ProtoCab

I've read some historical posts that seemed to indicate that aftermarket 993TT headers are not *that much* better than the OEM heat exchangers in terms of performance and durability. i.e: people have had aftermarket FabSpeed's & B&B's crack on them, resulting in exhaust gases leaking into the cabin.

Is there a mod that can be done to the OEM heat exchangers that will allow them to flow a bit better? Perhaps some sort of porting or polishing around the collector section that will make them perform a bit better?

Also, what sort of HP do the OEM HE's typically max out at? I've read that they are good for maybe 550HP or so, but that's it?

I ask because I have an opportunity to purchase a good used set of HE's which are a few hundred dollars cheaper than aftermarket FabSpeeds

ca993twin

Merv,

I have no direct knowledge... just what I've read on this board. It pretty much confirms what you said... very little if any gains with aftermarket headers. On the other hand, Kevin (UMW) recommends some simple grinding in the collector to smooth out that section. With your monster HP, you should really notice a difference!

md11plt

How does that go? Neener, neener, neener, isn't that it?

Here is the thread https://rennlist.com/forums/showthre...ferrerid=39883

Stay away from B&B (piece of crap). I ended up spending big bucks for a set of stock heat exchangers after the B&B (piece of crap) cracked.

Tom

ProtoCab

Thanks for your input guys. That link to Kevin's post is helpful, but it doesn't have any pics

Anyway, the set of 993TT HE's I can get are pretty damn expensive! They are USD$1600! Still, they are $400 cheaper than FabSpeeds (with heater boxes) and they won't crack too

I'm not really after monster HP... 550HP at the crank will suffice for me. I plan to have a set of K16's modified into hybrids, possibly using Mitsu 16G compressors. But that's later down the track.

md11plt

If you would like to spend a little more, Kevin might be able to set you up with a pair already ported.

ProtoCab

How much more power would the ported ones flow?

Acropora

There's no dyno or any other evidence demonstrating the benefits of porting the stock HE's yet.
I did post a dyno showing that stock non ported HE's flowed well enough for 600+ rwhp and 660+rwtq. That said I'd be interested in the HE mod or a fabspeed manifold to run someday except the chassis is overpowered for the track ask is..

ProtoCab

Thanks, Brad. If they are flowing ~600RWHP in original form, then that would suit my application. I'm not aiming for more than 550HP. I want fast spool as my car is purely street and never tracked