Which exhaust manifold should I use?

[Bruce Crowthorne]

One of the things I will need to replace is the exhaust manifold on my S4 Baby Elan.
I want to use a stainless, tubular type (similar to Sprint type).

When I was looking at Elans before I bought mine I noticed that a cut out seems to be necessary in the chassis rail.
If a cut out is required, does anyone have a pattern for the least damaging shape?

Is there a brand of manifold that minimises the cut out required?
Any opinions on which manifold is preferred - and why?

Thanks
Bruce

[pereirac]

Bruce,
You should not have to cut the chassis rail to fit a tubular manifold (at least not on RHD cars). My Sprint does not have any cutout and while it's a tight fit (you have to remove the engine mount to fit the manifold) I have never had any problems. I would be very wary ofd oing anyting to my chassis which may cause stress cracks later.
Check the manifold if you buy a stainless one, I bought one a few years back and the quality is not a good as I would have hoped for - I even sent the first one back. Susan Miller suggests a mild steel manifold and stainless rear box...

[rgh0]

The original Lotus tubular extractors just fitted without a cut out in the chassis rail. A lot of after market extractors dont fit as the bends are not tight enough and any extractors with larger diameter primary tubes than the Lotus original require a cut out.

The original extractors tube sizes are just OK for a standard or big valve engine, but beyond that the engine responds well to bigger exhaust pipe diameters in combination with improved porting, bigger carb chokes and a high lift cam etc etc.

regards
Rohan

[reb53]

Assume you want stainless for the looks rather than longevity. My standard steel one is over 20 years old and is fine. Probably because it can't collect water like a steel silencer box and it gets a lot hotter so moisture doesn't stay in it and rot it out.

Ralph.

[M100]

Only cut the chassis the minimum you need to keep clearance. Shapewise a smooth curve blending into the top rail and avoiding corners/sharp edges is best. Ideally doing the above and adding a gusset onto the vertical part of the chassis would be even better.

My manifold is I think original - if it is then it's almost 33 years old. I blasted and painted it with white high temperature paint about 20 years ago, most of which has now gone a cruddy brown. I suspect I'll need a new system shortly though as I had to weld up another crack in the backbox bracing over the winter.

[Bruce Crowthorne]

The Stainless preferance is really for longer life. However, even that is a trade off since stailess is more prone to cracking.....

The mild steel suggestion is agood one, but the trade off there is that my Elan won't be an every day car, so it may well get condensation even in the headers.

I was speaking to one of the guys at Paul Matty - they are waiting for a batch to arrive - but have been waiting since last December!

Time to start phoning round ....

[pereirac]

My mild steel manifold is about 33 years old and has only ever needed welding once where a bit of the original weld broke off. The steel itself is fine and I have it blasted and painted it twice, so I would not worry about durability.

My stainless maniford came from DoubleS and is nowhere as well made as the original, it's also the stainless which rusts (as I found out later) not the nice 'expensive' stainless so watch out as there are different types of stainless! When I bought my manifold I 'assumed' it was the stainless which just goes dark with heat but looks nice and shiny like the manifolds on expensive race cars....

I have not even fitted the stainless manifold so if you really want one let me know..(I live on the Cambridge/Beds border)

Carl

[twincamman]

I think I would dimple the manifold tubes before I would cut the chassis ---mine fits with out any drama --but its mighty close ----ed

[twincamman]

if you want to keep your manifold nice-- spray it with wd40 when its hot for a few weeks ------keeps the rust off -- --ed

[pereirac]

Sounds like a neat trick, I would just be concerned that the fumes caught fire

[W9S2S3FHC]

Try Never seize on your Ex, run it hot. it will smoke a lot but its a guard from rust. the smoke go's away. STAY AWAY FROM THE SMOKE PLEASE.

[StressCraxx]

I have a set of Dave Bean 4 into 2 into 1 headers. I had a set of nickel plated steel ones and they lasted for 25 years, until I removed the collector to fit an AFR O2 sensor bung and cracked one of the tubes at the seam.

I fitted a new stainless steel set and found that by slotting the motor mounts horizontally about 1/8" gave me plenty of clearance.

Regards,
Dan Wise

[elanner]

My backbone has two small cutouts to allow the manifold/headers to fit. About 3/8" I would think. They curve around the two down pipes. From the Elans I've looked at it's just a matter of down pipe fabrication, some need cutouts, others don't. Obviously, if you can get a manifold that doesn't require cutouts, then do.

I don't worry about it because (1) Brian Buckland's book mentions that they're OK if small and rounded and (2) if the backbone can't handle such a tiny removal then we need to consider the rationality of driving the car at all!

The noise made by the down pipes clunking against the backbone is really something (ask me how I know) and probably doesn't do the head/exhaust studs much good.

I don't know about stainless manifolds, but the mild steel muffler/silencer that I fitted to my car sounded a lot better than the stainless steel one I removed. The stainless one sounded horrible and stupidly loud. If the mild steel one rusts away in a few years it'll still be worth it.

Nick

[S2Jay]

Dan, are you suggesting that you are moving the engine forward by that 1/8? to gain some extra space as the ?Y? of the frame opens, or is it just the motor mount that moves?
[This is just a clarification for any of the more thick-headed readers, like me.]

Jay

[StressCraxx]

Dan, are you suggesting that you are moving the engine forward by that 1/8? to gain some extra space as the ?Y? of the frame opens, or is it just the motor mount that moves?
[This is just a clarification for any of the more thick-headed readers, like me.]

Jay

Hello Jay,

My apologies. After reading what I wrote I realized I was not completely clear.
I am suggesting moving the engine driver's right by slotting the bolt holes in the replaceable motor mounts. I slotted the bolt holes about 1/8" and pushed the engine towards the carb side. Took only about 20 minutes with a round file and dremel to slot and deburr the holes.

Regards,
Dan