Superformance Exhaust

[wanab5150]

I certainly understand the quieter pipes and if I had not heard the 3 inch mufflers and found out how much HP is lost because of, in my opinion poor set up, then I would have been happy. Fortunately or unfortunately, I did find out!

I went the extra mile for the Roush 427R and assumed the superformance dealer would provide a correct set up for the engine they recommended to me.

I paid extra for a bunch of options such as the 17" wheels, non standard color choice, seat modification, and more. I would have sprung for a correct complete exhaust system if I had an inkling it didn't match up to the Roush motor.

If I only wanted 400 HP, I would have just put the Roush 347 inch motor in it and saved a bunch of money. Even the 347 makes 450 HP.

As far as the headers go, the heads on a 402 have smaller intake runners and intake valves. I can't imagine the exhaust port would be the same on both heads....what would be the use? larger intake runners and valves require larger exhaust ports and headers unless you want all torque and no top end HP.

If what you say is true, I still need a larger header. I would feel a little better if I knew I had a header more set up for my engine like yours. I might even pass on larger headers if the size difference in relatively small. Still investigating!

[thudmaster]

Tom, the 402 headers are much larger than the standard superformance headers. They match your roush heads.

[wanab5150]

Ed I hope so. I will ask Steve in Reno tomorrow.thanks

[decooney]

Jim,
Your car sure sounds incredible after you made the change.

I have been meaning to ask you, did you notice any change in the low-end performance with less back pressure, worse/better?

When I redid my exhuaust, I was certain I would lose just a little low-end grunt, and to my amazement it gained low, mid, top end performance across the board. Just wondering how it was with your motor setup. DC

[terry lee]

Tom,
The SS sidepipes came from Ron Roberts in MI. (Check with SCOF for info how to contact).
My headers are the stock SPF headers that have been ported. Dennis O. did have some special tube headers several years ago, but they were too expensive to mass produce for a small market.
If you can't find Ron Roberts, PM me and I'll try to find his contact info buried in my files. OR, Look him up here on CC.
TL

[Rare Iron]

I reached out to several of the Cobra Kit mfgs. a while after I started building the Cobrapacks & NONE of them had any interest in offering a better flowing muffler with their kits (except for Lonestar). Factory Five asked me to quote them & my mufflers were about $25.00 more apiece than the ones they were using already - they said "no thanks - we'll go with the cheaper ones." All they care about is the $$. I suggested the car owners just MIGHT spring for a little extra $$ to gain some major HP - they disagreed. They must know something more about this than me - I dunno. One of them said they had never heard about the Cobrapacks - they didn't want to know any more than that. Great attitudes - I was really impressed.

[Jim Norris]

Originally Posted by decooney

Jim,
Your car sure sounds incredible after you made the change.

I have been meaning to ask you, did you notice any change in the low-end performance with less back pressure, worse/better?

When I redid my exhuaust, I was certain I would lose just a little low-end grunt, and to my amazement it gained low, mid, top end performance across the board. Just wondering how it was with your motor setup. DC

Duane,
Thanks for the compliment. I do like the sound.
As for the low end performance, I did notice a seat-of-the-pants decrease. I don't know what the numbers are, but the neck-snap seems milder. However, as the RPMs increase so does my grin.

[greg schroeder]

Originally Posted by madmaxx

Greg,

You have figured the roush 427 better than anyone. Can you list your suppliers for the headers and sidepipes you used. If the muffler in the side pipe was exchangeble which one did you use?

Thanks

I'm not sure if I figured anything out other than more air through the engine allows for more fuel to make power. Air is the tricky part. Fuel is simple.

Quite honestly I would be skeptical of my headers being anything special other than they were larger to not block part of the exhaust port and that I matched the gasket to the head so there wouldn't be material blocking flow. I think the headers I had were Superformance big block headers re-flanged to fit a small block. They were from the Olthoffs www.olthoffracing.com The headers were about a 10 wheel HP increase.

The side pipes I used were from Buckshot Racefab. www.buckshotracefab.net The 3 inch core had the louvers facing forward as I recall and the collector was a basic unit which had internal fabrication at the merge point. The side pipes I had did not have the same collector as what is currently displayed on the web page above the video of my car. I'm not sure of the science behind the intent with either version of the side pipes, but the side pipes I had were about a 25 HP gain and it made a wider torque curve. The change was notable for acceleration as the power gain was not only at top, but all over.

The mechanical secondary carburetor was from www.pro-systems.com I'll just tell you right off this is the most notable power gain of anything. It made about 30 more wheel HP and made the car a pleasure to drive with instant throttle response and was extremely linear and could move the car along the freeway at 1800 rpm in 5th gear no problem.

Then there was the increased size air filter, fuel line upsized to 8AN from fuel tank pick up to carb, fuel filter replaced to large 100 micron Aeromotive, and rev limit increased for use of a bit more top end. All that was good for about another 10 wheel HP.

I also changed to stronger half shafts because one broke inside the 8.8 ford rear. I replaced the limited slip with a Detroit TruTrac and kept a 3.73 rear gear. I also went to a light weight McLeod flywheel and a stronger SPEC stage 3 clutch.

Mickey Thompson ET street drag radials in a 275/60 15 are the best modification I did to make the car fun to drive.

Other than all that I'd like to see an image of the new Superformance 402 header and be curious to know what size primary they have.

It would be interesting also to see some of the cars trap speeds which had side pipe change. Trap speed tells the real story of power if you know the DA too.

