lorenolson888

I have been hearing a bit about the OTT X pipe etc... that sounds cool...

I was wondering what peoples opinions are on Headers... Anyone making a custom setup or are most using headers for american V8s that have been modified at the flanges? Are the MSDS header a custom for the 928?

Is manifold replacement possible with the engine in the Bay??? I just did the motor mounts, crossmember, and pan gasket.... so Maybe I should have done this while I was in there but just wondering...

Has anyone passed smog in Cali using an aftermarket dual high flow cat setup???

Thanks All,

LO

Mongo

Devek and MSDS headers show a great improvement across the whole power range. I've heard people claim more torque as well as provided a dyno sheet for both types of headers. MSDS headers are custom for the 928 and need to have the collecor welded to the header (unless they came out with a newer style that requires no welding). Devek sells a header and exhaust system all the way back that will really open the respiration up on the 928. I reccommend a 3"-3.5" exhaust piping diameter if both banks of the engine are collecting into 1 big pipe after the cats.

bcdavis

I have passed CA smog with headers and cats on the car...

And yes, it is a LOT easier to put the headers in while the engine is up, and things are out of the way.
Trying to install headers is a tight job with everything in place...

mspiegle

Steve Pappin was able to pass smog with flying colors using an x-pipe and random-tech cats. Make sure the air-pump goes AFTER the cats though.

Jim bailey - 928 International

78-85 16 valve engines use a ugly rough restrictive cast iron exhaust manifold better suited to Briggs and Stratton. The 32 valve engines use very nice FACTORY tubular stainless steel "headers" with the pipe diameter increasing as pipes merge. With a very low restriction dual exhaust and NO CATS plus an adjustable fuel pressure regulator bumped about 4 PSI the ADDITION of MSDS headers to an 89 GT added 20 hp. But this was on a already catless X- piped dual 2 1/2 system which already was up nearly 30 HP. Much of the improvement often seen is the result of removing the cat and increasing the overall size of the exhaust. Twin "high flow" cats should function OK for smog even in California ,I am not sure of the effect on power. Even this example it got the headers and adjustable fuel pressure at the same time so how much of the 20 hp was headers ?? good question !

bcdavis

One really good, cheap option for the early cars, is to adapt the later s4 headers to use on an early car...

But yes, anything is better than those lame stock manifolds on the early cars...

lorenolson888

Just dreamin a bit,

I definitely want to ad some relatively easy "bolt on" Low risk power to my stock 86 ...

I like the idea of the devek twin fan shroud setup..( not sure on thermostatic control of the fans...) as my car had a single belt driven fan now...

I like the look of the matching radiator also!!!

Maybe 5 hp there???

Then the chips I have heard make apretty nice seemless improvement to the 85-86 32 valve engines... but some are saying stay away from chips??? plus pulling 2 eproms out of my box sounds a little risky...

But lets say 15 hp there...

Then on the back end.... header, high flow cats, and borlas... I would really like to get the full devek system and maybe just have them do the whole enchilada... but was not sure about drivability, smog and how custom the header actually were... I saw their cat back setup dual 3 to single 3.5 it was bad ***!!!! but would headers make a bigger difference i wonder.. you guys are suggesting that the 32 valve "headers so to speak" are not so bad?

~$2500 how much hp ??? maybe 30!!! or too optimistic

It would be great to squeeze and extra 50 CHP out of bolt on mods that would not effect the nice manners that the car has and the practical driving that I have enjoyed so far..... I imagine that the exhausts we are taling about are pretty loud huh...

http://members.rennlist.com/bigdave/my928.wav

Above biddave , blau928 and a few others put a links up a couple of weeks ago with their setups... The sound was awesome.... but my fiancee begged to differ... she said my car was already too loud....hahaha... Wait till she hears the sound of my "tune up" that Devek will give me hehehehe

LO

rjtw

I've got an '83. How about grafting on an entire later S4 dual exhaust system into the earlier cars like mine; anyone BTDT -- is modification to the head or manifold required? Jim, any guesstimate on just how restrictive the early cast manifolds are? May not be a bad way to free up the top end a bit.

Thanks
Rick

mark kibort

ive done both!
on my 84 with no mods, we went from 188hp to 200 at the wheels with just a set of the devek headers.

on the holbert car we went from 285 rear wheel stock, with no cats, to 335 with only a set of equal length headers, and some air box, MAF screen removal, slight tuneup , and fuel tweeking.

mk

Jim bailey - 928 International

Mark on the 84 at what point did you remove the cat ? and you got 12 hp at the wheels. As I mentioned the 89 GT was plus 30 hp before the headers and added about 20 hp more so total plus about 50 RWHP Your experience 285-335 looks much the same which considering your "ringer" motor has more like GT cams makes sense. But both cases we are talking race exhaust with no cats !

mark kibort

I hink it was 175 to 188 for the headers, but we left on the stock exhaust stuff.
then, we did the exhaust system with the removal of the cat, and it went to 200hp. (im trying to remember, have to check the dyno sheets) so, it turned out to be 12hp for headers and 12hp for exhaust gains. Then, it was 200 to 243hp for the euro cams, intake plus fuel regs, then 293 for 5 liter bottomend and euro heads. we got down over a few years to 275hp for whatever reasons( age) , and the equal length headers got it back to 285 at the rears. (all still with the old AFM!!!! that they said, " the Ljet AFM doesnt adapt well to changes to intake, exhaust, cam changes, etc" ha ha. Id say it adapted extrememly WELL from 175hp to 293hp!!!!!!!) just shows the guys that write the books are not all that smart! (ie probst, author of "Modern Fuel injection") the rest of his book is good though!

mk

Jim bailey - 928 International

Mark if you remember perhaps you can put some rough dollar signs on each step of the progression that shows the HP return for the $$ . Headers start out at about $500 ,adj press reg ?,race exhaust ?, Euro cams ?, Euro heads?, 5 liter short block ?

rjtw

Ha! I should have known Mark had been there already -- and not only that, but with data to back it up. Way to go Mark.

How did it sound with the Devek headers going into the stock cats/exhaust? I really like the stock sound and ideally don't want to change it at all.

Thanks!!
Rick