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  #16 (permalink)  
Old 07-07-2010, 08:50 AM
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Quote:
Originally Posted by sqzbox
Have you considered going smaller on the jet sizes or trying a different heat range on the plugs?

I think that since you've got the idle quality tamed, that may be your next step being your carbon build up is happening beyond the idle circuit according to your plug read at hard and WOT passes.
I did try different heat range plugs (hotter and colder) before re-installing the PVC but there wasnt a signitifcant difference.. I do have a complete holley jet kit here (64 through 99) so I could try dropping down.. My concern is that I'm nearly all the way closed on the 4 corner idle mixture screws yet still have a rich idle condition. I'm also still getting some pretty heavy fumes while idling too.

Edit: BTW, the car is still running great otherwise and launches hard from an idle and pulls good throughout.

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  #17 (permalink)  
Old 07-07-2010, 10:10 AM
Technical Support Barry Grant
 
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Typically we consider anything from 3/4 of a turn out acceptable on the idle mixture screws.

If you feel everything else is correct and within spec but want more of a range on the idle mixture screws you have a couple of options. The idle air bleeds can be made larger but you will see very little from doing this. If less fuel is needed then the ifr's in the block can be stepped down 2 thousand which will decrease idle fuel and increase the range of adjustment on the screws. Leave the pcv system hooked upas others have advised.

Something else you may wish to verify is the voltage going to the ignition as well as some of the older GM stuff uses a resistance style of wire that shows 12 volts with the key on yet drops in the 8.5 or so once running.
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Old 07-07-2010, 10:28 AM
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Quote:
Originally Posted by Tech @ BG
Typically we consider anything from 3/4 of a turn out acceptable on the idle mixture screws.

If you feel everything else is correct and within spec but want more of a range on the idle mixture screws you have a couple of options. The idle air bleeds can be made larger but you will see very little from doing this. If less fuel is needed then the ifr's in the block can be stepped down 2 thousand which will decrease idle fuel and increase the range of adjustment on the screws. Leave the pcv system hooked upas others have advised.

Something else you may wish to verify is the voltage going to the ignition as well as some of the older GM stuff uses a resistance style of wire that shows 12 volts with the key on yet drops in the 8.5 or so once running.
Are the IFR's removable and if so do you sell the smaller sizes? Also, do you have any links or information on where the IFR's are located on the block and/or how to change them out or restrict them (tech article?)?

Meanwhile I'll check voltage at the distrbutor too.

Thanks!!
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Old 07-07-2010, 10:44 AM
Technical Support Barry Grant
 
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#2 in this picture is the ifr. Your block will look a little different in that it doesn't have the other adj bleeds but will have a screw in ifr where #2 is shown.

These are blank in 10 packs through our dealers and then you drill to size with apin drill set as needed. Best to use the same pin drill set to measure the ones currently in place and then step them down accordingly.
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Old 07-07-2010, 11:33 AM
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Quote:
Originally Posted by Tech @ BG
#2 in this picture is the ifr. Your block will look a little different in that it doesn't have the other adj bleeds but will have a screw in ifr where #2 is shown.

These are blank in 10 packs through our dealers and then you drill to size with apin drill set as needed. Best to use the same pin drill set to measure the ones currently in place and then step them down accordingly.
The default IFR's are .033, what size would you recommend dropping down to?
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Old 07-07-2010, 01:26 PM
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Quote:
Originally Posted by My68Vette
The default IFR's are .033, what size would you recommend dropping down to?
Would verify their size first but we normally only drop them 2 thousands at a time . They are real sensitive to size changes and if you go too far you will create an off idle stumble problem.
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Old 07-07-2010, 03:37 PM
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The ifr is a simple screw them out and screw the new ones in . If it doesn't help or correct the issue the carb can easily be returned to stock with no harm done. Most cases the gasket can be re-used and if he wants to test it prior to buying bleeds he can restrict those bleeds with a small piece of wire which will have the same effect.

Have to disagree on the iab's though as .002 on the ifr can have a greater effect then .004 - .006 on the iab's . You can go out of the range of what the iab will correct long before the ifr. If one is just slightly rich then the iab can help but not in a case of "pig rich".

If the car runs right everywhere else other then idle and everything is correct then the ifr would be the next logical choice.

We would not change jetting for a rich idle unless it was a case where you are at altitude but then it would be rich at wot whereas that is not the complaint here.
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  #23 (permalink)  
Old 07-07-2010, 05:39 PM
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Do you have a recommended AFR Gauge (brand or type)?
Meanwhile I will verify full voltage at the dist and then try installing a temporary .017 staple in the IFR to see what effect it has and/or if it resolves the rich idle issue (provided I find full voltage at the dist).. So far, in the past few days, I only made a few short trips and the plugs lool like hell already. I understand that it would be good to drive it longer but what If I haul it to the dragstrip 2 weekends in a row, isnt that bascially the same thing I just simulated (a bunch of ideling, a few burnouts and a few hard pulls)? I also had a 73 camaro that had a similar motor set-up that ran 11.40's and it never fouled plugs this easy. I even had a modfied Holley 800dp on it with twin 30cc acc pumps and #36 squirters.

