fastlane396

I am just doing bolt ons right now to my 93 trans am. I was wondering what size headers to get. Right now I was kinda just wanting to go for shorty headers, but later I wanna do some decent engine work. I was wondering if I would probably need to change to 1 3/4. The only shortys that I have seen that are 1 3/4 are MAC i think and SLP. I think hooker shortys are just 1 5/8. Thanks for the advice guys.

Stephen 87 IROC

Unless it's a strip only car or you plan on adding a supercharger, 1 5/8" is all you need.

1 3/4" is large for a SBC. To get the most benefit from them you need to be making over 500 HP or shifting around 7000 rpm.

1 5/8" are good enough for up to a 406. For a 305, 1 5/8" are huge. Anything bigger than a 406 (434) should have 1 3/4".

Shon Herron

If it were me, I would get some Edelbrock Shorties.
And then later if things go nutty and you need more header get the LTs but for the ease and usefullness, the Edels are all you need.

TedH

If you plan on doing more than just bolt ons within roughly a 2-3 year time frame I would go with the 1 3/4 and have them coated. If not, save the effort and money and get some shorties.

I had Edelbrock 1 5/8 for two years and after I blew a wrist pin and put in a new shortblock I needed to go to a bigger size. The Edelbrocks worked fine for me with just a bolt on configuration but I did not have them coated so they were really ugly.

Whatever you get, if you want to keep them a long time, get them coated.

TheNovaMan

When determining what size headers to get, you have to decide where yo want your torque peak to be. Here's what to do:
Multiply your peak torque RPM by the volume of ONE cylinder
Divide that by 277088.5
Take the square root
Add 0.040 (for tubing thickness)
Multiply by 2
...and voila! You have the diameter that you need. Now get the closest diameter to that, and you're good to go!

Stephen 87 IROC

Hey! That's pretty close. My BBC uses 1 7/8" tubes and that formula puts it very close to the proper tube size. I'm guessing I make peak torque around 4000 rpm.

mongse_1

Great formula, mine came to just a tad over 1-3/4" PERFECT!!

I would like to know where some of the numbers come from in the formula though.

TheNovaMan

The actual formula is pipe area = rpm × cyl vol ÷ 88,200. I don't know where the 88,200 comes from, though. When you convert area to radius, you have to divide the area by pi and then take the square root. (88,200 × pi = 277088.5 approximately) The rest is just adding the tubing thickness and multiplying by 2 to get the diameter. Hope this helps.