size headers for 2.4 S MFI

[svandamme]

Does anybody know , what size headers are optimal for a 2.4S MFI?

i have SS HE's now , but want to switch for headers
i would stick with the normal muffler

[911SCfanatic]

I have the same question, but for a '72T. Anyone?

[Tyson Schmidt]

The inside diameter of SSI's is 35mm. That is what your exhaust ports are as well. If you got to headers, then a small size increase over 35mm may yield a little more HP, but SSI's are just fine.
They are essentially equal-length headers already, with some shrouding around them for heat. I'm planning on running SSI's on my 2.5 I'm building for VARA and POC racing. If I port the heads more than "S" spec, I'll go to 1-1/2" headers.

I wouldn't go bigger than 1 1/2" for your motor, or you'll run into many problems tuning your MFI to match. You'll end up with flat spots that you just can't get rid of. If it were me, I'd keep the SSI's.

[jpachard]

I would run 1 1/2"ID headers in 26 inch length. Anything larger will kill your midrange. The Bursch headers are a good option but I would chop off the collector and install a Burns merge collector to further enhance the midrange. After that you can fab up an adapter to fit the muffler of your choice.

Cheers, James

[Grady Clay]

Stijn & Bill,

A 2.7RS and 2.4T-E-S and earlier all have the same OE header (heat exchanger) pipe ID.

Larger (racing) headers and twin pipes will give you a little more power and at a higher RPM. But only a little. You may give up a lot in low (3000 – 4500 RPM) speed performance.

Yes, you probably can “tune” the engine to get lots more high RPM power and give up even more low RPM performance. Unless you are willing to build a “track only” set-up, I recommend keeping your car with nice new SSI and an OEM muffler. Sometimes a little gain in high end can cost far more in overall performance.

Everything is a compromise.

Best,
Grady

[svandamme]

Thanks guys, the SSI's have to go , the voices inside my head said so...no arguement there.. if the smaller Bursch means loss of low end power.... then i can always put in a metal plate between muffler en headers, and drill a hole with a diameter of smaller size...

[911SCfanatic]

Sorry to bring this thread up again, but I ran across something that made me think.

The sheet metal on my '72 stock HEs is rotting off. I've already decided that I'm not going to have heat on the car. My plan was to remove the sheet metal, bead blast and then have the exhaust jet hot coated.

My question is: how do you supply heat to the MFI pump (just learned that it has a heat duct going to it) if you just have headers? How did the RS do it, which I'm assuming didn't have heat?

[jpachard]

On the RS they deleted it and set the engine to run correctly without the thermostat. They made a blanking plate to go over the hole on the MFI pump. I think I have a picture of this somewhere...
Cheers, James

[911SCfanatic]

Thanks. Please post the pic if you find it. Do you know what had to be set to get it to run right?

[andyjboy]

James - I think you may be referring to the RSR.

The Carrera RS used std heat exchangers as fitted to the T/E/S models from the same year.

[jpachard]

Originally posted by andyjboy
James - I think you may be referring to the RSR.

The Carrera RS used std heat exchangers as fitted to the T/E/S models from the same year.

Whoops, that's what I meant...RSR had the thermostat deleted. RS did not

Cheers, James

[Bill Verburg]

Just my HO but it would be hard to beat the headers that are wrapped in the SSI heat boxes

[911SCfanatic]

Just my HO but it would be hard to beat the headers that are wrapped in the SSI heat boxes

Bill, if I understand you correctly you are confirming that what I intend to do makes since because I will still be using original exhaust set-up--just without the sheet metal. Right?

The sheet metal on my '72 stock HEs is rotting off. I've already decided that I'm not going to have heat on the car. My plan was to remove the sheet metal, bead blast and then have the exhaust jet hot coated.

[Early_S_Man]

Bill G.,

Unless you are extremely lucky, I suspect that you will find that the mild steel tubing under those rotted heater boxes is badly pitted and rusted ... just a pinhole or two away from being ready for the scrap heap! I seriously doubt that it would be worth the expense of Jet-Hot coating! If you want to keep them alive for a couple of years or so ... sandblast and coat them with Sperex VHT ... and repeat the process every year and inspect carefully for signs when the pinholes start to appear! Like rust spreading on the chassis ... pinholes tend to multiply very rapidly in old HEs!

SSIs are worth the money ... and add to the appearance AND value of the car as well!

[Bill Verburg]

if I understand you correctly you are confirming that what I intend to do makes since because I will still be using original exhaust set-up--just without the sheet metal. Right?

Yes, I believe that you can purchase them w/o the heat shroud. Here is a pic w/ part of the shroud cut away

[Jeroen]

Hey Stijn,

The headers won't give you any performance over the SS heat exchangers (yours are Dansks, not SSI's)
You'll loose the heater and the Bursch headers will rust...

No reason to go for headers

cheers,

Jeroen

[svandamme]

don't want heater
as for rust, well , powdercoating should fix that

anyway , bit late to change my mind as my HE's are long gone and the Bursch are long delivered