Next batch of 105 extractors begins

[Colin Byrne]

Getting a set of extractors to last for any considerable time on a 105 engine seems particularly difficult.  And after putting a set of thermocouples on the header pipes and witnessing the amount of heat cycles they are constantly put through I'm not surprised, particularly when you couple this with a large amount of engine movement. One of the most important factors is to increase their life is to ensure that the rest of the exhaust does not ,,hang" off the back of the headers, in fact I've gone to the extent of not even having a ridged connection but an almost non-contact telescopic joint.
This approach proved very effective, however I inevitable gave the headers a massive hit to the ground whilst they were hot during a rally, which cracked them, and whilst it is repairable, I've started the process of making another batch of headers so both cars can start with a fresh set for Targa Tas next year.
One problem we ran into with the first set was when attempting to match the exhaust port outlet angle from the head, the 2D laser cut exhaust flange left massive empty fillet due to its thickness, this then had to be filled which meant excessive welding around the area that was prone to failure.  So this time around I designed a Jig to hold the flange on the required angle in the lath so I could machine the correct clearance for the tube
So here's a short video of the tool, It was doing my head in design the Jig in CAD, so i was pretty happy when everything lined up first time in the lathe!

http://youtu.be/BICaUdH5agE
(Couldn't get the youtube link working??)

[LukeC]

Lathes are SO versatile! My first trade was as a fitter and machinist. A colleague at work has new HAFCO lathe that would suit my "needs" for a pretty good price. I think I may not be able to pass the oppurtunity up.

I built a couple of sets of headers a few years ago. My method of getting the exit angle was to draw the flange so that only metal was required to be removed at the top outer and bottom inner. The method of machining was not as sophisticated (a burr held horizontal while the flanges were in a timber jig... but it worked:

http://www.alfabb.com/bb/forums/engine-rebuilding/123580-headers-no-1-a.html

Just for interest:

http://www.alfabb.com/bb/forums/engine-rebuilding/123586-headers-no-2-105-a.html

And on an Alfetta engine:

http://www.alfabb.com/bb/forums/engine-rebuilding/123588-headers-no-3-116-a.html

The Alfetta GTV was used in the Targa Tas once. Unfortunately, the headers did crack even though I thought I had taken enough precautionary measures. I never saw if they had taken a knock so can't conmment on the failure mode.

[festy]

I made mine by drawing up the flange from head measurements, had a couple laser cut (2d), then bored the ports to the correct angle on a mill.
I was pretty happy with the result considering it was my first try at CAD.

[Colin Byrne]

haha, that is a serious Mill Cutter!

Did you have any trouble with sealing, warping or aligning with a one piece flange?

[LukeC]

No problems on the two vehicles I built these for.

I am probably going to make a couple more sets soon. One for a 1750 GTV, and one for my GTV-TS. I will draw up a one piece TS flange soon and post the Acad files (and in PDF) for anyone that wants to get exhaust flanges laser cut.

[festy]

haha, that is a serious Mill Cutter!
Did you have any trouble with sealing, warping or aligning with a one piece flange?

I haven't started welding it up yet, I need to get a 32A circuit run to the garage for my tig so it's on hold until after christmas.
Precautions will be taken to prevent warping (heatsink, jig, weld pattern, cooling etc) but I expect I'll still have to mill the face afterwards.
I had the mounting holes cut a bit oversized to try to prevent heat expansion snapping studs - this first one will be a log manifold for a t3/t4 so I think there will be a bit of latent heat involved...
If I end up having sealing issues due to warping, I can cut the joiners between each cylinder and end up with 4 seperate flanges.