Sticky #4: Pantera Exhaust Systems

quote:
Originally posted by OSOFAST:
I saw this companies website on a post here somewhere, they can make you anything. Jeff


Yup, they seemed like good guys. I bought mandrel bends, v-band clamps, and various odds and ends from them. They were competively priced and had American milled 304L stainless and had a good selection of 16 gauge. Most folks go 18 gauge but 16 gauge stainless is .062 wall and since I was building step headers stepping twice by 1/8" increments this meant each step nested tightly inside the next making it self-fixturing. The slightly heavier wall and half lap joints will be very strong and TIG up nicely. I figure I gave up 6 lbs going 16 gauge instead of 18 Ga on the primaries but probably a good concession considering the aforementioned.

Their bends were very smooth but the only downside was when I received them they were still full of mandrel lube on the inside. I'll need to have them all vapor degreased before any welding or I'll have a total mess. I'm thinking I'll only have the inside ceramic coated and polish the outside. I'm hoping the inside coating will slow down the heat and rate of oxidation and discloration. I can always re-polish them. I'm just having a hard time bringing myself to putting a coating on a stainless exterior given that I'll have to be crawling all over them.

Best,
Kelly
This is an old shot of the rear on Pantera 4384.
But the exhaust system is still the same.
Headers are ceramic coated.
Rear connector pipes are 2 1/2", (63.5mm) diameter & they go over the driveshafts instead of under.
Nothing touches, has full clearance in bounce & droop.
This makes the pipe slightly longer which helps to muffle the sound a little more & I'm told by my Dyno guy, better to tune.
Stainless mufflers purchased from PI motorsports.
I Tig welded a trangular stainless flange onto the input pipe of the muffler instead of having the slip joint.
The connector pipe spigots into the muffler after the flange so there's no exhaust pressure on the gasket.
This is also done on the end of the headers.
At the rear of the mufflers I Tigged on a mount plate which in turn has a bolt on rubber insulated mount to the chassis to support the muffler weight.

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quote:
Originally posted by Garvino:
Kelly,

I am also interested in running 180s on my car and have thought about fabricating a set myself. I ran across this thread a few months ago and found it to be very informative: 180 Header Fab on 400 Swap


Thta's a good one. I have that thread pasted in my favorites. Hope Brooke's business is picking up so he can resume his build and post here some more.

I'll look forward to the Quella pictures.

Best,
K
quote:
Originally posted by JTpantera: Pic with Heat Shield on GT5. When I refresh the paint on the car, I will shift the heatshield to the decklid so as to better expose the 180s.


Thanks John. Looks nice. I agree, mounting the shield on the engine keeps the weight of the deck lid but is one more thing to remove for service and obstructs the view of that purdy hardware Eeker

Best,
K
I have been looking at doing 180's for a long time while planning my build. I have saved about 125 pics of various cars with these set ups from the forum here as well as other places on the net.

If I were to build them I would consider doing a flange between the right and left so you can bolt them up without slip joints.

Also it looks like most people don't have any muffler supports. I would think this would lead to cracks. I was planning on a muffler support bracket using the trans mounting bolts or something.

Now this is nul and void as I am leaning heavily to go 5.0L modular.
Kelly,

Here are a few photos of the Group 4 Pantera that Quella’s son was building in Castle Rock when I was last there. I did not take as many photos of the car as I thought, but hopefully these will give you some more ideas for your 180’s. I do not know who builds the actual 180 headers for Quella’s cars, but I don’t believe they build them in house.

The car was still a long ways from being finished but already looked great. The Group 4 conversion was all steel. On the 180’s, I particularly liked the rear support that Quella had fabricated for the mufflers. Quella’s son also mentioned that the muffler exits would have rings around them when he was finished fabricating the muffler system, etc.

I hope this helps and please keep us posted on your build.

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Thanks for those Garvino. That exit and mounting configuration is very similar to what I have in mind. Not much progress but I did manage to get the VBands welded onto my mufflers which was no small task. The mufflers are very light and have a spun end cap that is very thin (like .030"). The extensions are usually slotted and secured with an external clamp. I had to make a stainless spud that fit down in the muffler and into the VBand socket. Even so, it needed a close fitting aluminum plug made to sink the heat and keep the thin walled material from burning away. Turned out pretty good but took some doing. Will have to repeat this on tail pipe section.

