Exhaust Manifolds for Twin Cam

[EuropaTC]

Resurrecting this thread to add a home-made variant to the list. At some point I'll detail the build if only for my own records but the basics are as follows;

1. I wanted a tubular header for the car, similar to the one I have on the Elan because when I installed that one the car did feel different afterwards. As I also wanted to learn TIG welding and it's always good to have something you will use afterwards rather than a bin full of test welds.

2. Design parameters were unashamedly copied from other authors. I settled on primary/secondary tube lengths based on Dave Vizard's book and  tried to keep as close as possible to that within the confines of the engine mounts/clutch cable/gear linkage.

3. The 4 primaries aren't identical lengths but pretty close (within 1") and the paired primaries (1-4, 2-3)are better matches. Overall primary/secondary tube lengths are within 1/2", so I'm ok with that.

4. At my level of welding skill (or lack of) I couldn't fabricate a Y piece as shown on t'interweb. I just couldn't get a decent weld in the sharp confines of the "Y" so made one up out of a 90deg bend and some patching which allowed me to weld the inside of the "Y" rather than the outside like everyone else does.

5. The welding started off very badly, a world of difference between doing flat plate and 38mm pipe walls. Lots of remedial work and grinding off excesses, but it got better the closer I got to the exhaust box. By the last section it was almost decent....

And that's about it. Basic pipe routing copied from examples shown here, nothing adventurous or ground breaking here.....

Brian

[Certified Lotus]

Impressive endeavor Brian! I'm always in awe of anyone that takes an idea and moves it to completed product even without the necessary skills to do so. I learned to weld 40 years ago and did it for several years then stopped. I shudder to think that I could just pick it up again.

Nicely done!

[BDA]

That looks pretty nice to me, Brian! I think you did yourself proud. Building headers seems like a very complex project and your first attempt looks very nice! Can you feel an improvement when you drive her?


I'll be watching for you to open Brian's Custom Headers! 

[Grumblebuns]

Brian, very impressive result especially this being your first time DIY attempt. How did you fabricate the header flanges and what did you use as a fixture jig during the welding process?

Joji Tokumoto
 

[Bainford]

Very impressive effort, Brian. The fit seems good. Looks like a nice pipe. Hats off to you, sir.

[RoddyMac]

Brian,
Looks great.  Are you using a gas lens on your TIG torch?  If not, I would recommend getting one (or a set if you are using different sized tungstens).   With the gas lens you can have a longer stick-out that will help welding in tight spots (the insides of Y's etc). 

Rod

[EuropaTC]

Last question first...   yes Rod, I had a gas lens on the torch with the smallest ceramic that came in my gas-lens set.  The problem isn't the tools, it's the guy using them; I'm just not steady enough and when I tried the arc kept wandering to the sides.  My welding isn't great close up but that first Y attempt was a real shambles, hence my trying another way.

And it worked out really well. Take a 90deg mandrel bend, split in two halves and then set them the correct distance apart, cutting the angles to suit and using the outer walls for the gas flow. That left enough room for me to weld inside the bore of the pipes with a little bit of patchwork to close it all up. Heavy on welding time but better on gas-tightness for me !

Joji, the flanges were bought pre-cut so I didn't have to cut them from plate.  They are 8mm 304 stainless with elongated holes for the studs which allows them to be used on several engines.  (I cheated wherever possible    )

For a fixture jig,  I happened to have a spare TC head lying around which I mounted on a portable workbench and used a sheet of cardboard to get the rough positions of the engine mount, which is the first clearance problem. I cut tubes and used gaffer tape to hold them together so I could transfer it to the real car for confirmation, back to the spare head for tack welds, back to the car for checking....   rinse, repeat. Now you know why it took me so long !

Jim, I don't know about improvements when driving, I was just glad when it fired up and didn't fill the engine bay with leaking exhaust fumes !   

Quite honestly I doubt there will be any noticeable difference as it stands but I've decided to change the camshafts this year and I think it will come into it's own then. There's a hint from one book I read which claimed a mid range improvement by NOT matching the port/tube bores even on standard engines and that's what I've done here. By coincidence I found a page detailing the Trikbits custom headers for the Elan using almost the same dimensions for tube bores, which gave me a bit of confidence in the idea.

[4129R]

But can you get the stud nuts to screw up tight using a normal socket?

I have had to buy allen headed 5/16" UNC S/S bolts so at least I can get them bolted up easily without making up strange tools or resorting to mole grips.

I have 3 complete systems being made in S/S ATM, plus one for across the pond.

I even bought extended brass nuts (like fitted to Minis back in the 60's. )

[EuropaTC]

But can you get the stud nuts to screw up tight using a normal socket?

Nope, the only way I could see that happening easily would be to bring the pipes out further at 90deg to the flanges so the nuts are all clear of the bends.  I'm sure that's practical because there's quite a bit of room on the Europa installation.

