4 corner idle conversion is finished!

[82 GT]

My carb. is on it's way back from getting the 4 corner idle done. The guy that did it, says he could tell by how far my idle speed screw was tuned, that it needed air. I was idling off the transfer circuit. I think Jester, PKRWUD and Head doctor called that one awhile ago!
So he went ahead and drilled a pair of 3/16 holes in the butterflies and cracked the secondaries open a little to lean out the idle mixture. That should take care of the burning eye syndrome!
He also installed a 8.5PV that I asked to do since he had it.
I'll let you know how it works when I get it.

[82 GT]

Who freakin cares....right?

[rwhite65]

I do prob more then most since we have been chasing the carb demons together.
Ryan

[82 GT]

Since you're interested in it Ryan, I'll send you a PM with my results.

[Rev]

Send me one too. I had to do something similar on my Road Demon. It already had 4 corner ildle, but I had to slightly enlarge the low speed air bleeds to get the idle/transition circuit to work just right.

Rev

[HeadDoctor]

Brian

Don't PM the results - post um - you never know who is really having problems and is either not saying it or doesn't really know its a problem.

Denny@JDS Induction Products

[82 GT]

I got the carb back on and running. I did notice a cleaner idle and didn't have to set the idle speed screw as high as I had it before.
It was a little tricky, at first, to get all 4 corners set to where it would idle right. It idles perfect now and maybe even sounds a little different than before. I also had him swap my 6.5pv to an 8.5 because of my leaning out problem I think I might have. I took it out for a test drive and I "thought" I could feel it pull harder since the 8.5 opens sooner now.(maybe it's just my imagination)
I WAS going to a T&T day Saturday but they already canceled it and that was the last day before they closed for the season!
Now, I'll have to wait til next year to find out if it did any good or not. I know the idle conversion didn't add any gains but I wanted to know if the new PV did the trick or not.
Since I was idling off the transfer circuit, this was something that needed to be done and was worth the money...$55 plus $15 return shipping.

[HeadDoctor]

Seems like the guy is an honest Carb guy - because that's a steel for $55 bucks - keep us posted on the results when you can get them

Thanks
Denny@JDS Induction Products

[82 GT]

Do you think I'm actually feeling a difference with the 8.5 valve? I did the math to calculate the correct PV to use and it came out to a 7.5 that I should have. The 8.5 seems to work fine so I'm just going to keep that in.

[Rev]

The PV will always be open at WOT no matter which one you install, because the manifold vacuum will be at or near 0. It won't make any difference at the drag strip. The higher # will make it open at a higher manifold vacuum though. That will be more noticeable at part throttle, depending on how much of your right foot you have in it.

Rev

[82 GT]

True, but the key thing is that it will close later, as manifold vacuum starts to rise again, thus, providing more fuel enrichment longer.
See what I'm trying to do here?

[Rev]

With the butterflies wide open, manifold vacuum won't rise at any time unless the carb itself is too restrictive.

Rev

[82 GT]

I need to do some more research before I dispute that answer....

[HeadDoctor]

Brian

Here's what happens - When you nail the throttle the vacuum drops to 3.2" HG or less, so if you have a 35 PV in there it won't open untill the vacuum gets below 3.5"HG

In oval track with a 390 carb and 9 to 1 engine we put a 45 PV in there so it will close when the vacuum returns to close the PV and lean the motor down. In a drag car you generally want low number PV's because you're always at WOT. That way the PV is closed unless you're "On the Gas"

In your case I would suggest that you get a series of PV's from 35 to 65 in every increment and find the best one for your application. Remember that you have to be 10 jets smaller when you run PV's so a #70 jet should be sufficient. Get smaller and smaller with the main jet until you can tell that its running to lean with a 35 or 45 PV. At normal cruse RPM.

With the 65 or 85 PV it's going to open as soon as the engine sees that vacuum signal. The best way to determine this is to have a friend ride with you while the vacuum gage is hooked up and let them watch and write down the various Numbers as you increase and decrease the throttle, based on the RPM of the engine. Then you will have a chart to go by and you can tune the motor with the PV system and still have a lean main jet. I don't recomend that you do the next part by yourself without "Do-Dilligence" - You can drill out the PV fuel passage to get more fuel if its absolutely necessary.

You can also stagger the PV's front to rear to get the thing even more manageble.

Mike Urich's Holley book is probably the best on this and he goes into great detail about tuning with the PV system.

Denny@JDS Induction Products

[82 GT]

Originally Posted by HeadDoctor

Brian

Here's what happens - When you nail the throttle the vacuum drops to 3.2" HG or less, so if you have a 35 PV in there it won't open untill the vacuum gets below 3.5"HG




With the 65 or 85 PV it's going to open as soon as the engine sees that vacuum signal.
Denny@JDS Induction Products

That's what I want. I don't want a delay of the PV opening.
I want the PV open from the time my foot hits the gas until the time I let off at the end of the run.