I need help with jetting and PV (509ci, 8-71, dual 800cfm, 825HP)
10-28-2008, 04:45 AM
#41
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Your boost will pressures will definately go up when the prop hooks up more. Mine went up almost 2# from 6# to almost 8# when I added another inch of drive spacer to lower the propslip. Your AF ratio's and EGT's might change also since there will be more load on the engine. I would take that into consideration before making a lot of changes. Its plenty safe now as long as you're not washing the cylinders with fuel and dilluting the oil too much. You may want to try and get a prop that hooks up better before you do any major adjustments.
10-28-2008, 01:13 PM
#42
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The answer is very simple in certain applications you can start to have boost below the supercharger (requiring more fuel) but yet still have vacuum on top of the supercharger which keeps the carburetors lean. For the majority of people it's a much simpler and safer solution to boost reference the power valves to prevent any potential issues.
10-29-2008, 09:57 PM
#43
Rum Runner, This is true but 0 boost, under the blower, is usually 4-6 inches under the carburetor. The lowest power valve opening point is 2.5 inches. Therefore the power valve referenced below the carb will open well before you actually go into boost. That is why reading both values is worthwhile, then determine where to reference and when to add enrichment. He has the ability to read his exhaust temperature, which makes this easy.
good post, John B
good post, John B
10-30-2008, 05:36 AM
#44
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I personally like progressive linkage. Only in drag race competition engines do I run a 1:1 ratio . The progressive linkage will keep the engine way "cleaner" under cruising conditions.
10-30-2008, 01:26 PM
#45
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Rum Runner, This is true but 0 boost, under the blower, is usually 4-6 inches under the carburetor. The lowest power valve opening point is 2.5 inches. Therefore the power valve referenced below the carb will open well before you actually go into boost. That is why reading both values is worthwhile, then determine where to reference and when to add enrichment. He has the ability to read his exhaust temperature, which makes this easy.
good post, John B
good post, John B
10-30-2008, 01:28 PM
#46
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Deano,
With sideways mounted carburetors that run the progressive linkage and a lot of part throttle usage you'll actually see a difference in the bearing life from side to side on the engine. Running the dual PV's and tuning the transfer circuits to run clean takes care of any cruising problems. Hope you're getting somewhere on your 500" deal (I've got some new toys for them)
10-30-2008, 08:03 PM
#47
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I had a twin turbo motor that would have 5 inches of vacumm under the carb and 4 lbs of boost in the intake when not under wot.
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