b&b headers: should i coat them or not ? poll

[moparracing]

b&b headers: should i coat them or not ?

i've ordered my b&b headers, my question is should i jet-hot coat them for heat or is it not necessary ??

please vote & give your opinions....

thanks.

 

[BigRed460]

I was wondering the same thing, the guy at B&B said that they have not heard of any melting or damage due to heat, but that he has had some of his custmers coat them...

 

[nycstev]

I spoke to Dave @ Roe racing he said they"ve done some testing and didn't
really make a difference:dontknow: :dontknow: :dontknow: :dontknow:

 

[nycstev]

Some people have mentioned that the headers will " run cooler" with this coating.
I don't understand how this works. Is it an insulated coating or a rust preventative coating? I would say that this coating might alter the rate of heat transfer but is the actual surface temperature reduced significantly?

Steve

 

[belgiumbarry]

I made a rough calculation :

assume exhaust gas 500 °C trough the tubes at 40 m/sec.
ambient air 30 °C at 20 m/sec ( as driving at 60 mph )

than the alfa values of heat transfer are about the same in en outside .
This means with stainless headers ( heat transfer rate 16 W/m2 °C ) the outside tube temperature will be around 250 °C.

If you now coat them with something that has a less heat transfer rate then stainless steel you will have a lower temperature outside the tubes , so less heat in the engine room.

I do not know what heat transfer rate has the coating but if i take 1 ( as for stone , ceramic etc. instead of 16 for stainless steel ) you become 230 °C , so not much of profit, and the coating should be really thick !

If i take 0.1 ( as insulation material ) we have 150 °C. That's better ! Almost the half heat in the engine room as it were not isolated.I think you become this by wrapping the exhaust with a few millimeters thick isolation material.

Those temperatures are ofcourse much higher if standing stil or driving at low speeds... Then the wind speed around the headers is not much , the alfa value drops outside the tubes so the material follows more and more the exhaust temperature as the inside gasflow velocity stil remains relativily high, so stil good inside alfa value.

just a rough calculation ...

 

[Chuck B]

I've used Jethot coatings for years on my race bikes. It is cooler and biggest advantage (not for SRT owners) was I could handle the headers within minutes from coming into the pits. Only downside is they will dull overtime. Becomes a silver satin finish. They will stain when hot when you get oil or clay mud on them (dont ask!). Brake clean removes all but for really stubborn stains "white" scotch pad works great.

Another coating company that I've heard nothing but great things about....
www.hpcoatings.com

 

[moparracing]

I spoke to Dave @ Roe racing he said they"ve done some testing and didn't
really make a difference:dontknow: :dontknow: :dontknow: :dontknow:

that's why i asked, roe told me the same thing ???:dontknow:

if heat is the enemy of our engines & headers are good for drawing the heat out of the engine (and ofcourse, sound better), then wouldn't coating them put the heat back in the engine ????

 

[Westxsrt10]

Here is some infomation that may help you decide.....


Below are the test parameters and results using Jet Hot® coated and uncoated headers:

(10 Laps, same engine and car with identical headers, one standard, one Jet Hot® coated. Engine is ran between 6,900 and 7,500 RPM and temperatures are measured immediately after the last lap with the engine idling at 2,000 RPM with identical sustained EGT's of 850º.)

MEASURED AT:
Jet Hot Coated No Coating DIFFERENCE
1" from engine port (on header) 300º 750º 450º
2" above header 210º 300º 90º
1" above floor pan (in car) 115º 165º 50º

Pretty impressive difference, and any of these coatings do not damage the headers, the coating becomes part of the header. Most of the other coating brands are comparable to these figures.

back to top


--------------------------------------------------------------------------------

Something else that few Racers and Car Owners realize:
Headers Oxidize!

Under normal use and even more with higher EGTs and header surface temperatures, headers will oxidize and material is actually removed from the headers. This means they get lighter and weaker.

Try these actual test numbers:
Mild Steel (1010) uncoated header exposed to 1200º F. in normal air will have a weight loss percentage of roughly 25% with only 10 hours use at this temperature.

Stainless Steel (410) uncoated header will have roughly 8% weight loss in the same 10 hour period.

A coated mild steel header will have NO weight loss at temperatures up to 1200º F. In fact it will actually gain a bit of weight! Between 1300º F. and 1600º F. the coating will begin to show signs of mud cracking or like the look of lacquer checking. However, limited diffusion takes place between the coating and the substrate, producing a very thin film of iron aluminide, which continues to inhibit oxidation.




Now, use the info above and then add the heat stress generated by the wraps. What do you see? Remember that the wrapped metal cannot cool properly and the header wrap is causing the material to super-heat and pre-maturely fail!

back to top

 

[Dominick572]

Mine are being coated as we speak should see them back here this friday coming up.

I suggest you do them...

 

[moparracing]

Here is some infomation that may help you decide.....


Below are the test parameters and results using Jet Hot® coated and uncoated headers:

(10 Laps, same engine and car with identical headers, one standard, one Jet Hot® coated. Engine is ran between 6,900 and 7,500 RPM and temperatures are measured immediately after the last lap with the engine idling at 2,000 RPM with identical sustained EGT's of 850º.)

MEASURED AT:
Jet Hot Coated No Coating DIFFERENCE
1" from engine port (on header) 300º 750º 450º
2" above header 210º 300º 90º
1" above floor pan (in car) 115º 165º 50º

Pretty impressive difference, and any of these coatings do not damage the headers, the coating becomes part of the header. Most of the other coating brands are comparable to these figures.

back to top


--------------------------------------------------------------------------------

Something else that few Racers and Car Owners realize:
Headers Oxidize!

Under normal use and even more with higher EGTs and header surface temperatures, headers will oxidize and material is actually removed from the headers. This means they get lighter and weaker.

Try these actual test numbers:
Mild Steel (1010) uncoated header exposed to 1200º F. in normal air will have a weight loss percentage of roughly 25% with only 10 hours use at this temperature.

Stainless Steel (410) uncoated header will have roughly 8% weight loss in the same 10 hour period.

A coated mild steel header will have NO weight loss at temperatures up to 1200º F. In fact it will actually gain a bit of weight! Between 1300º F. and 1600º F. the coating will begin to show signs of mud cracking or like the look of lacquer checking. However, limited diffusion takes place between the coating and the substrate, producing a very thin film of iron aluminide, which continues to inhibit oxidation.




Now, use the info above and then add the heat stress generated by the wraps. What do you see? Remember that the wrapped metal cannot cool properly and the header wrap is causing the material to super-heat and pre-maturely fail!

back to top

so based on what i've read, the coating is more like a heat sink to better draw heat away from the engine -- much better than without ?

 

[Sharpimage]

what's the cost diff? i can't imagine that it would hurt to get it coated..

Sharpi

 

[avmech]

i cant tell you the teck side of the coatings but after getting my B&B headers coated I noticed a big drop of under hood temps vs stock manifolds. now i cant tell you the differance between coated and un coated header temps, but i coated all my headers and noticed a drop in temp on at least 4 different cars.