However I haven't had to resort to anything fancy to assemble this set up.  I used 1/4" drive sockets with extensions for most of them with a stubby 1/2" spanner on two nuts where the bend comes back across the stud.  It looks awkward but it's gone together very easily. I used conventional brass nuts with stainless washers but that's a good idea about extended ones, they'd fit a treat for the ones hidden underneath the thermostat housing. I must check out Mini-Spares.

Finally I hope your welder isn't spending the time to make yours that I did on this one. If so, I can see a second mortgage or a car being sold to pay his bill !

Brian

Edit to add - a good shout on the extended brass nuts Alex, just bought 10 from Ebay. And I was expecting to struggle to find any !

[4129R]

£850 + VAT per S/S complete system. Man in Norwich.

The extended brass nuts 5/16 UNF are available on eBay. So are the UNC S/S allen headed bolts.

Man with Lotus fibreglass molds in Snetterton Ind Est is repairing my boot box for £30. "Just put it in the mold and repair it"

Man near Lotus factory is spraying 3089R from Tawny Brown to Lagoon Blue.

Man near Lotus factory is upholstering batch 5 of 7.

Man in Loughborough still has my seat for a pattern for making ally ones.

Meanwhile 4688R is nearly ready for engine. Just the dashboard to go in with the spaghetti behind and a few minor things, then the interesting stuff starts. Trimming a bare shell is time consuming. Cutting the thick dense underfelt lost skin from middle finger from scissors. There must be an easier way of cutting it than a Stanley blade then scissors. It has new loom, rechromed bumpers, new rad, new fuel tanks, new rubber and all pipes, new dash, lights, locks, door handles, alternator, starter cylinder head, new vent discs, new rear discs, Minilites and 185 Yoko tyres, 40 DCOEs and chassis. Just about the only originals are the bottom engine, the gearbox, the repaired shell, repaired doors and window frame, the rear screen, and the suspension arms.

[EuropaTC]

Wow, loads of work going on there. I bet you've got as much going on as Richard, and it's supposed to be his day job   

4688R sounds like it's going to be a stunner, is this the "Keeper Car" ?

Circa £1k for a complete system looks very upsetting at first sight but with the benefit of the last month I can well understand it.

The costs for mine were roughly - 1st order, mandrel bends, straights, flanges - £130 (ish). 2nd order - £25 (due to re-design once I had the bits    ). That was enough tubing to make the system you've seen, basically the pipework to the rear box. Rear boxes were available from the same source, IIRC it was around £60 for the bare box which would need inlet/outlets welding on.  Flat sheet for collectors, etc, £24 (304 kitchen splashback offcuts from Ebay)  Say around £240-50 if you wanted a complete system in kit form.

I also used most of a gas bottle, cutting discs, welding wire, etc. Say another £100 for sundries to do the job, so it would have come  in at £350 for a complete system. Ok, much cheaper than your bill but.....      this has taken me the best part of 2 weeks to fabricate and although a professional will be much faster I could see a week's work.  So very easy to run up £1k for a custom system. In fact I can't see how SJS sell tubular headers at £225(ish) a set unless it's ferritic SS and smaller bores.

All of which makes the headers supplied by the specialists seem very good value. I spent more on making mine than I would have done buying one from SJS. Fortunately that's something I realised before I started but this wasn't about saving cash, it was "because I want to".....  something the wife struggles with at times   

"why not just buy one and bolt it on ?  then you can do the fireplace.... "

Brian

[Grumblebuns]

All of which makes the headers supplied by the specialists seem very good value. I spent more on making mine than I would have done buying one from SJS. Fortunately that's something I realised before I started but this wasn't about saving cash, it was "because I want to".....  something the wife struggles with at times   

"why not just buy one and bolt it on ?  then you can do the fireplace.... "

Brian

Brian, I know exactly where you are coming from. This is my thinking when I go forward with my brake projects. It's fun and I learn a lot during the process. Good job.

[Certified Lotus]

Thanks to Alex (he brought one of his Europa's over to 1st Performance and Exhausts Ltd. in Norwich) for getting the pattern made for these custom Stainless Steel exhaust systems.

I now have one here in the US😎

[4129R]

I am glad the box of bits arrived safely. What do you think about the quality? I thought it is very well made, the welding is very good, the clamps are excellent, and you can actually do the manifold nuts up.

I have used extended brass nuts which cover the whole stud thread, so rusting of the thread just shouldn't happen. I have even thought about drilling the nuts and lock wiring them in place. I will see if they work loose in time to see if this is necessary.

Alex in Norfolk.

[Certified Lotus]

Alex, it is very well made and I was very pleased that it comes with all the clamps. I greatly appreciate that you let me be part of the "production run". 1st performance told me it was the first time they shipped an exhaust system to the US.

It will be months before it get's installed as I'm waiting for my engine to come back from Quicksilver Racing, but I will follow your lead and use the extended brass nuts.