411 (Series 3-5) Exhaust Tailpipes
 

Could somebody please let me know how far the exhaust tailpipes extend past the rear bumper on the Series 3-5 411s? I have changes the outlets to my 410 to tidy up the overall appearance of the rear of the car and while the result is far better than it originally looked, I am getting two problems:

1. When the windows are opened on the move at any speed, fumes make their way into the cabin.
2. The rear bumper has exhaust stains after the car has been run.

Obviously there is a degree of some low pressure areas around the rear of the car which is causing fumes to be sucked forwards. I suspect that because the outlets terminate directly under the bumper, the disturbance to the air around the bumper is directing exhaust in other directions instead of straight behind. Extending the tailpipes is obviously the solution but I'm not sure how far this should be. As can be seen, the exhaust stains on the bumper are quite evident.
John Keighley.

411 (Series 3-5) Exhaust Tailpipes
 

Bristol did tests along the runway at Filton on the aero dynes exhausts and
found that if the exit was at the back of the car the fumes became
ingested, hence the cars had an exit on the RHS and thus prevented the problem.
One would need to know how the air flows over the rear of the later cars to
see where to place the pipes, wether Bristol did any aerodynamic work on the
later cars I do not know.
My regards,
Bellerophon

411 (Series 3-5) Exhaust Tailpipes
 

Amazing that you should know this!
But how could exhaust fumes get back into the car from the rear of the
vehicle?
Surely there would have to be a leak somewhere in the engine compartment??

John,
The answer to your question is they don't, extend past the rear bumper that is. BUT, there is something else you should know - on the Series 3-5 411s the exhaust pipes exit downwards. The tailpipes are blanked off a couple of inches inside the pipe. See attached photos

According to legend, Bristol did this because under certain conditions (50mph with window down 1 inch) exhaust fumes were sucked back into the car. Air flow around cars doesn't always do what one expects it to do!

411 (Series 3-5) Exhaust Tailpipes
 

Don't know about the 410, and I may be stating the obvious, but the 411's
exhaust pipes are blanked off a few inches in and the gas exits via holes in
the bottom of the pipes, I believe to get round the problem of exhaust gases
entering the car.

I don't have any problems with fumes, only 4 round black marks on the garage
floor from starting from cold.....

Andy Bernard

John,
I meant to say that I have seen numerous earlier V8 Bristols with exhaust tail pipes that angle downwards at the end, often with what I suspect is an aftermarket chrome tailpipe extension.

I should also mention that the Series 3-5 411s have a vent in the rear wings through to the cabin (beneath the rear parcel shelf) which could also have a bearing on why they had an exhaust ingestion problem in certain conditions.

A dodgy boot seal can be the culprit if there is any airway, regardless of how small, between the boot and the cabin.

And as rubbond said, exhaust smells can also be down to a leak into the cabin from the engine bay. Check the rubber belows on the accelerator pedal rod that runs through the firewall (it's basically a flexible seal).

Kevin

The explanation is that all cars have a smaller or larger region of separated or stagnant air at their rear-end depending on the design. If the exhaust exits into this area the fumes will be dragged along with the car and enter any cavity where there is a region of lower pressure ie. leaky boot seals or open rear windows etc.
If the exhaust gases are vented downwards they will enter a region of turbulent air and thus be dissipated.
Richard

411 (Series 3-5) Exhaust Tailpipes
 

I think it more likely that (if the tail pipes dip down and then back up),
the holes and blanked off pipes are to prevent condensed water remaining
in the exhaust.

411 (Series 3-5) Exhaust Tailpipes
 

I only have two black marks having a 407 and on this the exhaust exit via
a curved stainless steel pointing
downwards at about 60 degrees for the same reason. To stop the gases bing
sucked inside the car by
the vacuum created by forward movment of the car.

Nick.

411 (Series 3-5) Exhaust Tailpipes
 

Thanks Kevin for your mention.
I would however challenge any engineer to devize a car design that would be
able to suck exhaust fumes back into the vehicle from behind the rear
bumper!
As an anecdote I was recently in the Science Museum in London with my son
(and was actually able to park in my old spot next door when a student at
Imperial!).
In the museum were of course fantastic steam engines and aeroplanes,
including the Rover JET 1, but when I saw as an addition what they claimed
to be a capsule that had actually landed on and returned from the moon, I
thought, no, that couldn't be possible in the 1970's.
I mean, consider the faulty door seals, and leaky exhausts!
Where were Bristol then?
With best regards,
Andrew Knox.

411 (Series 3-5) Exhaust Tailpipes
 

Bent Exhaust Tips (Tips for the unwary!)
As an aside, you will recall that the original XJ6 tail pipes had a curious
'S' bend. As you elaborated, the airflow helped direct the fumes away from
the car. My father in the 80's didn't like the look of his old XJ6's tail
pipes, so, you guessed it, he replaced them with some straight stainless
sections. After only a few miles, it became apparent that the fumes were
being reingested into the rear of the cockpit and indeed, stained the rear
hood lining. The message - the factory knew what they were doing!

