Using Holley on SBC
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Using Holley on SBC
Im using a 750 vac sec holley. I am running vortec heads and a cam with 495/503 lift and 218/224 duration. Edelbrock RPM air-gap. Im pushing close to 375hp turning about 5300RPMs...I know some of you small block guys are running somewhat similar combo's..My question is this..I am looking for a ballpark figure on my jets. Just a place to start.....I know the carb was calibrated for a big block/electric fuel pump 3-1/2psi and I don't know how the base calibration would differ from a small block/mech fuel pump 6psi...Im running 78primarys and 80secondary jets...Not sure on the accel pump cam or vac secondary spring..Main thing is I am curious as to what everybody else is running..Since this is my first REAL go-around with a holley since running the "Brock" I wondering if I am even in the ballpark starting off....
BH
BH
#2
I can't tell you what jet's to use but another thing is the power valve. They make a bunch of different sizes. You'll need to see how much vacuum you've got and use the appropriate valve.
My brother just went through this with his Demon that's on a built 460 (in a car) Made a big difference in around performance.
Probably would be best to buy a book on Holley's.
My brother just went through this with his Demon that's on a built 460 (in a car) Made a big difference in around performance.
Probably would be best to buy a book on Holley's.
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A slight comparison
I have almost the same exact setup. 350, Comp XM264HR (you have the 270), 1.6 ratio comp rockers, rpm airgap, IMCO risers, MSD and pro-action 220 CC heads. My compression ratio with 0.015 steel shim gaskets is 9.39:1 static with a .039 quench distance
I run a 600 vac sec dual feed (center hung float) holley (in a quest to try out a 750 - and put an O2 sensor in the pipe). I run 66 primary & 72 secondary, purple sec spring, pink cam - hole #1 w/ 31 squirter. I really need to go to a 28 squirter and drop down on the power valve... if my memory recalls correctly i have a 8.5 power valve in there and that is too high, i need to drop down an inch at least since i cruise in the 3000 - 4000 range... i average around 4 miles / gallon in that cruise range...
my vacuum curve under load is such: (all in Inches of Hg)
15 1/2 @ 750 rpm idle
11 1/2 @ 2500 rpm
10 1/2 @ 3000 rpm
9 @ 3500
8 @ 4000
7 1/2 @ 4500
5 - 5 1/2 @ WOT - 5500 rpm
I run a 600 vac sec dual feed (center hung float) holley (in a quest to try out a 750 - and put an O2 sensor in the pipe). I run 66 primary & 72 secondary, purple sec spring, pink cam - hole #1 w/ 31 squirter. I really need to go to a 28 squirter and drop down on the power valve... if my memory recalls correctly i have a 8.5 power valve in there and that is too high, i need to drop down an inch at least since i cruise in the 3000 - 4000 range... i average around 4 miles / gallon in that cruise range...
my vacuum curve under load is such: (all in Inches of Hg)
15 1/2 @ 750 rpm idle
11 1/2 @ 2500 rpm
10 1/2 @ 3000 rpm
9 @ 3500
8 @ 4000
7 1/2 @ 4500
5 - 5 1/2 @ WOT - 5500 rpm
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The 73 primarys and 76 secondaries I gave you in those carbs were the jets that crusader had in them for their 500 horse 454...so you probably are gonna go down from there. I think I was running 80's on the secondaries and 78's on the primaries with merlin heads and the 415 horse roller cam on my 502. I think the number on the power valve was stamped into them too.....Glenn
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BAD HABBIT, what kind of prop and what kind of top end do you get out of that.. I am still trying ot figure out the jets on my SBC with a Perf RPM with a Rochester carb. I can crank 5100 RPM with a 19" pitch prop. Just curious
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Interesting note. Ive found out that using a bigger than usual (necessary) carb means that the carb will require more of a accelerator shot and larger jets than a bigger motor will. Ive tried to do as much reading as possible lately on the holleys and have read this several places. I guess it's because the vaccum signal is less on a smaller motor. The smaller motor will still use the same amount of fuel with a 750 as a 600. The pounds per hour are the same just the velocity will be different hence the need for a bigger shot and jets....
BH
BH
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Originally posted by powerqrudy
BAD HABBIT, what kind of prop and what kind of top end do you get out of that.. I am still trying ot figure out the jets on my SBC with a Perf RPM with a Rochester carb. I can crank 5100 RPM with a 19" pitch prop. Just curious
BAD HABBIT, what kind of prop and what kind of top end do you get out of that.. I am still trying ot figure out the jets on my SBC with a Perf RPM with a Rochester carb. I can crank 5100 RPM with a 19" pitch prop. Just curious
BH
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I am running a 750 holley vac secondary non marine carb.
Last years motor.
383
vortech heads
9.9:1 comp ratio
222/230 .509/.528 roller cam
air gap dual plane intake.
ran great with 72's in the primarys. This carb has no jets in the secondaies
New motor
383
afr heads
10.8:1 comp ratio with 110 octane
single plane intake
234/242 .575/.595 lift roller cam
same carb Rejetted to 74's in the primaries last weekend and plugs look great. no jets in secondaries
Last years motor.
383
vortech heads
9.9:1 comp ratio
222/230 .509/.528 roller cam
air gap dual plane intake.
ran great with 72's in the primarys. This carb has no jets in the secondaies
New motor
383
afr heads
10.8:1 comp ratio with 110 octane
single plane intake
234/242 .575/.595 lift roller cam
same carb Rejetted to 74's in the primaries last weekend and plugs look great. no jets in secondaries