I’m having a 69 455 built for my convertible. I'm not racing it but I wanted a modern feeling, pro touring car with power across the rpm spectrum. I saw the following post:
https://classicoldsmobile.com/forums...s-headers.html and I’m thinking of just buying W/Z manifolds for it rather than headers.

I've only done paper comparisons of long tube, and short tube headers tube dimensions and outlet sizes. (http://www.442.com/oldsfaq/ofexm.htm).

I've searched all over the net (http://www.hotrod.com/how-to/engine/...-vs-manifolds/) and can't seem to find any information on power or torque numbers for a stock manifold vs. the 442 W/Z exhaust manifold vs. headers. If I can believe the hotrod numeric trends, I could conceivably see ~20hp and ~10ft/lb tq loss using W/Z manifolds over a long tube header.

I don't mind since the manifolds will readily bolt in. Does anyone have any information?
Thanks.

Cast number F 386021 with a + .030” bore. C heads, Edel. Performer intake with plenum modification, Crower compu pro level 2 cam, Edel. 750cfm, ICON pistons ~9.5-10:1 comp, 700r4, 2200rpm stall, 3.73 diff.

 

I don't have any numbers for you, but I can tell you the headers on the car I have are not very user friendly. The driver's side goes over the frame and makes for tire clearance issues. I'm going back to regular exhaust manifolds and stock exhaust in a year or two. I don't plan on racing, so the stock power is enough for me.

I'm sure someone else that has some dyno numbers will step in and let you know how those are. I'm interested in knowing myself.

 

Your experience is not normal. MOST Olds headers stay within the frame rails. I suspect you have Super Comps.

 

Judging by the amount of dents on the underneath of them, they weren't the easiest to get to fit either. Unless that's just performance tuning.

 

Dents don't hurt performance. I agree with Joe P you have 2 inch super comps if it goes around the frame. I used those for years and didn't like them. I have a 70 442 and went with ARH and never looked back. The super comps went to the engine run stand. I doubt they will find there way back to a car. To the op you could just buy a set of cheap $200. china headers. Some guys like them because of price. If you go with headers i suggest you use a mini starter. I suggest the power master starter. Good luck which ever way you go.

 

IIRC - BTR did a stock appearing 455 build, can't remember if it was a stroker or not but it had some goodies inside & made some nice power. I think it was a 40ish (actually 49 comes to mind) hp difference between manifolds & headers on the dyno. On a stockish BBO I would guess 20 hp would be a reasonable estimate.


Maybe someone can remember the thread or the proud owner of that engine will comment.

 

Years ago there was an article in one of the musclecar magazines documenting a dyno session of a 455 Olds in which one of the experiments was headers vs. manifolds. I don't have it in front of me, but it might have been the '71 stock W-30 build up that Dad Jensen did. As I recall, compression was lower than it should've been, but the engine put out factory numbers anyway. Strapping on the headers boosted HP about 20; but more importantly, the improvement was across the entire RPM range, not just peak.

If someone has the article in front of them, please correct me.

 

Thanks for the information and input. If I chose to go with a header, can anyone recommend one that requires minimal mucking with that will fit a convertible 455 f block, with an automatic 700r4? It would be nice to find a direct bolt in. I'm looking at the Hooker Competition 3902-1HKR (1 3/4" tube and 3" collector). If anyone installed these please let me know.

 

70cutty (Eden) would be a good guy to ask. You may want to send him a PM. I know he had a few problems before finding a good fitting header for his 455 build.

Eric

 

I am in the finishing stages of my A body cutlass. I ordered Dick Miller Racing headers for mine. They are 1 7/8" into 3.5" collectors. These headers fit with very little modification. There was a small piece that had to be trimmed from the upper A arm and the A arm bolts were trimmed off just so they would never be an issue. The only other modification was the tube on the passenger front cylinder was dented just a small amount as it came close to the frame member. I also have a 700R4 transmission and the ear on the passenger side had to be trimmed. Not a big issue at all.

Just be aware that DMR headers did NOT come with any hardware or reducers. Also, I did not get their coated headers as I did not want to bang up on ceramic coating. They are at the shop getting ceramic coated at this time.