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Old 08-30-2002, 02:36 PM
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Question To Carb space or not ?

I have a 350 CI street small block Chevy with Pro Action Lightening iron heads with 2.02 I, 1.60 E valves, 200 cc intake runners, Holley Street 770 CFM street avenger Carb, Edelbrock performer intake, .470 Lift 230 duration hydraulic cam, headers with dual exhaust, HEI ignition with 50,000 Volt coil, 3.73 Posi rear end. My question is, for street use, will a 1 or 2 inch carb spacer help low end & Midrange torque ?
Thanks for the help.
Joe

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Old 08-30-2002, 02:58 PM
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From what i understand, that the big spacers are better for high RPM aplications. Allows better air flow to cool down the the gas it also helps insure vaccum since its a bigger resevour of vacum between when the intake valve opens and closes. A spacer will also reduce throttle responce. I would not recomend one for low end and midrange tourqe. Also if u wanna make your engine only for low end and mid range tourqe, you would need a more stock cam new heads with 1.84 valves and you would wanna get an edelbroke S-p-2-P intake with small runners. with all that stuff you would have and engine that would give great low end tourqe and even better throttle responce
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Old 08-30-2002, 03:52 PM
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Low end torque is a function of air flow dymanics in the manifold runners. Long runner lengths (around 18"), small plenums under the carb, small diameter runners all help low end (normal driving) performance because they accentuate and take advantage of the perssure waves that are bouncing around in every system. Unfortunately, these same parameters limit the flow at top end and result in low horsepower readings. Any rodder worth his salt wants an engine that puts out at least 300hp. An intake manifold I described will probably limit the engine to 200hp or less so we all opt for the big number. We ignore the fact that the 300HP comes at 5500rpm where we will NEVER run our engines and the 'low power' engine will put out twice the horsepower of the 'high power' engine at all lower rpms we run at. Engine design is a compromise and if you truly want low end performance, it is a practical fact that you must give up the top end and vice versa. True, there are ways to mitigate the problem (there will be adozen posts following this one claiming to outsmart physics) but in general, them's the facts. The one thing that can give the best of both of those worlds, low end torque and high end power, is more cubic inches but then you struggle with fuel economy.
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Old 09-03-2002, 11:38 AM
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on HRM's 383 the plenum spacer actually cost them 15 ft lbs of torque. as for 350's? dont know but sent my 1" spacer back to summit without opening it. i want the low end torque. don't care bout HP but yeah it seems like it would work making runner length longer but.. they had it on a dyno and it said no.
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Old 09-03-2002, 02:21 PM
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Adding spacers doesn't make runners longer it comes more under the catagory of a bigger plenum thus is not conducive to more low end torque. Do you have a 180deg (divided plenum) or 360deg Open plenum manifold? The former is the ticket for low end torque, the latter for high end power.
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