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8 & 10 cyl Bristol cars Type 407 onwards - restoration, repair, maintenance etc

Next 408 exhaust question - tips

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Old 20-12-21, 06:54 PM
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Default Next 408 exhaust question - tips

My car's non-original 360 engine has a Mopar performance cam so it sounds a bit like a muscle car at idle and low speed. It has dual 2.25" exhausts attached to stock cast iron manifolds. It had glasspacks but I had them replaced with a pair of larger, baffle-type silencers/mufflers. That helped the noise a bit but I am still thinking it's too much like a muscle car for a Bristol. Things I am considering are : adding an H-pipe ahead of the mufflers/silencers or adding a second muffler/silencer aft of the rear axle la later 411. However, before I do either, I had a question about the exhaust tips. Mine are straight out with a slant cut on the end but I see the cars left the factory with downturned tips. Even later 411s had fake straight tips with the actual exhaust exit pointing down (see here 411 (Series 3-5) Exhaust Tailpipes.

Fitting downturn tips would be cheap and easy - is it going to help sound reduction by directing sound down? If not, what is the purpose of the factory pointing them down?

Thanks

David
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Old 20-12-21, 07:20 PM
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Quote:
Originally Posted by dwomby View Post
If not, what is the purpose of the factory pointing them down?

Thanks

David
To stop the exhaust gases from discolouring and eventually destroying the chrome on the bumper.
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Old 20-12-21, 09:22 PM
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Originally Posted by Barrie View Post
To stop the exhaust gases from discolouring and eventually destroying the chrome on the bumper.
Hmmmm. Thanks. I never thought of that!

David
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Old 20-12-21, 11:04 PM
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I believe the stated reason was to overcome gases coming into the cockpit although I have never had this problem in my 411.

My 411 has 4 mufflers as you described and isnt loud
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Old 21-12-21, 04:16 AM
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I was always under the impression the downturned tips were to prevent black spots on the back wall of your garage.

When I got my 410 it came with lovely chromed brass tips, but sadly one got pulled off leaving a very steep driveway and the then squashed by a following car. Since then I have had a number of cheap Halfords downturned chrome tips, which were always dreadful quality and only lasted a year or two before rusting and looking terrible. However a couple of years ago I found some on eBay (https://www.ebay.co.uk/itm/322995767559) which I am very happy with - stainless steel, decent thickness, and still in good condition nearly 15,000 miles later.
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Old 21-12-21, 02:15 PM
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I am not sure of the exact reason for the 411 pipes having down-pointing exhaust exit ports but from my experience :

1) To stop soot spots on the garage wall, possible but petrol engines don't produce much soot.
2) To stop soot spots on the front of your caravan, possible but not many tow things with Bristol cars.
3) To reduce fumes getting back into the cabin, very possible, the aerodynamics of gases in the slipstream are weird and at certain speeds the gas might well come back around the car.
4) To reduce projected noise, most likely, as the change of direction and the small size of the final outlets make for useful reduction of the impact of exhaust noise.

People often say 'it would be worth someone making those as spare parts' and they are often wrong, but in this case, you would think that there are enough 411s around and they each need 4 pipes !
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Old 22-12-21, 08:19 PM
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Quote:
Originally Posted by Sam410 View Post
I was always under the impression the downturned tips were to prevent black spots on the back wall of your garage.

When I got my 410 it came with lovely chromed brass tips, but sadly one got pulled off leaving a very steep driveway and the then squashed by a following car. Since then I have had a number of cheap Halfords downturned chrome tips, which were always dreadful quality and only lasted a year or two before rusting and looking terrible. However a couple of years ago I found some on eBay (https://www.ebay.co.uk/itm/322995767559) which I am very happy with - stainless steel, decent thickness, and still in good condition nearly 15,000 miles later.
Thanks, Sam. Those do look good. I'll ask him about cost to ship here.

David
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Old 22-12-21, 08:20 PM
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Quote:
Originally Posted by Thor View Post
I am not sure of the exact reason for the 411 pipes having down-pointing exhaust exit ports but from my experience :

1) To stop soot spots on the garage wall, possible but petrol engines don't produce much soot.
2) To stop soot spots on the front of your caravan, possible but not many tow things with Bristol cars.
3) To reduce fumes getting back into the cabin, very possible, the aerodynamics of gases in the slipstream are weird and at certain speeds the gas might well come back around the car.
4) To reduce projected noise, most likely, as the change of direction and the small size of the final outlets make for useful reduction of the impact of exhaust noise.

People often say 'it would be worth someone making those as spare parts' and they are often wrong, but in this case, you would think that there are enough 411s around and they each need 4 pipes !
I hope you are right about #4. I'm going to try it in the new year.

David
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Old 24-12-21, 11:15 AM
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Default exhaust

I think the reason for the gases leaving the tailpipe were to thwart the MOT man from putting the emission probe up the pipe, thus letting the car pass the MOT.
I hope you all have a merry Christmas.
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Old 30-03-22, 10:54 PM
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Quote:
Originally Posted by Sam410 View Post
I was always under the impression the downturned tips were to prevent black spots on the back wall of your garage.

When I got my 410 it came with lovely chromed brass tips, but sadly one got pulled off leaving a very steep driveway and the then squashed by a following car. Since then I have had a number of cheap Halfords downturned chrome tips, which were always dreadful quality and only lasted a year or two before rusting and looking terrible. However a couple of years ago I found some on eBay (https://www.ebay.co.uk/itm/322995767559) which I am very happy with - stainless steel, decent thickness, and still in good condition nearly 15,000 miles later.
Just wanted to thank you again, Sam. I was in UK for the last month and picked up a pair of these from the maker while I was there. They are beautiful and will look terrific on the car.

David
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Old 07-04-22, 06:16 AM
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Great news, glad I could help.
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