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Discussion Starter · #1 ·
Nice to see the differences of quality materials being discussed on the board.

Especially regarding 304 and 321 stainless. Most important the use of 321 stainless in turbo applications. :nod:

Turbo Systems

SVS pioneered using Burns Collectors into their header design back in 1996.

Header Design

Quality in Engine Management is the biggest consideration for completing an entire system.

Turbo system engine management

Quality has always been the focus of SVS and it's very exciting to see discussions about it on the board. :thumb:
 

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For turbo headers, plain mild steel would be better for street use. Stainless steels expand 5x more than mild steel -- and at turbo temps they'll crack with repeated temp cycling. I turbo'd a 4 cylinder and had both 304 and 321 burns manifolds prototyped (the latter by an aircraft guy who did helicopter manifolds). Both cracked within 6 months in daily use -- and not at the seams either. If one really wanted to use stainless for 1000+ degree temp cycling, you'd have to use slip joints or expensive stainless bellows. My application was just too tight for slip joints or bellows, but one might be able to fit them on Viper manifolds. I'd still prefer mild steel, as that will quickly sink the heat into the heads rather than glow orange-red. Inasmuch as these manifolds are also used to carry structural loads (supporting the turbo), keeping the manifold temps low is important. Stainless will get brittle at high temps -- and it also has the problem of not conducting heat well...

Just my 0.02 cents...
 

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DHK said:
For turbo headers, plain mild steel would be better for street use. Stainless steels expand 5x more than mild steel -- and at turbo temps they'll crack with repeated temp cycling. I turbo'd a 4 cylinder and had both 304 and 321 burns manifolds prototyped (the latter by an aircraft guy who did helicopter manifolds). Both cracked within 6 months in daily use -- and not at the seams either. If one really wanted to use stainless for 1000+ degree temp cycling, you'd have to use slip joints or expensive stainless bellows. My application was just too tight for slip joints or bellows, but one might be able to fit them on Viper manifolds. I'd still prefer mild steel, as that will quickly sink the heat into the heads rather than glow orange-red. Inasmuch as these manifolds are also used to carry structural loads (supporting the turbo), keeping the manifold temps low is important. Stainless will get brittle at high temps -- and it also has the problem of not conducting heat well...

Just my 0.02 cents...
DHK, most of the Viper turbo systems on the market mount the turbos to the frame and have a flex pipe in between the collector and the turbo. The higher end ones mount the turbos to the engine. So the manifolds never really bear any substantial weight. On th Viper there is plenty of room to put double slip joints.

I think you are willing to sacrafice too much by letting the mild steel headers heat soak the heads just to keep the heat out of the manifolds. This is a bad idea from a tuning perspective to have more heat in the heads as far as making for control of the detonation threshold. You are also forgetting the heat from the mild headers will also radiate into the engine compartment minimizing the efficiency of the cooling system and at the same time making less power from a relatively hotter engine.

"and it also has the problem of not conducting heat well..." ==> Ah yes, the lower coefficient of thermal conductivity of stainless increases the efficiency of the exhaust manifold by keeping the velocity of the gases higher for maximum kinetic energy to spool the turbo.


"Stainless steels expand 5x more than mild steel" ==> I do not know where you heard this wives' tale, but here is some raw data from the Burns website:

Elongation percent: Mild 304 321
20 55 55
Modulus of elasticity x 106lb/insq 29.5 28 28
Coefficient of thermal expansion 7.228 9.9 9.6
Coefficient of thermal conductivity 26.98 9.4 9.3

So you see, for the elongation percentage, the 304 and 321 are 2.75 what the mild steel is.
For the modulus of elasticity, all three are almost identical.

For the coefficient of thermal expansion, 304 expands 1.36 times more than mild and 321 expands 1.33 times more than mild steel(not 5 times more)

For the coefficient of thermal conductivity(how much heat radiates out from the inside if the pipes) the mild steel radiates almost 3 times(2.9=26.98/9.3) the heat of what 321 radiates. ==>You might think that is a bad thing, but the people who design the most efficient turbo systems beg to differ.

