Help with exhaust leaks...warped Nouvalari header.

I doubt they were delivered warped as they appear to be ground after welding.

How thick are the flanges? About 3/8?

 

That does not appear to be warpage. I suspect that the flanges were eroded by hot exhaust gases escaping. To check for warpage you'd need to place a machinist's straight edge across all four flanges at the same time.

My guess is that the fasteners were not tightened sufficiently on installation. The fix would be to machine all four surfaces flat, and on the same plane. Then install using new gaskets, high-temp anti-seize on the fasteners, and torque to spec. If there is no spec, use the appropriate one for the diameter of the fasteners.

Good luck!

 

Just a guess but it's possible the original cast stainless flanges are more rigid than these.

It seems these are bowing in the center due to leverage over the embossed surface of the gasket.

I think they would seal if they were resurfaced and installed with a thin coating of high temp rtv and no gaskets. JMO!

 

Just reread your original post and saw that the headers only have 2500 miles on them, making erosion seem unlikely. Should be able to tell by looking at the "low" part of the surface-- if the original grinding marks are present then it wasn't erosion, but if they're gone it could very well be erosion. Were the fasteners really tight when you tried to retorque them, or were they loose? Or neither?

 

Nouvalari does not make them anymore, so swapping for another set will not be an option I'm afraid.
Best is to visit a machine shop that will re-grind them straight.
Then, as said above, new gaskets and torque to the correct spec.

 

Very common on any header with too weak a flange. The Ferrari flange is made from very tough material.

 

Seems odd that they all leaked at the same relative angle on the flange. It could be that they were over torqued. Over torqueing could result in two possible modes for warping: 1) simply warping due to overly crushed gaskets under the bolts and 2) excessive clamping not allowing the flange to expand (slip under the bolts) laterally as it heats up.

 

since when did Nouvalari stop making/offering headers.?
I was thinking of buying a set and install over winter when my engine is out..

this is the first ive heard of any 355 header ( oem or aftermarket) warping at the flanges..?

 

They are still listed on Nouvalari USA's web site, so,???

 

Why don't you take some emery cloth on a flat smooth surface and clean up each of those flanges and put them back on instead of the factory headers?

If the leak returns, then replace them in a year and half....

Make sure you are using the best gasket available.

 

Making them thinner isn't great but your options are limited there. You are experiencing what we experienced for many years installing headers on American V8's until some of the manufacturers wised up and started using good flanges. The composition gaskets are making a bad situation worse. If an embossed steel gasket was available it would be a better choice. Also if the flange is not a good choice of material, even if installed in a way that no distortion takes place, with the exhaust heat it will be exposed to the flat flange may turn back into a potato chip anyway.

The torque spec is 18 lbs/ft but little chance of getting a torque wrench in there.

Sorry to say but I will. This in one of a few reasons I am very selective about the parts I use. Can't stay in business using badly engineered parts. I would never have installed them in the first place. Don't blame you, you didn't know but if a shop refuses to do a desired modification this is one of the reasons. Too many junk parts being sold.

I saw something different the first time I looked. You already have embossed gaskets. May need to leave them out entirely.

 

Using the factory embossed gasket is going to 100% insure you have constant exhaust leaks, the flange is bowing around the gasket. Actually as John alluded to, the more you torque them the greater the gap will be in the center of the flange due to this. Not because it's over torqued but because there isn't enough flange rigidity.

I've dealt with this on similar fabricated parts. If you grind the flanges flat, clean the header and head with alcohol and assemble with a very thin coating of permatex "right stuff" rtv you will not have any leaks. (as you now have 2 near perfectly flat surfaces and torquing the bolts will put no bending action into the flange as it currently does with a gasket).

It may not seem logical to remove a gasket to fix a leak, just trying to help based on past experience with similar parts.

 

No gaskets and a little high temp sealant.

 

The gaskets are perfectly fine with factory headers. They were engineered to remain flat/true at specified torque and factory gaskets.

You will see a witness mark from the embossed gasket 360deg around each factory header flange that you do not see on your aftermarket headers.

 

Weak flanges, they bowed out

Try as they say or toss them

 

are those the oem gaskets that were re-used when installing the Novalari headers ?
or were those gaskets supplied with the headers when you bought them?