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Looking for flow numbers
https://slantsix.org/forum/viewtopic.php?t=11999
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Author:  Pacer225/6 [ Mon Feb 28, 2005 11:14 pm ]
Post subject:  Looking for flow numbers

Hi. Can anyone help me? I'm looking for some Slant head flow numbers to compare with my own results that I gained from the head porting project I worked on during my Xmas holidays. I would just like to see if I'm heading in the right direction before I start playing with my next test head.
Here's where I'm up to, all numbers are at 28" and with a 1.72" Chev Intake / 1.5 Chev Exhaust.
Lift -----Int-------Exh
--.05----29.6------25.3
--.10----60.3------54.5
--.15----94.0------77.5
--.20---116.5-----96.8
--.25---140.0----112.0
--.30---163.2----124.0
--.35---179.9----134.5
--.40---186.8----142.4
--.45---190.6----145.4
--.50---185.6----147.4
--.55----N/A------151.4

Thanks Andrew

Author:  sandy in BC [ Tue Mar 01, 2005 8:19 am ]
Post subject: 

Welcome Andrew! I was hoping this info wasn t lost when the other site went down. Did you modify the combustion chamber in any way?

Author:  Pacer225 [ Tue Mar 01, 2005 8:29 pm ]
Post subject: 

The only combustion chamber mod I've tried so far was this. I placed an old head gasket on the head and scribed near the intake valve. If you imagined the chamber as a clock face, the spark plug as the 12.00 o'clock position and intake valve on the left hand side, I blended from the scribe mark down to the valve seat between about the 7.30 to the 10.00 o'clock position. I felt it was worth the effort for the CFM gains made.

Andrew

P.S. I did make some exhaust templates but I've damaged my digital camera and I can't download the photo's it takes.

Author:  Doctor Dodge [ Wed Mar 02, 2005 8:51 pm ]
Post subject: 

As a rule of thumb, I use 200 on the intakes and 150 on the exhaust side.
This is based on a well ported, big valve head at 27 inches.
I looks like you are pretty close to that.
DD

Author:  Pacer225 [ Thu Mar 03, 2005 8:26 pm ]
Post subject: 

Thanks for the reply DD.
Those numbers will give me something to aim for.
I did get 202 CFM out of one practice intake port but I wasn't happy with the loss of low lift flow, now that I know 200 CFM is what you would expect I'll keep working on it. What lift were you getting your numbers at?
Have you noticed in the past a tendency for flow in the stock to mildly modified intake ports to quite suddenly stall in the .400" to .450" lift range?

Thanks Andrew

Author:  Doctor Dodge [ Thu Mar 03, 2005 9:37 pm ]
Post subject: 

.500 to .525 lift is about the max.
To get good flow at those lifts you will loose some of the low end velocity.
DD

Author:  Guest [ Thu Mar 03, 2005 10:17 pm ]
Post subject: 

Thanks again DD
Any advice regarding combustion chamber mods other than what I have already listed above?

Thanks Andrew

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