"Stainless will get brittle at high temps " ==> what kind of stainless? 304? Was it a higher percentage based carbon grade of stainless without the metalurgy to stabilize the chromium at the elevated temperatures? 321 is the best material for turbo headers aside from Inconel period for all the reasons listed above. :thumb:
 

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While that just made my head spin, I'd like to point out That both Tuners are from the Chicago area and their combined numeric RWHP/RWTQ Results will outperform any THREE cars on this site and or the Morgue once they are finished!

Jay "Supporting the Local Scene" K.
 

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Paolo, no question 321 is "the good stuff" and can be made bullet proof. All I know is from what I ran and had built -- i.e. from direct experience. The afformentioned 321 manifold was from an A&P airframe certified outfit out at Troutdale airport in Oregon who does that kind of stuff -- but it still wouldn't hold up. EGT's were running from 800 to 1100 degrees (used water injection). The manifold was TIG welded from Burns tube sections, and as overkill it was welded up in a sulpher hexaflouride tank and packed with that expensive white paste to boot (whatever it is). It was a thing of beauty, but after 6 months it cracked anyway... The guy who did it had fantastic welds -- it fractured along a straight section of tubing, not a weld. I was told that in practice stainless would expand much more than mild steel as the mild steel would sink the heat to the heads and therefore wouldn't reach as high a temperature. But, I chose 321 as it seemed the best at the time (I thought it would be much better than 304 -- which failed). In retrospect, other guys who were cutting up and altering cast iron manifolds didn't have these cracking problems. But, their manifolds looked like a mangled mess worthy of a kitchen garbage disposal -- visually very ugly.

There seems to be two schools of thought when it comes to exhaust manifolds... #1 Use stainless. #2 Use mild steel. Both sides have very good points and both types are currently made. Turbo manifolds are different in that the temps will be higher. This is why I chose stainless alloys to begin with! However, depending on the geometry of the manifold and whether or not slip-joints or bellows can be used, mild steel may end up being more durable. I found out the hard way, not once but twice, that stainless wasn't the best material for the manifold shape I needed. If I had to do all this over again, I'd get myself an infrared camera and check the manifold for hot spots. No doubt, it was a high turbulence hot spot just after a junction which failed. Had I spotted that, I probably would have ceramic coated the inside of the manifold and just run the risk of a few particles of that stuff going into the turbine... But, that was before IR cameras and thermometers were readily available. Heck, now-a-days you can get an IR thermometer with a built in laser pointer for something like $70. As a digression, I went through 2 turbo CHRA's because of particulates mangling the turbine. The first manifold, made out of 304 stainless, had rough spots inside where a dremel just couldn't reach. Some of that stuff burnt off, hit the turbine and threw the rotating assembly out of balance. Talk about weirds sounds! That and smoke from oil going out the exhaust...

Paolo -- I'm sure you'll have trouble-free results... The Viper block is way longer and there's much more elbow room under the hood. Slip joints and bellows won't be a problem. The tubing is much larger in diameter to boot, so the insides can be smoothed out. The gotcha's for me were high thermal stresses -- everything was packed into 3/4 of a square foot including turbo. When heat cycled as a daily driver (3 to 4 start/stop cycles a day) both 304 and 321 alloys failed within 6 months. I used the very best stuff I could get my hands on and spared no expense -- yet I was humbled by the backyard mechanics and their mangled cast iron turbo manifolds. Well -- I was humbled until I got a Viper that is ;-)
 

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DHK said:
Paolo, no question 321 is "the good stuff" and can be made bullet proof. All I know is from what I ran and had built -- i.e. from direct experience. The afformentioned 321 manifold was from an A&P airframe certified outfit out at Troutdale airport in Oregon who does that kind of stuff -- but it still wouldn't hold up. EGT's were running from 800 to 1100 degrees (used water injection). The manifold was TIG welded from Burns tube sections, and as overkill it was welded up in a sulpher hexaflouride tank and packed with that expensive white paste to boot (whatever it is). It was a thing of beauty, but after 6 months it cracked anyway... The guy who did it had fantastic welds -- it fractured along a straight section of tubing, not a weld. I was told that in practice stainless would expand much more than mild steel as the mild steel would sink the heat to the heads and therefore wouldn't reach as high a temperature. But, I chose 321 as it seemed the best at the time (I thought it would be much better than 304 -- which failed). In retrospect, other guys who were cutting up and altering cast iron manifolds didn't have these cracking problems. But, their manifolds looked like a mangled mess worthy of a kitchen garbage disposal -- visually very ugly.

