dannymoz71

Have a 70 Cutlass with the 350 in it. Just swapped the 2 barrel intake and carb out for a 4 barrel Q-jet and factory intake. The intake is off a 74 and im unsure of the year of carb. Everything seems to have went pretty smoothly except for a couple things. First off shes running a little hotter than she used too, not much maybe 15 - 20 degrees. Big thing is that I cant get it too stay running at an idle unless I keep it about 1000 RPM or choke it some by closing the air flap some. Any help would be greatly appreciated. Thanks.

MDchanic

Thought number one: Vacuum Leak.

Check all the intake tracts and all around carb flange gasket with the flammable substance of your choice (car-start ether, gasoline from an eye dropper, etc). If the idle goes up, you've got a leak there.

Thought Number two: Are you sure the carb is good? Gummed up idle jets / passages will do what you describe.

I have no idea about the temperature - that's a huge jump, and changing a manifold shouldn't cause that. Could an intake manifold water passage be blocked, changing the flow through the block?

Final Thought: Why? Why are you changing the carb and manifold?
You will not get better performance by putting a 4-bbl on a car that came with a 2-bbl.

- Eric

citcapp

Sounds like a vacuum leak. Take some WD-40 and spray it around the peremiter of the intake where it is connected to the head and block and at the base of the carb. if the rpm's rise while you are doing this then you have a leak. Check to make sure all of your vacuum hoses are connected and you have no unused vacuum fittings at the base of the carb and on the manifold.

don71

Sounds like you have a vacum leak. Something isn't sealed right.

I would look at the carb base plate gasket...Double check all the vacum hoses again and make sure any fittings are tight that they hook up to.

Did you remove the distributor by any chance?

dannymoz71

Didnt remove distributor. I will check with some wd-40 when I get a hance this weekend.

Wyze

I've never heard this before!!!!
Can someone explain more please!!!!!

MDchanic

I gave a basic answer to this question last month here. Basically, if you don't have the displacement, the RPM, and the volumetric efficiency (hot enough cam), then you can't pull enough air through to make use of the extra capacity of a four barrel, and it will either not improve anything, or will actually reduce performance.

- Eric

Redog

More fuel will help, plus it's be proven time and time again that a 4 barrel will get better MPG than a 2 barrel

MDchanic

IF you can keep your right foot under control.

- Eric

Rickman48

I really have to disagree with the 2-bbl. vs. 4-bbl. controversy!!
4-bbl. Q-jet wins every time!!!
We did this on a '73 Monte Carlo 350, and not only did it pick-up 4 MPG, 0-60 was reduced over a second!
Smaller primaries made the motor more responsive = better driveability = less pressure on the gas pedal!

As for the Temp. problem, I agree with the vacuum leak, but once corrected, if it still persists, I'd be checking the carb primary jets - '73 and up were lean even for the compression at the time, which will cause overheating.
Might also check the primary throttle shafts for wear - big vacuum leak there!
[Hazards of using a unknown Q-jet]
Good luck!

Run to Rund

The Qjet will help power and mileage over the 2 barrel. The 74 version is very lean and you may need to richen the primary metering rods and/or jets a couple thousandths for best performance and mileage.