I'm in the process of building an exhaust system using 1 7/8" hedman "weldup" headers, 3 1/2" collectors into a flowmaster ypipe, 5" single w/ dynomax race muffler. The drivers side crosses over above the transmission and behind the distributor. I am just not sure about primary tube length, I've read that shorter gives more high rpm power 28-32" and also that longer gives more bottomend/midrange power @ 34-36" I'm at 33 1/2" right now with everything mocked up and tack welded. Engine/driveline is listed below, planning a "power range" of 3000-6000 rpm with 6,000rpm as redline.

415ci world block 3.875 stroke, 6" rods, ross pistons 10.5:1
edelbrock victor Jr. heads
" " Jr. intake
750cfm carb.
comp cams custom grind hyd. roller 3000-6000
T56/ 3.90 or 4.10 gears (currently 3.42, will change soon)
100hp nitrous edelbrock performer kit

Aluminum flywheel/driveshaft/small damper, this engine revs quick and I'm leaning towards a shorter primary length to better match the intake/heads just not sure exactly how long to go (or is that short to go). :shrug:

Any help or experience is greatly appreciated!

 

I've also read some things recently that have me second guessing my tubing size of 1 7/8. Mainly, the hot rod article from last month titled "ultimate daily driver" where they asked a bunch of experts what sbc combo they would choose. Most, if not all, reccommended at least 427c.i., huge cam, and 1 3/4" headers. It's too late to turn back now, are the 1 7/8" size going to do actually hurt my performance?

 

Pic's so far..

 

question??? why are your headers on top of the engine????? could they not fit going down??? that's going to create SOOO much heat..

 

To defrost the window.

Okay, not really. There's a couple of reasons, ground clearance, trying to fit the exhaust through the trans. tunnel, etc. Running in the tunnel would've required just as much work imo, I've seen a lot of nice true dual setups, done properly, I couldn't run an x pipe until after the trans.. Then I've heard arguments that properly built headers don't need an xpipe because they are already balanced.. I guess I didn't know what to believe so I wanted to run into a single asap after the headers. I do know this way will be easier to change plugs/pull starter/trans/etc and the exhaust will merge just after the headers like I want. I don't see it creating any more underhood heat than a couple of turbos. The heat will be soaking into the valve covers instead of the oil pan/transmission. I know it's gonna be a pita rigging up a cold air inlet what do they call those a pan/gasket setup? I won't really know if there's a heat problem till it's done though so i'm not going to say you're wrong, i might end up changing it all back if it doesn't do what it's supposed to or melts a hole in the hood, etc. lol

The upswept headers might vent the exhaust better. It has to go back down into the Ypipe tho so I'm not too sure about any gains there. It probably won't have flow problems seeing that its all overkill. The only real down sides that I can see is having to make heat shields for the dist./brake resevoir. It's also adding weight to the top of the car instead of keeping it low to the ground.

 

i dont know about those headers.
looks like something from a ASA roundy round car......

 

Something like this?

 

I love new and out there ideas, but this doens't look like it is going to work. Also 5"!!!!!!!!! I am sure you want flow and stuff, but c'mon a 4" is still a crap load of volumetric area. Oh and why even put that muffler there, it is going to do absolutly nothing. I have 2 3" dynomax bullets on my dumps and they don't do a thing... nothing. just cost more than pipe. It is really, truely a waste to even call that a muffler. As for going over the motor, I still think it is a horrible idea. You should cut your looses now, and have that exhaust go down. If you really wanna do something different and more efficient that take a lot of time, then go into your fenders or something, have 2 tubes go the stock way and have the other 2 go another way, that way you can tuck them WAY up. That is sorta the idea that sthal uses. Maybe you can make some tri-Ys that way. Anyways, good luck and hope you that somehting good comes from all this.

 

try to mock yours up like the BBC custom headers do where some pop out the fenders instead. I don't think that the over the motor idea is a good idea at all.

 

ONE WORD.. FIRE! Im not saying its stupid but it definatly not safe running headers right near your wires and fuel source and look how close they are to the plastic brake res.

 

didnt notice this before, but looking at it again, you have your inner fender portion of the uni body cut out and your firewall?
any info or more pics of this?

 

On a 415 your fine with 1 7/8s and 33 1/2 long is good with your 3,000 to 6,000 cam.

Jerry

A link for more info on cross-over headers. The 180 degree sound bad a$$

http://www.schoenfeldheaders.com/180_crossover.htm
http://www.schoenfeldheaders.com/crossover.htm

 

Ok I am a big fan of modifications but that just looks wrong. I see a huge amount of heat in the engine comaprtment as well as a good chance for a fire with all of the wiring so close to the exhaust. On top of all that I see that your using an HEI dist and everyone know they do not like heat either.

With the cutting that you have done on your car you should have been easly able to modify your car to fit exhaust like I did in my post. If you look under fabrication and check out my thread 1982 silver state project you can see that I was able to get a set of large tube headers and nice true 3" exhaust in my can and keep lots fo ground clearance. Some thing just take a bit of work.

I do like creativity and that is very creative. I just think that your going to create lots more issues then your going to resolve.

Just my 2 cents!!