Kevin

A few weeks ago I posted a DIY header mod for the 993TT owners.. So with that theme, I want to take the time to bring some good ol fun to our cars... Now, this isn't something new.. I have done this for a 1 1/2 years already.. For those that do this the payback is huge... I feel that you can shave 400-500 RPM off of your turbocharger/boost lag... Yes, I can build big turbochargers, but for the street, I want NO lag... In order to do this one has to address the factory header issue.. I will also say, that I would take anyones modded factory header over a aftermarket system... Why, the answer is high velocity and short primary tube lengths coupled with an excellent flat collector.. I need to clarify that I'm not saying that the aftermarket systems are bad, they serve a purpose, however, I'd put the monies somewhere else.. And spend the time on the weekend and do this mod...

I want to say that when Stephen and I sat down with Sharkster, we had the option to buy headers.. I strongly suggested that we install the reworked ported/polished ceramic coated set. With the turbocharger choice, the numbers speak for themselves...

Kevin

Here is the picture of a 996TT header, I have sand blasted it, this is one of the steps required for ceramic coating.. Anyway if you look at the opening at the top, that is the flange that the turbo mounts to. You can see the large weld ring, this really disturbs the airflow going into the turbine housing... Just forgetting all the other ports and jumping in and porting this one will greatly help your acceleration and quest for lag reduction..



Word of caution, the intent is to grind 90% of the weld smooth. We do not want it flat.. We need some metal to aid in the adhesion of the metals.. Rest assured the robotic welders did get good penetration of the weld. It is constructed by having the primary turbing slide into the flange which by the way is a 2 piece flange to reduce warping and movement on the head/exhaust port surface. The robot welds with 2 Passes, one for penetration the other for build.. This building of the surfaces fills the high heat fusion weld of the first pass. Again what we want to do is to grind most of the weld.. Not all of it, you should feel a small consistant ridge of bump.. Now there have been people who have asked me if you need to weld the backside of the header flange.. My answer is no, do not promote heat/stress cracks.. This will occur to most stainless steel repair jobs. When you weld on the header the molecular structure of carbon molecules break up, this infact weakens the steel.. You will have a crack develop, not at the weld that you just laid, but at the outer edge.. So with that said, don't weld on them...

This photo show my tool of choice, and 35 minutes of grinding.. Figure 60 minutes a port... In the original welding process, molten metal will and did splatter inside of the tubing. One can address this with the porting/grinding bit... Speaking of bits and tools.. Bill Cho did this a few weeks ago, without the aid of my DIY, I coached him through the process, he did it with a Dremel... For everyday use I have a few Chicago Pnuematic die grinders, they are very inexpensive and you do get your monies worth.. The bits are a different story, I prefer Pfero brand porting bits, the one shown cost around $35.00.. they are Made in Germany..

Warning... You must clean the headers after porting... Give your wife some cash and send her shopping, stick the headers in the dishwasher.. get a babies bottle brush and scrub em good.. Take them to the car wash and blast them... You don't want any metal particles left inside the headers.. They will damage your turbine wheel....

NC Bob

Great post, Kevin. I already have a die grinder. Instead of buying a porting bit, can I use die grinding stones shaped like the porting bit? I know they probably will not last as long, but I have several stones to use up. Also, do I need to use thread lock on the bolts before reinstalling the headers? This is a perfect project for a rainy day this Fall.

Kevin

Bob;

The high alloy stainless will chew up your grinding stones, I'd use the grinding stones for the final touch up.. I can set up a group buy for the bits.. or I have a few decent ones that I don't use, a little dull for production use. I toss in to the group. My next picture will show the polishing tools.. Also, you will have to replace the factory gasket located between the header and head... The factory bolts are fine to re-use. But must be torque in a pattern.. You will also have to replace the oring at the turbo exhaust inlet..

sharkster

I just wanted to add these headers rock... I'll post a pic of mine in a bit (you can see how much they were ported) but these go great with bigger turbos and to date I've yet to see any better headers. The factory did a great job on them to begin with and what Kevin has done is to improve upon them. Unfortunately for Kevin it's a lot of man hours but boy does it work....

Craig.

I purchased a VERY expensive set of headers that were being heavily hyped a year and a half ago, only to later discover that they caused a reduction in power (according to dyno results perfomed by another). Moreover, the headers developed bilateral leaks at the manifold. I subsequently switched to ported, polished, ceramic coated stock headers, just as described by Kevin. I don't have the skills to mod the stock headers myself, so I purchased my set from Speed Gallery: (818) 766-2321.

Craig

Oak

curious as to how long do you think the welds will last after grinding?

Kevin

Oak;

The weld is still intact.. There is good penetration by the factory welding. I have applied these techniques to the 993 for many years without problems.. Yes, if one got carried away with the grinder and started to bore out the opening, you could run into problems.. It wouldn't be problems with the weld, but problems with thickness of material which would promote fatigue and thus cracking.. You guy owe it to yourselves to find a stock header and look at the design before you rule it out..

Kevin

Craig I think that you are a perfect candidate to port a set of headers, I think that when I come to La next month, you and I will be porting a set of headers...

Craig.

Sounds like a plan Kevin . . . dinner on me.

Craig

Kevin

This picture shows the headers/turbo flange that really needs some grinding.. I'd say that I opened it up >1/4"

The next picture shows the polishing of the primary tubes..

sharkster

with that set up my car had so very little lag. it spooled up so darn fast.... this actually a perfect solution for k16s and hybrid k16 turbos...

ColorChange

Thanks Ken. What do you recommend if we want to go past ceramic coating and wrap the headers to help even more?

BigBagBen

Kevin, Great write up!

How will this mod work with the EVO stage 4 or GT640 Turbo's. I intend to do the stage 4 or GT640 later on this year...if I can skip the EVO headers in their package that would be great, I could then spend the money I saved on the EVO silicon hoses or venturi CAI etc.. The header mod is an easy mod I can do anyway.

Cheers,

Ben

Oak

realistically, how much gain is there by grinding only 10% of the weld? I can see if it was a true match port with some additional porting done to the heads, there could be some very slight gain. I doubt it would be really worth the hassle. Does anyone that has done this have a dyno chart to quantify?