Mopar headers - my bad move

[Meister]

So far I've been quite fortunate in my long modding path. I've only made one certifiably wrong purchase - Mopar Performance (MP) "long-tube" headers. Here is my less-than-ideal experience with them. Other's mileage may vary:

Inferior materials and non-existent quality control: Flange surfaces as delivered were outrageously crooked. Snugging one end of the header-to-head flange created a gap of nearly 1/2" at the opposite end. The gross warpage necessitated having a machine shop remove approx half of the 3/8" flange thickness to get them flat, leaving the header flange in a questionable state. Both headers required extensive milling to attain flat surfaces where needed. Thanks to Breslin locking header bolts I've had no leakage yet at the primary flange(s). Even the 3-bolt flanges at the collectors were noticeably warped and had to be machined to get a flat surface. This set of headers should never have left the factory. Even the most cursory quality control check would have rejected them out of hand.

EDIT: Due to time constraints I had no option but to machine these to work and press on. Here are more details for the curious:

Due to the typical beyond-our-control delays associated with any major automotive upgrade the header installation began scant hours before I needed to hit the road for MFO5. No way was I going to be a no-show or a late arrival for a scheduled obligation. A frantic search of all other Mopar dealers within 3 hours driving time found only one other set of Mopar headers and the SOBs wouldn't release them. So I exercised the only viable option left and took the badly warped headers to the best machinist in the area and had him make them usable.

Learning just how soft the metal was, learning the hard facts of life about fragile, restrictive, ceramic cats vs robust, true high flow stainless steel cats, and realizing how much power I'd left on the table by going with this design all came later.

Additionally, the metal used in the tubing and flanges is a very soft iron. The collectors are prone to strip threads when snugging the bolts in an attempt to stop the inevitable exhaust leaks which occur as a result of the tendency to warp when heated. Had to drill out the bad hole and use a bolt and nut to remedy.

CELs & codes: Mopar touts no codes or CELs. Correct, until cats are broken by road damage and exhaust collector threads are stripped by warping flanges. Though not a recommended practice, one occasionally bounces over something they should have avoided. For me it was a low curb at the immediate entrance of a walled parking lot. With my attention on the vehicles I was following I turned in too soon and transited the curb, smacking the lower front of each cat in the process. Had these been stainless steel cats it would have been had no problem whatsoever. However, knowing these cats were ceramic I resigned myself to my fate - these cats were doomed and would need to be replaced, sooner than later.

Sure enough, the inevitable CEL and codes came a thousand miles later, then repeated again in 150 miles. By this time I'd located some tougher stainless steel HF cats, and had them installed next day. With the new cats welded in place it was time to check for exhaust leaks. The right collector had a nasty exhaust leak shooting upward against the underbody, a worst-case scenario. The left collector had a slight leak, again at the upper surface. After a several-hour battle we got the collector fittings to not leak, on both sides. Permatex high temp silicone was required to gunk up the new fiber gaskets though to stop the leakage.

Major warpage occurs with the soft iron that whoever makes the Mopars uses. When bolts are tightened to stop the inevitable leaks, threads strip easily. Drilling out the threads and using a new bolt with nut was required on the right-side collector flange. The Dynatechs are stainless steel throughout and should be virtually free of both issues.

Shortage of power: MP claims their headers make as much power as any headers on the market. This is simply not true, and by at least an estimated 15 hp vs. true long-tube headers & true high-flow cats. Read "Dynatech". Here's what engine builder, quarter-mile world record holder, and DR heads sales agent "FastMatt" Matt Monett told me when I reported my dyno results from MFO5:

"...at 330 RWHP your car is still 16hp shy from what PRDave's Charger dynoed with the same heads/cam, also on a DynoJet. A lot of things can account for this, but on the top of my list would be the Mopar headers, Despite that Mopar calls them Full-length headers, they are not what I would call Full Length - at best they are "mid-length" headers. Next, the cats they use are "brick" cats similar to cats sold by exhaust shops under the name cat-co. Cats such as these are far inferior IMO to the super high flow all-metal cats that Dynatech uses." Everything I've seen verifies that assessment.

My error: Placing too much priority on being code-free, and too little on quality of materials and superior design - both in headers and in cats. My bad, and I'm paying the price. Hopefully I can help someone else to not make the same mistake.

