Tune after Headers only?

[-tWv-]

Update here... holy &$&! that was a nightmare. Thought I was doing all the right things by letting the car soak with some penetrant fluid for a couple days and taking it slow trying to back the manifold bolts out. Wrong. Ended up snapping 10/12 bolts inside the head... For reference if anyone else gets into this situation the trial and error extraction process was as follows:

1) Tried to drill out a bolt and use an easy out... snapped the easy out inside the bolt even using very gradual pressure. F...

2) Had a friend with a welder. Tried to weld nuts onto the ends of the broken studs and back them out. By all internet accounts this method *should* work the majority of the time. Tried on like 6 of the studs and each time the bolt continued to shear off. The welds held firm but the bolts seem to be so brittle they snap in an instant. We also used a torch during this step to try to heat the head up, didn’t make any difference. Damn you Porsche for using M8 manifold bolts....

3) Resorted to drilling out.
- We made a drill guide out of the old manifold and marked drill bits to the correct depth.

- Drilled out the holes on the manifold to a 1/2” and had some custom bushings made to guide a “H” bit (luckily have friends who work in a machine shop). This is the correct size if you were going to re-tap the holes to the original size.

- Started with a small bit and progressively drilled out the bolt until using the H. Even with the hole completely drilled out it was still super tough to get a tap to go in cleanly due to tiny flecks of the steel bolt remaining. After 3 days and about 10 hours at this point I was getting impatient, so we resorted to boring out the holes more with a 21/64” bit and using helicoils instead. This was vastly easier as we had clean aluminum to tap into. The helicoils held firm and were easy to put in with the freshly tapped holes. All in the drilling/tapping process took 10-12 hours over 2 days with many swear words in-between.

Some notes: During this process there is limited clearance to drill straight holes, so we had to remove the thermostat and partially drain the coolant to get to one of them. I would also highly recommend getting some extended 6” bits as it was nearly impossible to reach a few of the holes without it. Cobalt is your friend here.

The only other major disruption we encountered was that snapped easy out from step 1. We tried using cobalt bits, carbide deburr tools and nothing was really working. Finally busted out the dremel and some aluminum oxide grind tools and after about 30 mins and 4-5 bits ground to dust we got through it. The grind bits seemed to work better since it allowed better precision and slowly removed material.

Finally, the fitment for the Manzo headers was fine with a bit of manipulation required of the exhaust to get everything to line up. The kit did not include the correct hardware however and the gaskets are sort of junk. Would highly recommend just purchasing new OEM gaskets to do this job and make sure you have all the right hardware.

All in all, 0/10 would do this again and would have just left the headers alone. But it’s done now! Filling up the car again with coolant today and hopefully back to driving.

[Robert986]

Man, that is brutal... Well done!

I just wonder why some run into this problem, I got my headers off without any issues.

[-tWv-]

Originally Posted by Robert986

Man, that is brutal... Well done!

I just wonder why some run into this problem, I got my headers off without any issues.

Brutal is an apt description! I had read a lot of experiences like yours before I embarked on this project so it was definitely unexpected to have so much trouble. Hopefully this helps others though if they get into it as bad as I did.

[flmont]

I don't know much about anything..But it looks like your stock exhaust header would flow very well compared to the new header's unless the pipe diameter is way small ?? Frank

PS..That truly sucks about those Damn bolts ,that's some work for sure !!

[-tWv-]

Originally Posted by flmont

I don't know much about anything..But it looks like your stock exhaust header would flow very well compared to the new header's unless the pipe diameter is way small ?? Frank

PS..That truly sucks about those Damn bolts ,that's some work for sure !!

The longer tubes in theory should allow the gas to exit at a higher velocity and promote scavenging even though there are some bends in there. Good scavenging normally helps with power delivery in the mid/high rev range since the gas can escape faster and is being sucked down the tube by the previous exhaust pulse. The stock headers don’t really have any sort of collector or design to promote good flow. Obviously they work just fine, but probably could be improved.

Now I’m not saying that these cheapy headers were designed with a lot of thought in mind so they may not be the most effective, but at least that’s the idea with longer tubes and a central collector.

