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Discussion Starter #1
Starting to drive car more on street .Carb works great at track WOT AFR 12.5

Holley HP 1000 Pump gas BBC 252/268 @.050 solid roller Timing locked at 39 added ported VA for street use NGK -7 @.045

2200-2400 cruise AFR is 13.8 Idle afr is 14.0-13.8 I can set idle AFR at 14.5 but seems to like the richer idle ..........idle does drop off 150 rpm after stop and go driving but never stalls .stik car ...would like to cure that for street use

AFR cruise 13.8........is that too rich ??
when I ease into throttle at cruise get slight spike to 15.5 afr then goes to 12-13 overall runs fine ......should I try to lean out cruise and or idle ??
 

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Mine cruises at 12.8-13.2 and idles about 15, but it's hard for a wb to get an accurate reading because of all the ambient air in the exhaust at idle, so says a rep at FAST. when I experienced a lean spike with tip in throttle I always richen up the idle air mixture and it goes away,I fit happens with more than just tip in id say you need a lil bigger squirter
 

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Discussion Starter #4
maybe try a 1/16 of a turn in on all 4 screws and see how it acts. It sounds to me like it is very close.
MY bad should have said with mix screws 1.5 out it idles at 14.5 but at 2 out 13.8 ........ so yes finer adjustment needed ............

So 13.8 cruise is not too rich ?? for this combo
 

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Every engine wants something different at idle, it depends on a lot of factors. It's all about combustion efficiency, the better it is at idle the leaner you you can make it. Big cams usually need to be richer, as a richer mixture is easier to light. If it wants more to run best give it to it.
 

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Discussion Starter #6
Every engine wants something different at idle, it depends on a lot of factors. It's all about combustion efficiency, the better it is at idle the leaner you you can make it. Big cams usually need to be richer, as a richer mixture is easier to light. If it wants more to run best give it to it.
Thanks for responding Mark ..........I hear you on the idle afr ........ would going to a projected tip plug be a good thing to try to clen up idle


..what do you think about the cruise AFR at 13.8 ??
 

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If you have clearance to run a projected nose it gets the spark out away from boundary layer gas in the combustion chamber. Some chambers are not as much of an issue, some it may help a little in overall efficiency.
 

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Discussion Starter #9
Thanks for all the feedback , appreciate it ......... have not street driven this car much so was looking others experience ...........I have clearance for projected tip plug so will try dont expect a huge improvement but as long as no downside will give it a shot ............. my idle losing about 200rpm rpm after long street drive .......may have a carb internal issue that I need to check out more ............ at track never an issue with carb, plugs look great at WOT and no driveability issues ......just now with real street use this idle issue has come up so was curious about AFR at idle and cruise
 

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How hot does it get on the street compared to the track? Maybe that's the issue
 

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Discussion Starter #11
How hot does it get on the street compared to the track? Maybe that's the issue

Good thought but no it does not run hotter on street 185-190 max if anything it does take a while to fully warm up and on cool days like now rarely gets over 180
 
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