Speed Hump Scraping - Custom Exhaust

[JoeLondon]

Howdy folks,

I finally got my car back after about 6 months - thanks Covid!

Driving in London I have the blessed speed hump issue with the S3 scraping the centre boxes when I drive over anything higher than a matchstick. Have replaced all the hanging rubbers but that didn't change much. As I now need to replace the back box anyway, I was thinking, there is quite a lot of room above the centre boxes and was considering a couple of options:

1) have a fabricator make a pair of pipes that bend upward, closer to the floor of the car for that section and back down to meet the back box pipes.

2) do away with the centre silencers completely.

3) have a fabricator make a new section with slimmer silencers but keep everything else as is


Only pitfall I can see is the extra heat from having things closer to the floor which can probably be shielded.

I don't really want the boy racer sound of removing the centre silencer, although I wouldn't mind being able to hear that V12 more.

I know theres the stainless/mild steel sound debate, but frankly the crunching of steel against tarmac is not exactly sexy.


Anyone tried any of these, or, is there a solution out there already and I'm reinventing the wheel?

[mgcjag]

Hi Joe...what about raising the rear ride height....just adding a spacer on top of the rear springs...available from SNGB....a friend done it to his S3 becaus of the speed humps....problem solved.....Steve

[MarekH]

1/ Undo all of the clamps front to back sufficiently for the exhaust to still be in place but allowed to move slightly if push comes to shove.
2/ Jack the car via the centre mufflers so they pushed upwards into the spare gap above. Don't overdo it.
3/ Start the engine.
4/ As it heats up, the exhaust will creep to its new position. Do all of the clamps up. Allow to cool. It ought to be good for six months or so.

The other strategy is to make the kink in the pipes of the rear exhaust section a more shallow angle. This will naturally make the rear of the centre section want to sit higher up as the gap between the pipes and the IRS will be smaller.

If the speed humps don't go all of the way across the road, then merely going over them with one side of the car or the other is usually enough to see you across.

kind regards
Marek

[AussieEtype]

The floor above the centre mufflers is already shielded with a fibrous plate.

[malcolm]

Someone I knew had the same problem until the engineer I used in Essexx pointed out he had the wrong hangers on. Fitted the correct hangers and problem went away.
My car is a series 2, but a 2+2 so same LWB. Exhaust system different I'm sure, but I never have speed hump issues.
Worth checking maybe?

[MSM]

The floor above the centre mufflers is already shielded with a fibrous plate.

Assuming that it is still there after 40 - 50 years, the same comment applies to the gearbox heat shield. Easy to reinstall when the exhaust is off but impossible otherwise.

[42south]

Hi.
Living down here in NZ we have lots of roads with poor surfaces, and lots of speed humps. My car used to graunch all over the place so serious intervention was required.
I would check your rear ride height, the figures are in the manual. To get it right required spacers under my Koni shocks.
Then I got my silencers up higher in the cavity, by using modified hangars, and also making sure that the pipes under the IRS had the correct flattened surface to get them up as high as possible.
By the way I use straight through silencers for the center silencers, with fibreglass packing, the sound is much better, well to my, and some Jaguar friends ears.
I now have no graunching on any roads, and take speed humps slowly, without problems.
Good luck
Mark

[JoeLondon]

Brilliant ideas all round. I have noticed today that after coming back from having the work done, unfortunately - the exhaust work was missed! Disappointing to say the least. Didn't even change the perished rubber exhaust hangers. So, Ill get me some new rubber hangers to start with and see what difference that makes - I still have an appointment to go to an exhaust manufacturer on Wednesday for assessing it.

Hopefully the £2 rubbers fix the £800 problem!!

[42south]

Hi
Here’s a couple of pics which may be of interest. I did use 2 1/4 inch pipes for my system. The hangers are modified to take modern rubber mounts, available at any exhaust shop.
The first pic shows the amount we flattened the pipe under the IRS
On the last pic you will see, if you look closely, that there is a small knob on the end of the hangar that stops the rubber slipping off.

cheers
Mark

[JoeLondon]

Update.

Yep. The old hangers had been left on, so obviously replacing those has made a huge difference and I can now make it of the ugliest bumps with a light scrape, rather than the bone chilling crunch on the tiniest bumps. So, great!

I still suffer greatly from the ingress of exhaust fumes into the cockpit. The back box is blown, I've been wanting to hear the V12 a little more. I've read through the numerous posts here on exhausts and decided a straight through pipe for the back section will be my inclination. I personally like the fantail though, and prefer as close to original as possible.

There were 2 straight through stainless solutions from 2 different companies.

1) company 1 is mail order, suggested to build a fake box to look stock but have the pipes just run straight through. Great idea, this would be my preferred option but at almost £600+ vat and shipping, and pay someone else to fit it, I decided it was prohibitive. Especially given that the standard mild back box is just £150+fitting, I don't think it's worth an extra £500+ just to hear the V12. Caveat, these guys have a lot of experience and specialise in the E.

2) the other company will build 2 straight pipes and split them to a YY to accommodate the fantail, but delete the box. At £300 all in, fitted, butting up the rest of the pipes where gaps have appeared at the joins, fit my replacement heat shield and polish the fantail. They are exhaust pros, and have done a few E's.

Assuming I take an exhaust to be fitted anywhere here in London, I doubt I'd get much change out of £60 tbh. So option 1 is looking like over £800, and option 2 is £300 and I get a bit of extra service, which is only about £80 more than a mild steel standard setup.