There seems to be two schools of thought when it comes to exhaust manifolds... #1 Use stainless. #2 Use mild steel. Both sides have very good points and both types are currently made. Turbo manifolds are different in that the temps will be higher. This is why I chose stainless alloys to begin with! However, depending on the geometry of the manifold and whether or not slip-joints or bellows can be used, mild steel may end up being more durable. I found out the hard way, not once but twice, that stainless wasn't the best material for the manifold shape I needed. If I had to do all this over again, I'd get myself an infrared camera and check the manifold for hot spots. No doubt, it was a high turbulence hot spot just after a junction which failed. Had I spotted that, I probably would have ceramic coated the inside of the manifold and just run the risk of a few particles of that stuff going into the turbine... But, that was before IR cameras and thermometers were readily available. Heck, now-a-days you can get an IR thermometer with a built in laser pointer for something like $70. As a digression, I went through 2 turbo CHRA's because of particulates mangling the turbine. The first manifold, made out of 304 stainless, had rough spots inside where a dremel just couldn't reach. Some of that stuff burnt off, hit the turbine and threw the rotating assembly out of balance. Talk about weirds sounds! That and smoke from oil going out the exhaust...

Paolo -- I'm sure you'll have trouble-free results... The Viper block is way longer and there's much more elbow room under the hood. Slip joints and bellows won't be a problem. The tubing is much larger in diameter to boot, so the insides can be smoothed out. The gotcha's for me were high thermal stresses -- everything was packed into 3/4 of a square foot including turbo. When heat cycled as a daily driver (3 to 4 start/stop cycles a day) both 304 and 321 alloys failed within 6 months. I used the very best stuff I could get my hands on and spared no expense -- yet I was humbled by the backyard mechanics and their mangled cast iron turbo manifolds. Well -- I was humbled until I got a Viper that is ;-)
DHK, Your real world experience is very informative and interesting. That is too bad that the physical displacement of what you had to work with led to limited ways to designing your setup that failed. The high turbulence hot spot is definitely going to cause problems. I remember initially thinking about doing a log style manifold for the Viper and was advised against it after several people advised me that having such a short primary would cause such a restriction that the heat generated by not having at least 6-8 inches before the log(Butthead," UUHH, he said..... 'LOG'") could possibly burn an exhaust valve. It was after this that I really got into designing a set of equal length exhaust manifolds with a double slip fit 5 into one burns collector whose primary tubes have beautiful sweeping radii for minimal restriction. Well, enough of my system on another's thread.

Sorry your high tech setup did not work, but there's hope for you to pick from the many growing possibilities of turbo systems that have been and are continuing to be developed for the Viper. You are obviously a man who knows his stuff and I am sure you will be making the best decision for yourself the your desired application. I am glad I cut and pasted the article off the Burns site and started the discussions about the qualities, properties and differences between 321,304, and mild steel on my thread. Take care and good luck! :thumb:
 

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Discussion Starter · #7 ·
For turbo headers, 321 stainless steel would be better for street use and all out performance.

DHK,

Sorry to hear about your troubles with your 4 banger. Sounds like you gave up.

If you could'nt get it right with stainless steel, no need to try a crusade against it :nod:

If you couldn't figure out how to drive the Ferrari and you kept hitting the wall.....must have got expensive for ya.