Who are some good sources for the various styles of 3" entry stainless tail pipes?

Best,
Kelly

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ALEX's Group 4 build has pictures of a nice setup with 180 exhaust. I don't know if he split the tips that way so he can have at least half a trunk or not.

My friend is also running this set up but with the pipes going out the center. The problem with this config is it leaks at the crossover pipes.



quote:
Originally posted by Panterror:
The mufflers are very light and have a spun end cap that is very thin (like .030"). The extensions are usually slotted and secured with an external clamp. I had to make a stainless spud that fit down in the muffler and into the VBand socket.


Kelly,

Nice work as always, can I ask whose mufflers are those and do you have any idea what sort of sound level they will have? With all the CA tracks moving to sound limits I need something to replace the current Ultima mufflers, which are not re-packable.

Thanks,
Julian
this is my next job , making a stainless exhaust. I have now the changed,cut,welded, result of the US installed version . I have the mufflers rotated so to have the tips à la Detomaso "sky" pointing with my ,now, euro style bumpers.( with the US bumper they were horizontal )
What i like visual about them now are the double wall exhaust tips with some sound reducing material in them , further they seem to be "open" ....which give a amazing sound now but ... for driving longer trips it can become "to much" as in terms of speaking with your passenger , phone,radio....sometimes important,alerting,traffic noise .... i would love to get it that bit softer grumble....
Also the steel version now , i got it painted black with high temperature paint , doesn't hold quite well , on some spots it's paint fals of , so i like more the ,even discoulored, look of a stainless one.
I come back here with my project and pics... Smiler Wink
quote:
Originally posted by Joules5: ....can I ask whose mufflers are those and do you have any idea what sort of sound level they will have?


They're made by Coast Fabrication. They manufacture the Burn's mufflers and are identical except they tac their logo on instead. Here's a link.

http://www.coastfab.com/mufflers.html

The website isn't particulary instructive and you have to hunt around a bit. I actually found the Burns site to have better visuals. I think prices are the same.

http://www.burnsstainless.com/...a-lightmufflers.aspx

I don't know about the sound level. I have a set 4.5" single stage units on my GT40 and I don't find those objectionable though they may be for some. I went with the 6 1/4" diameter single stage units 3" in & out and am expecting them to be somewhat more mellow than the ones on my 40 although they are a little shorter so we'll see. Coast also has a 2-stage unit that is identical in dimension.


quote:
With all the CA tracks moving to sound limits I need something to replace the current Ultima mufflers, which are not re-packable. Thanks, Julian


Coast will make custom lengths for you at request and pretty much same $ within reason. Your choice of packing. Glass only if you want to save weight or stainless scrubble or mesh if you want more durability.

Best,
Kelly
Well, I can say at long last I’ve had an opportunity to devote some time to the header projects. I’ve done a number of exhaust mods but I can honestly say there is a lot more to fabbing a set of equal length 180’s for a Pantera than meets the eye. Simply stated, there just isn’t much space in a Pantera to route the primaries or even much length for collectors and mufflers for that matter. My GT40 is much roomier. I might have preferred to buy a set, but my combo is C302B heads on 9.5 deck. Twice I have tried vendor supplied headers on my Pantera (ordinary set up for 4V heads on 9.2 Cleveland, and my current set up) that were supposed to be bolt-ons and twice I ended up having to cut and weld. I just got back from visiting with a fellow Pantera owner who is in the process of earning some frequent flier miles his “bolt on” headers too. Nothing against the vendors at all, but my experience says there are no off the shelf bolt-ons for my car. After doing the deed, it’s easy to see why such work is quite pricey to hire. I’ll share a couple of observations for any that are contemplating such a build. You might want to get a cup of coffee or drink.

