6000rpm

347 · #1 (**permalink**) 03-17-2003, 04:39 AM

can anybody tell me why my engine peaks at 6000rpm ,when my cam has an rpm range of 2500 to 6500? i have a 347 with quad 44mm idf webers ported windsor snr's and intake to match?...............my guess is the 44mm webers,am i correct?

Hotfingrs · #2 (**permalink**) 03-17-2003, 06:16 AM

The power range is only useful if you have the engine to go with it. The webers might be to small, the runners on the intake might be to small, the heads might be to small...there's a number of places to look and see where the restriction is.....

hound dog · #3 (**permalink**) 03-17-2003, 06:27 AM

Also, if you have hydraulic lifters you may be encountering float. 6000 is about the max for hydraulics even if they're rollers. Otherwise the webers may be a little small. But there are many possibilities.
h dog

George Snyder · #4 (**permalink**) 03-17-2003, 07:18 PM

347,

There are many things that could be causing it. I am assuming that your were using an Engine or Chassis Dyno at the time.
If so did the engine flat line or drop off at 6K?
If we are talking flat line three things that come to mind are fuel, ignition, not enough air.
It it drops it also could be springs too light and floating valves, lifters, etc.
Maybe if you post more information, others here can better help.

750hp · #5 (**permalink**) 03-19-2003, 02:42 AM

From a previous time you asked this same question.....

Quote:

Originally posted by Bob Putnam

My "guestimate" is that the 44s with stock venturi will be great from 2000-5500 rpm. After that, the horsepower will flatten out quickly.

Cal Metal · #6 (**permalink**) 03-20-2003, 08:34 AM

347:

The 44mm venturi could be a little larger for your 347 cid but it really should pull 6,000 with a 44mm venturi. The 347 equates to around 600cc per cylinder which means you need to be at 44mm minimum if you want to achieve your desired RPM. I have a chart that I can post to show what I mean.

Before you do that, however, check the size of your air correction jet. If it is too large (200-210 or beyond) that can be a problem, as it will limit your top end RPM. It is a cheap, easy fix. I would try that first if the other variables (cam, heads) are within range.

Also make sure the aux. venturi is not necked down to, say, 34mm. 37mm. would be more applicable.

computerworks · #7 (**permalink**) 03-20-2003, 08:52 AM

Cal posted this chart a while back:

http://www.clubcobra.com/forums/atta...&postid=328557