Cobain03 said:im in the processs of a rebuild, do you think it would be worth the 150 bucks (summit) to go ahead and get the RPM intake? will i notice a difference?
Wrong info. He will not notice any sluggishness off idle with an RPM intake. He WILL get SOME extra performance up top. How much? That depends.Edbert said:With a factory cam and heads switching to an RPM from a Perf will make a negligible difference performance wise. Most noticeable will be a little more sluggishness off idle and a little more willingness at high RPM, plus a little worse mileage. But very small differences overall.
Match the intake with the right heads and cam and the difference will be night and day. My recommendation is to wait until you can do all of them together.
Compared to the non RPM performer he will, particularly so with a stock cam which is around 190 duration (at 50) and .400 lift (IIRC). The perf-RPM is designed for a 1500-6000 operating range while the base unit is for idle (600-700) to 5000. Until the motor gets to 1500 the mixture velocity will be too low for crisp throttle response.D.Hearne said:Wrong info. He will not notice any sluggishness off idle with an RPM intake. He WILL get SOME extra performance up top. How much? That depends.
Have you ever actually tried one with a stock cam ? I had one on a stock, 88 Crown Vic roller 5.0, and there was NO lack of response in the off-idle performance. Even with it's crappy cam ( probably the smallest roller you can get for one, with sub .400 lift and less than 260 degree advertised duration) it STILL performed flawlessly. High rise, dual plane, large runner carb intakes just do not lack in bottom end performance like single planes do. I've used too many on basically stock motors to know for sure. Just because it was "designed" to give better performance in the mid to upper rpms, doesn't mean it absolutely doesn't work on off idle situations. About the only situation where one wouldn't, would be where the owner planted a larger than needed mechanical secondary carb on top, and/or combined that with an automatic trans and/or rear gears that were meant for highway crusing. (i.e: putting a 650+cfm Holley double pumper on a stock 302/5.0, and a stock stall C-4 or AOD and a 2.50 to 3.00 geared rear) The carb then would be the culprit in the off idle performance, the trans. and rear gear ratio would just exasperate it.Edbert said:Compared to the non RPM performer he will, particularly so with a stock cam which is around 190 duration (at 50) and .400 lift (IIRC). The perf-RPM is designed for a 1500-6000 operating range while the base unit is for idle (600-700) to 5000. Until the motor gets to 1500 the mixture velocity will be too low for crisp throttle response.
Dark Knight said:Personally, I'd keep the performer for now..put the cam in that you want, but with the smaller ports, you'll keep the intake velocity up. Get the intake when you get the heads, you're going to have to pull it anyway.
I agree.pabear89 said:I have a 600 holley on top of a off brand Air-gap intake using the rv cam and long tube headers in my 68 cougar with auto and 2.79 rear.
It has preformed quite well in this set up on a 66 block with 67 smog heads.
Seems to have a peppy off idle responce and good top end for a daily type driver.
the plus is No carb spacer and now it doesn't get that gas boil when it is shut off after a long hard run.
PB
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