Guess it's better to drive a Fiat now right? /images/graemlins/laughing.gif

Good luck with the mild steel :thumb:
 

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Ron,

I have a Viper as a 2nd sports car, though I have to say it's mostly a garage queen. I can't stand to see so much as a bug-splat on my baby. My comments on stainless aren't a crusade against it... Heat cycling definitely has it's durability problems. I was a machinist -- tool & die -- so I'm familiar with heat and metals. Both the 304 and 321 manifolds I had on the 4-banger did a super job for about 700 heat cycles... When that boost came up you got that dizzy pushed-back-in-the-seat feeling that built with RPM's. Felt like a Wankel engine. Around town, the turbo had great driveability and no decrement in fuel economy. It was simply great. The one bug-a-boo was durability.

When it comes to mild steel tubing, Belangers and Pro Turbo Kits use the stuff in their manifolds. Does this mean it's better? No -- it depends on how and where it's used. You do have to acknowledge that they have their points of merit to argue. [I have no affiliation or interest in either company.]

It all comes down to choice. If you want stainless -- you buy stainless. If you want mild steel, you can buy that too. Viper owners are lucky in that they have choices from some of the best guys in the performance business. Other makes and models don't have this luxury...
 

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JGK95 said:
While that just made my head spin, I'd like to point out That both Tuners are from the Chicago area and their combined numeric RWHP/RWTQ Results will outperform any THREE cars on this site and or the Morgue once they are finished!

Jay "Supporting the Local Scene" K.


That's putting it mildly. /images/graemlins/toothy


Thanks for putting up the spec Poalo.
 

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Discussion Starter · #10 ·
DHK said:
It all comes down to choice. If you want stainless -- you buy stainless. If you want mild steel, you can buy that too.
I agree, that's what makes life great... choices.

In those choices we all need to find happiness at what level we are able to attain.

Some schools of thought justify lesser quality as happiness even though frustration follows that justification.....on the other hand another school might think of paying more for what they believe is quality, but couldn't tell the difference between the two. The knowledge school of quality is low by attendance and will pay for the top shelf because they can. The scam school needs to be condemned. Are any of these schools any better than the other? They all profess to be. Definitely all of them over the scam school, but other than that...No. It's all a state of mind and you're going to support the school that you made the choice or were able to attend.

As long as you're happy with your choice and you can live with it, that's all that matters.

I started this thread because I was happy that subjects from the school that I attend were being talked about......But, it would be pretty boring without throwing in that rivalry support for your own cause.......So....

mild steel blows, it's crap, and you can call me when it falls apart and I will weld it back together for you every 6 months, until you finally figure out that you could have payed for quality up front and saved yourself the hassle :rofl: :bowdown: :thumb: /images/graemlins/smiles
 

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I agree with SVS, The 321 stainless is a very nice material to go with.
And life is about choices, That is why PTK allows you to choose. You can
go with mild steel with 2000* ceramic coating. Or 304 stainless, Or 321
stainless. It is all about what you want.

Why do we work with mild steel?

Our fabricators have been building street and race turbo systems for over
15 years. Off course for various company's like Axis, Cartech. What I am
getting at is that our guys have been building systems for a long time that
are still on the road today. And this is because of mild steel.

Every stainless system will eventually have stress cracks.

Our mild steel system is guaranteed for the life of the product.
Our stainless steel is not.

This does not mean that our guys do not build great stainless products.
It is due to the nature of stainless. When it comes to welding, our guys
are masters of the trade. True Artist.


I must say, SVS does have one of the nicest looking turbo system that
I have seen.
 

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Whoa... Hey -- be nice... Just THINK about this... What IS mild steel? It's iron with some chromium, molybdenum and some other traces in it. "Mild steel" is actually a catch-all for a wide range of alloys. What IS stainless? It's iron with more chromium (particularly, up to 18%), molybdenum and other traces in it. Stainless is "stainless" because it has enough chromium in it to form a chromium oxide layer on the outside -- that shiney surface you see. This gives it corrosion protection. I know that most people think of jet turbine blades and stuff when they hear the word stainless. But "stainless" is a catch-all too. Jet turbines aren't built from 304, 316 or 321... "Mild steel" has chromium in it too. But unlike "stainless" it has just enough to increase tensile strength. Stainless has more chromium to give it corrosion protection, but at the expense of tensile strength (in general -- I'm not talking about exotic alloys here). You wouldn't use stainless bolts as head bolts would you? They would stretch far too much. The point is, both mild steel and garden variety stainless are low carbon steels. Both are subject to work hardening and embrittlement at high temps. But anyone who's machined stainless will tell you -- it's easy to work harden it and "burn" it. Far easier than mild steels and not just because it's hard to cut... For a tube-manifold, I'd want something which remains ductile for durability. Stainless wouldn't be my choice -- and I have to say I've learned this the hard way. Now the rest of you can go learn it this way too if you like... It's a big classroom, and it's always open!
 

