Yellow Bullet Forums banner

1 - 11 of 11 Posts

·
Mstr Of Useless Knowledge
Joined
·
3,446 Posts
Discussion Starter #1 (Edited)
Alright, .060" over 350 SBC Lunati cam .490 lift 290/297 duration.
Holly 600 vac secondary carb. (NEW) The engine starts and idles fine and runs fine under acceleration or with abit of load on it.. But when you are just cruising off idle it has a roughness or a miss... the car has a manual transmission so you can feel it... jerking a bit.......but when you roll in the throttle a bit it seems to go away and then comes back when the load is off the engine......... we have changed the plug wires and power valve... got new plugs in the engine. I'm sure it carb or ignition related.... where should the vacuum advance be hooked up... ported or manifold vacuum?..... we have it on the ported port at the moment... Any Ideas will be greatly appreciated....:confused:
 

·
I like IceCream
Joined
·
11,029 Posts
If it is a new holley.........you need to take it apart and clean all the shit out of it............My wifey runs that same car, and it did that..........I had to take the blocks apart and clean all the chips out of it.
 

·
Registered
Joined
·
5,193 Posts
Sounds like its getting a little drip of raw gas ---------------- I agree with Jake
 

·
Registered
Joined
·
20,012 Posts
Did you check the vacuum at idle and install a power valve with a 1"-2" lower number.If the power valve is not opening when vacuum drops off idle it can cause a lean miss.
Just my thought.
 

·
Mstr Of Useless Knowledge
Joined
·
3,446 Posts
Discussion Starter #6
We have already changed the power valve.. We went up 2 on the jet sizes. 65's to 67's It still has the same issue of a miss or roughness when driving at speed... you can also here it out the exhaust. like a flutter. when you give it a little throttle it goes away till it levels off again then its back.... Driving us crazy....... :confused::confused::confused:
 

·
Registered
Joined
·
20,012 Posts
BIG did you tune the power valve. example if you have a 4 power valve and12 in of vacuum at idle the power valve will not open at part throttle.

Monty
 

·
Mstr Of Useless Knowledge
Joined
·
3,446 Posts
Discussion Starter #10
I'm thinking maybe something going on during the transition from idle to main circuit.... Today I backed the idle mixture screws out another 1/4 turn and it seemed to make a it better.... It still has the flutter but it seemed to have narrowed the window in which it happens... Maybe tomorrow I will try to go another 1/8 or 1/4 turn out and see what happens....
 
1 - 11 of 11 Posts
Top