71cajunvette

First attempt for help so please be patient with me.

Have a 71 Corvette with 350 small block, 270 HP.

Car will start and idle fine but when put in gear it as if it want do die. When you start off it runs okay but if we pay attention, there is a slight missing as you accelerate. After driving the car for about 30 minutes, everything gets worse. The missing is pronounced and when you stop, the car will eventually die. At stop signs or lights, you need to put the car back into park or neutral to keep it from killing.

I have already done the following:

-new carburetor set properly
-new coil and radio capacitor
-new plugs and wires
-new distributor/rotor
-timed
-followed fuel line, no in-line fuel filter
-engine compression is good
-all vacuum ports on carburetor in use or plugged

Please help, I have run out of ideas and cannot find anything on line suggesting checking something else.

I am handy but I am not a mechanic so I might need detailed suggestions.

Thank you in advance for your attention to my request for help.

Paul

HeadsU.P.

I had the same symptoms yrs ago. Was losing power by the minute. Got the car home checked everything. Almost everything. Could not figure it out. Then I checked my brand new chrome plated distributor hold-down clamp. Bingo!
Its design made it impossible to hold the dizzy.

SB64

see what the psi of the fuel to carb is, might be low. You can maybe borrow one if you don't have it. I believe it should be 7-9psi.

lvmyvt76

did you change the fuel filter in the carb?? assuming there is one somewhere in the fuel system. WELCOME to the forum!!!

71cajunvette

Checked this but seems fine. Thanks

71cajunvette

I believe I will actually change out the fuel pump because there is no memory how long it has been on the car. Car has been in the family since 71. Thanks

71cajunvette

Yes, filter changed at the carburetor. No in-line filter.

derekderek

this is a 71. POINTS! what are they like? if ignition is all good, then most likely the carb. brand new doesn't mean flawless-perfect.

OzzyTom

Just another suggestion..... is the fuel cap vented?

lars

Paul -
You can't buy a new Q-Jet. Is this a commercially rebuilt carb that you've procured from an auto parts store or through a Corvette parts supplier? If so, the carb has major problems... e-mail me for a paper listing all the problems with that carb...

Lars
V8FastCars@msn.com

SB64

Do that Paul, no one better then Lars.

Duane4238

When you set the timing, did you plug the vacuum line and was the engine fully warmed up? Also, did you replace the points and condenser? Did you set the dwell angle using a dwell meter? After you've done these things correctly, then move on to carb setup and adjustments. Good luck.
Duane

calwldlife

i am leaning to the carb being the issue.
starts cold fine? but low idle?
as car gets to operating temp it runs worse?

electrical would die not just run slower until stalling?

float
idle circuit not setup
power valve opening from transition and at idle
bog at acceleration

new doesn't mean proper

just a quick guess with the info

dmruschell

I had the same sort of symptoms in my 72 Buick 455 a few years ago. The engine would run fine when cold, but as it got hotter, it would idle rough, and then die if put in gear.

It turns out, the main bearings were wrecked. A fuel pump had failed when the arm broke off. It gouged the camshaft and sent metal bits throughout the engine and wrecked the bearings. So, as the crank heated up, it would bind against the bearing surface. I hope your issue isn't quite that serious, but I also went through the carb and ignition systems not finding the answer.

calwldlife

a big ole wow