Cherry Red Exhaust Header
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 1,043
Likes: 4
From: Va
Cherry Red Exhaust Header
Was testing out the new Dual Span Fans to try and get the temp up to 200 degrees for the second fan to turn on. Rev'd engine to around 2500, after about 5 minutes (still not at 200 degrees), noticed the rear exhaust/header tube on passenger side/and one center header tube on driver side turned cherry red. Immediately left off the throttle, but it was too late , the Jet-Hot coating on these two pipes had turned a dull gray and will not polish out.
What would be causing just these two pipes to heat-up; I'm thinking the engine builder may have set the exhaust valve rocker clearance too tight on these cylinders (mechanical roller), will be checking those on Sunday.
What do you all think could be causing it?
Any way to get the shine back on the Jet-Hot other than re-coating?
Thanks for your help
What would be causing just these two pipes to heat-up; I'm thinking the engine builder may have set the exhaust valve rocker clearance too tight on these cylinders (mechanical roller), will be checking those on Sunday.
What do you all think could be causing it?
Any way to get the shine back on the Jet-Hot other than re-coating?
Thanks for your help
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
I remember reading that headers that are coated should not be installed on a new engine, running the rpm's up to break-in the cam will ruin the plating. When you run the engine at elevated rpm's without the vehicle in motion, you lose alot of air movement under the hood. This is what probably did the deed. Some cylinders run leaner (hotter), hence only 2 were cherry red.
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 1,043
Likes: 4
From: Va
thanks for the info. big G
Engine was already broken in on the dyno for two hours before installed and it's been run many times while sitting in the drive-way not driven/no brakes
. This was the first time we ran at 2500 for more than 1 minute, dang those new Dual Spals are great but sorry I ended up dulling the finish while testing.
Engine was already broken in on the dyno for two hours before installed and it's been run many times while sitting in the drive-way not driven/no brakes
. This was the first time we ran at 2500 for more than 1 minute, dang those new Dual Spals are great but sorry I ended up dulling the finish while testing.
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 1,043
Likes: 4
From: Va
Originally Posted by JoeRags
ehhh, s**t happens.
at least you didnt break anything. good luck with the spal's... i love mine.
at least you didnt break anything. good luck with the spal's... i love mine.
I was aware not to break the engine in with the newly coated so I bought the headers bare and ran them for a while like that, after the engine builder did the dyno break-in, then sent off for coating.
I am going to call Jet-Hot to see what they say, hasn't been a year yet since coating and they may re-coat, easy part, it's taking them off the car that's such a bear.
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Originally Posted by Yellow73SB
You do know you don't have to break the cam in for 5 minutes straight. You just have to total 5 minutes of break in time. Have your heads been ported?
BigBlockk
Later.....
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Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
I understand b71vette has a mechanical roller cam ... roller requires no extended breakin ... I agree that some exhaust valves may be too tight.
Sorry, have no info on how to get the shine back ... hopefully someone knows.
Sorry, have no info on how to get the shine back ... hopefully someone knows.
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 1,043
Likes: 4
From: Va
Thanks for the feedback on this. I found at least one of the cylinders which had dulled the headers, the exhaust valve was set at .006 lash, Comp calls for .018. Tried breaking the polylock loose to adjust but couldn't do it with a allen wrench and adjustable wrench. Gonna buy a 7/32" T-Handle allen wrench and try that, would it loosen easier when it was cold?
I am also going to richen the carb idle mixture a bit.
Today I checked the temp on the two cylinders which dulled the headers and they were 200-250 degrees hotter at idle than the other six cylinders. Sorry for the dup, I posted this in another thread too.
Sad thing is these valves had been set like this since the engine builder dynoed it back in 05/2005. I don't think anything is mechanically damaged cause it idles and revs fine and no popping or missing, etc.
I am also going to richen the carb idle mixture a bit.
Today I checked the temp on the two cylinders which dulled the headers and they were 200-250 degrees hotter at idle than the other six cylinders. Sorry for the dup, I posted this in another thread too.
Sad thing is these valves had been set like this since the engine builder dynoed it back in 05/2005. I don't think anything is mechanically damaged cause it idles and revs fine and no popping or missing, etc.
