[mooktank]

I'm thinking of building a header for my truck since I had to modify my manifold anyway. It moved the turbo to a perfect spot where there was plenty of space. I was just wondering if anyone else had any interest in some sort of 1 5/8 stainless header for their setup since I may build a few sets depending on interest.

 

[65scout4bt]

I would be interested if it works for my set up.

How much (ballpark)??
What position for the turbo?

Right now I am partial to the 6bt manifold chopped and flipped...

 

[dieselcruiserhead]

I am in about the same boat too. My first manifold arrived today...

 

[mooktank]

I'm checking out prices on materials right now. The placement would be similar to mine which allows you to get rid of the steep 90 at the intake.

 

[bcowanwheels]

stainless is bad to crack at least it did on my 855 bc3 engine headers. the company went out of busness cause of it. just run a heavy gauge of mild steel. i,am gonna have some flanges cut on the water jet to experment with a header also. just to play around. stock manifolds seem very restrictive .
bob in tn.

 

[Charles]

FWIW, Stainless is an excellent material for an exhaust system. Just like any other material, grade is important. Low grade material will not hold up well.

Mild steel is economical and easy to work with, but is inferior to stainless for the high temperature environment of a header. The usefull lifetime of a mild steel component will not be near that of a quality stainless piece in this application.

The experience with the stainless cracking was likely due to low grade material, or improper grade, but could also be due to a bad design not accounting for expansion/contraction or some other design flaw. If the design was at fault, you could have expected mild steel to have failed even sooner.

Price and workability are good reasons to use mild steel in place of stainless for a header. But strength and durability are not.

 

[bcowanwheels]

Heat Plays Into It Also and the 855 manifolds had expansion bellows installed and still cracked

 

[Charles]

Point taken.

But bare in mind that things like bolt holes also need to be enlarged to allow for expansion as well. Stainless has a higher rate of expansion than "mild" steel. So care has to be taken with stainless in that respect.

My only point is that when extreme heat cycles are involved, mild steel is an inferior material for durability when compared to a properly setup piece constructed of quality stainless steel. Mild steel is easier to work with and much cheaper to purchase, but those are it's only pros. Fatigue cracks to the point of total failure are to be expected when using mild steel in a pre-turbo environment that sees any real amount of power.

If I was doing it, I would use mild steel until it failed because I cannot easily weld stainless at home. But you can bet, that after making a set, round two would be for someone to take my prototype and produce a set made from 321 stainless for a durable solution.

Do you have any pictures of the failure with the stainless, or happen to know the grade used?

I understand your point completely, (you used it...it failed you in practice). That's completely understandable. I just think it would be good to understand if it was really the material at fault, or design.

Take Care

 

[bcowanwheels]

when i get some time i,am gonna have some mild steel flanges water jet cut along with a turbo flage. i think it would be a great improvement if the exhaust runners had 4 equal length tubes all comming together at the turbo as compared to the restrictive stock manifold.
bob

 

[Dougal]

Point taken.

But bare in mind that things like bolt holes also need to be enlarged to allow for expansion as well. Stainless has a higher rate of expansion than "mild" steel. So care has to be taken with stainless in that respect.

Yes, stainless expands 50% more than mild steel for the same temp change.

Mild steel headers work great in a diesel, our exhaust temps aren't high enough to cause problems and diesel exhaust doesn't have a lot of water vapour in it.

 

[Charles]

I have to run stainless on my powerstroke. Any diesel engine making much power is likely going to have relatively high exhaust gas temperatures unless multiple chargers, nitrous oxide, or a very large single charger are used.

I had completely destroyed the OEM steel up-pipes 3 times before switching to 321 stainless.

Granted, the truck could use a larger charger, but my egt's pin the gauge at 1719 degrees before I get the truck out of 3rd gear at WOT. Heavily fueled diesel engines commonly run very high exhaust gas temperatures. 2000 degrees is not uncommon.

But the point is, mild steel is MUCH cheaper to buy. You can actually weld it with the stuff most of us have at home anyway, and it will be decently durable for most applications as long as the thickness is kept up high enough.

In the end, if you don't mind fabrication, you could probably build a set from mild steel, have it fail and build another set by the time you reached the price of a completed stainless piece.

Proffesional race teams don't use stainless exhaust components just because it sounds nice, looks cool and they've got money to burn. They got tired of trying to finish on no boost because the manifold broke in half 3/4 of the way through the race.

Mild steel will "Probably" work for "most" cases for a decent amount of time before failure. True enough.

Course quality stainless properly welded with a good design incorporating expansion/contraction will work in all cases for a good long time.

$0.02

 

[Dougal]

Granted, the truck could use a larger charger, but my egt's pin the gauge at 1719 degrees before I get the truck out of 3rd gear at WOT. Heavily fueled diesel engines commonly run very high exhaust gas temperatures. 2000 degrees is not uncommon.

