LoneStarV

I emailed Lars about a quadrajet rebuild. From what i have read he does a heck of a job. So here's my question based on his response to my email. Am i better off going to a Holley so i don't deal with this hard start issue that he points out is a short coming of quadrajets with modern fuel?

A note on hard-starting Q-Jets: A common problem on the Q-Jet carbs is “hard starting.” Owners report needing to crank the engine while pumping the gas pedal many times after the car has been sitting for a few days. The common diagnosis is that the “bowl plugs are leaky” and the carb is draining itself of the gas. Fact is that this is seldom the case. There are several issues that will cause the fuel to drain out of a Q-Jet bowl, and few of them have to do with the carb:

1. Modern Fuels. The fuel currently available has significantly higher vapor pressure than the fuels that these carbs were designed for. Since the Q-Jet float bowls are vented, the modern fuels will evaporate out the vent tube, dropping the float bowl level just enough so that the accel pump well will not fill with fuel (the Q-Jet accel pump does not get its fuel from the bottom of the float bowl: the bowl must be nearly full for the pump to function). If you have ethanol-additives and high vapor pressure fuel in your area, I cannot solve your Q-Jet hard-start problem with a rebuild.

Shark Racer

I'm in CA and do not have hard start issues.

How often do you drive the car? If it's less than once a week you're going to have to fill the bowls regardless of issue.

A holley has a bit more fuel capacity in the bowls but will still vapor out after a while as well.

LoneStarV

That answers my question. I thought this might be just a quadrajet problem. I've read a lot of threads holley vs quadrajet and it's almost a fist fight every time.

fazang

Assuming Q-jet is fine
i think too it is how the car is used.
If i drive my car every day then it is easy to start.
let it sit a few days and you gotta crank it to let the fuel pump fill the bowl again.

no big deal, but if it annoys you you have to find another solution.
GL
-ALF out...

gcusmano74

Well, it all comes down to one thing:
There's a reason why no manufacturer has installed a carburetor in a new car for almost 30 years.
Just sayin'.

jotto

Just a query really....
how about putting an electric fuel pump on? That way, it would prime and fill the bowl before you cranked the engine? On a car that isnt used much I wonder if that would be a solution?
Only downside I can think of is after sitting for a few days, the oil could have all drained down and so an instant start might cause a bit more wear???

LoneStarV

Thanks for the replies. It's just a quirk i'll have to deal with if my vette sits a few days. As for electric fuel pumps and efi etc etc....i have ZERO interest i don't care how much better the tech is. I dumped a cherry low mile 35th Anniversary C4 to buy a C3. So i'll stick to the old school tech. It's part of what the car is.

jotto

I wasnt suggesting EFI, just a pump to help with hard starts after having sat for a while.

Easy Mike

What did Lars say? Did he recommend you replace your Q-Jet with a Holley?

LoneStarV

My reply was in reference to no carbs for 30 years. Also not interested in an electric fuel pump. The mechanical one will do just fine. Thanks for the suggestion however.

larrywalk

I agree with Lars' explanation. If my '78 with the Q-jet hasn't been started in a few days (or weeks), I just set the choke and then count out 4 potatoes while cranking - it then bursts to life without any further pumps or cursing!

LoneStarV

Lol! Oh well it's part of the charm of these old school vetoes.

Shark Racer

This would solve the problem of empty float bowls. Good advice. I also understand the owner's reticence.

Not a big deal to pump.

I actually find that once warm, the 78 starts a lot easier than my EFI vehicles do (OEM style mechanical fuel pump + M4M quadrajet, running CA E5+ gas).

spinadog

Careful with an electric fuel pump, often the pressures are too high and overwhelm the carb.

Running Chevron 91 in CA for 5 years and 5000 miles with no issues apart from a swollen accel pump, which Lars helped me debug. Great guy.

Best of luck to the OP.

7t9l82

i keep a squeeze bottle full of gas and squirt it in the bowl vent, this keeps me from having to crank it alot. and i don't risk dumping too much down the venturies.

LoneStarV

Lars strikes again. He knows his carbs....thanks for the replies.

Stewart's74

I heart Lars.

TimAT

FWIW: I've got a Demon carb and run VP110 fuel. It's still vapors away after setting. No choke, but it never fails to start either. Just have to crank on it a bit. Not a bad thing- I always see oil pressure before it fires.