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DHK said:
Whoa... Hey -- be nice... Just THINK about this... What IS mild steel? It's iron with some chromium, molybdenum and some other traces in it. "Mild steel" is actually a catch-all for a wide range of alloys. What IS stainless? It's iron with more chromium (particularly, up to 18%), molybdenum and other traces in it. Stainless is "stainless" because it has enough chromium in it to form a chromium oxide layer on the outside -- that shiney surface you see. This gives it corrosion protection. I know that most people think of jet turbine blades and stuff when they hear the word stainless. But "stainless" is a catch-all too. Jet turbines aren't built from 304, 316 or 321... "Mild steel" has chromium in it too. But unlike "stainless" it has just enough to increase tensile strength. Stainless has more chromium to give it corrosion protection, but at the expense of tensile strength (in general -- I'm not talking about exotic alloys here). You wouldn't use stainless bolts as head bolts would you? They would stretch far too much. The point is, both mild steel and garden variety stainless are low carbon steels. Both are subject to work hardening and embrittlement at high temps. But anyone who's machined stainless will tell you -- it's easy to work harden it and "burn" it. Far easier than mild steels and not just because it's hard to cut... For a tube-manifold, I'd want something which remains ductile for durability. Stainless wouldn't be my choice -- and I have to say I've learned this the hard way. Now the rest of you can go learn it this way too if you like... It's a big classroom, and it's always open!
DHK, I have learned some new things from your post and admire how you are keeping it clean. You bring up some good points. One thing I would like to dispute is the part of your post where you mention that the mild steel has a greater tensile strength than stainless. If you look at the chart at the end of the page I cut and pasted at the Burns site, you will see just the opposite.

It says tha at 70 degrees farenheit, the tensile strength of mild steel is 55,000 lbs per square inch. While that initially seems impressive, the tensile strength of 304 is 85,000 lbs per square inch, and that of 321 is 90,000 lbs per square inch. ==> So to keep to the discussion at hand, 321 stainless has 45,000 MORE lbs per square inch than mild steel. 45,000/55,000 =.818 or is 82%. So relative to mild steel's tensile strength, that of 321 stainless steel is almost double.

It all comes down to what somebody wants, hell for 700 less for 304 or 1100 less for 321 to make a system out of mild steel when mild is 1/6 to 1/7 the cost of 321, the tuner seems to be making out like a bandit. Not to mention how much less wear and tear on all the cutting wheels, belt sander belts, carbide tips and so on.

The main problem I have with mild is its coefficient of thermal conductivity being almost three times that of the 321 stainless, which for the engine compartment of a stock Viper V-10(no turbos) is still hot 3 hours after shutoff. I think mild is not the way to go. IF the 321 pipe were to crack, I would just make another one still enjoy the benefit of increased exhaust velocity to spool the turbo and the exhaust getting out of the car as fast as possible which is the true measure of the quality and design for the real world application V-10 Viper turbo system . IMO.

