NOPE!!! I'm just WRONG as HECK.
Those are just like the ones I have.... I just remembered them WRONG.
I got to be getting that oldtimers disease.
#%@%!@$ I hate it when I'm wrong.
Mia Culpa,Mia Culpa.
I just got back from the garage where I checked and MEASURED the port sizes on the LT1/LT4 exhaust as well as the L98 exhaust manifolds.
Here's the LT1/LT4 exhasut port sizes.
Yes, there is a GIGANTIC middle port that would be split by the seperator in the head....
LT4/LT1 both end ports... 1 7/16 x 1 9/16
Middle Port.....................1 9/16 x 2 1/2
Exit Port at the collectors.... 2 1/2"
L98 ALL ports 1 1/4" kind of square... round edges in the corners
Exit Port a the collectors.......2 1/4"
L98.....There are TWO of the tubes (on each header) that are squished down looks like to clear the heat shields
The LT1/LT4 exhaust manifolds DO LOOK, TO ME like they would flow a little more than the L98 shorty manifolds.
A LOT more maybe????
The L98 headers are poorly made with a lot of weld covering the port in the exhaust manifold. I don'y know how much there is to gain by cleaning that up but I did it to mine. Probably about 1/2 HP gain for all 8. Not worth all the grinding and sweating, LOL.
The LT1/LT4 exhaust are a lot nicer made piece IMHO.
The LT1/LT4 exhaust manifold HAS a center port 'injection' fitting for the A.I.R. system. I only checked one of mine but I think they have 'one each' of these holes in both manifolds.
Knew I had those back for there for something, guess I just forgot what they looked like and I still don't remember why I have them. Must's been planing something for my L98.
Sorry for the erroenous info above guys. Memory ain't working good as it used'ta.
OH, head port exit sizes..I almost forgot.... I JUST measured these also.
128 Head Exhaust ports..... 1 3/8" x 1 5/16" 'Square" ports....rounded a little in the corners
113 Head Exhaust ports...... 1 1/4" x 1 1/4" "D" shaped ports.
Again, sorry for the wrong info I posted, guys.