Vizard says that well designed headers can accomplish the equivalent of 3-4 lbs boost if done properly. ….I’ll have some of that thank you. As a bonus, I dropped my engine off at the builder last week and it looks like the 180s will fit while on his engine dyno……exxxcccccelllent Smiler. I expect one of the biggest benefits of going to 180s will be the ability to use zero loss mufflers and eliminate the losses of the GTS style Pantera mufflers though I will miss the look.

So I provided my engine specs and Vince at Burns recommended triple stepped headers (1 ¾-1 7/8 – 2”). He commented they would actually be easier to build than a single diameter non-stepped primary and perform better. I figured what the heck, why not, in for a penny in for pound. The optimal length depends upon your engine specs but in most all cases, the primaries will need to be longer because it’s physically not possible to complete the cross over legs (#2, #3, #6 & #7) at that length. I started targeting 36” length primaries and ended up at 38” length. I just couldn’t get there and found the routing on cross over primaries were the pacing cylinders. This will vary depending upon your layout. I looked at a lot of 180s on Panteras and GT40s. There are lots of ways to get there. I opted for the layout pictured below which causes a rotational, equally timed, firing order around the collector to promote symmetry in scavenging. The fact that I used 6 ¼” diameter mufflers also contributed to the challenge with the crossover primaries because spacing the collectors further apart creates more disparity in length between crossover and non-cross over primaries, so 4” mufflers would help this aspect but be louder as well, especially with only about 13” of active length.
As noted in my previous posts, I opted to mock up the long block and build these out of the car because I didn’t want to take my car out of action for the build (wise move since it’s been a year now), and just couldn’t see crawling around the engine compartment to do this; better off in a chair on the shop floor. It took me as long to establish all the critical/corresponding dimensions and create the mock up as it did to cut and piece all the stainless together!!






I opted for 16 gauge instead of 18 gauge stainless mandrel bends. My first instinct was to save weight and go with the 18 gauge but I went with 16 ga for a couple reasons. Each leg of the primary would nest neatly inside the next making it self-fixturing. I also felt it would be quite strong and this was a plus since 180s grow significantly as they heat and create quite a bit of stress when they do. 16 gauge is also a little more weld friendly. I only give up 6 lbs using 16ga compared to 18ga. I didn’t find that the step headers were easier than a single diameter from a fab standpoint. For one, you need to buy three sizes of mandrel bends. In reality, I did not get to fully utilize the nesting of the tubes in each step transition since the space constraints and routing inevitably dictated that a step would need to occur in a bend rather than a straight section where the tubes could nest. The one thing I would do differently on the routing would be to make the first step from the collectors head for the target area with a 45 degree bend rather than a 90 degree bend. I might have been able to achieve 36” if I did so or perhaps if I routed the crossover primaries first. The first step from collector at 45 degrees would also keep these primaries further from the IR induction inlet air filters. I’ll need to make some shielding to minimize cylinders 4 & 8 from sucking hot air.



A wanted to use a good merge collector to maximize scavenging potential and the recommendation was 2 3/8” merge and cone back to a 3” ring. This is quite a bit tighter than what would be recommended for a normal 4 into 1 but the equal spacing of the 180 firing requires smaller collector area for proper velocity and scavenging. This all adds up to quite a bit of length and if you look at my mock up, you can see it doesn’t provide much space for mufflers and to make the initial turns on the primaries.





With all the effort to plan and fab, I figured it was worth using stainless. Big cost adder but hey, you only go around once right? The most pleasant surprise of the whole process so far was the ability to cut the 304 stainless. After doing some searching, I found DeWalt offered a 12” circular saw blade that they claimed could be specifically used to dry-cut stainless up to 16 ga. I was very skeptical. I found the blade online and gave it a shot. It was recommended to be used at about 1000 rpm. I had a speed control for AC brush motor so I put it to use on my circular saw. It worked OK but was kind of slow going as the speed reduction seemed to be a significant power reduction as well but once you got through the initial cut and broke through the tubing cutting across the two walls of the tube, it went fast until it hit the other side. You could see it would build some heat there. So, for grins, I just decided to try it at full speed rpm. To my amazement, if I applied proper pressure, it blasted right through .062” wall 2” stainless tube throwing a little bit of amber on the initial and final break through. The cuts were fairly clean and square, and each cut only took 3-5 seconds. No odor, and believe it or not, very little heat! I could touch very close to the cut immediately afterward and the cutting part of the saw blade as well? I would then dress the cut tube on the belt sander (also dry) and deburr. I never would have believed dry cutting stainless tube was possible in this manner. I did make some wooden fixturing to clamp and hold the tubes in place for the trickier cuts. Surprising, most of the cuts were quite easy to hold and I did not feel like I would lose control of any pieces holding them firmly against the fence. I did use face shield and ear protection.

