Don Terrill’s Speed-Talk

cfm / sq / inch graph as cast vs. rough ported

Mean port velocity and port energy graph. Nice boost in cfm, velocity and port energy.

16 posts just to setup. Seeing double at the moment but as anyone who has done some back to back ported vs. unported work even mild porting packs a huge punch if done fairly well. More cfm, more velocity, more port energy with a slight increase in port volume. Input welcome. Thanks, Charlie

might be my computer but a few of the pics you posted aren't showing.. great information amazing how a lil work makes a huge difference

Kbails wrote:might be my computer but a few of the pics you posted aren't showing.. great information amazing how a lil work makes a huge difference

My thread looks as posted. Nice gain and a good amount of the steepest cut of the valve job has been removed! Thanks, Charlie

Charlie,
Do you feel the program has allowed you to more quickly identify a heads potential strong points.
This is what I used to develop the heads for vintage racing. From 238 cfm at 0.625 I managed to develop enough port energy to get just one hp shy of 500 from a 12/1 289 along with 411 lbs-ft. Bottom line here is that old casting you are playing with is showing a lot better than most folk would think.

DV

David Vizard wrote:Charlie,
Do you feel the program has allowed you to more quickly identify a heads potential strong points.
This is what I used to develop the heads for vintage racing. From 238 cfm at 0.625 I managed to develop enough port energy to get just one hp shy of 500 from a 12/1 289 along with 411 lbs-ft. Bottom line here is that old casting you are playing with is showing a lot better than most folk would think.

DV

Even with small valves and a questionable valve job these could make some steam! Thanks, Charlie

no offense, and I realize you're just using what you had on hand, but it sure seems like you went backwards on valve sizing. Seems much better to be .060" oversized than .060" undersized on an already too small intake valve. Easy to get a smaller valves CD up because the port size is not the biggest limiting factor on the flow curtain. As you've already found.. fix the horribly transitioned throat cut, remove some obstructions, smooth the SSR shape out a bit.. and you're most of the way there. Bigger valve lifted way up will make you work much harder.

Maybe just step up to a 1.84" or 1.90" valve rather than trying to maximize the port around this smaller than stock intake valve size?

WoW as I remember these castings start out not much bigger than the width of my thumb in several areas of the port. If I am I remembering this right?

1.84" valve and 1.6" valve right after 1.72" 1.46" valves after kline guides and retest after touch up of stock size valve job.

Carnut1 wrote:1.84" valve and 1.6" valve right after 1.72" 1.46" valves after kline guides and retest after touch up of stock size valve job.

Sounds like a plan. Thanks for the heads up, Charlie. Done several sets of these heads.. one set developed on my old flow bench(a big thanks to DV on that one).. really looking forward to your results.

Yes, old speed is the most expensive kind. I wasted some of the best years of my life trying to make horsepower with those buzzing little 289" chokers. When the 351" heads came along, we thought them a miracle. No more hours and days of breathing pounds of cast iron dust; larger valves and larger ports across the FoMoCo parts counter.

Today's checkbook SBF horsepower is the natural evolution; not an OEM part left in there. I have a friend from the Sunbeam Tiger days who's still running a genuine Shelby American LeMans 289" with Webers. He can only sneer at the new 347" 1x4-bbl EFIs which have much better street manners, better fuel economy; they win every time.

What variables go into calculating port energy? Velocity I assume ... but is it average port Velocity or at MCSA?? Flowbench velocity or running velocity? and area is probably included ... but again the question of which area ... avg or min? What about engine or cylinder cid or port length? What all is used to determine this Port Energy calculation?

Rick

gvx wrote:WoW as I remember these castings start out not much bigger than the width of my thumb in several areas of the port. If I am I remembering this right?

They are pretty small stock but have nice velocity for a mild combo which was the plan for getting some torque for a stock application.

Rick360 wrote:What variables go into calculating port energy? Velocity I assume ... but is it average port Velocity or at MCSA?? Flowbench velocity or running velocity? and area is probably included ... but again the question of which area ... avg or min? What about engine or cylinder cid or port length? What all is used to determine this Port Energy calculation?

Rick

Rick,
Port energy uses mean area, CFM, resultant velocity and mass of port air. The real comparative deal here, and it is not in this current program but will be, is the 'port energy density per foot length'. With this you can make caparisons across the board including 2 v vs 4 v heads.

If you need to know the mean velocity at any give point down the port you can enter that area instead of the mean area.

The Mach Index uses the mean area and the numbers generated are by my method not Charles Fayette Taylor's. My method returns numbers more akin to high rpm engines not blown 2800 rpm 2800 cube units Taylor experimented with. Beautiful though those big radials are I don't have a Bear Cat, Thunderbolt or a Corsair to put one in.
DV