I have a 1973 Buick Riviera and I am looking to get some more power out of the 455. The motor has mildly ported heads with stock valve size and milled slightly. It has the TA 284-88H cam and an Edelbrock intake. I am running stock exhaust manifolds. Would headers show much of a gain? The motor runs great, but I just want a bit more power.
I would guestimate, that you could expect somewhere between 20-30 hp....it will not be a night and day difference but on the verge of noticable...
long tube headers will give you more of an increase in torque then horsepower in most cases, also at a lower rpm.
on average, headers will show a gain of 25hp, more if the car is higher HP to start with, ( 300hp 350 would on average, show 25hp, where as 500 hp 350 would show closer to 40-50 hp increase,) headers usually lean out the engine, as there more efficient, so to realize there potential, you would need to keep an eye on the plugs, and listen for lean knock, then there is the exhaust , how much back pressure,, etc.
TA shorty's are made for Riv's Long tubes will run into problems with the X type chassis I am getting some soon
I don't think your bolting on 30 or even 20 horse with headers with that combo. Your best bang for the buck would be a better converter.
you need bigger valves and cam to benifit from headers. Make sure you have at least a 3.07 rear ratio, anything lower is gonna feel slow. and a switch pitch will help. what carb you got? and distributer ?
Often people upgrade the exhaust system when they put headers on and that contributes to the hp gain...plus usually louder so they think they have even more power. I would leave the manifolds if they aren't leaking and put a good low restriction exhaust on.
If your going to continue on to build more power in the future, then your at the point now where your stock exhaust is the limitation. Headers will be the basis for more power in the future, if that is the way your going, but with your current setup, they are worth probably 10-15 ft lbs, so not worth the cost, if this is as far as your going to go with the car. Your at 400-425 HP now, the need for headers manifests itself after the airflow goes up into the range that will produce about 475HP.. that's when the headers will show the 25-30 number gain.. Of course the free flowing exhaust with 2.5" pipes goes without saying.. JW
Interesting I am running close to the same combo, but with T/A Stg-2 S.E. heads and shorty headers. I wonder if I would notice a difference with long tube headers? It hauls a-- the way it is! Bob H.
Bob... I tested it on a motor like yours.. 8 HP is the difference between the shorties an the long tubes.. no biggy JW
I don't intend to hijack, but more information and perspective is better, right? Due to funds and the fact that the strips don't open for a couple months, I am currently running shorty headers through my stock Riviera exhaust with 2" magnaflow glasspacks, which apparently flow awful. I know this is effectively on a per-case basis, but would you expect me to gain over .3/3 mph by switching to TA's 2.5" mandrel bent system and dynomax ultraflows? Engine is very similar to this quote of yours from years ago: "Don't get me wrong, I love manifolds for some builds.. I just pulled a 375HP 437 for a 67 Riv off the dyno last week.. all iron, all stock, with a 212 cam. No reason in the world to put headers on that motor. Love the nice quiet manifolds.." Just has a Scott brown cam with 219/238 @ .050, similar to the 212, and Stg 1 springs, 12" Switch pitch, 3.42 posi rear
