Dogleg or annular boosters?
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Dogleg or annular boosters?
Im building a 421 sbc 650+ HP 13.0:1 compression 80% race 20% street engine. Im looking at the pro systems carbs pro series 4150 carbs and just wondering if I shoud go with the dogleg boosters or the annular boosters? also not too sure what cfm I should go with either. I was thinking around the 950 range?
Annular vs. Downleg
Recommend the "annular" over the "dogleg's".
Personally, would also have used 14:1 (minimum) as a starting point for C.R. We like closer to 15:1 in "fuel" builds.
Recently delivered a "pump-gas" (93 octane/11:1) 406" SB, 615+ HP, 1050 Holley (annular), fairly small solid-roller, RHS235's (minimal porting), 2.000" primaries.
There was no HP "chasing" here, bolt the parts together and go racing!
Runs a '72 Camino (3600#) to a some 10.70's at 124.
Thanks, Gary in N.Y.
P.S. Thanks to Frank Lupo at Dynamic Convertors! One "super" convertor in this ride!
Personally, would also have used 14:1 (minimum) as a starting point for C.R. We like closer to 15:1 in "fuel" builds.
Recently delivered a "pump-gas" (93 octane/11:1) 406" SB, 615+ HP, 1050 Holley (annular), fairly small solid-roller, RHS235's (minimal porting), 2.000" primaries.
There was no HP "chasing" here, bolt the parts together and go racing!
Runs a '72 Camino (3600#) to a some 10.70's at 124.
Thanks, Gary in N.Y.
P.S. Thanks to Frank Lupo at Dynamic Convertors! One "super" convertor in this ride!
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RayJE Carburetors wrote:annular boosters in a 4150 body kill the flow of the carb... even with a 1.57 venturi the 900 thou outside and 550 inside diameter annular booster kills flow..... for 650+ HP out of a 421 ci small block a 1000HP body with downlegs will make the most power.
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From what we have seen it hurts power by about 6 to 8hp on a 850 to 900hp engine.richyrich wrote:I was wondering the same thing. From what I have read in almost all magazines and websites, the annular boosters always come out on top. But most racers still prefer the downleg design right? Is it true the the annular booster only helps with the fuel atomization and simply kills the flow?
Engine size and rpm will change this.
Tom
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I had a pair of 850 CFM Holleys converted to annular boosters and choke horns removed for my Rip Van Winkle 495 BBC project and did my own throttle shaft slabbing and airfoiling of the blades. They flow 965 CFM dry and one or the other has out-powered all comers (3 pro-built and another 4 off the shelf 830 to 950 CFM non-annular units) on two chassis dyno and 3 engine dyno tests on SBCs in the 540 to 670 HP range...
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annular boosters
The main feature of the annular boosters is it will work over a very broad RPM range( especially down at very low RPM) where the normal boosters will not function correctly at very low speeds9 Once the RPM is up pretty high( 6000-7000) the boosters no longer have an advantage, and they might actually hurt top end performance. On race carts, if the converter is way too tight, the annular boosters can makr a reral big differance in performance.
JOE SHERMAN RACING
JOE SHERMAN RACING