How much additional horsepower and torque will be provided with headers that have 2 inch primaries into a 4 inch collector on a basic 460 engine. The headers are made by schoenfeld and are tractor pull type and will be run straight with no mufflers or exaust system.

 

Hmmm..........**stares blankly at the question with slobber dripping out of the corner of his mouth**............

After pondering for a moment, I decided to throw my uneducated guess in....I would expect 40 hp give or take for a basic mild application, maybe 60-80 if it had the heads ready to breath with a cam that can allow the breathing and cylinder to be at its best, but then the heads and cam would add an additional amount and together you would see possible huge gains depending on what combination you tossed together. This is pure speculation and voodoo, as I never dyno tested manifolds against headers on the same engine back-to-back.

I did dyno stock intake and manifolds and a 4150 750cfm carb with a small cam against the same engine the following year after swapping to a sollid flat tappet cam, headers, victor, and a 1100cfm dominator and saw 105 hp at the rear wheels improvement.

 

I disagree with 40 horsepower or more gain on a stock engine. Maybe 20 horsepower and 25-30 lbs. torque on a bone stock engine will be all you'll see ans that will be above 4000 rpms. Now bolt on a couple more gooddies and those numbers will rise more from the use of headers. But don't expect it to run like a raped ape just from bolting on headers.

 

Thats what I would say. Add the cam, whatever you can do to your intake system, chip if EFI, and then you are talking about serious gains. With a mild truck/towing cam, you could add nearly 100 HP and godawfull torque with the right parts. Probably not quite that much with EFI, unless you really got into it.

 

i do have a mild cam in it...what intake should i look at? Weiand stealth? What kind of #'s am i looking at then.

 

The general rule of thumb is that you will get about a 10% HP improvement assuming all else being equal. You can get a lot more but you will need to lots more homework.

There are a lot of gotchas and what ifs. Any engine is a system and performance is dependent on many parts of the system working together.

For example a really big carb and ported heads and hot cam with stock exhaust may actually perform less well than a stock engine for normal driving. Another example, say you use really big tube headers and wide open exhaust but no other mods. Most likely you will lose low end performance(important for trucks) and you might only find gains at high RPM.

If I was looking at headers, I would first ask myself what I wanted from my truck. Do I want towing power, and off the line performance or do I want top end high RPM performance?

It has been too long since I worried about all the variations but in general big tube short headers work good for top end while small tube long headers work better for torque.

Matching the cam and carb and pistons, headers, porting, gears, torque converter and lots of other stuff will maximize performance for what you want.

On looking at your posting, I assume you are planning to do a lot of high RPM pulling or racing? Open headers with 2 inch tubes and 4inch collector is most likely for that type application. Since you don't plan any mufflers that also points to the track right?
So assuming a stock engine(which would be a waste if you plan what I guess) you might get about 30hp or so.

You didn't tell us much about your set up so anything we say is an educated guess.

Good Luck,

Jim Henderson