Had my X heads ported - results

512Stroker said

Just got my old LA 340 X heads back from a local retired engine builder.
I left the heads with him for some economy street performance porting as this is not a track engine. I had to remove the heads to swap out some bogus hyd roller lifters so I thought what the hell I'll have them cleaned up. These heads were prior used on a NHRA stock Eliminator LA 340 and had been acid ported. I also provided a new in the box Edelbrock AirGap intake that he touched up. The flow numbers shown below are through the intake and the head.
I would have liked to seen a little better exhaust numbers, but for $200 I'm not going to *****.
The Gent that did the work told me, which I agree, that its not so much the numbers but the shape of the port that really makes them work. Maybe when I get my back in better shape I'll post some pic's of the heads.
Jim K

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Looks pretty good numbers even compared to some aftermarket.
The fellow is correct, exhaust flow at 28" depression is not a big deal. Remember in a NA engine, the intake only has atmospheric pressure to push the air into the cylinder. When the exhaust valve opens, the cylinder pressure is still about 70 to 100PSI. This causes supersonic velocity exhaust gases passing out the barely open valve. This is important for pulse tuning of the exhaust, to get the high velocity colume of exhaust in the head pipe. When tuned correctly this arrives at the collector and transmits a negative pressure back up the exhaust which should arrive at the almost closed exhaust valve, just about the time the intake valve is opening. The negative exhaust pressure at the valve helps vacate the combustion chamber. Whatever atmospheric pressure is at the port side of the intake valve at valve opening is aided in initiating intake flow by the negative pressure in the cylinder, while the piston is still approaching TDC.