Hi all. I'm re-camming my 70 and porting/polishing and installing new guides. I just finished match porting the intake manifold. Next inline are the exhaust manifolds, then I'm going to tackle the heads. I wasn't going to do a whole lot to the exhaust manifolds untill I saw the hump inside each port. I believe the humps are cast into the manifolds for the A.I.R. fittings. Since my car is a Canadian built car, the AIR was never installed (and the manifolds never drilled for the fittings).
However, these humps are about 1/2 inch wide and tall and taper away from the heads. They have to restict the exhaust flow, so, is it worth my time to grind them out. I am keeping averything stock appearing on the outside, so installing headers is out. Thanks, Jim.

Hi Jim,

I did exactly that - removed the "hump" from mine. It's anyone's guess if it's actually worth anything or not but it does at least make me think I'm going faster without them. I was a little concerned about making the casting too thin so I didn't gind them out completely. If you click on the link below there are a couple of before and after photos.

Dan

Dan, good pics. I've already decided to do it. Like you said, how much it helps is anyones quess, but I don't want to put it back together and then second quess myself. So, chips are flying tonight. I figure a couple hours per manifold, plus its good practice prior to hitting the heads with the grinder.
Jim

Before I would spend much time grinding the humps out, I would try to find a set of manifolds that didn't have them and then clean them up!!

A lot less grinding, imho... But go ahead if you want to b/c it sounds like a good plan..

pdq67

Yeah Jim, it's just a little bit of time and a few stones - taking them out certainly can't hurt. Hope you took some before and after pics.

PDQ - no one has ever accused me of taking the easy, or smart, way out. In my case the manifolds are the correct casting and date and keeping them fits with my whole, sometimes unexplainable, keep it stock looking.

Dan

I'm also into the 'Factory Appearing Stock' look. My manifolds are the originals, and I just want more HP, so thats why I stick with em and am 'improving' them. I not only ground out the humps, but also opened up the perimeter of the manifold ports to creat a anti-reversion mis-match to the head ports. I have left the size of the head ports alone, and polished the runners and bowl...what a ton of work. I fugure I still have 10-15 hours of work left on the heads, before I put in the new guides.
JIm