SSI header port size boring/maching...

[OTSS]

Hello,
Like 1000's of us I have SSi headers and I like them.
I now want to improve them even more.
My header ports are now 38mm but I want to enlarge them again to 42mm.

My question,being stainless steel,what method or tool/s did you use to enlargen the port diamter ? (I wouldn't ask with mild steel or alloy).
Many thanks.

[AndrewCologne]

What kind of music is playing on top? A K-Jet or Carburettors/EFI?
Cause with K-Jet and its centered small size single throttle air inlet, simply more diameter at the heads intake wont give you any gain. It could result even worse as the air flow itself will be affected.

[OTSS]

Andrew,
It is the standard 3.2 FI (1988 coupe).
The outlet of the port in the head is 42mm and the inlet of the header is 38mm.
There is a sharp shoulder blocking flow,as can be seen by the carbon markings.

I was asking for advice on methods/tools to work the stainless steel,from people that are experienced at it ?

I am not planning any crazy porting actions,I just want to take the 'edge' off.

[Arlo911]

Hi, looks like you have the wrong SSI, 3.2 needs a protrusion that goes up into the exhaust port.
If you look (or feel) inside your exhaust port you will notice the step, from 42mm to 38mm or so further in the port.

[OTSS]

Arlo911,
It was removed by the previous owner.You can still see a slight lip left over,before they ported to 38mm.
I believe this was done because it was not fitted to a 3.2 motor.

[fred cook]

I had the same issues when I used Carrera heads on a 3.3SS engine I was building. Here are some pictures showing the "step" in the exhaust port and the flanges on the SSI exhausts.

Carrera head exhaust port


SSI exhaust flange


To make the exhaust flow as smooth as possible, I used a torch and hammer and flared out the tubes so that while there is a step down from the head to the exhaust is is smooth and helps to keep the airflow laminar.

[RarlyL8]

... or you could get headers the correct size for the application. Just sayin'

[fred cook]

Originally Posted by RarlyL8

... or you could get headers the correct size for the application. Just sayin'

This is true, but as it turned out, my 3.3SS will pull hard all the way up to 7500 rpms using a much modified CIS system. Besides, by the time I got around to adding the exhaust system I had already spent a ton of $$$ on parts and I already had this set of SSI exhausts. Don't know what the horsepower is as there is not a dyno around that my (low) car will go up on. However, the "seat of the pants" dyno seems to indicate some serious power!

[Peter M]

Originally Posted by RarlyL8

... or you could get headers the correct size for the application. Just sayin'

Brian,
What is the reason that Porsche made the 3.2 heads with the 42mm counterbore?

To deliberately shorten the port and "effectively" extend the headers to reduce head temperatures? (Ducati did something similar on their 1000DS engines. Porsche used cast in ceramic liners in subsequent engines so reduced heat temperatures was an interest to theirs.)

When you say "correct size" are you talking 1 3/4' tube as the id for 1 5/8" would still be smaller than 42mm?

Thanks!
Peter

[OTSS]

SSi headers for the 3.2 had a tube protrusion to protect gasket blow out.
I am not afraid of this or looking for opinions on whether my SSi are correct or not.
I was just asking,who has experience and/or tips on working the SS material?

Not trying to re-invent the wheel,just asking for guidance on porting headers at home.
I think,think,most SSi are 35mm ports.
I just want to take the edge of,to sleep at night.

@fred cook,yes, similar circumstances.

I have found a small narrow hand held belt sander that may work.

I was quoted 600eu !! From a German firm,to enlargen 6x 38mm to 42 mm.
That seems excessive.

[RarlyL8]

Yes optimal primary size for a stock 3.2L engine would be 1-5/8"OD.
Yes the machined sleeve in the exhaust port is for the gasket protector which creates a better seal and lines up the bore for smooth flow.
Yes if your SSI have gasket protectors you can use a metal cone to bump them up so they slide in flush with the machined gasket protector portion of the Carrera exhaust port for a more smooth transition. If your SSI do not have gasket protectors they can be ported by hand with a hardened porting tool that will cut into the stainless. It's slow work to do a nice job. Other than that you would need to take them to a machine shop.

[OTSS]

@RarlyL8
That's what I was asking for,'a hardened porting tool'.
I have the skills and patience I just needed some tips specific to SS.
Many thanks.

And thanks to all for joining in.
If or when I succeed I will post a pic.
If you don't hear from me again on this topic,best guess is,it went a&$ up.
Cheers.

[r lane]

This doesn't address your question, but is there enough material to widen the ID by 4mm

[OTSS]

@r lane
On the thicker flange model that I have,the answer is yes,outwards by 2mm each side,and downwards in a conical manor.
I have seen it done,I wanted to know the best approach for me to do it myself.

[1979-930]

Stainless is tough to work with. Get a couple bits. I don't think one will last for all six.
Honestly I believe 30 min in and one partial port you will regret starting.
If you can have a small flair welded on like Brian mentioned will be a lot easier and get the same result.

[spyerx]

well I had Brian make a custom pair of headers w/ heat for mine... to match the exhaust ports.

[stownsen914]

To the OP - so you are looking to port the SSIs at the flange to 42mm, presumably to match the exhaust port in your heads? I guess you have the thickness of the flange (1/2" or so?) to do a taper down to 38mm or whatever the tubing ID is. That's a little better than hitting a hard 90 degree transition of 42 down to 38, but I wonder if your heads have the machined recess like the 3.2 heads do - another option might be to have some tapered inserts made 42mm on the leading edge and 38mm on the trailing edge. They would be held in place by the headers.

[r lane]

I built a tapered boring bar to machine a set of 2.2 MFI stacks out to 47/42. That material was considerably softer than stainless and I was able to secure the bar at the top and bottom. In your case, a custom made cutter at the angle that you want, secured in a mill might do it and as one commented, you will probably need more than one. Brian might have a better solution.

[OTSS]

Thank you everyone for your input,your thoughts.
I was able to get two separate quotes from machinists in NL and BE for 600eu + tax.
So,I tackled it myself.After some research I bought a Makita die grinder (with the really big switch not the newer tiny one),and a Sealy carbide tungsten burr.I think buying a top quality burr was my best decision as it looks and feels unused after the job.
I did the job on my balcony in Amsterdam.I waited until it got a bit colder and one morning at 3dgs I was able to finish all six ports in two hours.I swapped back and forth between ports quite quickly,avoiding heating up the SS.
I am happy with the result.I spent 135 eu and I have some satisfaction.
I also noticed a big shoulder on the Dansk mufflar to the headers so I took that hasrh edge off also.
Here is a photo of the port before I finished the final sanding,but you get the point.The sharp shoulder has now gone.

[OTSS]

Thank you everyone for your input,your thoughts.

I was able to get two separate quotes from machinists in NL and BE for 600eu + tax.
So,I tackled it myself.After some research I bought a Makita die grinder (with the really big switch not the newer tiny one),and a Sealy carbide tungsten burr.I think buying a top quality burr was my best decision as it looks and feels unused after the job.
I did the job on my balcony in Amsterdam.I waited until it got a bit colder and one morning at 3dgs I was able to finish all six ports in two hours.I swapped back and forth between ports quite quickly,avoiding heating up the SS.
I made a tappered plug that showed me when I had gone deep enough and wide enough and I tested this every couple of minutes I guess.
I am happy with the result. I spent 135 eu in total and I also have some job satisfaction.
I also noticed a big shoulder on the Dansk mufflar to the headers so I took that harsh edge off also.
Here is a photo of the port before I finished the final sanding,but you get the point.The sharp shoulder has now gone.