MGB V8 Exhaust Pipe Diameter??

[v8250]

Chaps, looking for some thoughts/advice here. As some of you are aware I'm converting the MGB Roadster to a V8[4.0ltr TVR/240bhp] +R380 'box +Ford Viscous Diff +Hoyle Suspension all round +RV8 Manifolds. I have access to as much as I need 2" 316L stainless steel and am planning twin pipes with balance bar with home made silencers to fit 'snuggly' underneath.

My Q? is, do you think twin 2"ID pipes will be a little too much for the conversion? I'm wanting a balanced V8 sound that's not too LOUD[!!] on long journeys.

Any help/suggestions from those who've completed this conversion would be greatly appreciated.

Thank you...

[roscobbc]

My experience with V8's is that smaller diameter piping will have a higher pitched sound - whilst larger diameter will have the opposite effect. Stainless steel piping tends to resonate more and possibly have a 'tinny' sound. A lot really depends on what cam you choose to use - a 'choppy' cam with lots of overlap will be noisier if only at certain rpm's. Type of silencer and location will again made a difference. A good place is just in front of the rear axle - far enough away from drivers seat yet allowing a reasonable tailpipe length to quieten things down. Good quality glass packs (not Cherry Bombs) like Jetex absorb a large amount of resonance and a quiet(ish) in normal use yet 'sing' when you hit the loud pedal.

[rolymo]

I am not to sure about the hoyle rear suspension layout but on the standard chassis your first consideration would be the clearance between the left rear leaf spring shocker link and the fuel tank.If you have converted to adjustable tube shocks the situation will be even worse. It will be necessary to be quite creative at ovaling the tubes to obtain a rattle free installation plus over engineering the rubber mountings to prevent the system colliding with the floor panel over rough road surfaces due to the extra weight of the system itself.

[v8250]

thanks guys, agree with all your notes. will be home-brewing the silencers specifically for this and that i want the silencers to give optimum ground clearance [will be making heatshields to aid heat reflection]. ref' hoyle rear suspension, the fuel tank is being replaced with an rv8 injection unit and is being centralised to provide left and right exiting tail pipes i.e. a proper twin pipe system. i'm reasonably comfortable that the 2"ID will be fine for the conversion and the 4.0ltr engine has only a midly tweaked cam so not expecting some overly loud chugga-boom-count-my-pistons-type sound coming out of the back end.

anymore input greatly received...

[nta16]

2" sounds too big to me, what size was on the 4.0l Chim and 4.0l Griff (IIRC those had a single centre pipe) and on the RV8 as you're usin the manifolds (don't forget the gap in the inner wings to let the heat out) - my 4.3 Griff was claimed at IIRC 280hp with the same exhaust(?) as the IIRC 240hp 4.0l Griff and there might still be capacity for more power in the standard

just thought, the Chim and Griff had two enormous gather boxes for the exhaust pipes just in front of the engine, V8S and MG RV8 don't of course

I had a TVR V8S (4.0l) and it had factory 'quiet' exhaust fitted because the previous (and original) owner found the standard exhaust too noisy and having heard standard exhausts (let alone the 'sports') version I'm glad he did

having had a few different cars with the RV8 engine and been with groups of others I'd say those in the car don't get the best of the sound that's about 20ft back from the car, plus the BGT is a closed car so if it sounds loud in the cabin it's probably very loud outside, I know some like that but it's no good for country roads as people think you're going a lot faster than you are, you can literally frighten horses and cyclists and the noise will be anti-social as you go through villages with the houses close to the road

some like as much noise as possible from exhausts I know and even have competitions but I blew my ears on loud hi-fi many years back so I'm ooot on this

btw, you probably know already, TVR engine power figures vary a lot on the same type and size of engine and are only slightly more accurate than 60s and 70s sportscars claimed figures

EFS

Edited by nta16 on Thursday 16th May 22:12

[CAPP0]

My Defender V8 (3.5 carbs) is running a 2.25" exhaust (fitted when I got it) and it's way too quiet, not V8-ish at all, so much so that I need to change it.

[nta16]

ETA: my Midget exhaust set off a car alarm in a multi-storey car park as I crawled by, I wish some of that power coming out of the exhaust went to the rear wheels instead

I remember two 1800 MGB roadsters both with the same 'sports' exhaust fitted, one belong to an 'engineer' (the type that explains why having one nut and bolt missing doesn't matter and always uses old fittings, a friend of my wife's, not mine) the other belonged to someone that made the casts for models with his car to show standards - one exhaust would set off car alarms parked down house drives the other was quite quiet - I'll leave you to guess which was which

the moral, before the exhaust feeding into it GIGO, and there's a lot more to tuning and building exhausts than you might think, sure if the basics are there it's going to work, possible well, possibly very well and possibly very basically

all my usual non-technical home spun story and explanation

ETA and EFS: I think some have to have a lot of exhaust noise on their cars to get passed the tyre noise

Edited by nta16 on Thursday 16th May 22:14