This has been very interesting and educational for me.

Thanks again
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Old 07-07-2010, 06:49 PM
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If this is a new engine, it can take a considerable amount of time and miles for the rings to be fully seated. Depending on the ring type, material and cylinder finish this can be upwards of 500 or more miles.

If that's the case, I would tend to want to keep the heat range and carb tuning safe, not overly rich but not set to "KILL", either. Get some miles on it and check the plugs along the way.

I'm not saying the IFR's won't need resizing smaller or the IAB's larger- I'm just suggesting there may be other circumstances preventing a good plug read at this time.

I'd suggest you look at all the plugs to get a reading of what is happening, not just the same one or two- this may be deceiving unless they're all seen together, and kept in order to determine if there's a cylinder outside the norm.
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Old 07-07-2010, 07:36 PM
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Once again I ask, does the mighty demon come with the idle ease option?
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Old 07-08-2010, 05:58 AM
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Quote:
Originally Posted by sqzbox
Once again I ask, does the mighty demon come with the idle ease option?
Yes, my Mighty Demon has the idle eaze feature
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  #27 (permalink)  
Old 07-08-2010, 01:24 PM
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Quote:
Originally Posted by sqzbox
Once again I ask, does the mighty demon come with the idle ease option?
It does but it is not relevant to what he is doing here as in his first post the butterflies are less then .020 .

The idle-eze is there for larger duration cams where the car will not idle with the butterflies at .020 or less at which time it would be opened to close the butterflies down.

He also stated it ran fine everywhere else and is not at elevation so we would not change the main jets to try and clean the idle up.

That seems to be a common misconception that keeps getting posted whenever someone complains of a rich idle guys want them to pull jet out.
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Old 07-08-2010, 01:29 PM
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BG tech, thanks for clearing that up for me. My thought was if the idle ease adds more air into the manifold it might lean out the idle A/F ratio. I've heard about the idle ease before on other threads but the only thing I know about the demon carb's is they kinda look like a holley. Thanks!
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  #29 (permalink)  
Old 07-08-2010, 01:37 PM
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Quote:
Originally Posted by sqzbox
BG tech, thanks for clearing that up for me. My thought was if the idle ease adds more air into the manifold it might lean out the idle A/F ratio. I've heard about the idle ease before on other threads but the only thing I know about the demon carb's is they kinda look like a holley. Thanks!
It can have a small affect in that manner but only band-aids something else that is wrong or out of range.

The idle-eze was done to keep guys from having to drill holes in the butterflies with the larger duration cams to get the butterflies out of the transfer slot.It basically acts as a controlled air leak.

What happens when the butterflies are too far up into the transfer slot is that the carburetor constantly pulls fuel from it and no amount of tuning will clear it up at that point until you can get the butterflies back down. Just a little more info for you.
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  #30 (permalink)  
Old 07-10-2010, 11:18 AM
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Quote:
Originally Posted by Tech @ BG

The idle-eze was done to keep guys from having to drill holes in the butterflies with the larger duration cams to get the butterflies out of the transfer slot.It basically acts as a controlled air leak..

Ok, I finally had a little time today to tag into this and found some of my information was totally incorrect.. Due to my findings this morning I held off on reducing the IFR's.. I originally stated my transfer slots were only exposed by .015 but after removing the carb this morning, I found they are actually .040.... I didn't realize the curb idle adjustment (primary and secondary) were so course.. I bench tested the screws this morning and found they will basically expose .020 every 1/2 turn or .040 every full turn.. When I first installed the carb, I measured and exposed .015 of the transfer slot but the idle speed was to low and it wanted to stall so I turned both curb idle screws another 1/2 turn... At that time I didn't realize this would have such a dramatic effect by exposing an additional .020

So this morning, I re-set the buttlerflies to expose .020, re-installed the carb and it would not idle high enough to keep it running.. So I tried opening the idle eaz and it didn't increase the idle enough to keep it running, even after opening the idle eaz all the way!!!!!! How can I keep the transition slot at or below .020 if I need more idle speed?????? Keep in mind I also have my timing locked out at 36, which should be helping matters.. By the way, its still running way to rich and even blowing blue tinted smoke out my exhaust.. While my son was feathering the throttle, I continually checked for 12v at the distributor and it was there.. I don't think that's a problem anyways because as stated earlier, the car launches and pulls hard so I think a weak spark would have more of an effect trying to burn more fuel under a heavy load (worse case) as opposed to an idle... I can still pick up an AFR gauge but at this point I don't need it to tell me its running majorly rich at idle..

So my question now is, how do I increase my idle if I cant turn the curb idle screws up anymore, which will begin to expose more than .020 on the transfer slots??

This really blows, its summertime, I finally got the car road worthy after 2 years, and I cant even drive it without fouling a new set of plugs everytime I start it.
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