mp71conv

What exactly are the bumps on olds heads.
I have no7 heads and have felt inside them
and found what i think are the bumps but they seem
to be a long gradual bump
Grinding those down should not go through
anything important will they?

joe_padavano

In some applications, Olds motors uses Air Injection Reactor (A.I.R), also know as air injectors or a "smog pump". The castings have these bumps to allow the holes to be machined for the A.I.R. tubes. The bumps are solid and can be ground down with no problems.

88 coupe

Whether is makes any difference, depends which "head porter" you ask.

Norm

joe_padavano

Fair enough. Most seem to agree that raising the roof of the exhaust port in conjunction with also raising the floor is a net benefit for Olds exhaust ports. Short of welding, the only easy method of raising the floor is to use the inserts that Dick Miller and others sell. I have not personally tried these and would welcome any comments from folks with firsthand experience.

captjim

"Most seem to agree that raising the roof of the exhaust port in conjunction with also raising the floor is a net benefit for Olds exhaust ports."

That seems to be the consensus on most engines.

I have those DM inserts. We have a new Land-N-Sea dyno at the shop. I may pull my 10.4 to 1 355 out of the wagon and fool around with a few things. I'll try the inserts, maybe even see what difference there is with shorty headers, long tubes, and manifolds, etc. If anyone has something they want to donate for the experiment, I'll be glad to try it out.

joe_padavano

Yeah, mine was kind of a "DUH" statement. Raising the exhaust ports makes the port straighter and thus better flowing. Olds engines are especially sensitive to this since the ports make about a 90 degree turn from the valves. Many engines, like Chebbies, already have straighter, higher exhaust ports.

88 coupe

How are they held in place?

Mine (both intake and exhaust) are filled/welded.

Norm

joe_padavano

The DMR inserts are actually flanges that sandwich between the headers and the exhaust face of the head. The flanges have tabs along the lower edge of the port cutouts that bend down into the ports to fill this space. The tabs must be custom fit to the ports. Not an ideal solution but a lot cheaper than welding/filling. The gas under the tabs stagnates and so the flow follows the raised path.

captjim

http://www.dickmillerracing.com/cgi-...db4+1233129627

Oldsguy

Not a bad price either.

88 coupe

I think that qualifies as an understatement.

Norm

captjim

The guy who owne's the shop I work at says they have been using a similar insert on SBFs for a long time, only difference is that they are individual instead of one piece. He has dyno, flow bench and track data that indicated they do work. Are they better than filling the floor, probably not. Are they better than nothing? I can't say.