I bought a series of the three diameters of mandrel bends in 90s, J-bends and J-45s. Everything I bought was on 3” center line. I looked at three methods of controlling/determining equal length; trial and error, bendable wire of prescribed length, flexible metal hose, and the new fangled modular blocks. I discarded trial and error immediately since I already had an eye watering investment in stainless and wasn’t too interested in a pile of scrap. After I got a good look at the bulls eye I needed to route through, I broke down and bought the “ICE” modular block basic kit which was supposed to be enough to do one side of normal 4:1 headers. Since there was going to be a lot of primary length in 180s and I already had all 3” CL bends, I opted for a custom set that had the majority in 3” centerline pieces since that is what I had in tubing, with 20” of 2” CL and 4” CL, and straight; the rest all 3” CL. I must say, I’m not sure I could have accomplished the routing with any confidence in the equal length without modular blocks. In all, I think the blocks are a clever idea though fragile for metal working environment and a bit overpriced. Nevertheless, I own them.







Now I have to disassemble everything and degrease the tube because although the bends I bought were nice quality tube and bends at a good price, they were also still full of the bending lube, so each segment needs to be scrubbed out with a tube brush in a bucket of degreaser before welding.

I estimate there are about 40 welds to be tigged up. That’s about 240”/20' of bead!! I think this is going to need to be done in two or three steps. The first will be to mark the position of the first step of each primary on the header flange. I think I’ll take a cylinder head and have my bud weld each of these segments first while bolted to the head. Firstly, the head will be a great heat sink and hopefully minimize header flange warpage. If there is warpage, I can correct this while there is still a fairly short and manageable tube length on it. Secondly, I suspect the tube will suck up in a slightly different position and will need to be tweeked with with a bit of bending and/or tweeking on the abrasive belts to keep the butt joints good and tight. I think at the same time, I’ll have a few of the other welds that occur within each step completed and also weld the lugs onto the collectors so they can be used to tighten the primaries into position on the collectors and fixture for final assembly and welding, tuning fit along the way.

Sooooo, anyone want to build a set of 180 degree headers for their Pantera?

Being stainless, they should already reduce heat transfer to the engine compartment. I just can’t get myself to coat the stainless exterior. I like the look of stainless. I would like to coat the interior and will probably use a jet hot distributor and the best thermal barrier possible. Can anyone with firsthand experience recommend a vendor to coat the internals of the headers? A Midwest US vendor is preferred but since it’s only the shipping cost I guess it doesn’t make much difference. It just needs to be someone that knows what they are doing and is willing pay attention to the details.

Best,
Kelly
I recall reading an article once about a real GT40 on Hot Rod Magazine a while back. It had a 180 degree exhaust in stainless but it looks like it was anodized yellow. They tolked about wiping down the exhaust with WD40 and heat-cycling inbetween coats. It had a nice look to it. I wish I had a picture of it.
Just a messenger,

Mark


I think, as regards thermal coatings, you get what you pay for. And that
may be in time as well as money. If you search Google under 'Swain Header
Coatings' you will have a ton of hits come up.

I say Swain because back like over 15 years ago that is where I sent our
new headers for #99 after researching it. Wanted the very best heat
retention. I just looked on Google and here is one comment from a user that rings
very true to me.


