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MG MGA - MGA Exhaust snarl

Hello fellow MGA fanatics,

You'll probably think we Canadians need something to do since I am even spending time thinking about this, but here goes.
I notice some MGAs and even a Magnette that is in our local Windsor-Detroit MG Club make a nice ripping sound in the exhaust when you lift off the throttle to shift etc. Does anyone know what makes that happen? Is it the type of muffler or exhaust system? My '57 1500
makes a kind of put....put, put, put when lifting off the throttle. Otherwise the car runs really well, pulls strongly, idles good, sounds great when I can hear it echoing off houses etc. You can hear that all the cylinders are hitting evenly, a clean sound. I'm just curious as to what makes the ripping sound when lifting off the throttle.

Ralph (I need something to do)
Ralph

I'll bite...

Ralph,

I've owned 3 A's. All 3 have had marginal mufflers and made the nice off-throttle note you speak of. If I had to guess, I would attribute this to air leakage in the exhaust system on the muffler end of things.

John
John

My stainless steel exhaust (I think it is made by Falcon) has a lovely tone as described above. I got exactly the same tone with my 1500 engine as I do now with the 1800. My colleague has the identical system but his sound is very wimpish. Must be something in the baffles. Maybe they forget to put any in mine!

Steve
Steve Gyles

The quality of the exhaust note (not the volume level) is affected by the state of tune of the motor, major factors being the correct air/fuel mixture and timing. I have no need for a radio in my car because the resonances produced by my MGA are music to my ears. -M.S.
Martin Straka

Martin is correct, mixture and timing make a big difference in the exhaust tone. I had a 20+ year old Stebro Monza exhaust on my 1500, the pipes were solid but the guts were gone, it was loud but sounded really good: great rumble at idle and nice bark on acceleration. My current Falcon system on the same car sounds OK but pretty tame compared to the Monza.
Bill
Bill Boorse

A slightly hotter cam will give a nice crackle to the exhaust, also. Marv
Marvin Stuart

I always had a good sound from a locally made Mini Cooper S fiberglass packed straight through muffler. Pipe sizes were ok, and it was an oval shape that fitted beside the tank.

I dont know what that translates to in Canada, but it could be worth a look round at your local muffler place.

Ian f
Ian Fraser

I know one answer from first hand experience. New glass pack = mellow and pleasant. Old glass pack = no guts and lots of glory (if you like that sort of thing). See here:
http://mgaguru.com/mgtech/carbs/ex102.htm

Barney
Barney Gaylord

Thanks for everyone's comments. I had a thought today. Do you think it could be in the carb needles? I'm not sure what needles are in the carbs now. I ordered a kit from Scarborough Faire about 8 years ago when I was restoring the car, but I don't recall what the number was. (OK, I guess I lose my SU repair licence, sorry :>) I suspect that it needs fuel flowing under the high vacuum that must be generated when lifting off the throttle. Maybe my needles don't allow that? I don't know if it is possible.

I wondered about the mixture & I checked the tailpipe today and it is the correct med. grey colour. I have recently moved the carbs one flat leaner with no difference in the exhaust sound when lifting off the throttle.

Ralph
Ralph

Ralph

I hear what some of comments say about the state of tuning affecting the exhaust sound. In my case I regularly tune (adjust) the carbs and ignition. All are absolutely spot on and I run 98 octane fuel, but the sound of the exhaust never alters. This was also the case with my earlier 1500 engine. The car performs absolutely brilliantly, never misses a beat. It is a true sports car sound and I love it. I would start to worry when mine does not make that sound!

Steve
Steve Gyles

A comment on the carb adjustments affecting the exhaust note. It was several years ago when I purchased my MGA 1500 with a recently rebuilt motor that was correctly done and all ran well. The carbs were rebuilt to factory specs. It sounded good but not the perfect sound we're talking about in this thread. Making certain all was in cortrect tune and with factory new compression reading for all cylinders. Pulling the plugs at idle showed they were sooty but not enough to foul. Pulling the plugs after a high speed shutdown showed they were lean but not where damage would occur from an overly lean mixture. The tailpipe was slightly dark but within the correct range after a mixed drive of city and highway.

(all ajustment results by seat of the pants and listening to the exhaust)


step 1) Synchronized the carbs with a uni-syn.

step 2) I richened the mixture by several flats which improved the high speed response and sound but resulted in too rich a mixture at idle.

step2) Using the SU needle specs chart I tested the following needles in this sequence (each time adusting the carbs mixtures uniformly using a vernier caliper and synchronizing the carbs with a uni-syn) GS, CC, 6, RO, R6, FA. FA gave me the richer high speed mixture I wanted while still allowing for the correct adjustment at idle.

step4) Tried different piston springs which only drastically reduced performance. The original spec (red?) springs were the best choice, although I replaced the originals with new ones as the old ones expanded to different lengths when removed from the piston chamber - the result was a nice immediate throttle response

step5) Thinned out the damper oil with Marvel Mystery oil which slightly added to the throttle response (quickening the piston movement and momentarily leaning mixture while accelerating.)

step6) Using a gunson color tune (the color change worked for me) I set the carbs to the optimum fuel mixture. - back and forth several times from front to rear as changing one carb's mixture had an effect on the other carb. I found that the rear carb jet needed to be screwed in slightly farther than the forward carb to get the same mixture strength. I was suspicious of this difference in setting and wrote down the caliper measurements, backed off the jet nuts so both carbs were the same, and did the same mixture adjustments using the factory workshop manual where you isolate each carb. When finished I came to the exact same adjustment (venier caliper) as with the Gunson tool. (This difference may be peculiar to my car.)

