[RWS]

It looks like the passenger side exhaust manifold on my 70 Formula has finally been repaired once too often (at the flange, of course).

While I will look for a shop that can properly weld cast iron, I should probably consider my options. I will try finding a used one, of course, but in the meantime does anybody have any experience with the repo units?

I am not really inlcined to switch to headers, by the way, but if someone has had really good experience with a set (meaning fitment, clearance, durability and performance), please chip in.

The car gets driven about 2000 miles a year and will probably never see a track, and low end grunt for the street is key.

[2manyT/A'S]

The R.A.R.E. repos are "worthy" replacements in MY experience.

You want to get the 69 GTO "D" port units as they have the extra bolt holes (to attach to heads).
Not exactly "correct" but they tend to do a way better job sealing.

Not sure which brand our host here sells. It would be worth giving them a shout on it.

[bird72]

You asked on headers, I have Super Comps, not cheapos. Very tight fit and can't change oil without dumping filter contents on them. Louder than stock. Have to tighten bolts once in a while. I'll be going to stock 72 HO manifolds when I ever do that HO engine way down road. Reasons: reliability, sound, appearance, ground clearance etc. The down side is I expect on a healthy 455 to give up 20-30HP on the "downgrade"......

[GETRIDAONE]

I had some 69 part# repro's I used instead of spending the money for ceramic coating the originals. The dividers were starting to split from the heat and I'm sure some hair line cracks even though I couldn't see any. Only one ear had been repaired with a stud and the flanges were still flat, and didn't appear to have been ground to thin. The numbers being on the back side so you don't see them, who's to know ? I used fel-pro gaskets so they sealed good. The picture shows about all you will see anyway.

[CaptCrunch]

I have the RARE oversize d ports on my formula with their cast iron color coating.......they look great and are a nicer and more accurate casting than the ones everybody else sells.......

[2manyT/A'S]

Originally Posted by bird72

You asked on headers, I have Super Comps, not cheapos. Very tight fit and can't change oil without dumping filter contents on them. Louder than stock. Have to tighten bolts once in a while. I'll be going to stock 72 HO manifolds when I ever do that HO engine way down road. Reasons: reliability, sound, appearance, ground clearance etc. The down side is I expect on a healthy 455 to give up 20-30HP on the "downgrade"......

That's pretty much the concensus with headers on a Pontiac V8 in a second generation chassis.

That 20-30 hp will NOT likely be noticed as it generally happens above 5000 rpm at WOT.

You will likely loose a bit of your bottom end "grunt" with headers.as well.

The 455 HO guys that run "stock" are DEEP into the 12's with cast iron Ram Air/HO exhaust manifolds & 068 factory cams.

[RWS]

Thanks for the info, 2manyT/A's in particular. I will be ordering a set of RARE factory-style headers...

[bird72]

Originally Posted by 2manyT/A'S

That's pretty much the concensus with headers on a Pontiac V8 in a second generation chassis.

That 20-30 hp will NOT likely be noticed as it generally happens above 5000 rpm at WOT.

You will likely loose a bit of your bottom end "grunt" with headers.as well.

The 455 HO guys that run "stock" are DEEP into the 12's with cast iron Ram Air/HO exhaust manifolds & 068 factory cams.

actually even with the headers with my set up I have severe traction problems and aggressive standing starts are a challenge to move and not spin and an exact pedal touch is needed to work around...... gaining more bottom end torque won't help

[thefirebirdm@n]

Good post on this same topic over at TAC:

http://transamcountry.com/community/...?topic=28289.0