What Headers for my 3.8 RSR build??

[matty74]

I'm planning my 3.8 RSR build with 50mm PMO's etc...

this is for street and track

Now I have 1 5/8 size headers on my current motor and was thinking of using these on my new motor flipping the flanges on the RH header.

here is a pic of my current headers, pic courtesy of EarlySport who I purchased from



Now I was looking at buying these a set of 993 cup headers, the the length of the pipes not being equal will this effect torque?



Not sure which way to go, what improvement would I get with the 993 cup headers over the ones I already have??

[rsscotty]

I think the 3.8 RSR motor is happier with a 1 3/4 inch header. We have used the long tube design with a dual in / dual out Flowmaster muffler with excellent results. Those were from S-Car-Go Racing in California. If the 3.8 is up to real RSR specs. you can expect 360-380hp with no problem with EFI.

The 1 5/8 headers I think are similar in size to the 993 Cup headers that dyno out to about 315-320 HP with throttle bodies and MoTec. These Cup headers work ok, but we did a siamese on the outlet pipes to form a balance pipe effect and then in to a dual in dual out muffler. This was just a natural since the cup header flanges somewhat face each other. I did one system like this and it worked good. I wish I had photos.

[matty74]

so you think the equal length pipes are the way to go?

[rsscotty]

Utilizing sound wave and pressure wave technology in our exhaust system is free power and once you have gone through the task of determining proper primary pipe length for your header and then not taking advantage of that imformation is an error. Design your header for your RPM range then use that length on all cylinders and get equal power from all cylinders. I know the length of the RSR long tube headers works good for the normal air cooled RPM range and other headers we use that perform well are in that same length category.

The Porsche engine is so exacting in every internal regard as far as things being the same for each cylinder, it would be a shame not to give the exhaust system high priority. I know from testing that proper exhaust scavenging can make a difference.

[Bill Verburg]

1 5/8 is going to be too small for any 3.8 excpt maybe a dd that is only driven around town.

The headers you want will largly depend on the rest of the engine, particularly the cam selection.

993Cup didn't use a really happy cam, and so they weren't overly concerned w/ the exhaust, the cams were only slightly lumpier than stock so a slightly warmed over stock exhaust was used.
here's the full exhaust from a Cup, They stripped the heater boxes from a stock 993 exhaust, gutted and modified the cat and voila a race exhaust.


You can do the same w/ a stock 993 exhaust.

The RSRs on the other hand used very happy cams and so needed an exhaust that would complement them
RSR exhaust, these are short tube design for high rpm use w/o mufflers


The other 2 considerations are heat and noise, if you need heat and want to drive this on the street then the choice of headers is more limited.

One of the nicer off the shelf headers w/ heat that is now available is the Fabspeed, available w/ heat and mufflers or not


S-Car-Go makes some very nice long tube headers, the longer tubes are more appropriate for dual use cars w/ milder cams, but no heat


Or you can make your own, using off the shelf parts, this is an example using Burns comllectors

[matty74]

thanks Bill,

the car will be dual purpose, I will need a muffler heat I don't car about so I could get away with some 993 stock headers striped out and a custom muffler?

[Bill Verburg]

On my 3.8RS I have used B&B headers and stock 993. W/ mufflers and the mild RS cams there is little to no difference btween them. The Fabspeed headers have a somewhat better collector design and may work a little better. W/ racier cams, I've seen close to 300 from Moteced 3.6 w/ the Fabspeeds.

It also sort of depends on the chassis
in a 993 where there is a lot of room for mufflers, the stock headers w/ Fabspeed cat by pass and stock or RSR modified mufflers works great, I have to use stock mufflers because of noise restrictions at most tracks.

If this is going in a 911 or 964 chassis it's much harder to get quiet and efficient mufflers. There just isn't the volume available to package them as w/ a 993. On my 911 chassis I use B&B headers w/ heat and a 2x2 Flowmaster muffler, but it's very loud, It'd never pass noise at most tracks.


stock 993 headers in an early chassis is tough to muffle because of the plumbing involved

So to sum it depends on a lot of other factors,

[911st]

Are you really building a 3.8 RSR motor or a 3.8 motor to go into an RSR bodied car?

Are you thinking $5k for a system optimized to your motor or a <$1k system made from off the shelf goodies that should work 97.5% as well?

If you want to keep heat M&K makes a muffler that will bolt on to the 993 HE's that might be worth looking into. Would save you a lot of time and effort. It is a very clean install.

If not look into a set of Euro Gorge headers. They are very close to the design of the early factory RSR headers I think and very reasonable.

[matty74]

911st

At this point I'm planning the building of a 3.8 with JE pistons 11.5:1 CR and CWM pots, RSR cams by webcam, the platform is a 96 varioram, which I am going to do a complete re-build removing the varioram for 50mm PMO carbys.

I have the carbys and the engine, I'm now looking at going from 3.6 to 3.8 although I may just stay at 3.6 with a new set of JE pistons, regardless
I want an off the shelf 1 3/4 equal length headers, and I'm leaning toward an M&K, I had on on my 2.7 and it was great.

So to answer your question I'm going for something under 2K for 97% performance, as I'm not racing just a track day car as well as street, its a race car/hot rod basically, with a g series turbo body & duck tail.

On my 3.0 I have a set of 1 5/8 headers no heat, equal length, and a 2X2 monty RSR sport muffler, which I wanted to use but too restricting for the 3.6 /3.8, I may even be over caming my engine, but in getting a bit of pier group pressure going the RSR cams.

Would DC62's be better for a track/street combo?

Any suggestions are welcome.

Matt

[911st]

I am not an expert but a 3.6 with carbs and free flowing exhaust can make something like 325hp. The stock Pistons and cams are actually a great set up.

I think you can have your piston valve reliefs cut if you need to run a more aggressive cam. 3.8s do not add that much capacity and HP for the cost. I would think if you are going to go with RSR style cams, money needs to be spend on making it live at the higher rpms.

Me, I would just to carbs and Euro Georges with Coast Race light weight race mufflers or the Flowmaster. 993's and Flowmaster or M&K if I needed heat. Stock HE's may not be a great combo for high overlap cams. You can always add the expensive stuff later for another kick in HP.

However, I would check with the real experts.