I'm wondering if anyone has a definitive answer with what to do with the big square lump next to the spark plug boss in the chambers? I can't help but think that it hurts flow out of the intake valve and swirl.

Cut it back, blend it, leave it? Pictures?

 

It promotes swirl.

The intake charge comes in along the "common" wall of the port and on the "roof" of the port, which leads to the "corner" of the chamber on the plug side of the valve but away from the plug; but it's coming in at an angle such that it wants to flow around the plug side of the head and run into that boss.

What I've always "heard" (though I have no proof) is that it's best to leave it, but to contour it so that as the intake charge hits it, it's directed more smoothly toward the center of the chamber. That is, make it less of an obstruction, and more of a guide, removing as little metal as possible. Won't necessarily show up in flow #s but may impact BSFC and other similar measures of efficiency.

 

I've heard the same thing, but I'm not sure I believe it. I've been trying to find a pic of lingenfelter's or someone else's 'vette heads to see what they do but I haven't been able to find any good ones that I trust...

 

LPE looks to cut it away/blend it into the chamber. when all else fails.. think like air.

 

Chamber pictures, one from Vizard and the other is Car Craft June '87, porting by AFR.

RBob.

 

Shape it like a guide. Plug boss should be rounded for smooth flow and shaped towards exhaust valve side

 

rbob, that's very helpful. thanks!

Now I wonder what the answer is about the spark plug? In those pics not only did they remove the locator, but cut diagonally across the spark plug boss, which would expose about half the threads on a stock plug, seems like that leaves you with either plug threads exposed (towards the center of the chamber) or plug boss threads exposed (towards the exhaust valve side of the chamber), neither seems optimal...

 

that made me smile for all the wrong reasons (think fart jokes)

Back in the day I intended to build a flow bench... then I ran out of time and space... now I have 18m/o twins and I wish I had the time and space from when I ran out of time and space...

 

I thought the same about the AFR modified head. The Vizard head appears to have a nice rounded boss for the end of the spark plug.

RBob.

 

The Vizard pics don't apply. They're for some other head casting, some other combustion chamber shape, some other casting thickness, some other spark plug location.

You can't just "get rid of it"; unless you know where to get a spark plug that only has about 1/8" of reach. NO MATTER WHAT you do to that boss, the plug is still going to be there.