Exhausting!

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My exhaust manifold is wrapped in Thermotec tape. This is an insulating material made from woven glass fibres (I think). It degrades over time and needs replacing. I first rewrapped the headers when the car was about five years old, noting that the mild steel pipes were gently corroding. When I pulled the engine in August, I noted that the tape needed renewing once again. But on unwrapping the pipes I found that they were now, at ten years old, heavily corroded. They weren't holed and would see out the summer, but would need replacing.

I ordered a new exhaust manifold from Westfield. My bad!

The cost for the mild steel manifold with slip-on stainless steel intermediate pipe was £380 delivered. Westfield, as ever, had nil stock. So, after SIX WEEKS, and after a little chasing, I received the new pipes.

The first thing that I noticed was how light the new manifold was. Sadly I failed to weigh either my old pipes or the new ones, but I'd say that the new pipes were between 25-30% lighter than the old ones. I admit that my first thought was, "Oh good! A useful weight saving." However, it soon dawned on me that the weight reduction could only be the result of a significant reduction of tube-wall thickness and a similar reduction in life span.

I then looked down the pipes.........

I've written before of the difference in quality between the factory-fabricated parts of my 2006 kit and those parts that I've received since all fabrication was outsourced. The front wishbone that I ordered a couple of years ago was shockingly badly welded. But the new manifold was an absolute joke. I didn't take any photos of the exterior of the system, which I must admit looked good. But here are the bores, alongside my old, corroded pipes (I should point out that my iPhone was held very close to the pipes, with my old system a couple of inches closer to the lens than the new pipes, hence the apparent difference in size!). Tap/click on any photo to see it full size:

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Just to be quite clear on this, tap on the following photo to enlarge it to fully appreciate the true horror of this fabrication:

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The new pipes went back into the box and back to Kingswinford. More on that later......

Salisbury is a fun, thirty-minute drive away from me and also home to Maniflo! So it was straight off to them with my old headers. I've dealt with them over the counter before, so I knew what to expect. It's old-school fabrication! complete with the topless girly calendars that you all thought had ceased to be printed a decade ago. It's an H&S nightmare and long may it remain so! It's also very much "wet finger in the air" when it comes to quotes.

Dave quoted VERY SIGNIFICANTLY less than Westfield for a mild steel direct copy, but then we started discussing what could be done instead. They've been producing manifolds, both intake and exhaust, for A-series installations for decades, so know their stuff. Dave pronounced that the standard bore would be adequate for a mildly-tuned 1275 engine, but no more. For my 105bhp, 1320 engine it would be holding back further tuning. We eventually settled on a big-bore system, with much longer primary pipes than the stock Westfield system, in stainless steel, for £480 inc. I also stipulated a bolted flange joint for the inter pipe.

Sadly, although I discussed the minutiae with Steve (the fabricator) alongside Dave (the boss), Dave returned from a week away to find that it had been fabricated in mild steel (with a stainless intermediary pipe and flanges). But then again, I had a beautifully made system fabricated in a week and offered to me for £275.

Once again, I failed to take some crucial photos for you, but here are some of the system painted in VHT Flameproof paint, prior to curing on the car:

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Here it is on the car for paint-curing. Note the length of the primary pipes. Also note that it's a tight fit where they come together between the chassis rails. Maniflo only had my old pipes for reference and were under instruction not to go any lower, due to the chassis rail running beneath. I'd quite forgotten about the diagonal tube above! If anybody orders a similar system, I'd recommend that they direct Maniflo to this thread and these photos and have the primaries come together horizontally rather than vertically. Still, I got lucky. It fits (just!) with no interference when the engine's running.

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And here it is wrapped and sealed:

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So, I've only covered about thirty miles, curing the VHT paint. I can't comment on power or torque; that'll have to wait until it's next on the Slark dyno. But the exhaust note is less rasping. Deeper and smoother, much as you'd expect from the increased bore. It's certainly beautifully made, with nice, clean transitions from square ports to tubular pipes.

Maniflo have labelled and stored my old header for use as a pattern. If you'd like something similar, give them a call and maybe a link to this thread.

Westfield took the returned manifold back to the fabricator. They weren't very happy with the quality either. But then, they did send it out to a customer. Nor is it the only recent fabrication from them that I've considered not up to scratch. They offered to send out a replacement straight away, but I refused it. They refused to give me a refund, on the grounds that they'd had the manifold fabricated especially for me. If that were the case, then how were they able to offer to send me an immediate replacement? Extremely poor customer service. So they're giving me credit instead. Twice bitten now, I shall not be ordering any further metal fabrications from them. But I do fancy a flatback........l

[Westfield 129]

I have been using the Maniflow system for several years (well, a decade), modifying a Mini Cooper big bore header to fit in the Westfield chassis.
I chose the Mini header as it had a bit more tubing so that I could re locate the bends without having to purchase any extra tubing. I have been able to re adjust the header to fit in the chassis and keep the optimum LCB length to the collector.

I cut the header several inches below the Y and did the tack welds on the car. This modification has been simplified over the years , reducing the number to only two cuts and welds. I also have put them together with a three bolt flange, or a Marmon V clamp for the exhaust pipe/muffler assembly. This is especially important on LHD cars, as it is possible to suffer CO poisoning if there is a leak at this (slip fit) pipe union. I speak from personal experience on this, having been gassed by both my own car when I acquired it, and the US press car during early testing. I know other W11 drivers that had this problem as well. Attach the exhaust pipe with a bolt on flange, or a Marmon clamp.

The modification of the system is covered in my build album on the Westyxiownersbuildersdrivers site.

If Maniflow would only build a specific header for the W11 so that I would not have to weld one up myself.

Now, for the warning about your current header:

I dont want to alarm you, but...
DONT WRAP THE HEADER!!! It will crack at the "Y" junction in short order (the Maniflow fabricated part of the pipe). You will notice some more crackle and pop in the exhaust when it cracks.

I will skip over the usual problems that exist with header wrap, especially when oil soaked or fuel soaked from carburetors that may be mounted directly above the wrapped pipes...

I mention this as I have had the problem in 100% of the Maniflow big bore exhaust headers that I have had, on several different W11s. When wrapped, they crack within a thousand miles or so. Then, I have to TIG weld them up, and... They will crack again. They crack when wrapped, and have cracked when coated, or painted, or coated inside and out... Always just above the Y, at or near the Maniflow welds. In one case, on a ceramic coated header, it cracked beneath the pipe, prior to the center weld.

Not wrapping the Maniflow header will give it longer life. Make a heat shield to keep the heat off of the carburetor(s). Aluminum or Stainless Steel, your choice. There is also a bolt on heat shield that can go below the Weber, but it blocks the ventury location screws, and you might want to be able to inspect these from time to time, even if you have tab locks or safety wire.

When the header is not wrapped, the cracks can be seen as they occur, and you can do the welding before they get too big. TIG welding is the best way to fix the cracks, and if you can get the pipe pressure tested, even better. Often. there are more cracks than you might see. Once, I found 3 additonal cracks during the pressure test.

I really like the design of the Maniflow header, and it would be fabulous if it were done in stainless (304 is OK, 320 would be better, but the header would cost £1000).

The cracking is not just with my modified header. My buddies with Mini Coopers have the same problem, with the same header, in unmodified form.

I have been looking into making a header from stainless tubing, ordering the bends, doing some cutting and having the bits welded together on a cylinder head (I have a spare just for header repair. It's that common). The design of the A series LCB header is pretty simple. The project is interesting enough to have me considering picking up a 110/220V TIG welder and taking a class...

In any case, make a heat shield, weld a couple of studs to the center branch to attach it, and get rid of the wrap. Watch the center Y pipe for cracks. Have a few extra big bore, graphite coated header/intake gaskets on hand if you need to remove the header for repairs.

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Hi Jan,

I'm aware of both your modification of the Maniflo Mini big-bore headers and the problems with cracking. Having both the VHT paint and the wrap and sealant spray to hand, I thought I'd give it a go and see how I fare. If it subsequently cracks, then Maniflo are only just down the road to effect repairs. The original welds appear to be very good though.

A trip to Slark Race Engineering's dyno is in order to ensure that I'm not running too rich. It's too much unburnt fuel igniting in the wrapped manifold that caused the excessive degradation of the original pipework. So I'll admit that wrapping is very much a double edged sword. It has upsides in heat control and improved gas flow.

Whatever, it's got to be better than the shoddy (and expensive) rubbish that Westfield supplied!

Simon

[Westfield 129]

I agree. If Maniflow will just make the things out of stainless, and perhaps put a gusset in the Y to prevent the cracking.

But, having done the wrapping for a few years, and found myself having to weld and wrap over and over... I decided to simply make a shield and see what happens.

The end result is that I only occasionally have to weld, and never have to wrap.

Since it is warm here in So. California all year around, and I have had no problems with percolation of fuel in the carburetor, I can testify that the simple heat shield works (as does a 5"~6" manifold that really moves the carb away from the header pipes).

The main problem is that the header will still crack, and you can't inspect the header with the wrap in place. I'd cut the stuff off, sand blast the header and re shoot it with VHT. It will still crack, but at least you wont be picking glass shards from your fingers removing and re wrapping the header.

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(This post is as much about drawing attention to the "quality" (ahem!) of Westfield's presently outsourced fabrications, as it is about exhausts. AFAIK, all welded fabrication and glasswork has been outsourced since Chris Smith sold the company to the Potenza group in late 2006. I'd be interested to hear what recent XI builders think of the quality of the supplied parts. In view of my intention to change the rear clip, I hope that the glassworks is better than the metalwork.)