Re: 950 too rich at cruise
[Re: DrCharles]
#2846057
11/14/20 12:03 PM
11/14/20 12:03 PM
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Thumperdart
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Other than 2-bbl dirt carbs, you should NEVER need bypass air and no, that carb wasn't right as delivered imo especially with the "I don't know how to lean it out so let's drill holes in the bleeds" bs......
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: 950 too rich at cruise
[Re: Thumperdart]
#2846063
11/14/20 12:30 PM
11/14/20 12:30 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
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Interesting, thanks Dom! I realize there are differences of opinion among tuners, but I'd have to open the secondaries into their t-slots to get enough air and most everything I've read/chatted with say not to do that (as the secondary slots are further up the bores). I thought the blades came that way, not drilled by builder. The holes are not for leaning it out per se, but to pass sufficient idle air for the idle speed. This cam has lots of overlap and needs a surprising (to me) amount of air for its 1200 rpm idle. What is your carb & combo? I seem to recall you having an even bigger cam (276@.050)? You've said that is OK to do, but won't that cause even more tuning difficulties by introducing yet another source of fuel? Edited to add: these plates come that way from Holley/QF. The ones I'm not using (with 1/8" holes) are stamped "325" which is factory-made.
Last edited by DrCharles; 11/14/20 12:50 PM.
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Re: 950 too rich at cruise
[Re: jb500]
#2846086
11/14/20 01:32 PM
11/14/20 01:32 PM
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DrCharles
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I've tried that too (backing off the primary to almost no t-slot)... didn't seem to make much difference. How big are your blade holes? How come you only have 6" idle vacuum with a smaller cam than my 451? Idling real slow and lumpy? Or a flat-tappet (mine is a mushroom)? What's special about the FV178 valve? A major difference I see is that your MAB is much smaller (and your emulsion stack is smaller too)... .028 MAB is the next thing I'm planning to try. Raining all through tonight, so no road testing today!
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Re: 950 too rich at cruise
[Re: jb500]
#2846102
11/14/20 02:31 PM
11/14/20 02:31 PM
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DrCharles
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That IS where my primary t-slot exposure is... and the secondaries are closed, because otherwise it idles too fast with the 4x .100" holes and the "grab whatever fits" PCV valve I'm running Fortunately I have a 4-speed and the idle is 1200+ anyway, so I don't have to worry about an in-gear drop. I found an old Speedtalk thread ( https://www.speed-talk.com/forum/viewtopic.php?t=2767) where the guy didn't like holes in the blades because that airflow comes past the boosters and tends to start them too early. Wonder if that's part of my problem... anyway he recommended bypass air without holes. Dom absolutely is against any bypass as you can see, above. Some others recommend turning off the secondary idle screws completely and just dealing with the primary idle circuit! To have even more things to change, as if I wasn't up to my ass in alligators already, I ordered some non-drilled blades and a Fram FV178
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Re: 950 too rich at cruise
[Re: DrCharles]
#2846118
11/14/20 03:11 PM
11/14/20 03:11 PM
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DrCharles
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I found an article from Innovate: https://www.innovatemotorsports.com/resources/carb_EFI_mileage.phpThey had the same problem I did (idle ok, but pig-rich on the t-slots). On a 750 "Mighty Demon" they reduced the IFR from .036 all the way down to .020, IAB down to .032 and MAB up to a whopping .090. No mention of a TSR. So their smallblock with a 253/259@.050 cam is on the idle circuit up to 2900 rpm and the mains start coming in at 2800. That's way different from most of the tuning advice I see!
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Re: 950 too rich at cruise
[Re: jb500]
#2846143
11/14/20 04:02 PM
11/14/20 04:02 PM
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DrCharles
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I agree, I'm posting on RFS too. But it's hard to argue with the Innovate results That engine has a 9" idle vacuum. And that was my biggest problem that started all this - idles fine, runs pig-rich at cruise. I went all the way down to a .041 TSR and it helped a lot, but also created a super-lean flat spot... If I tried their approach, I would want a bit more idle fuel (doubt my combo would even run when off the mains with a .020 IFR!) So rather than return to what I know didn't work (as-delivered), I'm thinking of something like this (along the unconventional lines of the article): Original Current Proposed IFR .033 .031 .029 - this is probably where I should have STARTED leaning, .031 helped but wasn't near enough IAB .070 .082 .063 TSR .081 .041 .074 - even with .041 it's not right, so go back to a normal size MAB .030 .082 .085 - want to delay the mains MJ 79/88 75/86 75/86 PV 5.5" 9.5" 9.5" - cruise vac 15" PVCR .059, will change last, probably .070 or so with the smaller PMJ This old thread: https://board.moparts.org/ubbthread...48706/holley-rich-at-light-throttle.htmlpoints out that it'll never be right when cruising on the t-slots, because the idle vacuum is less than the cruise vacuum... but I think I can get closer than it is. What is most important to me is to drive at 60 mph without being overrich, also 25-30 mph - because that's where the car spends most of its time on the 8 mile drive to town, then cruising on the street. Rough idle is a given with a 272 @.050 cam, and I can live with a little flat spot at small throttle settings.
