Well im going to fabricate a new 3" exaust on my nova. My old one just wasnt working with the mufflers under the driver and passenger seats. Im going to have extra pipe so im going to fabricate "quick tubes" to come 16" straight out of the collectors and weld a flange on and make a cap. Then out the side of them im going to run the exaust in tward the drive shaft at a hard angle just missing the flange and cap on the quick tubes, run it all the way down into some 50 series flowmasters and dump them. Question is...would i see a benifit from an H pipe on the street and where should i locate it? Motors an 11:1 350 RR200 heads, 1 7/8" primary super comp headers, 3 1/2 collector into a 3" exaust. I know the headers are too big but i got em for a hell of a deal. So what do you all think?

I would personally use any kind of balance tube,whether H or X,it helps scavenge the cylinders and improves performance thru the exhaust. I used an H pipe 20 years ago and still use one today,not much more to be had with an X from what I hear,but I've never tried one.

Yes, the H or X will improve power in a street/strip car.

A bigger improvement would be changing to 1-5/8" headers....Stockers in the mid-low 11 second range with a SBC typically are using a 1-1/2" tube.

If you can build a welded exhaust system, then you're capable of building headers.


What helped me out big time was buying a box of 10 random degree stainless mandrel bends, and starting the project with them. I made my own stainless dumps with those, and did 3/4 of the system with 1 box.

I used 18 ga. stainless for the pipes and bends, nice and light.

if you wanted to make headers, you could buy a couple "grab bags" of 1-1/2" or 1-5/8" mandrel bends, a lenght of tubing, and go to work.

Stainlessworks.net has the best prices on stainless mandrel bends and tubing.

My suggestion would be Dynomax Ultraflo over the flowmasters, Dynomax are lighter (14lbs ea. for the 14" big case) and are a through design.

Nickel,

On my low 11 second 383 SBC powered '71 Chevelle (3600+ lbs. with driver) I saw no difference in ET/MPH from adding an H-pipe. Nada.

That being said it did smooth out the idle and quiet the car down. I run 22" long case Straightline mufflers. For what it was, it was surprisingly tame. Several people would usually stop by and ask about how it ran what it did and was so quiet.

Granted I did run a 4200 stall 8" ATI converter and 4.56 gears. I may have pulled through the range where the H-pipe may have been useful.

Good Luck

Not trying to step on anyone’s toes, but. Why would you want 1 5/8 header with a 3 inch exhaust? I've talked to some professionals about the header diameter theory and what they've told me is, the header diameter only moves where your torque band is. So a smaller diameter header will cause the torque band to be lower in the RPM range. Thus, the opposite with a larger diameter header peak torque happens at a higher RPM. Seems like stockers are hell bent on getting really low 60 ft times why they run extremely low rear gear ratios and low transmission gear ratios. Maybe the reason your friend has the 1 1/2 header?

If anyone has a better explanation or can enlighten me with some good hard facts please do. graemlins/waving.gif

60 foot is everything, You cannot make up what you lose off the line in a heavy street/strip car,unless you have a BIG blue bottle on board.

Originally posted by Aaron Kelley:
Not trying to step on anyone’s toes, but. Why would you want 1 5/8 header with a 3 inch exhaust? I've talked to some professionals about the header diameter theory and what they've told me is, the header diameter only moves where your torque band is. So a smaller diameter header will cause the torque band to be lower in the RPM range. Thus, the opposite with a larger diameter header peak torque happens at a higher RPM. Seems like stockers are hell bent on getting really low 60 ft times why they run extremely low rear gear ratios and low transmission gear ratios. Maybe the reason your friend has the 1 1/2 header?

If anyone has a better explanation or can enlighten me with some good hard facts please do. graemlins/waving.gif =
Would you settle for some excellent reading ;)


HeaderDesign (http://www.headerdesign.com/index.asp)

More then just my friend are running 1-1/2" tube primary headers with a 3" collector.

Brian, id go to a 1 3/4 because i know the motor would pick up everywhere on bottom and on top and im willing to trade anyone who has a set of 1 3/4" hooker Super Comps for my 1 7/8" but i havent found anyone yet. I just got an incerdible deal on the headers from a good friend who had no use for them. Im not too concerned about my power from idle to 3,000 RPM where i think the 1 5/8" pipes would shine, and i think from 5,000 to 7,500 RPM those pipes would kill a conciderable amount of power where ill be running my motor most of its race. Ill never see anywhere below 3,500 RPM racing. The way im geared currently its like running somthing around a 5.1X gear in the first 4 gears and then dropping to a 4.11 in 5th. So i have plenty of gear in fact i could probably go a little less but testing will tell that. I was just wondering if it would give me some more power to play with around town, as ill be opening up my quickie tubes @ the track.

1-5/8" is what you want, 1-3/4" at the Largest, although i would not suggest them.

To compair, a typical H/SA with 1-1/2" headers is using an 8" converter and more then likely 5.13 +/- gears with a 30" radial tire.

Hey, you can do what you want, its your car/money, but thats just my suggestion.

I run a 1 3/4 inch super comp header and my best 60 ft was a 1.69 only suspension upgrade was a small slick (28 inch) with 3.70 gear ratio SBC 350. My converter flashes somewhere above 3500. Like Nickle I don't believe I need the smaller diameter header size.

I guess what I meant by my comment is; header size should be chosen to work well with the other components of the engine (engine can only be as strong as the weakest link). Like the web site said on wolf's suggested reading (I haven't finished the reading but skimmed through some of it).

I'll agree that 60 ft times are proportionate to the elapsed time. But you don't want to go so crazy with gears that your blasting through the final trap at 7000 rpm with a engine that only pulls to 6000. Or you have so much gear that you’re not consistent with 60 ft because the rest of your suspension isn't up to the task to handle all the torque multiplication. With that said 60 ft isn't everthing but it dose count.

What dose it really mater anyway? If it don't work the first time just keep throwing money at it, right? ;)

Have a great weekend