Smog Bump: How much to grind?

[goodfastncheap]

I am port-matching a set of D4 351W heads, and as long as I'm in there with a die grinder, can anyone tell me exactly how much of the air-injection feeder bump is safe to take off? Any photos?

 

[jrichker]

See http://www.diyporting.com/ for some help with your porting job.

 

[goodfastncheap]

Thanks for the link! He says, among other things:

"Removing the thermactor boss did raise the high lift numbers about 1 -2 cfm, after porting, but then leveling the lateral roll near the exit roof, lowered them again a couple CFM."

This is for E7TE, which have a MUCH smaller "smog bumps". He cautions that on E7TE heads that the exhaust ports are very sensitive to small changes, and he got a lot of negative results on the exhaust side.

Very informative for these heads - he shows photos with the air injection boss completely removed, leveled off at the roof of the port. My question is, on a D4 head if I completely remove the bumps, will I run into any structural issues?

 

[thumper460]

Remove ALL of it.. yes this is a pix of the E7's cause those are the heads I do... but cut it all out and make a straight shot back into the bowl!! floe is on the top of the port!! cool??

Just me...................................

Thumper

 

[ninety15.0]

excellent looking E7 port thumper! It's no wonder your heads make the power they do!

 

[thumper460]

cool!!

Tpr