Carburetor Power Piston Spring Selection
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,198
Likes: 2
From: Eastern Connecticut
Carburetor Power Piston Spring Selection
I am going to experiment with the power piston spring in my Q-jet. I hooked up a vacuum gauge and drove around with my son taking readings. I have the Edelbrock spring kit that contains springs for 4", 5", 6" and 8" vacuum. I think I know what spring to select, but want some advice. I can always change it if it isn't working out.
Idle vacuum: 12-14" in drive, 16-17" in park
Cruise vacuum: 11-17"
Light acceleration vacuum: 8-9"
Medium acceleration vacuum: 6-6.5"
Heavy acceleration vacuum: 4-5"
Kickdown WOT acceleration vacuum: 0.5-1"
Thanks,
Joe
Idle vacuum: 12-14" in drive, 16-17" in park
Cruise vacuum: 11-17"
Light acceleration vacuum: 8-9"
Medium acceleration vacuum: 6-6.5"
Heavy acceleration vacuum: 4-5"
Kickdown WOT acceleration vacuum: 0.5-1"
Thanks,
Joe
Last edited by joe73vette; Apr 30, 2005 at 11:09 AM.
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,198
Likes: 2
From: Eastern Connecticut
Originally Posted by comp
i'd follow him 
Last edited by joe73vette; May 2, 2005 at 06:24 PM.
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
I fiddled with these springs to cure a midrange "burble"...and ended up going in the wrong direction! The strongest spring did the trick for me. And I'd been thinking weaker springs would help. I was able to go back to the original spring when I did the head swap.
I think it's a pretty much a trial-and-error thing (except in Lars' case, due to his experience at this...)
I think it's a pretty much a trial-and-error thing (except in Lars' case, due to his experience at this...)
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,198
Likes: 2
From: Eastern Connecticut
AARRRGGGHHH! Why can't anything be simple? 
I was looking at the springs, the 6" spring is supposed to be black. But instead of Gold, Orange, Black and Yellow springs, I have Gold, Orange, Silver and (2) Yellow. I guess they forgot to paint the black one! The bag was still sealed, so I'll give it a shot. Joe
I was looking at the springs, the 6" spring is supposed to be black. But instead of Gold, Orange, Black and Yellow springs, I have Gold, Orange, Silver and (2) Yellow. I guess they forgot to paint the black one! The bag was still sealed, so I'll give it a shot. Joe
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Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,198
Likes: 2
From: Eastern Connecticut
Just to let you know, the 6" spring smoothed out the low- to mid-throttle stumble real well. I still have a stumble when just opening the throttle after coasting with the throttle closed. I will re-set my idle mixture screws and also see if the primaries drip. My idle speed is a little high, 850 in park, but I don't think the throttle is open enough to engage the main circuit. Any other suggestions? Thanks, Joe
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Haven't measured my vacuum but i already know my car really sucks.
Thanks for sharing the test results Joe. Since our engine combo's are very similar (crane energizer 266, WP heads, Qjet) i'll know what to expect.
U think the carb pp needed a bigger spring from the cam change?
cardo0
U think the carb pp needed a bigger spring from the cam change?
cardo0
Last edited by cardo0; May 7, 2005 at 11:59 PM. Reason: typo
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,198
Likes: 2
From: Eastern Connecticut
I don't know, but I have to tell you the results were skewed. I found two good sized vacuum leaks yesterday, haven't started it since. I'll have to recheck my vacuum at various speeds. Joe
