SBM Edelbrock/Speedmaster Head Data

Earlie A said

I actually expected plane 6 and plane 1 (on the second row) to react the same as plane 7. I thought the velocity would go to 0 at the seat in all 3 locations. I think it actually does, but I could not get the pitot all the way to the seat. As a matter of fact, at the seat, the flow actually changes directions and is moving up the port at about 170 fps. I measured this with a different pitot in a different test a few weeks ago. I might try that again in the morning.

I may also try taking velocity readings at these same lift points around the guide boss. In this port I have noticed that the guide boss has impacted turbulence/separation more than any other port I have worked on.

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An interesting side note to your last paragraph is the W5 head has the bolt boss right across from the guide.

That little bump, like the pushrod pinch forces what air there is along that wall over to the guide.

And when it does (man I miss my notes) it pushes the air across the guide and into the common wall.

I don’t remember what made me even start looking at it but I ended up using some strings down the port and you can watch the air move off that bolt boss right across the guide.

I do know I had the brilliant idea to use a cigarette to get some smoke in the port to see what was happening.

Bad idea. Unless the cigarette is 14 inches long and an inch in diameter it burns so fast your fingers get toasted.

They go quick. Not being a quitter (I’m not a smoker either) I decided to go get some cigars and use those.


Bad idea. You get about 4 seconds more with a Swisher Sweet than you do with an unfiltered camel. That’s it.

Hence the string.

I took the bolt boss out entirely and it cleaned that up.