The Number 1 Question I get is “Do you CNC Port?”
The answer is no, however, people do not realize that the head has to be hand ported to program the CNC Machine. Everybody is worried about whether or not every runner is going to be exactly the same, They do not realize that after the CNC Program has been complete, that each runner flows 3% less than the hand ported head which programmed the CNC Machine.
The biggest concern needs to lie into your intake, people spend $100’s of dollars on a set of good ported heads, and just bolt their intake on AS CAST, when the intake was formed it was intended for it to be match ported to your heads. The companies do not know what type of heads you will be running with your intake so they make the mouth of the port smaller for you to match to your heads.
Why people are getting so caught up in CNC porting, they do not realize that your intake could be as much as 20 CFM’s plus (+) off from one runner to another. So unless your runners on your intake are balanced out, even your CNC Ported head will be unbalanced from runner to runner. Just a little food for thought!!
At Abbotts SuperFlow Port & Polish we take a lot of pride in porting and polishing intakes and cylinder heads. When we port a set of heads, we gauge each runner in certain KEY Locations for MAX FLOW. It is recorded for future reference on a computer program. So, more or less, we port a set of heads, we get the peak CFM’s from each runner from the same heads consistently.
CNC Programmers claim that a hand ported head can not match a CNC ported head. However, it depends on the person doing the port work. Half the time you see somebody that does CNC Port Work only offers it on certain heads, so the rest of the heads they receive they are doing hand porting.
On Intake Manifolds, as cast, no port work, Showing how on an Intake Mainfold Runner Can be unbalanced.
The BBC Victor flows 39 CFM's off from best runner flow to worst.
The SBC Victor 20 CFM's off from best runner flow to worst.
The SBC Super Victor 30 CFM's off from best runner flow to worst.
The SBC Motown 58 CFM's off from best runner flow to worst.
The SBC RPM 19 CFM's off from best runner flow to worst.
The SBF RPM 28 CFM's off from best runner flow to worst.
The SBF Super Victor 24 CFM's off from best runner flow to worst.
** Our Stage 2 & 3 port work will balance out your flow #'s on your intakes. Stage 1 is a match port to your heads only.
There is an article in Super Chevy High Performance Magazine, June 2008 issue, that shows that Dart CNC ported Pro 1's at .500 lift from right to left port, they were flowing 21 CFM's off from one runner to the next. That is 6% off. Dart is one of the biggest head companies around, they have great quality control and flow great numbers.
I just wanted to show you that the CNC porting is not 100% perfect. There are a lot of people out there that believe that if their heads are CNC ported every runner is going to flow the EXACT CFM's. This is not the case. There are a lot of good CNC porters, however, it all is dependent upon who is hand porting the head to program the CNC machine for your heads.