I recently (2 weeks ago) had the carb replaced. They put on a Holly 600 on my L-48. Since then I've noticed a couple of things and I'm wondering if it's carb related or worse:

1) Terrible gas mileage. Not that it was all that great to begin with, but used up 3/4 tank in 2 hours highway. This is after a new tune-up, plugs, wires, distributer, etc. Engine has 95K on it and it is just recently back on the road after not running for 16 years.

2) Car was parked during the past week (5 days). Went to start it on day 6 - was about 40 degreed (F) out so a little chilly. Cranked and cranked and no hint of life. Tried again - pumped and cranked and finally started to catch. Once it did catch, had to keep my foot on the gas or it would stall. Choke never seemed to kick in.

Thoughts?

Eric,
Have you checked for fuel leaks,lines,pump and gas tank etc?

RoY

I have checked for leaks - everything seems 'ok'. I know that when the did the restoration they found a leak in the gas tank and repaired that. I checked and I don't see it leaking. I don't think the fuel pump was replaced - have to go back and check the lists.

Check for vacuum leaks. Spray carburetor cleaner around the base and see if any bubbles show and check all the vacuum tubes that they're hooked up to the appropriate fittings and that there are no open fittings that should be capped off or plugged. Vacuum leaks can cause all kind of problems with idle, fuel mileage, etc.

What kind of choke is on the Holley? Hot air, electric, or divorced style? OE on the car is a hot air choke I believe. Make sure the choke on the new car is operable and correctly adjusted. It sounds like the choke is inoperable, badly adjusted or maybe isn't even there.

WARNING! THIS PICTURE MAY NOT BE SUITABLE FOR SOME CORVETTE OWNERS!

(Please keep in mind that this car is being restored after being parked for 16 years so it's dirty, rusty, but she is loved and soon will be fully recovered - so be nice!)

OK - to begin with - the Holly they put on says "Quadrajet" on it. I just got back from looking around to see what I could find, and here's what I came up with:

First of all, the choke doesn't close. Took the air cleaner off before starting and notice it was open. Moved the throttle and it doesn't close all the way. (see picture below to see position - is that right?)

I started the car and again it needed to crank many times. Stopped. Tried again and pumped and it caught. Runs really rough and as before I have to keep my foot on the gas to keep it going.

When it would finally stay running on it's own, I got out and rev'd it manually at the carb throttle. It's sounded at first like it was going to stall - then caught and rev'd. I did it again and noticed that when it starts to stall, gas was spitting up from the carb! That can't be good!

Once it's fully warmed up, then everything "seems" to be fine. No stalling when I step on the gas.

I did a close visual inspection and I found what appears to be a vacuum connection on the intake that doesn't have a hose connected. Someone has tried to "fill" it in to seal it? What's this for? (see pic below where yellow arrow is pointing) Should something be connected here?



|UPDATED|10/26/2003 12:49:19 PM|/UPDATED|

The carb in the picture is a QuadraJet. It ain't a Holley, but it may have been rebuilt by Holley. The hole that your yellow arrow is pointing to is the hot air port for the hot air choke that was on the original carb. The choke you are running is an electric one, and from your description, it isn't working. Make sure that the choke is actually getting current, it may not even be hooked up to a power supply. If I recall correctly it requires a 12 volt constant source. Plug that hole! You're losing vacuum through it, because there is another port that runs to the back of your carb at the top.

don't worry about that hole, it's for the old choke hot air tube. you have an electric choke now. the choke should close all the way, then pop open to near that position when the motor first starts. try cupping your hand over the choke (or holding a balled up rag over it) when tryng to start it, see if it works better. it sounds like the choke needs adjusting. that means turning the black part of the choke (loosen three screws around it). joe

OK - I'll check the current on the choke and see what I can do about adjusting it.

I'll do a proper plug on the hole so not to lose vacuum. I have other vacuum problems apparently too since the headlights won't close.

What about the fact that the carb is "spitting" gas when cold and rev'd?

OK, I'm on board with most of what everyone else has said about that carb. Choke not workin right, Q-jet definetley, my issue is with the vacuum leaks, if they were severe enuff you'd be noticing a pretty big performance loss. Put a vacuum guage on the motor and find out for sure. And I wouldnt be afraid to do a little bitchin and moanin at whoever sold you that carb

First the hole in the manifold is in the exhaust crossover which quickly warms the carb to lower emissions. Therefore if unplugged, exhaust gas would come out until the heat riser valve on the right side below the exhaust manifold opens (unless someone has blocked it off on the intake gasket). That aside, to adjust the choke, start with a completely cold engine and rotate the black housing after loosening the screws until the choke is just completely closed. Then the vacuum unloader needs to be adjusted to the spec in your particular service manual. This is what partially opens the choke as soon as the engine starts and keeps it from flooding and dying. If it opens too far, it will go lean and die. These are both critical and essential adjustments to get it to cold start and not stall. Then after it starts, the resistive element inside the black housing heats up the thermostatic spring causing it to open the choke. A possible way to plug the old choke stove heater hole would be to tap it and put in a plug. Hope this helps.