71 Chevelle
zz502 BB

I currently have Super Comps(2217) with 2" primaries and 3 1/2" collectors. They hang extremely low. It's to the point where I have a couple tubes on the bottom that have flat spots from hitting so much. :o

Do the regular Competition(2245) headers have better ground clearance? I was hoping I can get away with these since my exhaust is already set up for the 3 1/2" collectors.

If that's a no go, what about the Headman Street(66002) headers with 2" primaries and 3" collectors? I've read they got good ground clearance, but most have to dimple them to clear the steering shaft. :(

Last resort... How much performance loss do you think I would have going to a 1 3/4" primary header?

Maybe this should be in the performance section?

They hang low on my car.

I ran 2217s on a couple of my cars, and always ended up with dents and flat spots in the primaries where they make the final turn toward the collector.

I switched to comps, and did not have as much trouble.

On to the '66 Chevelle chassis:
I ran regular comps and then switched to stainless steel versions, fit exactly-precisely as the comps did, made on the same jig, and the only issues are flat spots on the collector flange, which I had with the comps (and naturally with the 2217s).

I also ran the Super Comps on the '66 chassis and they did hang down a little lower, but not by all that much, really. There is a lot of space between the header primaries/collectors and the floor of the car. Enough for about another inch of clearance if modified.

On the chassis(s) using 2217s, I switched to Hedman 1-3/4 primaries, and there was a noticeable increase in bottom end torque.
However, at the time of the switch the engine was a fairly mild 454. These headers would not have been a good choice with more cubes and more breathing, or same cubes and much more breathing.
The cam was a Comp 270 Magnum, the heads stock peanut ports, with a Performer intake and 3.08 gears with a Super T-10W.

With 240 or more duration @.050" and appropriate lift dynamics, the 1-3/4 primary, IMO, would start costing you power above around 4500 or so.

That makes the 1-3/4" primary (with 3" collector) a good all-around street header for mild-to-medium motors of 454 cubes or less.
A smooth-idle torque motor 496 might get use from this tube size, but it would likely have to be a tow motor or similar tune.

Gears have a lot to do with header selection-- simply because they determine how long the engine will spend at/in any given rpm or rpm range.
This is something that is commonly overlooked, but is actually a very important part of a professional tune up that can be accomplished by regular guys in their own garage, unlike re-building intake tracts with epoxy for example.
That 1-3/4" tube size would fall in love with taller gears, but would be overwhelmed by shorter (numerically higher) gearset combos.

Also ran 2217s on this car as well. Plenty of clearance issues, could not go over speed bumps or gas station lumps.
http://i20.photobucket.com/albums/b203/aero80/camarotypecx.jpg

Eric

I ran my comps for years on my BBC. The front sat low and no flat tubes. The headers (I think dynomax??) had flat tubes when I got the car.

Eric,

Thanks for taking the time to type all that out. That info will help a great deal!


2k3Chevelle468,

What headers and size are on your car in this picture? click (http://i291.photobucket.com/albums/ll300/littlerat468/DSCN0029.jpg) Those things are tucked up real nice.



This is an old pic, but you can see how low the super comps hang on my car. The grass might make it look worse, but I have about 3 inch ground clearance.

http://img146.imageshack.us/img146/5133/chevelle004640x480cx1.jpg (http://imageshack.us)

2k3Chevelle468, I just realized that you're running a small block. :clonk:

No wonder why your headers are tucked up nice.