My thought about marketed HP gains is at times they may be exagerated.

[wanab5150]

Yesterday I was at a fellow Cobra owners house for the 4th. He has a 1600 serial numbered car (mine is 2769). His car also has a Roush 427R but his headers are different than mine in a BAD way!

Right off the flange about an inch is a weld where it appears a smaller port size tube is welded on. It is much smaller than mine and VERY RECTANGULAR. I stated mine also appeared somewhat squared, but I will recant, and after looking at his say that mine have dimples in the side to make room for the header bolts. The center tubes do not have the dimples like the outside tubes and mine only have one weld which is about 6 inches off the flange where the tubes are increased from about 1 5/8 inch to close to 1 7/8 inch.

Stephen at Full Throttle sent me some photos which clear things up. The photos are of both the 402's and the old 351 headers. If Superformance only made two different headers them mine are the "402" headers.

I would suggest anyone with a Superformance check to see what they have. After seeing how tiny the old 351 headers are it's ridiculous to use them with a big inch motor.....almost as bad as using the stock 2" mufflers.

If you have the old headers and don't swap them for the bigger ones, it WOULD NOT benefit you to got to a larger muffler because it is completely choked by the exhaust port/header anyway. You would need to swap the entire system for a real HP gain

So...basically if you look at your headers and they have a weld out 1 inch from the flange and another 5 inches out, and the tubes are rectangular at the flange, then you have headers for a stock port 351 head.

If anyone wants photos of the two different headers drop me an email and I'll send them to you. Meantime, I will be waiting for the 3" mufflers and report back with the results.

[wanab5150]

If anyone wants to explain how to add photos here I will add them to this post.

[wanab5150]

I tried..........failed.

[RedBarchetta]

Originally Posted by wanab5150

If anyone wants photos of the two different headers drop me an email and I'll send them to you. Meantime, I will be waiting for the 3" mufflers and report back with the results.

Greg Schroeder has posted this pic before. The "original 402" header on top (not sure they make this configuration any longer), old style on bottom.



-Dean #747

[FrankM1]

Anybody know where we can get the one's on top of the picture?

[RedBarchetta]

Frank, you might want to call Olthoff's in NC. Not sure if they make them any longer or not, but with enough interest I'm sure someone will crank up the TIG and start building a batch. The problem I had with going to these was that they were originally designed to work best with the AFR heads/ports. My Victor Jr. ports were still off a bit and it wasn't worth the expense for a marginal improvement, at best. So I spent my money on bigger mufflers and at least improved the sound component to a far better degree (and picked up a little bit of power, though I can't substantiate it via before/after dyno pulls).


-Dean

[decooney]

Originally Posted by Jim Norris

Duane,
Thanks for the compliment. I do like the sound.
As for the low end performance, I did notice a seat-of-the-pants decrease. I don't know what the numbers are, but the neck-snap seems milder. However, as the RPMs increase so does my grin.

Hey Jim,
After you changed the pipes out, did you have to rejet the carb at all?

I had to go up 4 jet sizes on primary and secondary. If not, there may be little more to be had there...

[Got the Bug]

Originally Posted by FrankM1

Anybody know where we can get the one's on top of the picture?

You might want to call Hillbank or Olthoff and have them send you a picture of the current SPF replacement header that they stock (or the header from a recent car).

http://www.shelbyshop.net/product_in...ucts_id=130648

I'm 99% sure that they are no longer shipping the old style headers with later cars.

BTW - Mine look like the new style and are stamped "AFR0082" on them. They came stock with car and weren't a special order.

[Got the Bug]

Here are the pics that Tom sent me via email.

402 Header


402 Header


Old Style


Old Style

[wanab5150]

Thanks, Doug.

[greg schroeder]

the headers I put on my 427R were not like the new 402 type. They were larger than the exhaust port by height and just really close on width and had 2 inch primaries to match the 2 inch primary side pipes. I can't say for certain, but I think they are big block headers reflanged, not positive. The other 402 type header looks really similar to the AFR 205 exhaust port shape. You'd have to measure the header width internally to tell if they're perfect. From the looks of them the bolt holes look like they might be a bit tight. The design of the new type looks nice compared to the old for sure. I had mentioned before the headers I had were good for about 10 wheel HP. Side pipes were about 25 wheel HP, Pro-Systems carb about 30 at the wheels and all the fuel delivery and intake changes were about 10 wheel HP.


These are my headers, old and new.


This is an AFR 205 head exhaust port according to an ebay ad were I got the image. Accordding to the tech line at AFR the 205 exhaust port is 1.342" wide and 1.375" high. The heads have both 2 inch wide bolt holes and 3 inch wide bolt holes. According to the tech line at AFR the 185 head is 1.335 wide and 1.4 high and have only a 2" wide bolt pattern.

[wanab5150]

Well, with the 205cc port being 1.342 x 1.375 the 1.650 O.D. "402" headers I have should be more than big enough to eliminate any restriction. As I mentioned...they expand to 1.75 about 6 inches from the flange and remain that size all the way to the collector.

I always matched gaskets and cleaned up welds on the flange in the past, but with the clearance I think I will just leave them alone. In the beginning of this thread I was afraid even the "402's" were to small, but I am relieved I won't have to spring for new headers.

I'm glad to see the port size numbers...thanks, Greg. I'll have the new 3 inch mufflers in 3 weeks. tom