condition of the motor, and if necessary have a shop do a valve job. Luckily, my roommate is pretty acquainted with motors, albeit mostly on Kawasaki and Harley bikes.

And while it's on my mind, do any of you know a good source for a new wiring harness? My truck is really bare-bones and the kits I've found include a ton of extra wires I know I won't need, and for around $450! I think at some point someone ripped out virtually every accessory in this thing. It also has no AC, no brake booster, manual steering rack too.

[Ride The Snake!]

So, I'm still trying to get my 2G to work following the rebuild I did. Maybe I should be creating a new post, but I'll post this update here first.

What caused me to do the rebuild was a sudden vacuum leak I got that caused an inability to idle. The truck would stall after several seconds unless I was opening the throttle, and an obvious hissing noise was present. I managed to drive it home that night.

I got the right kit for it, tried to rebuild it, and have gotten it to start and run once. (I know I shouldn't have introduced additional new variables, but I changed out the PCV valve and hose at the same time, as the old one sat really loose in the valve cover). Anyway, I think it was running lean and still had a vacuum leak somewhere, because the idle was high and the mixture screws seemed to have little effect when I adjusted them. The truck also got hot after several minutes, I could smell overheated coolant, but no boiling over or steam. I've never had an overheating problem before. The thermostat is working fine. I tried adjusting the timing somewhat to no help, and put it back where it was. Now it will start sometimes, idle at best for a couple seconds, and die. Try to rev the motor and it still dies. The fuel filter just in front of the carb inlet fills with gas and I can see a small air bubble.

Since then, I have removed the carb again and replaced the big 1/4" mounting gasket that was in the rebuild kit with a thinner one (also from the kit) that looks like the original that was on there. When I first rebuilt it and subsequently had it starting, I also had neglected to replace the o-ring and small paper gasket at the fuel inlet, so i replaced those the other day. The unused vacuum lines on the carb were capped off with small pieces of hose and screws pushed into them; I replaced the pieces of hose and fitted rubber caps.

I remounted the carb and tried to start it. Now the fuel bowl overfills and gas is leaking out in significant amounts through the air horn to fuel bowl gasket. The motor coughs and almost starts, but dies immediately.

I'm going to crack open the carb again and have a look around. When I first rebuilt it, I adjusted the float bowl height and float drop to spec according to the kit (23/32", it was at about 26/32" before, so this effectively raised the level of fuel in the bowl). When I rebuilt it, I had soaked it in paint thinner before cleaning everything off and replacing parts. I made sure to blast compressed air through all the little passages. The only thing I didn't replace in the rebuild was the accelerator pump, as the new one I tried fitting in there didn't seem to have free play on the armature it connected to. Instead, it seemed to bind somewhat, so I used the original.

I'm also curious what this hole is in the throttle body. It goes all the way through and is not threaded, and I cannot recall any component ever being there. Does anyone know what this channel is for? It seems like it just allows a bunch of unmetered air into the the area by the butterfly valves (source of vacuum leak??). Here's pictures of what I'm talking about.

http://67-72chevytrucks.com/vboard/a...1&d=1348004486

http://67-72chevytrucks.com/vboard/a...1&d=1348004486

The arrow points to the hole, and the small red dots are the approximate locations of the vacuum line channels that are capped off. They are in the same vicinity of this large port. In the second picture, one arrow points to the aforementioned hole in the throttle body, and the other to a vacuum port on top of the air horn. The airhorn port isn't shown in the diagrams I have for the carb and I don't recall it ever being capped off (I know, I'm an idiot for not taking a ton of pictures before I stripped the thing apart). Maybe it had something to do with the choke mechanism (this carb never had any automatic choke parts or even manual linkage, just the choke plate itself).

If the fuel level is too high in the bowl, should it be able to leak out the gasket? I imagine not.

I'm going to give this one last attempt before I throw in the towel and admit I'm in over my head here. If I can get it to start again, I'll use carb cleaner to check for any vacuum leaks.

Any advice or brainstorming is welcome.

[rogergodding]

So many opinions on carb choice.... I say you can't go wrong with an Edelbrock 1406.

[GASoline71]

So the OP has a 2 bbl carb and everybody keeps recommending 4 bbls? Just trying to understand here...

Gary

[geezer#99]

Originally Posted by GASoline71

So the OP has a 2 bbl carb and everybody keeps recommending 4 bbls? Just trying to understand here...

Gary

Ya Gary!! I don't get either. Everybody wants to sell him a different carb but not to many want to help him get the one he's got running.

[Ride The Snake!]

Originally Posted by geezer#99

Ya Gary!! I don't get either. Everybody wants to sell him a different carb but not to many want to help him get the one he's got running.

It might be because at the time I posted this thread I was thinking I'd have to replace my carb, so i titled it as such. Now I'm more determined to try to get this one running.

Seems you sent me a PM but my pop-up blocker wouldn't let me see it. Let me try again.

[Ride The Snake!]

Yeah, at this point given my limited funds and the fact that I may need to do other work on the truck in the near future, I'd rather keep my intake and use the same type of carb...either my 2G rebuilt by a shop if necessary, or a replacement 2G...or some other quality 2bbl. I haven't quite given up on fixing mine yet. I posted above where I'm at in terms of troubleshooting, so if anybody's got any ideas how to proceed, feel free to shout 'em out, haha.

[geezer#99]

Your links don't work.
Here's a link to identify your carb. And they sell rebuilt ones too. PLus parts diagrams.
http://www.carburetion.com/CarbID/RochesterID.htm

And if the fuel level is to high the top bowl gasket will leak.
Still be nice to see pics but it is what it is.

And here's a better exploded view for you.
http://quadrajetparts.com/exploded-view-t-16.html

[Ride The Snake!]

That's odd...when I click on the links I posted, I get the pictures. Is there some way to inbed the image directly in a post? I suck at forums.

http://67-72chevytrucks.com/vboard/a...1&d=1348008490

http://67-72chevytrucks.com/vboard/a...1&d=1348008490

Do those work? don't copy and paste, since I think it shortens the link's url with an ellipsis (...), so it wouldn't work to just copy/paste.

[Ride The Snake!]

Originally Posted by geezer#99

Your links don't work.
Here's a link to identify your carb. And they sell rebuilt ones too. PLus parts diagrams.
http://www.carburetion.com/CarbID/RochesterID.htm

And if the fuel level is to high the top bowl gasket will leak.
Still be nice to see pics but it is what it is.

And here's a better exploded view for you.
http://quadrajetparts.com/exploded-view-t-16.html

The parts diagram on that first site got me a 404 error. It's weird, but my 2G has the fuel inlet mounted sideways, towards the passenger side, not facing the front of the car. I guess mine is one of the earlier ones.

[geezer#99]

All I do is click on the address to highlight it, type control c to copy it and type control v where I want to insert it.
My pos Dell might be blocking it.