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Re: 950 too rich at cruise
[Re: DrCharles]
#2846432
11/15/20 09:31 AM
11/15/20 09:31 AM
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madscientist
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That IS where my primary t-slot exposure is... and the secondaries are closed, because otherwise it idles too fast with the 4x .100" holes and the "grab whatever fits" PCV valve I'm running Fortunately I have a 4-speed and the idle is 1200+ anyway, so I don't have to worry about an in-gear drop. I found an old Speedtalk thread ( https://www.speed-talk.com/forum/viewtopic.php?t=2767) where the guy didn't like holes in the blades because that airflow comes past the boosters and tends to start them too early. Wonder if that's part of my problem... anyway he recommended bypass air without holes. Dom absolutely is against any bypass as you can see, above. Some others recommend turning off the secondary idle screws completely and just dealing with the primary idle circuit! To have even more things to change, as if I wasn't up to my ass in alligators already, I ordered some non-drilled blades and a Fram FV178 I would suggest saving the 6 bucks and spending the money on the only tuneable PCV valve out there. And that’s the ME Wagner PCV valve. I have no idea of what the flow rates are of that Fram part number, but whatever it is, the absolute improbability of it being correct for a combination like yours is astronomical. I doubt Fram has anyone developing a PCV valve for applications like this because because any fixed orifice PCV valve that would work for you would never work for me. So they would literally be developing a part number to sell what?? maybe, maybe 5 of them for the entire country and it may work correctly on one application. I can’t stress the importance of not only using a PCV valve but on using a tunable one. And Wagner makes the only one. With your manifold vacuum at idle you can still use it in dual mode and it will change the tune up. Just my .02 cents, but I use one and use one on any engine I do that has much more than a pretty mild street cam in it. Worth every penny.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: 950 too rich at cruise
[Re: DrCharles]
#2846434
11/15/20 09:34 AM
11/15/20 09:34 AM
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I agree, I'm posting on RFS too. But it's hard to argue with the Innovate results That engine has a 9" idle vacuum. And that was my biggest problem that started all this - idles fine, runs pig-rich at cruise. I went all the way down to a .041 TSR and it helped a lot, but also created a super-lean flat spot... If I tried their approach, I would want a bit more idle fuel (doubt my combo would even run when off the mains with a .020 IFR!) So rather than return to what I know didn't work (as-delivered), I'm thinking of something like this (along the unconventional lines of the article): Original Current Proposed IFR .033 .031 .029 - this is probably where I should have STARTED leaning, .031 helped but wasn't near enough IAB .070 .082 .063 TSR .081 .041 .074 - even with .041 it's not right, so go back to a normal size MAB .030 .082 .085 - want to delay the mains MJ 79/88 75/86 75/86 PV 5.5" 9.5" 9.5" - cruise vac 15" PVCR .059, will change last, probably .070 or so with the smaller PMJ This old thread: https://board.moparts.org/ubbthread...48706/holley-rich-at-light-throttle.htmlpoints out that it'll never be right when cruising on the t-slots, because the idle vacuum is less than the cruise vacuum... but I think I can get closer than it is. What is most important to me is to drive at 60 mph without being overrich, also 25-30 mph - because that's where the car spends most of its time on the 8 mile drive to town, then cruising on the street. Rough idle is a given with a 272 @.050 cam, and I can live with a little flat spot at small throttle settings. An .085 MAB a will not delay the mains. Don’t forget that the MAB feeds the emulsion stack too. So if you have an assload of emulsion (you don’t need it) the MAB has to be big enough to feed the emulsion bleeds and correct booster timing. I’ll go read the link because I’m interested but that big MAB they used got the mains going earlier unless they have something else funky.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: 950 too rich at cruise
[Re: madscientist]
#2846436
11/15/20 09:46 AM
11/15/20 09:46 AM
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Yeah, the article specifically said they were delaying the mains with that big MAB and that is DEAD wrong. I need to click on the link to see the full article but a bigger MAB starts the flow to the boosters sooner and leans out the fuel curve at high RPM and the opposite happens with a smaller MAB.
I guess maybe that that big MAB could be killing any signal to the booster, but I’d have to think about it for a bit but that seems a queer w.any to do it if that’s what’s happening.
