on lots of the really powerful cars. The continuation cars from Shelby (427s and the like) use these gaskets, and don't have issues, but overtightening can be an issue. Also, the issue of engine motion stressing the joints must be considered. I don't know if the current junctions is well engineered for our applications.

Matt

 

As I started up the car to drive home from work today, I noticed that she idled louder than usual. Pulling out of the parking lot onto the main streets, the engine roared at 2K RPM. At 35 mph, I heard a rattle under the chassis, as if a small object was hitting an exhaust part as it fell out. That's when I knew something was wrong with the OBX header.

My ramps/jacks are at a friend's garage, and I asked him if I could bring my car by to look under the car. He was stuck out of town, but I was dying to see what could be wrong so it can be fixed ASAP. I couldn't fit under the car without lifting it, so I laid on the ground with my camera and got this photograph:


The gasket seems to have slipped loose - it also looks quite chewed-up. The sound of something falling may have been the spring bolt on the other side of the photograph (I didn't have clearance on the ground to take a photograph from the other side).

Anyone have recommendations for how I should proceed to fix this? Should I obtain a new gasket? Going through OBX's distributors to obtain replacement parts seems to be a pain, and it seems like certain members have recommended having the gasket made by a local muffler shop. Would the local muffler shop also be likely to have a spring-loaded bolt if I did lose one? Anything else to consider? I'd like to do the repair job myself if at all possible.

Sorry if these are silly questions, but I'm not terribly experienced with exhaust systems.

 

... On second thought, should that piece be called a gasket or flange? Pardon my ignorance.

 

no expert here but i think its called flange

and see a local muffler shop to get it fixed.

 

I think those are called donut gaskets. Flanges are the metal connectors between the pipes that have the bolts that go through them

 

Thanks for info

 

Sometimes called flange gasket or donut gasket. Most exhaust shops should have the gasket in stock unless it is an off the wall size. Same goes for the bolt and spring. On a side note, I bet you could put a nut on the springed bolt on the oposite side of the header after it goes through the hole, it would keep you from loosing a bolt in the future. Any idea on what did happen? Only thing I can see is if the bolt wasnt torqued properly and backed out on you causing the gasket to slip.

 

Im going to try

 

Interesting? clearly at some point the two pulled apart (significantly!) to allow the gasket/donut/flange to slip down that far. Its hanging over the header bolt lip.

Causes?

you hit something?
perhaps over tightened and springs failed?
perhaps too lose?

 

Absolutely none is needed.

Sizing exhaust pipes is about maintaining heat and velocity, not the creation of backpressure. I'm not sure why so many people believe in this backpressure myth.

Exhaust restrictions are always a bad thing on forced induction cars.

 

Thanks for everyone who offered input regarding the slipped donut gasket.

I stopped by the local muffler shop, and when the car was on lifts, it was evident that the nuts had fallen off the spring-loaded bolts. A sawzall to cut some off the nut-end of the bolt (it was touching the cat) and a few minutes later, the gasket was back in place and looks to stay. I did express some concern that the gasket, being chewed up, will not form a proper seal, but I'm not going to worry too much unless a leak begins to develop again. The shop charged me only $10 for the labour.

Looking back, I should have realized that something was wrong when my idles began getting rougher (as the result of the nuts beginning to come loose and the donut gasket becoming unseated), but it was so gradual I suppose I just didn't catch it. Now that the OBX header is properly mated, it's a world of difference again. For the price, it's still unbeatable.

 

While you could double nut each screw so that they don't come off again. My mechanic insisted on using copper nuts and assured me that they would never come lose. If you haven't done one of the above, you'll be addressing this problem again down the road.

 

One of mine fell out as well. Double nut!

 

Backpressure is good in some cases. I think when it comes to forced induction exhausts, they say back pressure isn't needed or should be as free flowing as possible because it applies to turbochargers where the turbo IS the backpressure.

 

The spring is probably cheap, and may not take the long term heat cycling well. The bolt is obviously nothing special either. I've seen crimped bolts (much harder to turn), and Cu is "grabby" so you get the same effect. Looking at some of these flange set ups at a muffler shop, there are some with a stepped bolt, so that the nut can be well torqued without coming loose.

But I agree with the post, that for the money, it's still can't be beat!

Matt

 

As Jeffs said " Absolutely none is needed.

Sizing exhaust pipes is about maintaining heat and velocity, not the creation of backpressure. I'm not sure why so many people believe in this backpressure myth.

Exhaust restrictions are always a bad thing ( The only thing I'll add is especially ) on forced induction cars."

If your interested enough to post please do some research rather than spread misinformation.
Please stop parroting what they say and perpetuating the backpressure myth.

 

Hi kettle, what can you tell us about this backpressure myth and what research do you have to show that no backpressure whatsoever will create the most power? Backpressure CREATES heat which has to do with the sizing of piping. The most resonated/mufflerless/catless exhaust will not always be the weakest producing in terms of power.So you're saying that exhaust leaks will produce massive power, right? Since that alleviates backpressure in the exhaust? Also when talking about forced induction cars, there needs to be a differentiation between turbos and superchargers since turbochargers utilize exhaust energy and creates the backpressure post engine

 

Wait just a sec here... This thead is about dyno results of the OBX header. If you want to get into backpressure, what it is etc. start another thread. We've gotten WAY off track.

EDIT: - new thread with some info. on the subject HERE.

 

My apologies. Just got a little annoyed from norm's remarks.

 

b.c its not a Myth.

 

I had the same thing happen to me,one bolt got loose without losing the spring.Putting two nuts on eack bolt fixed the problem.

 

Then what would you say it is? There's a lot of misinformation floating around.

Backpressure... Myth? Debunked

 

"I’m fairly certain that many of you have been exposed to a “bench racing legend” that would have you believe that increased backpressure will improve low rpm power and that low backpressure will increase high rpm output. Nothing could be further from the truth. An exhaust system is sized for maximum flow at wide-open-throttle and peak rpm. All exhaust systems are “oversized” for lower engine speeds (rpm), as backpressure is so insignificant that it can’t even be measured. Less back-pressure always results in more power at higher rpm, with no negative effect on lower engine speed performance. The amount of power that can be extracted from an engine at a given rpm as a result of exhaust design is really limited by the exhaust manifold or header. After the header, less backpressure is always better."

This is from the Dinan website. Click here to go to the full tech article.

Matt

 

After reading all of the posts in this thread, I am definitely interested in the OBX, but still have a few questions. Is the benefit from ceramic coating, if the cost is between $150-200, worth the extra expense? Will under hood temps be dramatically different between a coated and uncoated header? Do you just send off the header for the coating and then weld the cat and do final construction? There seemed to be some discussion of the order of coating/construction in the thread, but I'm not sure what the consensus, if any, was about the best way to do it.

Is it correct that from the limited data we have at this time, coupled with driving impressions, that HP gains are minimal, but torque gains are pretty significant? (Seems like observations of more low end or consistent).

It seems like it would be wise to double-nut or use copper nuts on the bolts initially as mentioned in some of the posts above, any other tips on installation?

I have a UUC exhaust, and think it would be a good match - any comments or opinions about whether that would be true?

 

Purely personal choice. For myself I couldn't see that the additional expenditure was worth it. Install = send header out to get powder coated, install header, attach cat to header, attach cat to UCC.

Minimal Hp gain (1-2 appr.) Tq gains (6-8 appr.).

Absolutely - one of the two. You can do it on install or you can do it when they fall off but you will do it!!

a header compliments any exhaust system