<< After researching header coatings for several hours, I came to the
conclusion that Swain may be a fair bit better than Jet-Hot as far as heat
retention. I spoke with Dan Swain this morning and my suspicions were confirmed.
I don’t think it is even fair to compare the two products anymore because
Jet-Hot is catering to a different market than Swain coatings.
Swain’s philosophy is to retain heat in the header and keep the engine bay
as cool as possible and damn the looks. Jet-hot is more appearance oriented
and their coatings heat retention properties suffer for it. I liken it to
comparing a great looking pair of thermal underwear to an ugly old fire suit.
If my car catches fire, my main concern is not looking good in my fancy
underwear. Nothing against Jet-Hot mind you, they have a fine looking product
and Swain often refers business to them for their great looks. Conversely Jet
hot refers business to Swain for their far superior heat retention
properties. Bottom line, Great looks = Jet-Hot, Great heat retention= Swain White
Lightning coating.
I had an interesting conversation with Dan Swain and it seems they have
quite a following among people who are familiar with their products but have no
intentions of becoming a national conglomerate. They advertise the
old-fashioned way, word of mouth. They like their relatively small business and
because of that and their popularity, wait times for getting things coated can
be substantial. Their turn around time is about three weeks right now and
that is probably pretty standard I am guessing. I however believe it to be
worth the wait and will be sending my headers to them for what I think is the
end all, be all, keep cool, White Lightning coating. It’s funny, I am really
excited about this coating whereas with Jet-Hot it was “oh well if this is
the best there is, I guess I’ll do it”. On a side note, if you don’t like the
color they come back as, you can use a caned high heat spray coating on
them and it WILL stick and WILL NOT burn off. I just can’t believe no one had
heard of these guys but you have now. By the way they quoted me 275-300 for
the pair. >>


I also remember talking to Dan Swain on the phone back then because I was
hesitating sending the headers all the way to the east coast. If you will
remember, those headers kept the engine bay temps WAY DOWN and we could pull
plugs or re tighten all the header bolts right after a track session. And we
could touch the headers without getting our skin fried. (No pun
intended...Mr. Fry) I know that Swain has a huge following in the Race Community such as
NASCAR because of a superior product.
Here's their web site: http://www.swaintech.com/
quote:
Originally posted by LIV1S: Did you design in the ability to partially break down the the system to allow servicing of the transaxle?


I installed a top fill port for lube on the transaxle in my car a long time ago. In the picture in the post above, it would reside under the driver's side rear muffler. That comes off with removal of the v-band clamp and whatever I come up with to support it at the rear. Other than changing lube, was there some other sort of in-car transaxle service you had in mind?

Best,
K
quote:
Originally posted by ehpantera: I think, as regards thermal coatings, you get what you pay for.............I don’t think it is even fair to compare the two products anymore because
Jet-Hot is catering to a different market than Swain coatings..........Bottom line, Great looks = Jet-Hot, Great heat retention= Swain White Lightning coating.


I had actually used Swain a long time ago but not for header coating. Definitely a high performance barrier coating. They cannot coat internal diameters of long, or winding tubes. I contacted them again to confirm this was still the case. Upon reflection, I dont think it makes any sense to use a cosmetic coating like Jet Hot on the interior. The Swain site caused me to revisit some heat transfer fundamentals and they are correct, there is not much that a .002" thick paint based coating can do in this regard especially considering the minority composition is actually cermaic. It does do a good job as corrosion, heat resistant, cosmetic coating.

The stainless will be somewhat better about lessening heat imparted to the engine compartment, this will easily be more than offset by the additional area of the 180s. Though I'd like to reduce engine compartment temps I dont think I can get myself coat the exterior of the stainless in the Pantera. It's more of a street/show car than a track car. My GT40 on the other hand may be a different story.

Best,
Kelly
So I’ve have made good progress and nearing completion. I decided it would be best to weld the headers up in two stages. First go was to complete any joints within each step, welding on the flanges, and also the collector lugs. In doing so, I figured I could correct any flange warpage while they were still short sections instead of a 36” long snaking tube.





I took an aluminum cylinder head over to my buds place thinking they would be great heat sinks and fixtures for welding on the flanges. It worked great. They all are nice and flat and didn’t have to touch them.




The other thing that worked surprising well was the use of foil tape for fixturing the tubes for tack welding. It has aggressive adhesive and I just applied two or three stripe to each section leaving accessible places for tacking. Simple, fast, and effective.

Having the collector lugs attached allows for pulling down the last stepped segment of the primary into the collector and firmly fixturing it in place.



When you have this many joints, it seems inevitable that things are going to move around a bit after welding so I was concerned they wouldn’t line up very well in the collectors if I did them all in one shot. This allows some mid stream tuning, only two joints with one loose section in each primary to manage and some of these were self fixturing by nesting inside of successive steps. This turned out to be a good move. Five of the primaries went right back in place with only some minor tweaking. The other three were way off. I had to redo a couple joints on the first step of #2, #3, and one on #6. But I got it all fitted up, back together and whole shooting match back over to my buds. He does great work but the welding must come to the welder, not the other way around. I’ll post upon the completion.

Best,
Kelly
So I'm coming down the home stretch.

I mounted the first and third steps of each primary, pulled them down tight and (re)fitted the second step to each primary. I strapped the entire mock up to a hand truck and along with my son pulled it up the hill from my basement shop on New Years Day. I figure the whole thing was about 400 lbs and it was a bit more than I bargained for. Cherry picked it into the truck and then it was back for welding. -I disassemble it to take it back down to my shop. Wink



After tuning of the pieces a bit, I used the same foil tape to fixture the second step of each primary in place and tacked all the primaries while they were on the mock up. Each primary was then removed and welded. The primaries stayed in place very nicely this time and there is definitely a required order of reassembly for the primaries.













So they’re pretty much done though I’ll need to make a good support bracket at the rear of the mufflers. I may get out the buffing wheel and polish them up too. The tail pipes polished up nicely.



Best,
Kelly
quote:
Originally posted by David_Nunn: Kelly, Your 180's are the nicest I've ever seen. Quite awesome! That being said and knowing you, I'm not at all surprised.

Thanks for that David. Very nice of you to say. You have a high standard and it shows on your car.
quote:
You didn't happen to make more than one set, did you???

Heh, heh. It’s a fairly unique combo. I do have an impressive collection of short stainless straights left over from cutting all the mandrel bends.
quote:
If you're looking for exhaust tips, try Fabspeed in PA.

I took a quick look at their site. They look like a very capable full service shop but I wasn’t able to home in on any tips. I’ll take a closer look later in some of their OE sections. I was just thinking something simple like straight through 3” I.D, 4” OD scrubble packed (maybe repackable?) resonators. The total active length of the mufflers is a little short and I suspect they might be a little on the loud side. Another 6-8” of resonator length might mellow that a bit, especially given they point at the ground. I couldn’t find anything suitable so I was going to roll up a piece of perforated stainless and rollover the lip on the outer piece, but for now, I just stuck the tail pipes on their so I could attend to other matter’s to keep things rolling. Given they come off easily at the VBands, it can be easily attended to at any time before I mode the AC opening cover.
quote:
So what's next?

Building EFI looms, sourcing fuel system components, and completing induction system air flow components. I’ll need to do a little work to isolate the rear cylinders from exhaust heat. When I get to install, I’ll need to come up with some inserts or novel treatment for the vacant mouse holes where the Ansa cans use to reside. My current thinking is to keep the mod reversible.

The Fontana Engine is at Dave McLain’s shop and is just going back together now. He has one of the water brake style dynos and can accommodate the headers being installed while testing so that’s kind of a nice fringe benefit.

Take care,
Kelly
Beautiful work Kelly.

Considering the recent improvements in the ceramic coatings available, I seriously doubt the need and desirability of building headers in stainless?

I had mine coated inside and outside and the coater has flow bench numbers that show the headers flowing a lot better coated inside.

I have seen several stainless sets recently and they turn all sorts of colors in usage. Cosmetic stainless, 303, 304 always had the reputation of splitting from the heat.

I already know it is very difficult to bend without kinks and ripples and it isn't that simple to weld.

Something to think about?
quote:
Originally posted by PanteraDoug: Beautiful work Kelly.

Thanks Doug, much appreciated.
quote:
Considering the recent improvements in the ceramic coatings available, I seriously doubt the need and desirability of building headers in stainless?

Does anyone really need a stainless exhaust system? Just depends on what you want out of them. Certainly more expensive but if offered the choice between a mild and stainless steel exhaust system I can’t imagine why anyone would choose mild steel.
quote:
I had mine coated inside and outside and the coater has flow bench numbers that show the headers flowing a lot better coated inside.

Other than cosmetics, there’s really no need to cosmetically coat mild steel headers either. As discussed earlier in this thread, they’re great cosmetic coatings, but after Mark (ehpantera) posted earlier, I revisited a little basic heat transfer and quickly concluded the heat reduction claims of the paint based cosmetic ceramic coatings are greatly exaggerated. As far as flowing better, don’t want to burst your bubble but I seriously doubt there are any material gains to be had. IMO, that’s mostly marketing BS that goes along with the claims of reduced heat transfer equating to higher velocity hot gas flow. Sure, the theoretical argument is sound but in practice is not material. It’s not like a cast iron exhaust manifold. The inside of a mandrel bent tube is already pretty nice surface and even extrude honing won’t do much to the welds as far as flow losses go.
quote:
I have seen several stainless sets recently and they turn all sorts of colors in usage.

Virtually all bare metals (at least the ones you would use for an exhaust system) will discolor to varying degrees depending upon the metal and usage temperature.
quote:
Cosmetic stainless, 303, 304 always had the reputation of splitting from the heat. I already know it is very difficult to bend without kinks and ripples and it isn't that simple to weld.

Not sure what you mean by 304 being cosmetic stainless. You see it used in a lot of cosmetic applications because in annealed state 304 is fairly easy to cold work as far a stainless steels go. It’s certainly not Inconel or even 321 but it is a true austenitic stainless steel. It’s 18% Chromium and 8% Nickel. Some folks still refer to it as 18/8. I used 304L which is typical for applications that will be welded because of lower carbon content the post weld heat treatment recommended on 304 is not required. As far as weldability, the guy who welded it says it’s very easy to weld compared to say aluminum which tends to puddle and flow all over the place.

The biggest reason for using austenitic stainless (other than avoiding rust) on a performance automotive exhaust system is that it retains its mechanical properties at elevated temperatures and only conducts heat at about 1/3 the rate of mild steel with thermal conductivity 16 versus 43 W/m.K. By way of comparison, Inconel is 14W/m.K in similar temperature range. Tell-ya-what, I’ll put that up against the heat transfer reduction afforded by paint based ceramic coatings on mild steel. I could really tell when I was cutting and using abrasive belt to fit the stainless pieces. You can get a localized area at the tip of the tube red on the belt and you can still touch near the point for quite a while before the heat is conducted up the tube.
Normally aspirated cars are not as hard on exhausts as turbo cars. If this was a turbo header, I would likely have used 321. Mild steel headers are typically short lived in on turbo cars (at least the header to turbine part). Strength at temperature is why lighter gauge material can typically used on stainless exhaust systems. I opted for 16 gauge because the heavier gauge bends more easily in tight radii and the price of bends reflected this. It was only an additional 6 lbs using 16ga vs 18 ga on the primaries.

Bottom line for me on this was given the amount of effort to plan and fabricate, with any reasonable valuation of time, it made sense to use the most durable material. It will handle the heat mechanically and be a very durable life-time exhaust system. It will also significantly reduce heat transfer and yes, will oxidize, but can be repeatedly re-polished if so desired. It’s a matter of taste but I like the look of stainless. Some guys on the GT40 forum wipe their stainless down with WD40 because it produces a more golden oxidation layer similar to Inconel. I haven’t decided how or if I’ll finish the surface.

Best,
Kelly
Personal taste is one thing but cost hasn't been discussed as a factor. If it is cost no object then who can argue? I am the original stainless guy.

I have a picture of the stainless headers here somewhere on the continuation Mark IV GT40s that were at VIR SAAC convention.

The color variation I saw now that you mention it must be oxidation. Looked a little like someone was polishing out their ss kitchen sink with SOS pads?

I had my 180s coated by Connecticut Coatings. They have their own blend of color which they say is their exclusive color. The coat fully inside and out, then polish them. They look a lot like a mill finish stainless. The color dosen't change.

