I just got my headers installed on my '72 302 and find now that there is a hesitation coming off of idle when I accelerate. Could this be due to too lean a mixture now that I have better exhaust flow?

Now that I have the headers on I don't have the air warmer thing connected to the air cleaner that used to wrap around the stock exhaust manifold. Could the cold air be causing the hesitation? I am up in Canada where the air is now 32-40F.

Thanks in advance for your help.

 

If this a carburated vehicle, increasing the accelerator pump shot might do the trick.

 

you might want to check your timing/vacuum -do you have points or electronic? I went through all that before i replaced my headers. I switched to pertronix I and a flame thrower coil, and replaced a problematic carb setup - 289 4v intake with an adapter to a 2100 (2v) carb. Now it has the right 4v 1" spacer with PCV port and an autolite 4100 (4v) carb. I have a dual port distributor- outer to base of carb(advance) and inner to port on manifold behind carb(retard), all these changes required an ultimate timing change - I didn't use a light - I used a tach/dwell meter and a vacuum guage, and several round the block tests. The guys at "pony" carburetors told that the harmonic balancers (outer ring with marks) inevitably move so you can't trust a timing light to be accurate. dwell set at about 32 degrees, idle at 750-800rpm, and vacuum at 18-20 inches.

also what's your choke setup? mine's automatic with heat riser tube - they have to be very clean(inside) or the little piston can sieze up, check your choke linkage too. see that your choke operates smoothly with a spring like action... Good luck... and thanks for the info on the headers.

 

Good mod!

Try opening the idle mixture screws a little, then if you still have a miss check the timing. Try advancing it just a little.

If you have the factory carb, you can adjust the accelerator pump by moving the rod up or down on the actuator holes. Just keep messing with it until you find the cure.

 

Check your choke..If you dont have the choke working properly
you will hesitate and bog...

 

 

[updated:LAST EDITED ON 26-Nov-02 AT 02:19 PM (EST)]>Check your choke..If you dont have the choke working
>properly
>you will hesitate and bog...
I had a 1986 geo metro that had the same problem all i did was inflate my rear tires an extra 5 psi,and i also went as far as to buying some new seat covers. After that my car never missed or hesitated. I also like to arabs

 

Does the hesitation clear up after the engine has been operated for 10-20 miles? If yes then I'd consider heating up the incoming air mix, the stuff you tossed when you installed the headders. You can fab up a collector using a chunk of exhaust pipe and some hose. If it boggs on a completly warm engine then I'd richen the mix by adding accelerator pump shot, larger main jet or backing the timing off a tad.
William in Atlanta

 

>I just got my headers installed on my '72 302 and find now
>that there is a hesitation coming off of idle when I
>accelerate. Could this be due to too lean a mixture now
>that I have better exhaust flow?

This is exactly what's happening. You might also try going up a size or two on the main jets.

>Now that I have the headers on I don't have the air warmer
>thing connected to the air cleaner that used to wrap around
>the stock exhaust manifold. Could the cold air be causing
>the hesitation?

Not likely. The hot air stove will help during warm-up, and will also help prevent carb iceing.

The bottom line is you installed a more effecient exhaust, now give it more gas !!