1979 C3 Carburetor
 

I just bought a 1979 Vette T-Top and the lady I bought it from said the carburetor is leaking real bad onto the engine and needs to be replaced. How do I find out what kind I should get? Should I stay with stock? The rest of the car is stock. Or what kind do you recommend I get? I am new to the Vette world and appreciate the help.

Dan

RE: 1979 C3 Carburetor
 

Forgot to put in there that it is a L48.

RE: 1979 C3 Carburetor
 

find out the horespower rating of the engine and go to autozone and ask to see a holley carb like a 600 cfm and check the side of the box they usually have a suggested carb size for the hp of your engine. Also check to see if you have a spread bore (rear holes on baseplate are larger than front) or a square bore (base plate is a perfect square) then get one with whatever choke style you are using now manual or electric, for drivability stay with a vaccum secondary type or for a bit more performance go with a mechanical secondary ( i wouldnt recommend the later unless the engine has been beefed a little)

RE: 1979 C3 Carburetor
 

A bad leak doesn't necessarily mean replacement. Achronic leak on Qjets is where the filter nut screws into the carb. because it has been overtightened and stripped the threads. There is a repair nut that is slightly oversize and cuts a new thread. If that's not it, and there's not an obvious crack where it's leaking, I'd invest in a rebuild kit. Contrary to urban legend, Qjets are relatively easy to rebuild. Lot cheaper than a new carb.

RE: 1979 C3 Carburetor
 

I agree with 73shark, rebuild it. You go changin' carb makes and you'll have to watch hood clearence.
First thing first, fix the leak, then let's talk mods! :)

RE: 1979 C3 Carburetor
 

I think I will try the rebuild. I assume that a rebuild kit is relatively easy to get right? Since the motor and everything is stock, should I be able to get the numbers off the carburetor and cross it over to a rebuild kit. Where do you recommend I get a kit? Thanks for your help. If the rebuild kit does not work, I will go with what blknblu68 says.

RE: 1979 C3 Carburetor
 

Most auto parts stores either stock them or can get them that day from warehouse. If you don't feel comfortable tearing into the carb, HP Books has a very good book on Quadrajets. Good luck.

RE: 1979 C3 Carburetor
 

Rebuild the Q-JET, if it's the original carb the number should be something like "17059212", you'll find the number on the left side of the carb, it will be stamped into the casting. Also buy a new float and choke pull off along with the rebuild kit, NAPA has good quality parts, total should be less than $50.

RE: 1979 C3 Carburetor
 

Thanks again and I will let you know how it goes.

RE: 1979 C3 Carburetor
 

78buckshot makes a good point re: replacing float. Qjet foam floats were notorious for becoming soaked with gas and no longer floating which means they wouldn't stop the gas from coming into the carb. This could be what's being perceived as a leak.

RE: 1979 C3 Carburetor
 

I was able to go home (I am in Rhode Island and the car is in Virginia) and look at the Carb this weekend and it was really beyond repair/overhaul. I bought a 0-80457s (electric choke) 600cfm 4 barrel Holley Carb and installed it according to the directions and hooked everything back up like it was on the old one (same type carb).

My problem is it runs fine in the driveway but on the road I can not get it above 80mph. The guy I bought it from says he installed a cam and it has an eldebrach intake so I think it should go a little bit faster than that... Exhaust is new from the headers back. Does anyone have any ideas or should I get on the phone with Holley and see what they say.

RE: 1979 C3 Carburetor
 

good idea changing it out. Now dose it just seem to run out of power at 80 mph or is your rpms at 5-6 grand at 80 mph?? if your rpms are low and it just bogs out at 80 your air fuel mixture screws may be set in to far (not getting enough fuel). turn one in all the way till it seats finger tight and count how many turns (complete) it goes in. I usually set mine at all the way in, then back them out 2 full 360 degree rotations then test drive and go 1/4 turn outs from there driving and feelin it out! make sure you set both equally. they are the small screws facing the front of the motor with the springs behind them on or near the base plate.
a 600 cfm may be a tad small if the motor has been beefed up some what. if its a mild built motor it should be fine.
try this and let me know how it turns out!! hope it helps!!

RE: 1979 C3 Carburetor
 

blknblu68,
thanks. I am going to go back home next week and try that out. When I floor it, I get up to about 3500-4000 RMPs and no more. Does this sound like a tranny problem to you? I know that there was a cable that connected to the bottom drivers side of the carb and doesn't that go to the tranny? Not sure. I will try the screws when I go back home next week.

Thanks

RE: 1979 C3 Carburetor
 

The cable sounds like it might be the kick down cable that downshifts with full throttle.

RE: 1979 C3 Carburetor
 

even with the kick down cable unhooked (good call 73 shark) eventually it should get more top end than 80 mph!!
the kick down cable is basiclly Passing gear when you stomp the gas it kicks the trans into a lower gear for faster accelleration.
let me know what happens when u toy with the a/f mix screws Riley.

RE: 1979 C3 Carburetor
 

One other thing to check is make sure the carb throttle is opening all the way when the gas pedal is pushed to the floor it may be that your not opening the carb up all the way !!! have someone depress the peadl and then see if you can open the carb (throttle) with your hand any further ? you may need to adjust the cable to compensate!!!

RE: 1979 C3 Carburetor
 

Thanks. I will try both of them this weekend.

RE: 1979 C3 Carburetor
 

blknblu68's comment re: throttle not opening all the way caused me to think that what might also be happening is the secondaries aren't opening. I'm guessing that they are vacuum operated secondaries on this carb. So if the primary butterflies are opening fully, then you need to check the secondaries. If there is a hose connected to a diaphragm that actuates the secondaries, I think disconnecting it should allow secondaries to open but not familiar w/ this carb.

RE: 1979 C3 Carburetor
 

Thanks for all the help. I drove back home this weekend and found the problem with the secondaries not opening. On the passenger side of the intake there was a small cover (2 bolts) that blocked some form of exhaust port and it was interfereing with the carb linkage. flipped the little cover over and the problem is fixed. Thanks for the help.

RE: 1979 C3 Carburetor
 

Sounds like someone replaced the EGR valve with a plate????

RE: 1979 C3 Carburetor
 

Do you think I need one? It seems to run fine without it.

RE: 1979 C3 Carburetor
 

not sure i remmeber what the egr dose i havent had a motor with one in so long!!!something to do withexhaust and a choke rod i think??but i think youll be fine!!
glad to hear you figured out the carb issue!!! glad i could help:D now put some miles on that thing!!

RE: 1979 C3 Carburetor
 

EGR = exhaust gas recirculation. Was used to add a small amount of exhaust gas to intake charge which slightly lowered the combustion temperature thereby reducing the amount of Nitrogen Oxide. Will run fine without it.