I've hesitated to post any of this as I'm terrible at documenting stuff like this properly. Here goes anyway. Long story short, my 69's Hooker sidepipes suffered terminal damage back in May due to a chunk of concrete in a poorly lit construction area. Knowing that the sidepipe headers look cool, but are not well design for exhaust velocity and scavenging, I decided to use this as an opportunity to replace them with a properly sized exhaust system. I ordered a set of 1 3/4 stainless headers from ARH and set out to learn to TIG weld.

The headers are well designed with excellent fit. I have a Borgeson steering box and a Kevko road race oil pan. These headers were very easy to install and clear the steering box and oil pan. The passenger side took all of 10 minutes. The bolts went in easily and I could even get a socket wrench on most of them. (Vintage AC did make that side easier). The drivers side took about an hour because I had to remove and reinstall the clutch Z-bar. Every fit well with no modification or dimpling needed anywhere.

Now, the rest of the fun. Snaking 3 inch exhaust under one of these is no fun. Doing it on you back with the car on Jack stands is even more challenging. Learning how to TIG weld Stainless when you've only ever MIG'd mild steel just adds to the excitement. Lots of mistakes and wasted pipe. Luckily, I have a neighbor with more skill than me who offered some guidance and scrap SS304. At this point, the exhaust is routed through the frame. I built an X-pipe behind the crossmember with 9.6 sq inches of cross section. (9.6sq in. should support 500 hp..I'll be close to that) After that, the exhaust transitions to oval pipe for additional ground clearance.

I can honestly say that I understand why this exhaust is not commercially available. Everything is so close and tight that even minimal production tolerance would make it not fit. I'll try to document the rest of the build and maybe put up some sound clips once it's done and the Borla's are on. I will say that I have done a short drive around the block with open pipes after the X-pipe. It is MUCH more responsive than the 4 inch side pipes(ope or with STS baffles) were and has an intensity/urgency that it never had before.

JUNK

not junk

one of my few halfway decent welds. There were many that were worse, but they won't be seen

Test fit. second version of X-pipe. Final version has more clearance through the crossmember.

X-pipe and transition to oval. The Oval gains 3/4 inch of ground clearance. It isn't much, but it helps.

 

Here's the "no side pipe" look. I used later model rocker panels...I think they look better. (just my opinion)

 

I think it looks great. I went from Hooker sidepipes to a custom built stainless system. I love it so much more than sidepipes. More power and less sound.

Bill

 

Thanks Bill. The difference in throttle response is amazing. The engine felt "and sounded "lazy" before. It will get even better as the Sniper relearns and adjusts the fuel curve.

 

I also have a sniper EFI on my big (427) sbc and welded up a dual 3” exhaust. I love it and the power is insane!

Well done, Jim!



Doug’s headers 1 3/4” primaries to 3” collectors. I used oval ss tubing for better clearance once through the crossmember.

I mig welded my 304ss using trigas. I’m just more comfortable and somewhat skilled with my Miller mig machine.

Into a single Magnaflow dual 3” in/ dual 3.5” out. Of course this is a C2, but same principle.

 

Thanks Mark. I love the center exhaust on your C2. I thought about doing that on mine, but got some resistance from my wife. She was honestly upset because I ditched the sidepipes and she hated the idea of center exit. I gave in and am going with a pair of Borla XR-1 tucked into the stock location.

 

Jim, with that x-pipe and 3” exhaust, those Borlas will sound killer!

I have the x-pipe and twin flowmasters in the stock location on my ‘69 and they sound great, but slightly raspy. Borlas are a great choice.

 

Since you are a welder, you could simplify your exhaust by modding your pass-through cross member. I saw the problem with the GM design back in the 80's and modified my cross member to keep the 3-inch pipes straight and heat away from the tranny. It also makes remove and replacement of rear end, trannies, and engines much easier.

 

Calling me a "welder" might be a stretch, but thank you. I considered The G-force crossmember or similar. Decided that I'll save that for when I eventually take the body off so I can make some other changes and reinforcements also. Nice job on yours. Looks great!!

 

I can't wait to hear the Borla's
I'll be running a 496 with Hedman 2 1/8" long tube headers into 3" collectors and three inch oval tubing all the way back.
I purchased the G Force crossmember to make things easier.
I'm still on the fence about adding an X or H pipe because I've heard it really smooths the exhaust tone to where it's more like an exotic.
I've always liked the deep sound of true duals but want the additional hp/tq of the X or H pipes.
I also want it to be a reasonably quiet rumble and not harsh.

 

I have a PYPES 2.5 setup with an X pipe. I'll let you know how it sounds in a few weeks

 

Local pro Streeter put 4 inch ovals after the collectors on his max ci BBC It makes for a deep sound. I went with 3.5 in and out box mufflers

 

Did you make your cross member removeable? Please show a pic of the attach points for it? Is that a through bolt mount I see?

 

It's the stock auto tranny 79 cross member. Unboltable like every other one at either end. I found a 7 inch diameter pipe and cut out the pieces that I needed.. I used a plasma cutter to cut out the arches and a mig welder to weld it back together

 

His car was an automatic so it was removeable from the start.

 

Looks nice man! Gonna sound and run so much better... you probably just picked up 20-30 rwhp at least....

I ended up using the BTR tubular trans crossmember when we built my 3” stainless system, it freed up some room for sure.

 

Thanks Alan. I think you are right. When Nick at ARH ran the numbers on my car, he estimated I would pick up 25-30 hp and 300 usable RPM up top. In the short drive that I took, I would say that is probably close also. The Butt Dyno says 50 hp, but it is often miscalibrated if the car has open headers or hasn't been exercised in more than 30 days. I can't wait to really see what I end up with.

If I find myself with a bigger small block down the road, I have an X-pipe ready for that too.(0.019xHP target=cross section sq in) This one should be about right for 580 hp. I really like the idea of a 427 SBC..My wallet doesn't though.

 

When you get up in the 500hp range it really gets hard to keep your horsepower with sidepipes. I did a bunch of dyno testing of sidepipe mufflers 18 years ago. The best muffler to not lose horsepower I ended up with were 3 inch Dynomax race bullet muffles spliced into the side tubes. Problem was it was so loud I hated driving the car. The baffles were good, but at 600hp I had to uncap them and cut them in half to get close to the race bullets. Again, very loud. The other problem is the long and bent primaries on the Hookers is just not nearly as close to ideal as a shorter primary without the big bend. I love my undercar system. I am going through the crossmember holes, but was built in such a way that I can have it off quicker than sidepipes. You will love the change, especially as you increase horsepower. Oh and I am sure some think it is heresy to say, but I think your car, and these cars in general, look better without sidepipes. Uh oh I gone and dunnit now lol!

Bill

 

Thanks gkull I made mine removable ages ago and now I'm gonna find me a 7"diameter pipe and copy your mods shown here..... plan to start my teardown within the next week.

hmmm.... now to find me a 7" diameter steel pipe......
panther-19
When I get under there again I'll get some pics of the way I modified mine, I have some pictures now but they're fairly crappy, but if I was to do it nowadays I would copy the stock automatic crossmember... keep the end pieces, slot the end pieces, weld some plates onto the centerpiece, and slide it up.... then a quality through bolt horizontally.....heck, if you're paranoid then 2 horizontal bolts!

oh well--- I went and got it....here is a picture of how mine is built. There are 4 grade-8 bolts holding up each end of the crossmember. I built it so that no part would hand lower than the original..... but really, copying the original and coming in from underneath unto the stubs would be easier---- gotta do cutting and welding anyway.

 

Bill,
I could not agree more.
This is truth, not Heresy!