[Midnightsun300c]

Meister...with Dynatech headers and the midrange CompCam cam you would be in the neighborhood of .4 tenths faster (1.5 for the headers and 2.5 for the cam)!! or in the low 12's!!! Then you'll need those bigger injectors and a re-tuned PCM and TCM and you'll be breaking into the 11's. I don't think you're ready yet to move up to the 392...you still seem to have a lot to show us with the 5.7.

P.S. Great writeup!

Edit 11-14-06: After taking the time to thoroughly read your post I see that it is more that just hp/performance issue. I was distracted by the notion that you would be replacing the Mopar with Dynatech and you would even be faster than you are now! I see that there is a manufacturing and design issue that the forum members should be aware of. Sorry to distract from the point of your post.

[crhemi]

Thanks again for all you've done!

[roadwing1]

Once you discovered that the headers were of poor construction, were you not able to return the set to the place of purchase for an exchange? I would not install a set of headers in the condition you described, as they would surely cause trouble down the road. Curious about your answer...

[RedSRT4Me]

Originally Posted by roadwing1

Once you discovered that the headers were of poor construction, were you not able to return the set to the place of purchase for an exchange? I would not install a set of headers in the condition you described, as they would surely cause trouble down the road. Curious about your answer...

I would agree why install something that required so much extra work just to get them to work right. I would have sent them back. You paid good money for a set of headers you should get your moneys worth.

[Meister]

A fair question, gents. Deserving of a fair answer.

Best short answer is that, due to time constraints, I had no option but to machine these to work and press on.

Here are more details for the curious:

Due to the typical beyond-our-control delays associated with any major automotive upgrade the header installation began scant hours before I needed to hit the road for MFO5. No way was I going to be a no-show or a late arrival for a scheduled obligation. A frantic search of all other Mopar dealers within 3 hours driving time found only one other set of Mopar headers and the SOBs wouldn't release them. So I exercised the only viable option left and took the badly warped headers to the best machinist in the area and had him make them usable.

Learning just how soft the metal was, learning the hard facts of life about fragile, restrictive, ceramic cats vs robust, true high flow stainless steel cats, and realizing how much power I'd left on the table by going with this design all came later.

Post #1 edited to add this info.

[RobAGD]

Shame to hear Jim, So are you looking at the Dynatechs now ? I dread having to replace my Gibsons down the road given the install price I paid ( ouch ). BUtthey have done well for me, I would say the JBA's maybe a tad better shortie but long term for mods and stuff LT's are the way to go.

I look forward to see how you end up resolving this issues with the MP TL's

Take care Meister !

-Robert

[lmhoward]

I understand perfectly. My first set of headers (not a 300c) didn't fit just right. In order to fit them I had to fabricate a new power steering bracket, notch the transmission support and scratch the heck out of my dipped and freshly painted white tubes. The power increase was dramatic in the upper RPM's so I quickly forgot the hard install. Being my only transportation I had to get it all done in one afternoon. I drove to work with open headers that night. (fun but nerve racking) I had no choice but to make them fit after cutting the old exhaust and disconnecting all the superflous stuff. I'm grateful that you continue to share what you have learned with us. Your opinion and reviews hold a lot of weight with me. Thanks.

[Wingman]

Originally Posted by roadwing1

Once you discovered that the headers were of poor construction, were you not able to return the set to the place of purchase for an exchange? I would not install a set of headers in the condition you described, as they would surely cause trouble down the road. Curious about your answer...

Good question Roadwing1. I too would have returned the headers rather than go through this effort to make them work. The distortion in the header flange is most likely caused by uncontrolled heat input while welding the flange to the header tubes. Machining is not the answer to this problem as it only removes flange material in an effort to true up the flange but actually creates a flange that is even more prone to distortion due to the thinner material. Too much money and time to invest in an inferior product only to make it worse by forcing it to work. Not a good move no mater what the prior commitment.

[greedyk]

Originally Posted by Wingman

Good question Roadwing1. I too would have returned the headers rather than go through this effort to make them work. The distortion in the header flange is most likely caused by uncontrolled heat input while welding the flange to the header tubes. Machining is not the answer to this problem as it only removes flange material in an effort to true up the flange but actually creates a flange that is even more prone to distortion due to the thinner material. Too much money and time to invest in an inferior product only to make it worse by forcing it to work. Not a good move no mater what the prior commitment.

I think meister explained it clearly in post #6 why he did what he did!
Gary