Each of these tuning steps contributed to the perfect exhaust sound and a more responsive car. Once set I've never had change the settings other than a yearly synchronization of the carbs and a frequent topping up of the thin damper oil. -M.S.
Martin Straka

All said and done the MGA is the best sounding car on the block. I was told by some of the older "experts" that it is a design feaure of the inlet and outlet manifolds as much as anything. Does not explain why the sound seems to live in the 1500, 1600, 1622 and even the 1800 blocks but I have seen a dozen or so A's around here and you can always tell when the come in on the show field before you actually see them. I have a 1622 block in an Austin Cambridge with almost no muffler on it and the thing is whisper quiet??????

Now if we could only package up that distinctive smell!!!!!!!!!!!!
Ralph H .

Hello All,

Three comments:

1) Martin Starka talked about the damper oil. Having had two A's and a B-GT in the mid-west and in Michigan, I found that castor oil (yes, from the drug store) has the right damping action and the viscosity seems to stay the same at 100 degrees as at 0 degrees (no unscrewing the dampers in the snow and pumping them to start the car).

2) Tuning SU carbs can be easily accomplished with two (2) equal lengths of surgical hose; one for each ear. Put the other ends in the carb intakes and match the pitch of the air rush into the jets (this assumes you don't work around jet engines and have lost most of your higher hearing range).

3) Any free-flow muffler (old Abarth or Thrush) really improves the sound. Basically, if you drop a marble down the exhaust manifold and it rolls out the tailpipe, your doing fine with an MGA.

Larry
Larry Gray

All,

I curious. Is the exhaust sound effected if you convert to Webers?

Please advice,

Larry
Larry Gray

I installed a " glass pak " muffler near the rear of the car, and the exhaust sound is not loud. It does resonate when letting the foot off the pedal. It has been on the car since 1987, and still turns heads because of that special exhaust sound. cliff
cliff hughes

As having only owned tractor engine TR's, I can say that a glass pack muff is probably the way to the bark. The TR's are a bit more in the baritone range, but similar, I'm sure. Early ones came without a resonator near the rear, one of mine has a loong glass pack bomb and a long pipe behind it, no resonator. It sounds great, but very little "ripping" on deceleration. The other one has a crimped end Thrush near the end of the pipe only (big outlet), and it rips more. My TR4 has baffle muffs, 2 of 'em, and it's pretty quiet, up to a point - so civilised! I want to replace the rear (resonator) with one that has a proper (r a little bigger) outlet to make it rumble just a bit.

Really off track here, I remember running my old 1200 VW with those tube headers, but without the glasspack once. What an ugly sound that was!! Almost as ugly is the little whistle flutes from the stock VW. My old machinist neighbor put iron pipes in his "flute receptacles" that he'd turned down to fit.

Sorry to lurk, if I ever get any real MG experience, I'll be sure to share. From examining MGA restoration pages, it's one of the better looking cars with its wings off.
Tom

Larry - interested to hear how you would convert to 'Webers'.

One on the engine and one in the trunk? ;-)

If you did indeed convert to a head that would allow fitment of more than one Weber (e.g. HRG) you would significantly change the sound of the engine.

PS - the best exhaust note is a Twincam at 6000 RPM plus with a low restriction silencer......
Bill Spohn

Cliff Hughes-
Hey, I remember you. Your the guy who removed the proper Queen's transmission from his MGA and replaced it with a 5spd. Nissan-Hirohito box from the crashed Jap Zero recently discovered in a Louisiana swamp! -M.S.
Martin Straka

A few years ago my A had that bark, and popped and crackled nicely on the downhill runs. Trouble was the head was knackered.

I put on a new head (Stage 2) and the noise changed, still loud, but then it became clear that the baffles in the exhaust were history. Brown and Gammons replaced it after a little exchange of emails, and I fitted it - crackle and bark gone immediately. It was the same Falcon exhaust.

I can only say that 13 years and a lot of driving had obviously done something to the interior of the old exhaust, and maybe the new one has a different internal arrangement, but it is definietly not the same. I'd have refitted the old one except for attracting unwanted attention with blue lighting! I kept it for a few more years, but trashed it very recently.

