no room between exhaust pipes and chassis

[lotusbzz]

Hallo everybody!!!



I need a good advice about the exhaust routing

My S4 1968 is nearly ready for the advance switch on after total restoration of the chassis and TwinCam.
the engine is already into the bay, everything is bolted, I fit the brand new exhaust manifold and .... big surprise ... there is no more room for the proper route of the pipes down to the 2->1 junction

I've shifted the engine rightward as much as possible ( adding spacers to the left engine mounting) , but no way, the pipes scratch the top frame of the chassis.

it seams that with this manifold I have to cut the top frame, but this is the very last chance that I have.

Any idea?

1) change a bit the shape of the 4 pipes in 2?....mmmm I see problem to get the right route again
I have to heat with the torch until it's red the stainless steel that then is no longer stainless
to do this I have to make a template to hold the exhaust flange and the 2->1 junction in position , it?s a work for artist/ sculptor .... it's a mess!!!

2) cut the exhaust flange and weld again with better angle ? who knows what's happen inside the pipe if the angle is too tight?!?!?!

3) cut the frame, but it means cut 20 mm x 100 mm long ..... the stiffness of the chassis could be seriously damaged

4) any other idea ?

Thanks for your comments and help!!!

Paolo

[StressCraxx]

Paolo,

If you have a standard twincam block, there should be four spacers on the driver's left side between the motor mount and the block.

You also can slot the bolt holes in the motor mounts to move the engine further away from the left side of the chassis. I had to do this with my new exhaust manifold and the new motor mounts I fitted.

Ciao,
Dan Wise

[rgh0]

Even with the correct spacers on the exhaust side of the block most after market exhausts headers will come very close to or hit the chassis. Most after market headers use bigger pipes than Lotus did originally with the sprint headers and their bending accuracy also varies.

The TTR headers for example need a fairly large cut out, other peoples version less so.

As a result many cars had had a section taken out of the chassis top rail to fit non original headers unless you have a Spyder chassis which has more room in this area.

Heating and re-bending the headers you have is an option but it is not easy to do as you need to make up a steel mounting plate to keep the head connection flat while doing the bending. I would not risk my expensive head by heating and bending them in place.

cheers
Rohan

[ecamiel]

I have the TTR big bore headers. I bent the horizontal lip down on the top of the chassis rather than cutting it and got adequate clearance with weakening it as much as cutting would have.

Hammer, vice grips, - easier than I thought it would be. That's soft metal.

Eric
64 S1 Hart

[rgh0]

I have the TTR big bore headers. I bent the horizontal lip down on the top of the chassis rather than cutting it and got adequate clearance with weakening it as much as cutting would have.

Hammer, vice grips, - easier than I thought it would be. That's soft metal.

Eric
64 S1 Hart

Yes i actually did the same as it makes the top flange more stable and stronger and less likely to buckle. About 1980 did a small bend when I fitted headers. A couple of years ago I had to increase the size of the bend to accommodate the TTR race headers

cheers
Rohan

[Certified Lotus]

Considering your still in the restoration phase, I would pull the engine back out, cut the frame (the same dimensions as a 26R cutout) and weld in the appropriate metal plate for strengthening. You need to remember the engine moves under acceleration and deceleration. If you only create enough space for the headers to fit and its tight you will probably have issues at some point in time.

I completely agree with Rohan about not heating your headers in place (attached to the head) as the heat transfer would be high.

[Terry Posma]

I have recently installed a TTR manifold and had some issues as well.

The Y piece on the end fouled the gearbox bell housing and the nut on the Y piece was also an issue.

The local exhaust fabricator advised me to make some cuts into the manifold at welds in certain places and he would squeeze the cut ends together again and TIG weld them. Worked a treat and only cost was the equivalent of a half a slab of beer.

I still had to put in a small semi circular cut in the chassis for clearance but considering this is at the same level as the motor mount there should not be too many problems with the manifold hitting the chassis.

The chassis has had triangulated braces put in place which makes the fit all the more hard. I can also say that once I had decided to take everything off the motor incl the mounts, the starter and the alternator it was all allot easier.

The biggest problem is getting the manifold in and out which involved putting it very loosely in place as the motor is slipped in sans gearbox. The gearbox is a very tight fit as it is a Izusu diesel 5 speed. I did replace the studs with cap screws, which also assisted in getting at them to tighten.

Once I figured out the way to do it and the sequence it is not overly difficult. It will probably be much harder when the body is back on the chassis. Heaven forbid that I would have to pull it out again soon!!!

[William2]

I have fitted an SS manifold from Sue Miller and a Y piece from SJ Sportscars. I had no issues with fitting it and it cleared the chassis rail easily with no cut out required.