750 DP holley carb jetting???? - Chevelle Tech
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post #1 of 11 (permalink) Old Jul 12th, 09, 12:33 PM Thread Starter
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Question 750 DP holley carb jetting????

Posted: Sun Jul 12, 2009 11:29 am Post subject: 750 holley carb jetting?????

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Well for years my DP 750 holley what i thought was a 4779 turns out to be 6109 tunnel ram carb after Rickster looked up numbers in holley book!(thanks Rick) I was running 76 primary and 84 sec. jets on 9.8 to 1 327 with vic. junior and 1 inch spacer and ported twisted old trickflow heads. Rick came up with 75,76 stock jetting for this 6109 carb so i jetted 72,74 on this single vic intake and took her out and car seems to run smoother with what seems to accel faster at 4 to 5 grand but as we all know sometimes seat of pants fools Ya. Any carb experts here have any advice or experience or set me in right direction OR if i may be in danger zone!!!! Thanks in advance for any feedback. Car has run best of 12.2 with steet BFG touring radials and 11.64 115.5 with hoosier QTP and 5 speed. thanks again, AL
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post #2 of 11 (permalink) Old Jul 12th, 09, 12:40 PM
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Mark
 
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Re: 750 DP holley carb jetting????

Without an A/F meter (and really even with one), I think the best way to do it is keep the primaries for a slightly lean cruise (no pinging, no surge), the secondaries for fastest MPH in the 1/4 mile. Take the car out, see what it does, make a change and try again until you get your best mph.

Reading your plugs (I'm not so hot at that myself) is also a good way to check.

Mark

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post #3 of 11 (permalink) Old Jul 12th, 09, 12:42 PM
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Re: 750 DP holley carb jetting????

76/84 is a bit rich for a normal 750, Are you running primary only or both powervalves? I would try between 72 and 74 on the primary with a power valve and between 82 and 84 on the secondary with the PV plugged. Start on the high side and go down, stop where you get the best MPH in the 1/4. You need the staggered jetting when running a power valve to compensate for the PVCR at WOT.
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post #4 of 11 (permalink) Old Jul 12th, 09, 12:52 PM Thread Starter
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Re: 750 DP holley carb jetting????

Primary valve only. Why does holley say 75 primary with P.V. and 76 secondary with no p.v. on this 6109 tunnel ram carb??? thanks, AL
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post #5 of 11 (permalink) Old Jul 12th, 09, 2:53 PM
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Re: 750 DP holley carb jetting????

The only reason for so little stagger would be if the secondary metering was drastically different, if you can, measure the main air bleeds for both primary and secondary, number and size of the e-bleeds on each block. I'm not familiar with that particular model, so maybe we can figure what will work best for you.
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post #6 of 11 (permalink) Old Jul 12th, 09, 4:28 PM
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Re: 750 DP holley carb jetting????

750HP Street comes jetted 75/80 w/ 4.5PV front. Runs very clean and crisp.
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post #7 of 11 (permalink) Old Jul 12th, 09, 5:19 PM Thread Starter
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Talking Re: 750 DP holley carb jetting????

The idle air bleeds on this 6109 are 69 and 70,high speed air bleeds are are 31 and 31 measured with cylinder pin gages and are pressed in! I alse have a HP main body i bought that has screw in air bleeds idle 73 and 75 ,high speed air bleeds 36 and 36, so is this possibly why the 6109 carb is jetted smaaller on secondaries? Wouldn't the smaller air bleeds pull more full on a given jet? I am curious what the 4779 750 has for air bleeds, being jetted different from holley!! thanks again, AL
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post #8 of 11 (permalink) Old Jul 12th, 09, 6:37 PM
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Re: 750 DP holley carb jetting????

al,how is the surging??

what jets were in it when you ran 11.64?

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post #9 of 11 (permalink) Old Jul 12th, 09, 7:55 PM Thread Starter
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Thumbs up Re: 750 DP holley carb jetting????

No noticable surging Rick! When i ran the 11.64 had 75,84 jets with the 4 hole on top of the open. THANKS, al
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post #10 of 11 (permalink) Old Jul 12th, 09, 8:43 PM
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Re: 750 DP holley carb jetting????

Nothing wrong with the 31 main bleeds or the idle bleeds. Any difference in the number or size of the emulsion bleeds between the primary and secondary metering blocks? What size is the PVCR?
Before you run it WOT with the new jets I would go back to the original stagger, after running a baseline run go down 2 each primary/secondary jets and see what your MPH does. If it improves go down 1 at a time each from there until you see it slow.
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post #11 of 11 (permalink) Old Jul 17th, 09, 7:03 PM Thread Starter
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Talking Re: 750 DP holley carb jetting????

I made a call to the holley tech and they asked what altitude i was at and he said to start at 79jet size primary and 80 secondary with this 6109 tunnel ram 750 carb on my victor junior! I guess i will try this over weekend and see how she feels! This would be 4 steps up over stock. Did not get a chance to measure any other holes. thanks again, AL
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