soccer794

Hi, I'm new to the forum, and a new corvette owner. I've always been in love with corvettes, and for my graduation my dad bought me a 1971 big block 454 convertible. I love it, but am affraid I don't know quite as much about it as I thought. The engine was just rebuilt when we bought it and the only miles on it are from Atlanta to Columbia and then to the beach and back. It runs great, but I'm looking for as much power out of it as I can. It has a cam in it, althogh I'm not sure what kind. I noticed that the headers are the original GM headers and thought that would be a good way to get some more power out of it. Having said that, I don't know what kind of headers to put on it or where to get them from. Can someone please let me know of some headers that will help me out, and will fit as well? Thanks a lot and if you have any other suggestions they are appreciated as well.

Gordonm

GM never installed a set of headers on a big block Vette. They are the stock iron ones if they are original. They look a little like shorty headers but a good set of full length headers will make some good HP along with a good flowing exhaust. As for which kind there are a few good ones. I run Hookers on my small block but there are others. Some others with big blocks will chime in on this and they will tell you which ones fit the best.

zwede

Headers make a big difference on 454's. Here's the dyno chart showing before and after headers on my 71:



I'm running Hooker super-comps with 1 7/8" primaries. Stay away from the 2 1/8" primary version. They hand very low. You also have the hedman 2" primary headers that work well.

soccer794

Thats what I meant when I said the original GM headers was the cast iron ones. As well as what kind of headers, where did you get them from, and are they direct bolt-ons or did you have to cut some?

Fevre

Ya but that's on a 'markus bad boy big block vette', what about a plain big block?

WA 2 FST

I think those dyno figures are before Markus did the heads and fuel injection. I mean he's only at ~325rwhp or so on that chart. He's ~400rwhp now.

Headers will make a huge difference, even on a stock big-block. The fact they put those tiny manifolds on these things from the factory makes me shake my head.

I run Hooker side-mount headers and they fit great. Some do not have as good of luck with them, but none of these cars are spot-on identical in fit from the factory.

I wholeheartedly agree with Markus on the 2 1/8" primaries if you want to run under-the-car headers. They sit too low most of the time.

scs2rescue

I also have a 71 454 & am interested in headers. I've been told the Hooker headers won't fit if you have air conditioning. I haven't researched it any further.

zwede

You are correct, sir. I think it's a great dyno test as it shows just how much of a difference headers make even on an almost stock 454. At the time the engine had an all stock short block, stock heads, a torker II intake (not very good) and a 750 holley vacuum secondary carb. The cam was a very mild flat tappet hydraulic, 219/229 duration.

soccer794

Is that true about the A/C? I have A/C is it true the hooker headers won't fit?

stingray72

Congratulations on the new car and your recent graduation.
Thats a pretty valuable car you have there. A 71 Big Block, convertible with AC might not be the car to modify. If it were me, I'd restore the car to stock and retain the value.
Whatever you choose, Good Luck!

George

Love My 72 and 77

"Cast iron headers" = Exhaust manifolds

Larry B.

While I appreciate the performance of headers and they do have their place, there are a few trade offs to consider. First, you do need small primary tubes or you will loose low end throttle response. Next the engine compartment will get much hotter as will the interior unless you add some insulation. You may find the headers leak at the flanges and burn plug wires, and make plug changes more difficult. Some bracketing may be a problem trying to install them. In general, headers can be a real pain. Changing a leaky gasket on BB headers is not a thing you will look forward to. Would I put headers on? Not on a Corvette that I drive daily. Now if you race and need some extra power then put them on. They look great on a street rod though.

zwede

The 1 7/8" version works fine with headers, power steering etc. My 71 is fully optioned and the headers fit fine.

[Edit] The above was supposed to read "The 1 7/8" version works fine with AC".

The stuff about burning plug wires is true. You have to spend some time routing the wires to avoid burning. I also use slip over boot protectors and I had to dimple two tubes (1 and 5) to get some clearence between the tube and the plug wire boot.

Ceramic coatings take care of the heat issue.

Mine, BTW, is a daily driver.



[Modified by zwede, 4:48 PM 7/7/2004]

mike229

Does this mean that there will be throttle response issues when I put on my Hooker 4" Sidemounts?

71'AirStrike

Ive allways heard that "going to headers wont gain you much" over the OEM 454 manafolds.

Zwede chart has me sold.

LemansBlue68

I found the choices for big block Vette headers to be pretty limited. Hooker Super Comps or Dyno Max are about the only choices that I am aware of for street headers. I went the Super Comp route because I got a great deal on them. Besides a being a bit close to the idler arm (which was easily fixed) , they fit very well. Buy uncoated and trial fit them. You may find that you have to dimple a couple tubes to get them to fit properly. After you're satisfied with the fit, then have them coated.

BTW, do you have room in your family for an older adopted brother???

Larry B.

The size of the primary tubes coming off of the head is what counts. The size of the pipe past the collector is not, assuming it is not too small. The back pressure needed for low end torque is futher helped by equal lenght primary tubes. All of the cylinders will have the same amount of back pressure.

Turbo-Jet

me too... but i'm not 100% sold on Zwede's results. he did have the ability to flow more air with the cam and intake even though they were pretty mild mods. on a stock BB, the intake manifold is just as much as a bottleneck as the exhaust.

btw, my stock LS5 dyno'd 226/321


[Modified by Turbo-Jet, 10:55 PM 7/7/2004]