gmrocket wrote: ↑Sun Sep 29, 2019 4:21 pm Dont worry about the valve shrouding on the cyl wall...very little flow goes that away,,its majority biased to the center of the cyl along the common wall of the port. You do not need a bigger exh valve than you have..its big enough.
Agree 100%.
X3
The 2.19 is worth power, the 1.72 can handle more than most people give it credit for ( assuming you are doing the proper sizing and shaping of the SSR and throat area for both valves)
Pete Graves
CPMotorworks,Inc.
Custom Engine Machining
Cylinder Head Fixture for Vertical / Surfacing Mills since 2008
A little back side work on the 2.07's and you'll be in good shape. The 1.72's will be fine as is. Take a look at what the rules restricted engines that have to use stock valve sizes and no porting make for power (think NHRA Stock Eliminator).
And the whole bore notching thing is more urban legend than anything.
Thanks for all the input. I think I will stick with the small valves for the 396. If I build a larger street motor later I will definitely up the valve size. It would be interesting to flow these heads with a small bore fixture on the flow bench, say 4.125 and compare numbers with a larger bore fixture 4.350, with both the small and large valves. Thanks again to everyone's input.
TLK396 wrote: ↑Tue Oct 01, 2019 6:06 pm
Thanks for all the input. I think I will stick with the small valves for the 396. If I build a larger street motor later I will definitely up the valve size. It would be interesting to flow these heads with a small bore fixture on the flow bench, say 4.125 and compare numbers with a larger bore fixture 4.350, with both the small and large valves. Thanks again to everyone's input.
You are going to like the way the 049 heads work on the 396. I did it back in the late 80's and the car was a lot quicker and faster with the change just make sure you do the best valve job you can afford.
TLK396 wrote: ↑Wed Oct 02, 2019 2:41 pm
I have a 396/375 style piston with a 39cc dome, at .008 in the hole with a .018 compressed steel shim head gasket.