Do those temps concern you?
Because they'd scare the crap out of me.

 

[Charles]

Yeah, they do. I don't like it because the pistons are not reliable at exhaust gas temperatures higher than 1250-1300 degrees. When towing in a steady-state environment I don't exceed 1200 degrees. But for a full power run up to top-end, you just can't get enough heat soak into the piston/valve/turbo material to actually kill it. The relatively "Thin-walled" OEM exhaust components on the other hand, couldn't take it. The pistons have oil cooling jets hitting the bottoms of them, and the valves relieve some heat through the guides and so on, but the exhaust work has no real way to relieve the heat other than through that radiated out into the engine bay.

Basically on a diesel engine with cooling jets and so forth setup for extended towing duty, a full power run for around 30 to 40 seconds just cannot get enough heat "soaked" in to damage the engine components.

But for the ability to run full power extended, air management is crutial. That's why I have to run two compounded chargers on this truck now. To keep the intake charge cool, and to get more o2 in those cylinders to cool this engine off.

 

[bcowanwheels]

i,ve melted alot of pistons at 1200 degrees.

 

[Charles]

These were almost certainly not pistons with individual dedicated cooling jets spraying the undersides of them.

International explicitly specs the powerstroke to run durated continuous duty at pre-turbo exhaust gas temperatures of 1250 degrees.

 

[Dougal]

i,ve melted alot of pistons at 1200 degrees.

Where was your probe located?

 

[tacoma]

Methinks this is a perfect application for coatings.

 

[bcowanwheels]

yes them were pistons, melted down the sides between the cyl. wall and piston. buggered em all up. done it at least 6 times on different ocasions. 1200 deg+ on the hot side of the turbo and your livin dangerous. but its my opinion. i like 900-1050 max. and get super long life, no piston dome cracks, no head cracks = no workin on it + a happy bob !!!!!!!!

 

[Charles]

It really depends on the engine in question. On a ford 302 Gasser, then by all means YES. I would never consider running egts like that extended.

But the fact of the matter is, that most commercially available diesel engines intended for durated use include piston dome cooling jets from the factory.

International Navistar (the maker of my powerstroke) specifies a durated Pre-turbo egt maximum of 1250 degrees. This is straight from the maker of the engine with the assumed saftey factors in place. This is the temperature at which they feel the engine will still run to its intended service life at full power without injury to pistons, valves, seats and so on.

The 6BT is rated to over 1300 degrees egt durated by cummins.

These engines are designed to shed piston and valve heat and have cooling systems dedicated to those tasks.

You don't usually see piston failure in a powerstroke until you start towing down the interstate running 1350-1400+ degrees sustained. And even then, it's more of a slow wearing out process. You really need 1500-1700 sustained to actually blow a hole in a piston like a torch on one.

I think these light diesels are tougher than they might be given credit for right now.

And this isn't just something I read out of a book. I have seen tons, and tons, and tons of failures with these powerstrokes, from ring lands cracked by nitrous, domes cracked in half from cyinder pressure spikes, cylinder walls blown open into the water passages, rods horseshoed around until the wristpin hits the big end, entire blocks ripped in half dumping the crank through the oilpan, pistons with holes that look like you hit them with the torch, bent, broken and mangled rockers/pushrods/valves from piston:valve contact through drive/boost pressure, so many head gaskets failures from stock to copper, to multilayer, to o-ringed, to fire-ringed, yada yada yada.........

I know where these engines fail all too well, and 1200 degrees egt is a joke. It's actually still 50 degrees below the OEM spec, lol. And the B series cummins is actually rated even higher than that (stock).

I'm somewhat against the grain on the coatings, but my personal opinion is, if you have even a shred of efficiency in your turbo design, you do not need any coatings to survive. I've seen engines with some coated and some uncoated pistons (due to running out of time). It was in a pulling truck running OVER 2000 degrees egt and the pistons that cracked in half were the coated, lol. Not that the coating explicitly caused it, but in a situation like that you just can't help but laugh at coating parts.

The point is just that, coating is a worthless expense on one of these engines not exceeding 1300 or so sustained. Because the engine is probably OEM spec'ed to run that temp from the factory sustained, 24-7 anyway.

 

[Dougal]

You really need 1500-1700 sustained to actually blow a hole in a piston like a torch on one.

The only reason I can see a sustained EGT being worse than running through on acceleration is heat-fatigue related. Such a failure would come down to number of cycles at a certain temp.

Which would imply that you've got a certain number of strokes exhausting at that temp before your pistons give you the middle finger.

In my experience you'll find that every individual puts their own safety factor on their equipment. In the case of diesel EGT's I've decided I'm comfortable with 700C (1300F).
Your comfort figure is guaranteed to vary, but yours is the highest I've heard.