Exhaust Port Heat Riser Filling?

[Staged70Lark]

Hey Guys (and Gals),

Has anyone out there ever filled the holes in the two center exhaust ports? If yes, what process did you use? Is there a flow gain?

Thanks

[Jim Weise]

Nope, very little to be had here.. just plug the holes on the intake side of the head, and call it a day. I have sets of iron heads here that flow 190- 200 cfm on the exhaust side, with no work done in this area.

JW

[Greg Gessler]

Most of the heads that I do have the exhaust cossovers plugged and filled flush on the inside of the port. I feel that it is a worthwhile modification. If you are inclined to do this you can fill up the holes with molten aluminum.

[Jim Weise]

So I went out and looked... I have a set of '67 heads, that flow 308 on the intake at .600 and 212 on the exhaust at .600, and they are filled..

I stand corrected, I am too used to the street heads... They don't require this to make 530+ HP, with low compression, dual plane intake, and a small cam.

I go aluminum for the race cars these days... those numbers will knock your socks off...

Like 300 cfm... at .400 lift :eek2:

JW

[Gold72GS]

I plugged them on my car just to cut down on the heat going under the carb. I used 18 mm exp plugs (thanks Yardley!) instead of the 3/4 recommended in the Buick performance engine building book. The 18 mm were a WHOLE lot easier to install! If I see any gains remains to be seen but it is a cheap easy idea if your intake is already off. If there are any cold weather startability issues I will find out in a few months. Brian