A helpful video to understand exhaust velocity/scavenging: https://youtu.be/jjPeP_Nn2B4

[Dave80GTSi]

Originally Posted by -tWv-

The longer tubes in theory should allow the gas to exit at a higher velocity and promote scavenging even though there are some bends in there. Good scavenging normally helps with power delivery in the mid/high rev range since the gas can escape faster and is being sucked down the tube by the previous exhaust pulse. The stock headers don’t really have any sort of collector or design to promote good flow. Obviously they work just fine, but probably could be improved.

Now I’m not saying that these cheapy headers were designed with a lot of thought in mind so they may not be the most effective, but at least that’s the idea with longer tubes and a central collector.

A helpful video to understand exhaust velocity/scavenging: https://youtu.be/jjPeP_Nn2B4

I agree with your philosophical points above, but in my opinion the benefits which you note above are pretty much moot for a car which will be driven primarily on the street. For a track car which lives at high rpm's, definitely, but for normal stop and go / freeway driving I genuinely doubt that you'll see any differences.

What you did not mention: Where the stock early tube manifolds shine are in their flow advantage over the stock 3-in-1 cat manifolds.



Wanting to replace my cat manifolds, I did not even consider aftermarket headers since I've wasted far too many hours of my life already struggling to make various aftermarket headers fit a variety of engines. Sometimes you get lucky and they fit well; other times you curse and swear and beat them up with a hammer. So, I found a pair of these early tube manifolds, Jet-Hot coated them, and used them:



These early manifolds have individual runner I.D.'s which perfectly match up to the head exhaust ports, so I fell that the gas flow potential is not compromised too much by their lack of a collector - again, for a street driven car. I consider these manifolds to be 'poor man headers', but for me their key advantage is that you know that they will 100% fit perfectly. Plus, they are more compact width-wise than are most splayed tube headers, which should serve to keep heat away from such things as power steering hoses and the valve cover area.

By the way - It's probably too late for you considering your broken bolt trauma, but I would have recommended that you replace the old broken bolts with studs and nuts. Your car's future owner would have thanked you:

[-tWv-]

Originally Posted by Dave80GTSi

I agree with your philosophical points above, but in my opinion the benefits which you note above are pretty much moot for a car which will be driven primarily on the street. For a track car which lives at high rpm's, definitely, but for normal stop and go / freeway driving I genuinely doubt that you'll see any differences.

What you did not mention: Where the stock early tube manifolds shine are in their flow advantage over the stock 3-in-1 cat manifolds.



Wanting to replace my cat manifolds, I did not even consider aftermarket headers since I've wasted far too many hours of my life already struggling to make various aftermarket headers fit a variety of engines. Sometimes you get lucky and they fit well; other times you curse and swear and beat them up with a hammer. So, I found a pair of these early tube manifolds, Jet-Hot coated them, and used them:



These early manifolds have individual runner I.D.'s which perfectly match up to the head exhaust ports, so I fell that the gas flow potential is not compromised too much by their lack of a collector - again, for a street driven car. I consider these manifolds to be 'poor man headers', but for me their key advantage is that you know that they will 100% fit perfectly. Plus, they are more compact width-wise than are most splayed tube headers, which should serve to keep heat away from such things as power steering hoses and the valve cover area.

By the way - It's probably too late for you considering your broken bolt trauma, but I would have recommended that you replace the old broken bolts with studs and nuts. Your car's future owner would have thanked you:

Definitely agree, the power benefits will likely be minimal but the theory behind it is there. I do use this car primarily for mountain driving where I am consistently in a lower gear and use the entire rev range pulling up hills so I might see some benefit. Either way, I’ll be replacing the rest of the exhaust in the next year or so to open it up more (high flow cat and muffler) so the headers were really just to remove a potential point of restriction.

That catted design is truly awful for flow so I definitely see why you went the direction you did. Looks great!

In terms of fit, the fitment on these was actually pretty good, so maybe i got lucky there but there is a surprising amount of space to work with. I did have to zip tie one hose out of the way and added some heat resistant tape to make sure there aren’t any issues.

While I’m back in there I’ll definitely consider the stud/nut option. Is the primary benefit here just less risk that you’ll snap bolts down the road?