Hi together, I`m planning on installing a 2.5" exhaust system on my 455 GS in the winter months to come. Until now, stock 350 ex. system from 1971... Basically I`d like to dump the stock exh. manifolds for some shorty headers. I`ve read an article that jet-hot coated shorties would reduce underhood temperature...right now I`m seeing 500°F when I point my IR-gun on them, that being in idle after some 20 min of driving. My question: can I assume less underhood temp. with coated shorties or, as I`ve also read (the internet gives all kind of confusing information for whatever you want to know), will the temperature even be higher...in that case I`d reconsider changing anything at all. Jens
Personally I’ve never considered headers to add heat to anything. The iron manifolds will retain heat once they get hot.ever notice how long an iron skillet stays hot compared to an aluminum or stainless pan after removed from heat?
Hey Mark, yep, they stay hot like forever. Some said because of the surface size, the header will disperse more heat to the engine compartment. Then I`ve read that the Jet Hot coating would significantly reduce heat of the header...since I trust my fellow Buick man the most I brought it up here Jens
If you want to run headers, do it You can have 'em coated or you can paint 'em (I do, its cheaper) Don't get concerned about underhood temps, or the 500 deg. temp.of the iron manifold
I saw an engine masters episode where they tested manifolds, shorties and long tube. Shorties only did slightly better than manifolds, were better with under hood heat. But long tubes made a real horsepower difference.
That's what I mean with the internet....you get all kinds of infos, pro and con, all the time and partly completely oposed views. I know of an article, think it was HotRodMag, that said it' s shorties and long tubes being close in output with the advantge always leaning towards the long tube headers in the end. Both way more effective thank stock manifolds... And also JetHotCoating being way more effective than other offerings, and esp. way more heat control than DIY paint....
I’d only run headers if your making way more than stock power, otherwise leave the manifolds in place
Engine is Mike Phillips AM&P Street 1, 425hp and 517ftlb on the dyno, very streetable. I`ve hooked it up to the stock exh. system. I once talked it over with Mike, I Think I recall him anticipating 20-25hp gain from going shorties and 2.5" exhaust. I`d consider that a nice jump for a street driven car.
With those numbers I'd run AT LEAST shorties. But if you want everything the build has to offer, run full length headers with 2.5" pipes. Shorties are a compromise for chassis that wont allow full length headers. Being you have an "A" body that readily accepts full length headers, I see no reason to just go halfway with shorties
Have a little headache with clearence issuses and heard not-so-good things about keeping the headers (long tubes more than shorties) sealed. But then, you`d also favor the improved exhaust system, that`s good to know. I`ll be looking for a more silent setup that doesn`t hurt performance. And maybe even going down the longtube-way....I`ll reconsider that, Mark. Jens
My GS sits at the stock height, I've only bottomed out on the collectors once, and that was with 4 people in the car pulling up from a grassy field and across a sidewalk, where the car high centered on the collectors, no big deal. Never had any leak issues, that only happens to Chevy guys LOL