Dominic
dominic clancy

Interesting stuff. Like Steve, I have a Falcon stainless exhaust on the B and it sounds very good. Glen Towery commented on what ya'll have described as its "snarl" on decel and it has that sweet spot around 2500 rpm on accel. It originally had the center muffler but made the car so quiet I might as well been driving a Miata so off it came. A tad more brash now but I like it. The PO of the MGA installed a new exhaust which is much too quiet for my taste; time for a little experimenting. Maybe a glasspak...

I think I'll get someone else to drive it so I can hear what it sounds like from a distance. That should be interesting.
Wray Lemke

Wray i'd be glad to drive it for you anytime! You may not remember me but we met at Kenny's one weekend, i was getting parts to put a TR6 gas cap on my B and some other odd bits. Still taking care of my folks in NC, but got the B here, it's going to the paint shop tomorrow, what i'm doing to it is sacrilege to some, but it's my car and i want something a bit different. Hope to have it back together by July 2nd, as it will be the 24th aniversary of the day i bought it. I usually hang out on the B general and tech boards, but am bored waiting for a buddy to get online. Got the A ready to go on the road yet? Take care, Jim Skinner.
LUVMYMG

Absolutely, Jim, I remember your plate and you talking about the apparent sacrilege you were going to do to the B. The MGA is indeedy on the road and a hit wherever it goes. A visit to the hardware store in MP is tough, it takes 30-40 minutes to get out of the parking lot. Everyone, including me, wants to yak about MGs.
Wray

Glad to hear you're getting to enjoy it! Mine went in the body shop today, will be 6 weeks before i get it back, in the mean time still got plenty of parts to clean and refurbish. Might have to take it to the car show this year if i can find out when and where it is.
LUVMYMG

Jim,

If you've restored a car or two before, please excuse or maybe the body shop guy is a good friend and will deliver--otherwise, you know the 6 week quote by the body shop is the universal bodyshoplingo for 6 months!! lol

Stay on 'em man, or it will take forever. You have to visit 3x a week and walk the fine line between being helpful and a pia. Slat towards the helpful-pia and maybe the car will be back in 3 months. Good luck.

Paul
Paul Hanley

Reply to Bill Spohn,

If you have lots of money and less sense, there is an installation for the MGA with the cross-flow head to put two two-barrel, side draft Webers on, but I'm thinking of either a single two-barrel side or down draft installation.

Anyone's comments?

Larry
Larry Gray

That was my point, Larry - that is one Weber, not 'Webers' as you stated originally.

The HRG head with twin DCOEs is here:

http://www.rhodo.citymax.com/albums/album_image/112402/316504.htm

An even better head ;-) with twin Webers is here:

http://www.rhodo.citymax.com/albums/album_image/112402/316518.htm
Bill Spohn

PS - Larry, don't bother with the downdraft Weber - the SUs are as good or better. Waste of money buying the DCD

In fact don't bother with a single sidedraft Weber either - the improvement without doing a tremendous amount of work on the engine is minimal.

1 3/4" SUs are a better bang for the buck.
Bill Spohn

Bill,

What are the 1 3/4" SUs installed on? Do they take a different intake manifold?

Larry
Larry Gray

Thanks SWG!
IW Scott

http://www.rhodo.citymax.com/albums/album_image/112402/78448.htm
Tom

Larry - you can buy a manifold for 1 3/4" SUs on a stock MG head, or you can use an MGB intake and modify the carbs.
Bill Spohn

In cas anyone is still interested in the original topic, I have just de-snarled my ailing stainless steel muffler (for cheap). See here: http://mgaguru.com/mgtech/carbs/ex103.htm

Barney
Barney Gaylord

Weber Answer.

Recently changed from twin 1-3/4" SU's to 45DCOE and found that my favourite crackling and popping sound (When going downhill at 3,000 rpm with the throttle closed) has gone!

The car revs more freely but has lost some of its original character.

Ross.
R Warner

Thanks Barney for your practical advice. I got a much better understanding of SU's from your site earlier. I like your style.
Tom

Question for Barney:

Nice job on the DIY glasspack! Do you think it would be more restrictive (i.e., rob HP) than a free-flow/baffle type muffler?
James Wolff

The Falcon stailness glass pack muffler (as most glass packs) has a cylindrical shell and a perforated straight through center pipe (slightly off center). The fiberglass packing fills the space outside of the center pipe. The fiberglass serves as a damper to attenuate the echo of the pressure waves.

New or used the center pipe is straight through, so if you hold it up to light you can see through it. It is hard to believe that this straight through pipe configuration could be more restrictive than any baffled muffler where the gas flow has to change direction as it passes through the muffler.

However, the effective back pressure may change slightly with or without the stuffing as the resonance characteristics change.

Barney
Barney Gaylord

Barney,
As a straight through pipe the sound deadening is similar to a silencer used on firearms. There should be no more restriction now than there was before, but the expanding gases will lose their force in the muffler.
mike parker

This thread was discussed between 27/05/2005 and 15/06/2005

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