News:

It appears that the upgrade forces a login and many, many of you have forgotten your passwords and didn't set up any reminders. Contact me directly through helpmelogin@dodgecharger.com and I'll help sort it out.

Main Menu

Powervalve A/F question

Started by XH29N0G, November 23, 2014, 06:04:15 PM

Previous topic - Next topic

XH29N0G

I recently swapped the powervalve in my QF 830 SS to make it open earlier (at higher vacuum - 10.5).  What I noticed was that my A/F at cruise (2200 - 3000 RPM) is now at 15.9 instead of sitting at A/F of 14.0  All else (see below) seems the same.

Could there have been a slight leak through or past the older (6.5) power valve that is not being seen with the 10.5 power valve?

Idle is still at 12.9 (manifold vacuum at idle appears similar (14 inches at  950 RPM)).  Idle is set the same at 0.75 turns out from bottom.
When I mash the pedal WOT is at A/F 12.5 which seems OK.   Both of these (and the manifold vacuum at idle) are the same as what I had before so I don't think my higher cruise A/F is due to a vacuum leak.  My best guess is that this powervalve is (for some reason working better to keep excess fuel out at higher vacuum on cruise) than the other one that is supposed to have opened at lower vacuum.  I do not have a vacuum reading at cruise.  I guess that is the next thing to do.  Does this make sense?  

Right now, I like the A/F curves I am getting, but I am puzzled by the higher A/F at cruise.  
Who in their right mind would say

"The science should not stand in the way of this."? 

Science is just observation and hypothesis.  Policy stands in the way.........

Or maybe it protects us. 

I suppose it depends on the specific case.....

justcruisin

As I am sure you are aware that if all is OK and the only change has been the power valve then it will make no difference to your cruise A/F ratio providing vacuum is over the valve rating. The 6.5 must have had a leak through the valve itself. If the diaphragm was torn it would be rich at idle. Pretty easy to check now you have it on the bench. What size mains are you using?

XH29N0G

The main jets are 73 and 83.  I don't think the diaphragm is torn, and I don't see anything obvious with the conical brass valve or seat on the 6.5  that might explain a small leak.  I just thought I would ask in case others had seen anything similar.  For now I am a little puzzled. :shruggy:
Who in their right mind would say

"The science should not stand in the way of this."? 

Science is just observation and hypothesis.  Policy stands in the way.........

Or maybe it protects us. 

I suppose it depends on the specific case.....


BSB67

Quote from: justcruisin on November 24, 2014, 04:01:34 PM
:shruggy:

I'm with you.  I think your explanation was about as good and clear as it could be.

500" NA, Eddy head, pump gas, exhaust manifold with 2 1/2 exhaust with tailpipes
4150 lbs with driver, 3.23 gear, stock converter
11.68 @ 120.2 mph

XH29N0G

Thank you both for responding.  If I every figure this out, I will post what I find.
Who in their right mind would say

"The science should not stand in the way of this."? 

Science is just observation and hypothesis.  Policy stands in the way.........

Or maybe it protects us. 

I suppose it depends on the specific case.....

rt green

is the power valve the same style as you took out?
third string oil changer

XH29N0G

The replacement power valve was a quick fuel type and looked just like the one that was in the carburetor (same number of slots etc...) - only the setting was different.    I saw a salt truck yesterday so my car is now off the road until a good soaking rain in Spring.  In Spring, I may try the old one to confirm this is the cause.


Who in their right mind would say

"The science should not stand in the way of this."? 

Science is just observation and hypothesis.  Policy stands in the way.........

Or maybe it protects us. 

I suppose it depends on the specific case.....