Brett

Ps Downward tips more than likely make a quieter car.

411 (Series 3-5) Exhaust Tailpipes
 

Aero Dynes were designed for the rear window to be left open when
travelling in order that a through flow of air through the car be established, and
would allow the heating to work properly.
Tony Crook was always insistent that the rear window be left open as anyone
who rode with him would know.
One word of warning regarding the exhaust protruding beyond the rear bumper
on the V8's. It can be very costly if you reverse into anything as it is
very easy to break one of the exhaust manifolds, which are not easy to
replace.
My regards,
Bellerophon

See attached image which is an excerpt from a (Dennis) Sevier Lecture published in the Bristol Owners Club bulletin issue 41 (Summer '76)

411 (Series 3-5) Exhaust Tailpipes
 

As a child I flew regularly from Hurn airport to Cherbourg in a Bristol (3
cars and 12 passengers).
I'm sure however you couldn't open the windows!
The stories about their cars are getting weirder and weirder!
Andrew Knox.

411 (Series 3-5) Exhaust Tailpipes
 

I remember many years ago ownning a Hillman Imp with an openong rear
window. The handbook stated that under no circumstances was the car to be
driven with this window open, as exhaust fumes would be sucked into the
car.
Regards,
David

411 (Series 3-5) Exhaust Tailpipes
 

The issue of fumes varies from car to car. It depends largely on the roof
line and design of the trunk (boot) and the angle of the exhaust pipe.
But why would Hillman go to the expense of fitting an opening window, and
then tell you not to open it? Maybe it was for necking couples, who having
parked in a secluded lay-by, wanted to avoid steaming up the windows!
Dorien

411 (Series 3-5) Exhaust Tailpipes
 

Necking couples! Have you ever been in a Hillman Imp?
David

411 (Series 3-5) Exhaust Tailpipes
 

Seen one once....well it's the only reason I could think of, for a window
that can be used ONLY when parked!
Dorien

Here in Australia the earlier iconic Holden "panel van", loved by surfies and tradies, used to have a large window which hinged up from the roof at the back. I'm sure this was intended only for use when parked but it was common to see people driving around with it open on a hot day.

Of course being a van with only front seats it was much more practical for amorous activities as well. Surfies would often have a mattress in the back!

It looks like Holden might be planning to make them again http://www.holden.com.au/concept-cars/sandman-panel-van-

Back to John's problem. The cheapest and quickest solution to the exhaust stains has to be aftermarket exhaust tips that point downwards. But I suspect there's also a leak into the cabin from either the front or rear of the car.

411 (Series 3-5) Exhaust Tailpipes
 

Kevin Howard wrote " The cheapest and quickest solution - has to be after
market
exhast tips that point downwards."

Just like the 407, the first use of a V8 in a Bristol.
Makes me think that the problem was always there and
an effective solution found. The 407 handbook advises
that the rear windows should be left open when driving
to facilitate the movement of air in the cockpit.

411 (Series 3-5) Exhaust Tailpipes
 

Many thanks to all who responded with these suggestions. On Monday I'll take the 410 to Cooma and the workshop with the only exhaust fabricating and pipe bending capability in town will blank off four metal tubes, weld these up, cut a hole in the bottom of each and then fit chrome caps over them to tidy up the job. As we have discovered, there are no exhaust tips of this type available Australia, so we will have to fabricate them. When all is complete I will post results and photos and let you know how we got on. Now armed with this information, I can throw some light for the workshop people on how the set-up should be. Many thanks for the photos, Kevin.
John Keighley

411 (Series 3-5) Exhaust Tailpipes
 

John,
It will be an exhaustive solution!

Brett

Cooma ? - I bet they don't see many Bristols there :-)

From memory the pipes on my 412 S1 pointed slightly up and had rectangular holes about four inches from the end on the underside and I'm quite sure they were not blanked off.
The mystery deepens!!

412 pipes
 

When I first had it the (non-standard) ss pipes were pointed upwards. No problems with fumes. But they seemed a small bore. The current ACCS items have the oblong slot at the bottom and blanking in the outlet.
PS: the rear window in the Imp was for loading luggage etc into the back. V practical it was too ...as was the car in other areas as well. And did it go if properly tuned. Peter

412 pipes
 

My 412 had on odd aftermarket exhaust which branched off in a Y shape splitting from the Diff so the exhausts protruded at the right place but pointed outward at about a 30 degree angle and cleared the rear bumper a little. The previous owner had attached lip spoiler to the rear bumper to stop fumes coming into the back of the car when the hood was down as his passengers had apparently noticed this. He said the bumper spoiler did the trick.

