Gold Lifetime Member
Join Date: Apr 1999
Location: Vancouver Island, Canada
Re: Carb problem
Questions: Is this a new carb or is it a used carb that you purchased? How long has it been running on this particular motor? Has it always had this problem or did it just start to have this problem.
Have you played with the distributor springs and or weights or put in a new distributor prior to problem occuring? Have you taken a vacuum reading and have you checked for vacuum leaks around base of carb, manifold, and vacume lines? If not i would do so before you start messing further with the carb.
Assuming your test shows no vacuum leaks and the distributor was not messed with and your timing is set correctly than i would pull the carb and check that it is setup properly especially if you purchased it used and previous owners messed with it. You may want to take this opportunity to get a carb kit and rebuild it so you know the condition of the carb inside and out.
I would make sure that the carb is set up to its stock configuration! That means if i am not mistaken that the jet sizes are 73's front and rear. (rears could go a couple jet sizes richer if need be) 73's for the primaries are great for the 355.
The squirters and pump cams are not the issue here. The squirter size stock is 31's and again is ample for your 355ci motor. Put the stock accel pump cam back in the #1 position and put back the 31's squirters.
power valve 6.5 stock and what you want for your application.
The 750 holley have had issues with the arm that is supposed to sit on the pump cam but when you look closely it is riding in the spring and not on the pump cam! This is the first thing to check with the carb off the motor on the bench.
1)Visually look at the arm and open and close the throttle while watching the actuating arm that is supposed to ride on the accel pump cam. Many times you will find that it is sitting/resting partially on the spring. The fix is to remove the actuating arm and bend the arm over so it rides on the cam.
2)You should also check that the accel pump arm is setup and does not have "excessive" play. Slowly move the throttle open and watch it make contact with the accel pump arm lever. It should make contact with the accel pump arm the moment you start to move the throttle. Many times this is just not the case and there is too much play. required by tightening the spring so that it is just touching the accel pump arm. Note: You also need to make sure that when the throttle is fully open you can fit a .20 feeler gauge between the arm and the spring pad.
3) Next is to check your primary butterfly's setup. looking from the bottom of the carb up note the amount of transfer slot that is exposed without touching the throttle linkage. The amount exposed should resemble a square. Taking a .20 feeler gauge and holding it against the throttle plate and side wall should just about cover the square gap you are after.
4) The secondaries also need to be setup properly. Holding the carb up to a light look at the secondary throttles bores and adjust the butterfly's to allow the same amount of light to show through as the primaries do now that you set them. ( The Very Small, adjustment screw for the secondaries is under the carb base plate on drivers side).
5) make sure that your float levels are set correctly!
These are the first issues to overcome or your carb will never run properly until they are adjusted correctly.
67 RSSS Van Nuys, 4th week Sept,1966
ps,tilt,headrest,spd warn,pw,am/fm,delux int,
remote mirror,rear defrost,tint glass.etc...
TKO 600 Extreme,12bolt 3:73 gears.