I'll ensure he makes the pipes with a good enough angle that it keeps the clearance of the centre boxes, to be fair he said that himself too.

Anything else I should be aware of? Do I need to concern myself with the carbs with a different system? My guess is that as it's just the back box it shouldn't make toooo much difference.

-Exhausted

[42south]

Hi
You will probably have to adjust the mixture if you open up the exhaust system. This shouldn't be too much of a challenge for a competent mechanic.
here is a link to a you tube video I did of my car with just straight through center boxes and no rear box.

You can probably stop the crackle on the overrun, if you wish, by having the bypass valves working. Mine are disabled. Personally I like the crackle.
We find the noise level just right, cruising at 100km/hr is very comfortable, not overly noisy at all.
Everyone who has heard ours reckons it sounds just great, even the jag purist mob.
Just ignore the rest of the video. I did the video as part of my promotions to sell the car. Not sold ye, but early days.

all the best
Mark

[JoeLondon]

Nice Mark!

She starts very easily, have you upgraded the starter? I was thinking of doing this, mine sometimes doesn't engage and needs a second go.

I managed to fix 2 more gremlins today - Brakes were binding when warm and in traffic, tap them and they grip on, bit of red rubber grease on the small piston in the Master Cylinder - magic!

I noticed fuel leaking from the bottom of the front 2 strombergs - removed the PUSH IN PLASTIC!!! stopper and added same red rubber grease to the rather square looking O ring - more magic.

Im considering coating the entire car in red rubber grease

In order to get to the carbs I had to remove my heater box as it's from an S2 and I couldn't get to the air filter bolts as it sits too close. - engineers decided that 5 or 6 bolts are needed to hold the heater box on, but the carb sump stoppers, which are the only thing between me and a 70mph burning fireball - PUSH IN PLASTIC!!!!

[42south]

Ah yes the Joy of Jaguar motoring.
Buy a set of Orings for those strombergs, the usuals have them. That fuel drips onto hot bits.
Yes I upgraded to the geared starter, a vast improvement. Check out British starters.com there is a different number of teeth for the 1971 engine, check this.

Red rubber grease is your friend

Cheers.

[42south]

The ease of starting is also helped by fitting the later HEI ignition system as fitted to the later V12s. Sng Barratt do a nice replacement with a rebuilt dizzy as well. There is one with the vacuum advance fitted, get that one. If you still have the original OPUS system fitted, watch out, it will fail, generally in an intermittent mode, when hot.
Cheers

[/quote]

[Ole-xke1974]

Just as an alternative to other exhaust modifications.
I deleted the rear box and replace it with two 2.5" straight pipes. All stainless steel and homegrown from straight pipe, reducers and bends bought online.
The sound is slightly louder and somewhat deeper.

[JoeLondon]

Jesus OLE - that underside is sparkling clean - mine's a little further along, I'm at the stage of rust preventer and flakey paint :)

Mark, I don't have the Opus system, I'm not sure what I have, I need to ask the fella that just did the work on it.

I am wondering about EFI though. I get a lot of fuel smell and exhaust fumes. Once I've had the exhaust sorted that should calm down, also not having fuel pouring out of the carbs is helping somewhat :)

With the new exhaust I'll need to take a look at the carbs and make sure that's all good. If once it's all in sync I still get that heady fuel/CO mix I'll look closer at the EFI. Spent a fair few quid on this puppy already :)

[42south]

Hi Joe,
The Opus system continued into the early 80s, so you may still have it. In the video title photo you can see a small aluminium ribbed box just forward of the distributor, that’s the opus box.
The SNG kit still uses the alloy box but fits the later HEI solid state module in it.
Oles exhaust system and mine are identical in construction.
Cheers
Mark

[PeterCrespin]

Oles exhaust system and mine are identical in construction.

And both cars are for sale. Good time to be a V12 buyer in the colonies! Ole's car will be on the front cover of Jaguar Journal in late October.

Mark, with your username being 42 South, I assume you're not related to Dave Brown in Invercargill, South Island?

[42south]

Hi Guys
Looking at Oles car should be an inspiration to any restorer, hes done such a nice job. My car is at best a good driver.
Hi Pete, no I’m not related to the South Island Browns.
However the original starter motor from my car went down there to Temporo Ltd, the outfit that builds those fantastic D type replicas.
Cheers
Mark

[Ole-xke1974]

Oles exhaust system and mine are identical in construction.

And both cars are for sale. Good time to be a V12 buyer in the colonies! Ole's car will be on the front cover of Jaguar Journal in late October.

Mark, with your username being 42 South, I assume you're not related to Dave Brown in Invercargill, South Island?

Jesus OLE - that underside is sparkling clean - mine's a little further along, I'm at the stage of rust preventer and flakey paint :)

Hi Guys
Looking at Oles car should be an inspiration to any restorer, hes done such a nice job. My car is at best a good driver.

Cheers
Mark

Gentlemen, thank you for the kind words.
Yes, unfortunately, due to a move from the US to England, I have decided to sell my 10 year project, which when I had it back from paint and ready to drive, had 1600 hours invested. Not to mention the initial cost and new parts. All meticulously accounted for in an excel spread sheet.
I could take it with me, but with no garage for the first 6 months or more and not a fan of remote storage, I'd rather it finds a new home in the country where the location of the steering wheel makes more sense.