The exit for the mufflers is in the stock Pantera location like the G4's were. Mufflers are polished 3" core full stainless bullet packs. Saves me a lot of time in reinventing the wheel.

They did the Hooker Comps on my 68 GT350 and when I find a set of headers that fit the 67 GT500, will go that route with them also.

My knowledge of stainless tubing is limited to 409 and 304. Afterall this is the NYC area and it is a veritable technology waisteland. You can't find anything here. Everything I need comes from the Midwest.

The only thing we have here is welfare, bankers and wall street tycoons. It isn't even children and women first, it's everyone for themselves from the start?

No one here knows WTF I'm talking about at all. Might as well be from Mars. Personally I'm from Zluto...but that's another story altogether? Roll Eyes

Good luck on the Pantera. Looks fantastic. Hope you finish it someday? LOL!
quote:
Originally posted by PanteraDoug: Personal taste is one thing but cost hasn't been discussed as a factor. If it is cost no object then who can argue? I am the original stainless guy.


If price was no object they would be Inconel or Ti. Big Grin

Ya-know, the difference between stainless and mild steel may not be as big as you think. Most of the decisions I made on my system that increased cost had nothing to do with material choice but I’m certainly pleased with those decisions.

I bought about $900 worth of stainless mandrel bends. If I did it again, I could do it in $750 easy. If I didn’t have three steps in diameter, probably $600. So do you want stepped headers or a single diameter primary? In general, in 16 ga, I’d say mild steel is about half the cost of 304L unless you’re buying from Burns. Anyway, mild steel saves you somewhere between $450 and $300 on the primaries.

The next big ticket item is the collectors. Do you want the performance of a true merge collector with the ease of assembly of slip joints or just a formed collector with no bullets? I bought stainless slips for $400 a pair (Burns were $800). You can buy a pair of formed collectors for $100. $200 if you want bullets. It’s all a trade on fab labor, your own skill level, and how you value your time. You don’t see many true merge slip collectors in mild steel because no one would bother to invest the time. Anyway, this is a $300 difference but it’s really driven by the choice collector style and degree of fab, not the material. So even though it’s $300 delta in cost it’s not a fair comparison because a simple open formed collector will not do what a merge collector will do performance-wise.

Flanges are also pricey. I paid a friend of mine to machine 8 pieces of 304L to my specs and it was $280. They were high port pattern but I suspect I could have gotten mild steel somewhere for half that somewhere.

The rest of my system is also purely choice but really not much to do with material.

I chose VBand clamps over flanges because of ease of service but a flange and gasket works just as well. I chose repackable light weight stainless mufflers but could have put a $60 mild steel glass pack on each side. Maybe they could be done in stainless for double that?

Anyway, the fair comparison of materials is at the primaries, and I think that is $900 vs $450 (but this might only be $600 vs $300 in a single diameter header). For the collectors its $400 vs $100, but as I said, still not apples to apples performance-wise. Another $150 for the flanges so maybe $1580 vs $690; stainless versus mild steel. $900 delta maybe?

Wouldnt have done me any good but I think you can buy a set for mild steel 180s for 4V Cleve heads on 9.2 deck from Hall for about $1100. That's the difference between someone who has done the layout work and has a CNC bender and inexpensive long mild steel sticks and someone that has to piece together mandrel bends. IMO they’re beat to fit and paint to match as a friend of mine says. If you hired someone to have set like I made in stainless, I think you’re talking North of $5k and >$3k of this would be labor. Dont see how someone could do it for less.

I can’t tell you how many hours I have invested in researching parts, design and planning the layout, but it’s way more than the fab time. It’s so fun for me it’s hard to consider it as cost. When it got down to the actual fab, I think I maybe had two full, solid weekends into it and I hired the welding.

I dunno, I just wanted the set of headers that was in my mind's eye. When it comes to cars, some things you just need to do and not grind too much about the dollars or the time. What else would we be doing?

Best,
Kelly


quote:
Good luck on the Pantera. Looks fantastic. Hope you finish it someday? LOL!

You eat the elephant one bite at a time. It will be done!

Best,
K

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