Centurion 73 headers?

[Guest Heavy]

I am trying to find out who makes headers for a 73 Centurion convertible? I have the 455 engine. Any ideas guys? I've tried Hooker and Hedman... they say they don't make 'em.

Heavy

[pphil]

ta performance claims to have headers for full size cars

hope this helps

scott

[Smartin]

TA headers require the following on 71+ big cars.

1. Rerouting of the transmission cooling lines

2. Permanent removal of two small braces that connect the front x-member to the frame

3. Modification of the transmission x-member OR the headers themselves to line up exhaust humps in the crossmember.

[NTX5467]

Adam, is there a particular cast iron exhaust manifold set-up (possibly from a Skylark GS, or Stage I) that might be a better (and easier) fit than trying to use tubular headers?

I suspect that a set of factory cast iron manifolds (for a higher performance 455) would hit the same basic architectural "hard points" on the chassis as the orig cast iron manifolds might. Are there some model years/applications which might have a larger exit hole than others, plus a more free-flowing design? Might the castings be thick enough to stand a decent ExtrudeHone procedure?

After being around hot rods in earlier times, I have observed the many "issues" with getting headers to fit where they are supposed to be. The "dimpling" of tubes for control arm pivot clearance, for example. The leaking gaskets and warped flanges, too, which might be fixed by using the "black" header gaskets (with internal reinforcement and better materials) rather than the soft "white" gaskets they all were shipped with. Plus finding out that thick-wall headers were almost as quiet as the factory cast iron manifolds, when everybody else was buying the less expensive thinner-wall products. Oh, and NOT to forget the "rigged" bracketry for the accessories on the engine! OR ground clearance issues!

I believe that a good set of factory HP cast iron manifolds, hooked up to a 2.5" exhaust system and quieter high-flow mufflers will probably be a decent set-up for one of those cars. And probably allow power production not that far off of what it might be with a set of headers in front of the exhaust pipes--with a LOT less hassles to get there, in installation or later on.

Your thoughts, Adam?

Just some curiousities . . .

Take care,

NTX5467

[Smartin]

To have a set of exhaust manifolds port matched and honed, I've been steered in the direction of www.gesslerheadporting.com . Greg Gessler is a Buick guy, and knows his stuff. But the work is very expensive. YOu pay the price for a stock appearing engine bay.

There is a set of manifolds that flow something like 10% more in stock form than the current ones. I believe they are ...

Found it:

http://www.buickperformance.com/Exhcompare.htm

[NTX5467]

Thanks, Adam. I know that the Chevy dirt track racers, who have to have "stock" castings used to use Brezinski to deeply massage the stock intake manifolds and exhaust Ram's Horn Chevy exhaust manifolds. What they would do was to hole-saw a hole in the intake runners and then use that access point to do their magic, then put the plug back in, weld/braze everything back up and it looked like it hadn't been touched. Same with the exhaust manifolds. That was waayyy before the extrude hone procedures came about.

I just feel that, outside of the visual affect of tubular headers, you can approach the same power output without all of the hassels and "rights of passage" with some factory HP manifolds and a free-flowing undercar exhaust system. One that is quiet, trouble-free, and is a flow improvement over stock. I don't know that you need to go to 3" pipes, though, but probably 2.5" duals would be doable (and bendable without kinks!).

Thanks,

NTX546

[Smartin]

The guys who run 3" and up with stock manifolds will mill the stock joint off, and use an adaptor plate to accept the bigger pipe.

[Guest BJM]

I have a 68 Riviera with 430 and I would like to add TA's "shorty" headers run a 2 1/2 inch exhaust back to Flowmasters, maybe even a crossover.

But reality is the headers are something like $450 last time I looked but supposedly get you 25 hp over stock.

I wonder how they measure that? I mean Flowmaster typically claims hp gains as well. If you add up all the individual hp gains from different engine mods including headers, some engines would give you 600hp! So I doubt that is possible.

On the other hand I have looked long and hard at these two exhaust manifolds on my Riviers. One, I think the right one - looks well shaped, header like. The other one looks horrible, it has a big rectangle lump of iron in the middle, all integrated. So I am thinking replacement for that one side.

The Riviera exhaust routing is no thing of beauty. It's basically straight back but it runs in the wheel wells, not over axle and is stuffed in behind the kidney shaped gas tank and the depressed spare area.

So I am thinking stock manifolds with 2 1/2 exxhaust and Flowmasters located in stock position basically under the front passengers (Rivieras have X frame). The Flowmasters scavenge and reduce back pressure while the 2 1/2 in. maximizes flow, gaining about 10hp. I save $450 to be applied to ???? maybe more internal modifications.

The goal is 425 to 450 hp but if all the internal mods result in a getting a slowdown by the stock manifolds, I'm just not sure.

[NTX5467]

The whole reason that Flowmasters (and similar Walker mufflers) "work" is that the factory items are somewhat restrictive for the engines they are placed behind. Same with pipe diameters, too. You can listen to the "It's got to have backpressure to run right" operatives, but not as much as the factory parts tend to have, yet you can still have a desired level of backpressure at WOT and more power too with appropriate exhaust system items installed.

In some ways, you can compensate for the exhaust system's inadequacies with careful camshaft selection--especially in the area of exhaust duration and lift. I might suggest using the Riviera GS engines as a guide rather than the similar SkylarkGS engines. Even some slight differences in this area, as Denny Manner noted in the engine seminar in Flint, can make significant differences when using the same engine in the heavier Riviera chassis. So, I might suggest that rather than "going to the bottom of the page" to pick a camshaft (where the bigger numbers are), choosing one which will build decent low and mid-range torque and THEN making sure it will "rpm" by having a better exhaust system under the car . . . so it doesn't stop flowing well and limiting engine output in the higher rpm ranges . . . and doesn't need a really deep gear in the rear axle to perform well in the lower-to-mid speed ranges (i.e., normal driving patterns) with the modified motor in the car.

In some cases, if you might need to "bleed off" a little low-end torque, you can retard the camshaft about 4 degrees and then let that additional retard help power on the top end. This has worked for some drag race friends in some of their big-inch street cars, but I don't know if it'll work as well (or similarly) with Buicks.

Just some thoughts,

NTX5467