No subject

Thu Nov 20 11:46:45 EST 2003

cylinder, even when the tests are run on the same day, on the same flow
bench.  My impression is that low lift numbers are particularly sensitive to
even slight variations in valve seat &/or valve face preparation.  My
feeling is that due to variable in flow bench setups etc., it's probably
difficult to make very precise or reliable comparisons of flow numbers
beyond broad generalizations between reports produced by different flow
benches, and maybe even different operators on the same flow bench.

FWIW, based on some old notes, on a new factory stock head, tested on a
SuperFlow 200 bench, I was given numbers that showed the following
variations from cylinder to cylinder across the 5 cylinders:
        Maximum# minus Minimum#
Lift in"   Intake  Exhaust
0.050	      3.90    1.40
0.100		3.30    2.10
0.150		4.10    1.80
0.200		3.70    3.30
0.250		5.90    3.70
0.300		3.50    4.30
0.350		6.00    4.50
0.400		6.20    5.30

           27.40   25.00

Total/Max difference between sum of cylinder flows from "best" flowing to
worst, was 27.40 cfm on the intake side, and 25.0 cfm for the exhaust ports,
with the "worst" intake cylinder -12.92 below the average; and the best
+14.48 cfm above the average sum of intake flow of 1,058.92.  On the exhaust
side, the "worst" exhaust cylinder was down -4.36 from the average for the 5
(799.6 cfm) and the best was up +12.94 cfm.  The Cylinder, #3, that produced
the best exhaust numbers also produced the best intake numbers.  If you look
closely at the head, you'll note that the ports are angled differently for
the cylinders, i.e. #1, #2 and #3 are "sort of" oriented to face back
towards the firewall, #4 and #5 twist slightly the other way, i.e. towards
the front of the engine.

This was for the head as it came off a factory engine, never been run in.  I
can't find the numbers for your head to know if the above variation in flows
is within the discrepancy you've noticed.


-----Original Message-----
From: CaptMagu at [mailto:CaptMagu at]
Sent: Wednesday, September 17, 2003 8:51 PM
To: mlped at
Subject: Re: FW: [s-cars] Re:  Air to Water intercoolers


Thanks for sharing. It looks like all the intakr numbers are better than
mine and the last part of the exhaust as well. I wonder why the lower lift
exhaust numbers weren't as good? Later.


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