I like what you said about life being a big classroom, and you're right, it's always open! I am always there trying make the grade! :thumb:
 

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Paolo -- make sure you're comparing the best apples to the best apples... Mild steel ranges from almost rebar quality, to angle iron kinda stuff (like 12L14 -- which machines like a dream!), to much better grades. The steel wire used in MIG welders has up to 90,000 PSI tensile ratings. I'd expect the better mild steel tubing sections that would be used in a turbo manifold would be DOM (drawn over mandrel) grades with up to 85000 PSI tensile ratings. Now, there are mild steel tubes which are only resistance welded (you'll see a rough seam). You often see cheap headers made from this stuff. That and children's swing sets, fences, etc., etc. That stuff would probably be well under 50000 PSI tensile strength. There's a whole world of metals out there. I've been machining and grinding metals for ages and I only recently find out that many suppliers of common T6 aluminum had put beryllium in it! Very toxic... No telling how much of that I've literally bathed in over the years. But, I eat lots of Italian salad dressing. The EDTA (ethylene dinitrilo tetra acetic acid) they add to it as an emulsifier (so you don't have to keep shaking the bottle) is a good chelating agent. Gets the metals out of you.

Paolo -- it'll be great to see your super-deluxe twin turbo! It's hard to believe there are factory cars out there with more than 600HP now. Just a decade ago it would have been something to have just half that. It's great to see people working to keep the Viper at the top of the HP list where it belongs.
 

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DHK said:
Paolo -- make sure you're comparing the best apples to the best apples... Mild steel ranges from almost rebar quality, to angle iron kinda stuff (like 12L14 -- which machines like a dream!), to much better grades. The steel wire used in MIG welders has up to 90,000 PSI tensile ratings. I'd expect the better mild steel tubing sections that would be used in a turbo manifold would be DOM (drawn over mandrel) grades with up to 85000 PSI tensile ratings. Now, there are mild steel tubes which are only resistance welded (you'll see a rough seam). You often see cheap headers made from this stuff. That and children's swing sets, fences, etc., etc. That stuff would probably be well under 50000 PSI tensile strength. There's a whole world of metals out there. I've been machining and grinding metals for ages and I only recently find out that many suppliers of common T6 aluminum had put beryllium in it! Very toxic... No telling how much of that I've literally bathed in over the years. But, I eat lots of Italian salad dressing. The EDTA (ethylene dinitrilo tetra acetic acid) they add to it as an emulsifier (so you don't have to keep shaking the bottle) is a good chelating agent. Gets the metals out of you.

Paolo -- it'll be great to see your super-deluxe twin turbo! It's hard to believe there are factory cars out there with more than 600HP now. Just a decade ago it would have been something to have just half that. It's great to see people working to keep the Viper at the top of the HP list where it belongs.
DHK, I am always learning from your posts. Wouldn't you know it, the Burns guys, would try to stack the deck in their favor with the grade of mild they use in their table. So the highest tensile strength rated mild steel has the same tensile strength as 304 and slightly less than 321.

Hey, I had better have my wife make me some more pasta salad with italian dressing in it as I inhaled quite a bit of aluminum dust while fabricating an aluminum bumper and all the intercooler and intake piping. That way, chelation can be my middle name! /images/graemlins/laughing.gif

Wait a minute, I need to go and put some Italian into my wife, I will catch up with you later! Metals out and Italian for my wife is my motto for tonight as I am out of propane for the garage heater tonight.... well, at least I can find another way to be warm! :rofl:

Take care, and I will talk to you soon! :thumb:
 

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Hey Ron, I really do like your stuff and your website is great.
But how many turbo systems have you built ? How many are on the
road everyday? Pro Turbo Kits knows quality and also know how to
provide for a whole spectrum of customers. If you would like to go
head to head in the design game, trust me we can play.

From what I can see your company has some of the best in this market.

But now the market just got a little more crowded. :thumb:
 

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Discussion Starter · #20 ·
proturbokits said:
Hey Ron, I really do like your stuff and your website is great.
But how many turbo systems have you built ? How many are on the
road everyday? Pro Turbo Kits knows quality and also know how to
provide for a whole spectrum of customers. If you would like to go
head to head in the design game, trust me we can play.

From what I can see your company has some of the best in this market.

But now the market just got a little more crowded. :thumb:
We don't need to fight :cheers:

I think we started on the wrong foot and after close consideration of our steps I see myself in my defense of the situation.

I really like your stuff too and thanks for the kudos on the site :thumb:

We can play, but I think side by side is a better game....It's not crowded, It's a team effort :thumb:
 
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