[zoey2]

on a 1971 350 i have a holley contender intake manifold and a holley-4160/4150 i am getting a hesitation-stumble on the take off after the stumble is gone it runs good and it idles good i am not sure what size pwer valve it has in it yet if that even matters any help would be greatly appreatiated.

[cool rockin daddy]

Time to buy a book on how to tune Holley carbs. Available at Barnes & Noble and other book stores. Every carb and engine is different and you need to learn what does what on a Holley and how to adjust them.

[cobalt327]

Originally Posted by zoey2

on a 1971 350 i have a holley contender intake manifold and a holley-4160/4150 i am getting a hesitation-stumble on the take off after the stumble is gone it runs good and it idles good i am not sure what size pwer valve it has in it yet if that even matters any help would be greatly appreatiated.

It could be a few different things- and could even be ignition timing and not the carb at all. But in any event, be sure you have no vacuum leaks and you can check into the timing as well. More on the ignition timing below.

In your case, if it IS carb related, there's a decent chance it's related to the accelerator pump circuit. Holley's instructions are on page 6 and 7 HERE.

Here are a couple links you might find useful:

Instruction Manuals by P/N- http://www.holley.com/TechService/Instructions.asp

Exploded View and Nomenclature
Manual for Models
2010, 2300, 4010, 4011, 4150, 4160, 4165, 4175, and 4500- http://www.holley.com/data/Products/.../199R10014.pdf. BTW- you have either a 4150 or a 4160, not both.

Technical Library-
http://www.holley.com/TechService/Library.asp

http://www.bob2000.com/carb.htm

Remember- a LOT of "carb" problems turn out to be ignition related. The timing advance curve is VERY important as to how the car drives.

Here's a basic set-up to get you in the ballpark:

For non "fast burn" heads, use about 34º-36º BTDC total (this does not include the vacuum advance. Remove the vacuum hose and plug it until the timing has been set before reconnecting it), all in by about 2800 RPM, with about 10º-15º of vacuum advance. See where this leaves you as far as initial timing. You'd like there to be at least 12º BTDC at idle speed, more would be OK, but do not exceed the 36º total timing. For fast burn heads like the SBC Vortec, use about 4 degrees less total timing.

Connect the vacuum advance to a manifold vacuum source. If you were using a ported vacuum source, this will cause the idle speed to increase. Lower the idle speed back to where it belongs (~800 RPM) w/the curb idle screw. Readjust the idle mixture screws as described above.

If needed, there are adjustable vacuum cans like the ACCEL #31035. It's an adjustable vacuum advance can for the GM HEI that allows adjustment to BOTH the amount and rate of advance. Comes w/instructions and tool. Crane offers a similar can.

If you find the can is OK but has too much advance, you will need to physically limit the vac can's travel w/a VACUUM ADVANCE LIMITER PLATE- Crane #99619-1

If you're unsure, or just want to check the accuracy of the tab/mark for TDC, DETERMINE TDC.

MAKE A TIMING TAPE will help you to see what your total timing is w/o having to use a dial back timing light.

[67MercCat]

check for vacuum leaks and if there are none, you have to adjust the idle mixture screws. Get a vacuum gauge and plug it into your vacuum tree on your intake. Then screw the idle mixture screws on the side of the carb in all the way, then back them out by a turn and a half. keep backing the screws out equally and watch the vacuum gauge for the highest vacuum. when the highest vacuum is reached then make sure both idle mixture screws are in equally. You should have any more problems if its done right

[willowbilly3]

Any drivability issue should be addressed by making sure the ignition system is up to snuff before attacking the carb. could be the vacuum advance.

[cool rockin daddy]

And it could be the accelerator pump needs to be adjusted or changed, hence he should learn how his CARB works.

[Dajerseyrat]

good info on this thread!!!