When it was rebuilt BCL fitted new SS exhausts (which are very quiet) with their stainless steel tips. These are blanked off internally and have the slots cut underneath as described elsewhere in the thread. The 'spoiler' was removed. I have done at least three thousand miles with the roof down and passengers in the rear with no complaints or comment, so this must work. I sprayed the interior of the tips with matt black barbecue paint so that you don't notice the blanking discs.

I have put my winter top on and as the S2 doesn't have vent slots the back of its hard hat like the Beaufighter of the car is pretty airtight. This does mean that you don't get a good airflow through the cabin though unless you crack a window open slightly hence the modification when they did the Beaufighter. My Brigand had vent slots in the parcel shelf to the wings and I am pretty sure that there are also breather panels in the parcel shelf into the boot, although I am happy to stand corrected on that. The 412 definitely doesn't have this.

Paul

Just a sidenote to the tailpipe question - and everyone may know this already:

The four pipes on my '79 603 S2 are blanked off, and have holes on the bottom side, from which the exhaust issues. This is easily seen from both the vapor emissions, and the moist spot on the concrete garage floor under the pipes.

411 (Series 3-5) Exhaust Tailpipes
 

Many thanks to all those on this forum who were able to help resolve this problem. Armed with the information given, the people in the workshop facility in Cooma were able to fabricate suitable tailpipes from four 2 ½ inch tubes. These were bent up to about 5-6°, the ends were blanked off about two inches in and holes cut into the underneath. The chrome tips we initially had installed were then relocated to the ends of the new pipes. A couple of photographs illustrate the modification.
The end results look quite respectable but I haven’t been able to really test the new arrangement to see if it works because it was raining on the trip home. Kevin, it’s funny that you should say that about Bristols rarely being seen in Cooma. There were more visitors to the service facility than usual on that day, apparently the 410’s presence caused a bit of interest.
It’s interesting to note that the solution to the issue of these cars creating areas of low pressure around the rear can be quite complex.
This exercise also illustrates how valuable a forum such as this can be to operators of these cars – thanks Kevin!
John Keighley

I'm glad you found this site useful John. Looks like the guys in Cooma did a good job. Let us know if it solves your problem with exhaust gases getting into the cabin.

Regards,
Kevin

PS. I have a "roadworthy" test appointment on Monday morning for the 411 and an appointment with Vic Roads to get it re-registered on 22 Dec (this year!), finger crossed it passes the roadworthy!

411 (Series 3-5) Exhaust Tailpipes
 

Kevin, Good luck with the roadworthy. I thought that almost three years for me was a test of patience to get a Bristol back again but for you, that time would pale into insignificance! I gather you've abandoned the idea of fuel injection for the time being. Are you running it on the original induction setup?
John Keighley.

Just a point of interest I've recently spoken to the guy who had my 412 S1 before me and he was the person who removed the blanking discs in order to create a “venturi” effect through the bottom slots to improve the exhaust flow.
All I can say is that I very often ran with the back section of the soft top down but with the middle section of the roof in and never had the hint of fumes in the cabin.

411 (Series 3-5) Exhaust Tailpipes
 

Kevin,
That's bad luck. Hopefully, you can get the leaks sorted out and hopefully its not the main seal at the rear of the crank - it's a rope seal and if that's leaking, I am told that the crank has to come out.
All exhaust fumes in the cabin seem to be now eliminated. I've had a good opportunity to test is and there's nothing noticeable.
I do however, have to upgrade the seal along the back of the boot lid as the one that is there isn't providing an adequate seal. It is where the lid joins the lower part of the body- where the locking mechanism is located.
There is a story (a brief history thereof and a brief description of the refurbishment on this 410 published in the current BOCA Club Express magazine.
John K.

411 (Series 3-5) Exhaust Tailpipes
 

Finally,
I have been able to take some photos of the completed work to the exhaust tailpipes. Pictures 005 & 006 show the finished work. I have also added a picture to show the arrangement when the car first came back. Why I chose a 411 quadruple tailpipe arrangement is that it looks far less ungainly than the original system and significantly neatens up the appearance of the back end of the car. Although not frequent, I've been in it enough to confirm that there are no exhaust odours in the cabin now. The one thing I do need to attend to is the rear boot lid seal which isn't sealing the boot all that effectively and that will settle any other exhaust seepage issues.
John Keighley.

Try to really research if you could have the best Tail Pipe for your 411. Try also other forums and websites to really see what you can have in your Bristol Car. I, myself don't own one, but you can find one in order to really see what your car can have.

tail pipes
 

i know its not the full real deal but we fitted a rolled tail pipe to our car and it did the jobs in terms of looks. we got it from a company called aftermarketsounds heres the link anyone else just wanted a simple tail pipe Rolled Tail Pipes - Car Accessories - AfterMarket Sounds really did tidy the car up