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  #16 (permalink)  
Old 07-06-2010, 05:39 AM
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I brought up the detail, w/o altering the image enough to prevent "reading" it (as best as can be done over a monitor, that is):



With your cam, any amount of idling will soot it up at least some- even if the carb was spot on. That's why doing a "plug chop" is often recommended.

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Old 07-06-2010, 07:19 AM
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I thought it was new. I would check a couple of other plugs and compare with that one. If they are the same, might want to try 1 step colder or keep running them and see how they hold up.
A white or light gray is hard to achieve with a carbed engine but is possible. That plug is showing WOT condition and might improve over normal driving.
Another thing you can try is using another style plug that uses side gap technology AKA multi ground platinum electrode that will help over the wide open and normal street driving. They produce spark exposed to the cyl. opposed to the single ground electrode which in some cyl. shrouds the spark. In the olden days, indexing the plugs or filing the ground electrode to end directly over the center of the tip would expose more spark to the center of the cyl. Thats why they invented the multi ground electrode plug to keep from having to index or file the electrode for performance applications.
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Old 07-07-2010, 06:41 AM
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Ok, went to my local car club meet last night. After leaving I drove the long way home (about 5 miles) and ran it at 3000rpm most of the way before idleing into the driveway and into the garage.. I pulled a few plugs this morning and here is what they like (see below picture).. Obviously, they are getting worse and still fouling.. My biggest concern is that most of the events I will be attending in the near future are to far to drive so I will be trailering the car, which means alot of idleing, which means an even worse case sanario than the past few days..

According to BG, if the idle adjustments are less than 1 full turn out (mine are 1/2), further restriction of the idle feed restrictors are required.. Is that an option yet?

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Old 07-07-2010, 07:13 AM
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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.
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Old 07-07-2010, 07:50 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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Old 07-07-2010, 09:10 AM
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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, 09:28 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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  #23 (permalink)  
Old 07-07-2010, 09:44 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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  #24 (permalink)  
Old 07-07-2010, 10:33 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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  #25 (permalink)  
Old 07-07-2010, 12:26 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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  #26 (permalink)  
Old 07-07-2010, 02:22 PM
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If you think its still rich why not get a simple AFR gauge/O2 sensor and stop shooting in the dark. A 4wire heated type narrow band setup is all you need for this.
You are very likely to screw up this carb if you start drilling.
You have barely drove the car. If the plugs were fouled they will get worse not better. You are still getting the carbon out of the chambers that built up. 5 miles is just enough to get things warmed up.
You need to drive the thing. On the hiway. Far. The AFR gauge will show you the idle/ off idle,,, primary cruise jetting, power valve opening point effect etc. best $60-$80 you will spend. You will save far more using this tool than buying countless jets, air bleeds, IFR orrifces , gaskets , fuel, spark plugs etc etc. Good call on the distributor supply voltage. It must be a full 12v all the time. Minor idle air bleed adjustment has a big effect.

In 30years I have never had to drill a IFR on any carb on any car.

What jets are in this carb now? what is the carb model number?

I recomend Champion RC12YC gaped at .035".
The ones you have are ok but will not "clean up" cause they are too cold to clean up by them selves now . They are about right (for racing) once you get it sorted thou. If you do more cruising than racing the hotter RC12YC is better.

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  #27 (permalink)  
Old 07-07-2010, 02:37 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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  #28 (permalink)  
Old 07-07-2010, 02:46 PM
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Quote:
Originally Posted by Tech @ BG
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.
I guess all in how you term/express things. The idle air bleeds have a big effect. Agreed the IFR's have a even bigger effect. +/-.001" .002" change really changes things.
The poster will learn more in 1 hour goofing around with a AFR gauge on his car than we can tell him in many multiple posts.
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  #29 (permalink)  
Old 07-07-2010, 04:39 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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  #30 (permalink)  
Old 07-07-2010, 05:49 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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