BTW, they still set power valve opening wrong. Damn, that lie won’t ever die.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: 950 too rich at cruise
[Re: madscientist]
#2846442
11/15/20 09:53 AM
11/15/20 09:53 AM
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DrCharles
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The full article doesn't seem to be there (goes to the magazine site but it's a 404 error). I agree that some of their explanations look hokey, and that PV vacuum is a crock but I ignored that. I know better I am hoping to find a small enough IFR that it can't run so darn rich at cruise (15") but still have enough to the idle screws (8"). It will end up being a compromise, of course. Going all the way down to .041 TSR helped lean the cruise some but it also created a lean flat spot. Then I can play with the air bleeds, IAB then MAB. Those are easy to change but I'm getting really tired of taking the bowls off! Do you think .028 is small enough?
Last edited by DrCharles; 11/15/20 09:54 AM.
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Re: 950 too rich at cruise
[Re: madscientist]
#2846448
11/15/20 10:09 AM
11/15/20 10:09 AM
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jb500
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That IS where my primary t-slot exposure is... and the secondaries are closed, because otherwise it idles too fast with the 4x .100" holes and the "grab whatever fits" PCV valve I'm running Fortunately I have a 4-speed and the idle is 1200+ anyway, so I don't have to worry about an in-gear drop. I found an old Speedtalk thread ( https://www.speed-talk.com/forum/viewtopic.php?t=2767) where the guy didn't like holes in the blades because that airflow comes past the boosters and tends to start them too early. Wonder if that's part of my problem... anyway he recommended bypass air without holes. Dom absolutely is against any bypass as you can see, above. Some others recommend turning off the secondary idle screws completely and just dealing with the primary idle circuit! To have even more things to change, as if I wasn't up to my ass in alligators already, I ordered some non-drilled blades and a Fram FV178 I would suggest saving the 6 bucks and spending the money on the only tuneable PCV valve out there. And that’s the ME Wagner PCV valve. I have no idea of what the flow rates are of that Fram part number, but whatever it is, the absolute improbability of it being correct for a combination like yours is astronomical. I doubt Fram has anyone developing a PCV valve for applications like this because because any fixed orifice PCV valve that would work for you would never work for me. So they would literally be developing a part number to sell what?? maybe, maybe 5 of them for the entire country and it may work correctly on one application. I can’t stress the importance of not only using a PCV valve but on using a tunable one. And Wagner makes the only one. With your manifold vacuum at idle you can still use it in dual mode and it will change the tune up. Just my .02 cents, but I use one and use one on any engine I do that has much more than a pretty mild street cam in it. Worth every penny. Well, if you are giving out Wagner PCV valves...I'll take one. However, spending $6.00 worked for me and no need to spend $130 for a PCV valve.
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Re: 950 too rich at cruise
[Re: jb500]
#2846494
11/15/20 11:38 AM
11/15/20 11:38 AM
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DrCharles
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Well, if you are giving out Wagner PCV valves...I'll take one. However, spending $6.00 worked for me and no need to spend $130 for a PCV valve. Yeah, that got my attention too... Meanwhile I'm wondering if I can't just use a fixed orifice instead of a PCV valve? At idle there's less vacuum (8"), so less air flow, and I need more air at 15" cruise vacuum anyway to help with the rich problem...
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Re: 950 too rich at cruise
[Re: DrCharles]
#2846505
11/15/20 11:58 AM
11/15/20 11:58 AM
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Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
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And another reason why baby carbs on hot motors suck, too peaky here, to sensitive there and why I'd put a proven Dommy on anything making over 500 hp and have for years with great results. Yes, my street cam is .680-.660 and 276-281 and idles and drives awesome with no issues anywhere in the power band BUT, it took time and patience to get there and yes, holes in blades are bypass air to smooth out rich idle/transition issues. I never said it's ok to drill blades in 4 barrels and I never do under any circumstances except like I said for high velocity 2-bbl dirt stuff.....
Last edited by Thumperdart; 11/15/20 11:59 AM.
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: 950 too rich at cruise
[Re: madscientist]
#2846509
11/15/20 12:02 PM
11/15/20 12:02 PM
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Thumperdart
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Too big of a main bleed = no fuel through the jets needing HUGH jets up top to be happy which floods part throttle cruise when on the mains.....
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: 950 too rich at cruise
[Re: DrCharles]
#2846511
11/15/20 12:05 PM
11/15/20 12:05 PM
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Joined: Jul 2004
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Thumperdart
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Even with my t-ram square jetted w/no p/v's I can cruise at whatever afr's I want with ease and it's happy in the upper 13's to mid 14's and your dual plane is making matters worse imo.......
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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