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 Post Posted: Thu Jul 05, 2012 11:49 am 
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Joined: Sun Sep 05, 2010 7:13 am
Posts: 68
Ok here we go... Recently picked up a Conv Camaro with a 396. I installed a XE 274 flat tapper cam, headers and a new 750 with 71 in front and 81 in back with plug. Had a part throttle stumble when primaries cracked while cruising. There is little to no t slot showing in front. I enlarged the IFR to .035 and shrunk the IAB to .070 from .075 and it cured it. Car was lazy wide open so I proceeded to jet down... I'm at 67 front and 73 rear with plug. Runs a lot stronger at wo and seems like I could go leaner based on the plugs. The tip in stumble re appeared but not as bad so I shrunk the IAB to .065 with no difference. The weird thing is I feel strongly I can lean the primaries out even more as there is no lean surging at all with cruising part throttle and the plugs are dark. It's got a 9.5 pv and pulls over 15 vac at idle. Wth is goin on? I'm almost ready to thin the plates and get slot showing on the primaries as I have it squared on the rears. Should I just close the rears more and get the slot showing in the fronts??


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 Post Posted: Thu Jul 05, 2012 3:49 pm 
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That 9.5 PV sounds a little high. Why don't you try the standard 6.5 that most use instead and see if that will lean the part throttle a bit more. Remember that the PV will not open until engine vacuum is seen at or under the number on it.

Those jet numbers for a 750 HP sound kinda small as the ones I've got came with 73s and 6.5 PVs front and rear. :-k

If you're only going to have the T slots showing on one end, then I'd make that the primaries although I normally try to balance it with both open about the same amount.

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 Post Posted: Thu Jul 05, 2012 4:17 pm 
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Joined: Sun Sep 05, 2010 7:13 am
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Fixed. I shut the sec and opened pri more. Also went to 64 primary and still driving fine. What is up with that!!??


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 Post Posted: Thu Jul 05, 2012 9:30 pm 
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Joined: Mon Oct 29, 2007 7:07 pm
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Location: Florida
You uncovered the t-slot on the primary, made it activate quicker.


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