924Board.org

[BionicBalls]

I've not gotten a conclusive answer from searching the board...

Which is the better option if money is not an issue?

Stahl header with Jethot coating or MSDS with ceramic coating and nickle plating?

I've got a Bursch header now (essentially the same as MSDS) and it keeps breaking at the #3 pipe. This is apparently a common problem. I know that neither one provides too much benefit on stock engine, but I plan on doind a stroker/931 head conversion and am wondering which will be the best option.

It appears as though the Stahl header will have enough material to make it work on a 931 head, if not I can get a custom manifold flange made.

I'm thinking Dan will have the most applicable info on the subject, but Vince has run Stahl headers and can provide some useful info. I have no knowledge of anybody else running them, but would love to hear opinions from the board.
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1980 924 NA
1982 931

[924RACR]

[tyfighter123]

Come on Vaughan put the CF down and lets make some headers! I would buy one.
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Porsche 924 1977 N/A
Mustang GT/CS 2007
Porsche 924S 1987 (parts car)(cut up and recycled)
Porsche 911S 1976
Porsche 931 1980
Porsche 931 1980 (parts car)

[Joes924Racer]

I had a bursch it cracked at the collector.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

[924RACR]

[tyfighter123]

Your racecar is looking pretty sweet in that CF!

[ideola]

If you look carefully at the photos on my site, you will see that the Bursch and MSDS units use similar designs, but are basically inverse of each other. The Bursch has the #2 & #3 runners tucked close to the block with #1 & #4 wrapped around further to the outside, while the MSDS unit does the exact opposite. Also note that the Bursch and MSDS are 4 into 2 into 1.

By contrast, the Stahl header takes the #1 & #2 and routes them in behind 3 & 4 routed over the top and out front; it is also a 4 into 1 design.

I cannot account for why the failures would be common to the #3 runner, and frankly, I'm not convinced that a few anecdotes on this or other forums constitutes a diagnosis or a statistically significant sample. I'm also not certain that Bursch and MSDS suffer from the same defects. The failure Vaughan had on his MSDS seemed to be more due to heat stress on a race application exacerbated by header wrap and trapped moisture (i.e. oxidation).

In some of my previous (and limited) research, I seem to remember reading that when designing header flanges, it is important to slot the mounting holes or de-couple the flanges to allow for thermal expansion where the header attaches to the head. None of these headers seem to have such a provision, and it seems like perhaps the coupled flanges could cause the pipes to be stretched as the manifold flanges heat and expand, perhaps putting stress on some of the runners and causing them to crack; but that is purely conjecture on my part.

As for whether the 4-1 Stahl is theoretically better performance-wise than the Bursch or MSDS 4-2-1 designs is also subject for debate, and as far as I know, lacking any scientific data (i.e. dyno numbers).

As for coatings, the options are JetHot, Ceramic, or Nickel. JetHot is basically a proprietary, trademarked process, and in my opinion is no better than Ceramic. For my money, black ceramic is the way to go. It's relatively cheap, readily available, and highly functional. I've been using a local source who gives me excellent rates on internal AND external ceramic coating of exhaust components, priced by the linear foot, and also somewhat based on the I.D. of the tubing. For example, he charged me $5 less per linear foot for the 1.5" diameter turbo stuff (J-pipe and dump pipe) than for the 2.75" main exhaust components and manifold.

My $.02, for whatever that's worth
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erstwhile owner of just about every 924 variant ever made

[924RACR]

One reason #3 might be at risk, now that I think about it, is that cylinder will tend to run the hottest, and therefore leanest, meaning the highest exhaust temps.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype