V12 Exhaust Downpipes.

[Rustyred]

Hi All,
I have purchased new cast Exhaust manifolds and Steel Downpipes from a major firm in UK for the V12 Im restoring.
Now! couple of Problems I'm having is the manifold casting is a lot larger in size and thicker in cast, although is does fit, I still had to grind a fair bit around the areas for the manifold nuts to fit.
The second problem is the downpipes, they supplied me 2 different parts numbers, but both pipes are exactly the same (length, height and size). Those part numbers are BSJR138 and BSJR139.
The originals were smaller in diameter and had a offset in them so the tri flanges moved closer to the sump to allow for clearance on the side rails, the new ones are straight, even though they do fit, they run next to the rails with only a 8mm clearance on the tri flange. When they are bolted up there is 90mm difference more in width between the new compared to originals. So there is no way my original exhaust will fit without adding and extension between the 2 pipes.
The supplier said:(the norm cliche")they have sold thousands, and never had a problem.
So I ask the question has anyone else had a issue with these, or are they Part Numbered incorrectly, if so how to rectify the problem.

Totally frustrated with parts for this car.

Cheers John

[MarekH]

Dear John,

It is difficult to see how to make a gap of 9cms if using correct parts or even remotely correctly sized parts.

One workaround is to have one extra doughnut/donut and 9cm length of flared pipe so that you'd use longer bolts between the triangles that side.

Surely the difference in length per side is offset by different length exhaust pieces before the intermediate silencers. If these have been transposed left and right then might that not magnify the error up to 9cms?

kind regards
Marek

[Rustyred]

Hi Marek,
Thanks for your reply, but the length is not a problem, it's more major than that. See all images.



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Attached is a Randon image I found on XKE Data, and this shows the set the downpipes have, which is the way mine where.

These have the ample clearance, but the new product, has bugger all. I have swapped these downpipes the opposite sides and made no difference at all. Where as if you swapped the genuines over it would be impossible to fit. Due to that offset.
Now if the Supplier said they have sold hundreds, there must be lots of purchasers out there who have the same issue ??????...or could someone let me in on to the secret to getting around it.
I have E Type Fabs frames, new engine mounts, Auto Trans is Standards and so is it mounting, the engine is sitting in the original location with no modifications what so ever. So in theory, that should rule all that out as being a problem.

Regards John

[MarekH]

Dear John,

I misunderstood your issue from your initial description, so ignore my previous post as it doesn't address your question.

It may be that the new downpipes are fatter than the originals, but the geometry that concerns you is ultimately a function of the angle of the face of the exhaust manifolds to head surface OR the relative thickness of the rear manifold at the exhaust mainifold studs relative to the front manifold.

In the former case, the downpipe would still sit parallel to the frames but further tucked into the sump.

In the latter case, when the downpipe is tightened to the exhaust manifolds, it has to rotate such that the eight downpipe studs become tight. This would leave the downpipe at an angle to the frames and sump, but point the ends of the downpipes inward if the rear exhaust manifolds are slightly thinner section than the fronts at the point where they contact the heads. That isn't a design feature, because the manifolds have the same part numbers left and right.

I will attempt to measure the distance across on my car for you and post the result.

kind regards
Marek

[mgcjag]

Hi John...I think you need to recontact your supplier.....mail there tech department and senior management.....send photos of your originals and new ones and dimensions....you never know there supplier may have manufactured them incorrectly.....you mention that the 138 and 139 are exactly the same but on your last photo it shows that left and right are different...hope this helps...
PS you do have the manifolds on the correctly.....LHF same as RHR and RHF same as L HR

[MarekH]

I am not sure how you'd conclude that the downpipes are different in the stock photo of the 1972 red roadster from XKEdata. The exhaust manifolds each side are offset which would account for the visible apparent length difference and the variation in the angle each has to the sump is explained earlier. They do look to be slightly smaller diameter, but that won't account for the lion's share of the geometry difference.

The tape measure distance on my car is about 44cms. Looking at your exhaust picture, the exhaust cans appear to touching in the middle. I would expect to see clear air between them so 398 is low. It is adjustable.

You can slightly lower the 485 measurement by tightening the crush washer between the downpipes and manifolds more at the sump side than the frame side. From memory, I used to be able to put a socket set between the frame and downpipe but I seem to remember that I can only do that on one side now, i.e. the freame to downpipe clearance of 5-8mm is low but not unusual.

kind regards
Marek

[Rustyred]

Hi John...I think you need to recontact your supplier.....mail there tech department and senior management.....send photos of your originals and new ones and dimensions....you never know there supplier may have manufactured them incorrectly.....you mention that the 138 and 139 are exactly the same but on your last photo it shows that left and right are different...hope this helps...
PS you do have the manifolds on the correctly.....LHF same as RHR and RHF same as L HR

G'Day Steve,

That last image is a random one from XKE Data, it's not of the car I'm doing, but the ones on my car were the same, smaller in diameter and had a offset on both downpipes. I just posted that pic to show how much of a difference it is.
Now with the manifolds I can't see how you can fit them incorrectly. Even if they didn't have part numbers it's pretty hard not to fit them right.
I'm leaning that they incorrectly supplied, but I'm 17000miles away from the Supplier, I have sent them quite a few emails and photos but it's getting nowhere, and it makes it pretty hard when I have nothing else to compare it to. As in same Part Number but different supplier.

Cheers John

[Rustyred]

I am not sure how you'd conclude that the downpipes are different in the stock photo of the 1972 red roadster from XKEdata. The exhaust manifolds each side are offset which would account for the visible apparent length difference and the variation in the angle each has to the sump is explained earlier. They do look to be slightly smaller diameter, but that won't account for the lion's share of the geometry difference.

I can't see how there is difference in those manifolds, unless they are a specific singular Part Number eg: L/H/Rear-L/H/Front-R/H/Rear-R/H/Front, to account for any tapering along the flange faces

The tape measure distance on my car is about 44cms. Looking at your exhaust picture, the exhaust cans appear to touching in the middle. I would expect to see clear air between them so 398 is low. It is adjustable.

Yes, the centre cans are touching the full length of the can, and they are tacked welded at each end. They have been replaced at some stage with larger stainless units. Your measurement of 440 makes me feel a little better, in that I will be able to cut the balance pipe and widen it a little, but that distance is how I pulled the pipes off the car

You can slightly lower the 485 measurement by tightening the crush washer between the downpipes and manifolds more at the sump side than the frame side. From memory, I used to be able to put a socket set between the frame and downpipe but I seem to remember that I can only do that on one side now, i.e. the freame to downpipe clearance of 5-8mm is low but not unusual.

I have tried tightening the closest side to the sump to see if that would work, the quality of fabrication on those downpipes is superb and the snug fit into the manifold itself is not lending me any favours so far as extra give to shift the angle of those pipes towards the sump

kind regards
Marek

Thank you for taking your time out and measuring those pipes for me, at least I have something to go off, I just can't believe that if a part is remade, then it should be pretty close to original, I have new manifolds and downpipes, so there are quite a few variables in there. I have sent the supplier these images, so hopefully they will get back to me pretty quickly with a answer. I can't be the only one that has had this issue.

Cheers John

[Rustyred]

If I have no luck with the supplier, the only option I have other than purchasing a set of headers, is to cut a series of pie cuts on the inside/ closest to the sump and re weld the downpipes to allow extra clearance.

Thanks Again John

[chrisfell]

This might be a bit late, but I've always assembled exhausts loosely until fully aligned. Particularly with the rear end, I've had problems getting tail pipes to line up dead centre and parallel. Keeping everything loose until aligned to my liking helped. Then it was a simple matter of tightening everything up slowly and a bit at a time.

Some fasteners cannot be left loose, like the body mounts of the hangers for the silencers, but clamps at the manifold and between pipes, loose is best until ready to tighten.

I'm aware the V12 might have accessibility issues so this may be a moot point for S3 owners. But for XK engined cars everything can accessed after system is in place.

[mgcjag]

Hi John....just checked this out and 138 and 139 should be defferent lengths by amout 10mm another thing to think about are your engine mounts...old ones could make the engine sit lower

[MarekH]

The exhaust manifolds available today are a totally different casting to that made back in 1971. The 1971 items are a thinner section all round and this means that when tightening up the ears onto the exhaust manifold studs, it is relatively easy to crack the manifolds through these eyelets. The newer (repro) ones have an SNGB stamp on them and are a much thicker casting. This does change the geometry subtly but it also makes it less likely to crack if poorly mounted.

If you replace only one manifold but retain one old one, then that's easily account the downpipe sitting at a skew angle vis-a-vis the frame. It also means that every time the car is run, if they are under tension against eachother, there is the possibility that the thinner sectioned manifold will be likely to crack if it moves relative to its newer, thicker, stronger replacement cousin. The lesson here is to replace them in pairs as it is a real chore of a task.

kind regards
Marek

[Rustyred]

Hi Marek.

I had replaced the 4 Manifolds, and new Downpipes and they are from Barrett's.
You are 100% correct is saying the new Manifolds are larger, compared to the standards. I can see that the new thicker casting will be far stronger and as you say, should eliminate the cracking the originals had. The quality of the casting looks very good, and is harder as I found when I had to grind some deeper reliefs for the nuts go on the flange.

If other users have these pipes fitted and they are running close to the rails (5mm) without hitting under driving conditions, then I will let it go. But at best there should be at least 10 to 15mm clearance for any driveline component and even more for exhaust. So I'm not really keen to let it go like that. I have sent these images to the SNG, and hopefully they will come back to me with some answers.

Just on the engine mounts, they are new, and sit in the approximate position of the originals, The engine is exactly the same distance from left to right rails (Dead Centre), but if I need to get clearance for the pipes, I would have to remove them completely.

Regards John

[abowie]

I'm guessing that maybe they have sent you pipes for some other iteration of the V12...

[PeterCrespin]

The E-type setup is the only one with manifolds that come down so low. All other versions would not be even close on either manifold or Y pipe, Those are all higher and swept back, due to the use of a suspension/steering subframe under the engine on every other V12.