Unbalanced Carbs can cause engine damage ??

PS. I've already got a Gunson Carbalancer

Colour tune are good, a very cheep way of getting accurate carb tuning results. Ideally though for your set up you would want two but you can do it with one and move it from side to side. Andy

You will risk damage if one carb's mixture is seriously weak, but there are

2 elements to tuning twins. The rough running is mainly caused by unbalanced throttles, which (if the mixtures are reasonably correct) won't cause any damage. You could have the mixtures spot on with the Colortune but still have unbalanced airflows. So you need to balance both mixtures and throttles.

You will not cause any damage by not having the carbs set correctly. To get a reasonable balance just use a length of garden hose, use this to listen to the hiss from each carb, it is fairly easy to get an even amount of hiss. Then slow the tickover back down again ! recheck. It is then best to check the co level. Then you need to ensure that when the throttle is pressed it opens both carbs at the same time.

mrcheerful

Carb balancer was/is a load of crap as it has a lack of damping unless you have 4 pots sucking smoothly on each carb like a V8 Rover with twin SU's. What you need is a vacuum gauge (with restriction to damp it) and whatever tappings are needed to plug/screw into the vac take off on each side or port. One gauge and a multi-way fishtank air valve will do, a single port fishtank valve will do as the restriction set it to give less than 1/2 psi flutter and leave it alone. A vac gauge will tell you so much more about the engine than an air meter.

Usually on multi carb set-ups one carb is master and the other(s) slave. Set the tickover, set master to give correct vacuum, set 2nd throttle to give same reading as master, switch between the two and check they are exactly the same but will not be correct vacuum as engine speed will change, re-set idle on master to give correct vacuum, move on the next throttle and match that to master, adjust idle to give correct vacuum, do next throttle etc. Finally switch gauge between each port in turn to double check. On some each bank is set up to a master on that bank and then a final adjustment is made on a cross link to match each bank.

Colour tune only works in the dark and then you can't see what screw you should be messing with. Colourtune only sets mixture not carb balance. If you have messed with the mixture screws lightly bottom them all and adjust to middle of number turns in book. eg 1 - 1 1/2 set at 1 1/4. Then take it to an MOT test station, most will do an emissions check for free.

-- Peter Hill Spamtrap reply domain as per NNTP-Posting-Host in header Can of worms - what every fisherman wants. Can of worms - what every PC owner gets!

On a similar note, just got the heap (Volvo 240 estate, 140K miles) back from the MoT, and the emissions seem amazingly low compared to the limits (vis 0.09% CO - against 3.5% limit and 151 ppm HC against 1200).

I assume that this is from running v. weak, though I have noticed no overheating / pinking / running on / difficult starting and it's difficult to tell if its gutless given that they have no go to begin with.

Any thoughts please.

MW

PS : to confound things even more its been well sodded up under the bonnet, with an after market Weber carb, the idle emmisions controls disconnected and points ignition in place of the original electronic - I assume it died before my ownership.

I reckon you can get just as close with a stethoscope and your ears.

The message from Mark W contains these words:

I've had carburetted cars this low with no ill effects. Yes, it's usually 'cos they're lean, but what it's doing at part throttle is anyone's guess. That's why that part of the MOT is a bit daft.

In news: snipped-for-privacy@argonet.co.uk, Dave Plowman decided to enlighten our sheltered souls with a rant as follows

I worked on a Ferrari Daytona replica (in fact, I helped build the bloody thing) a few years ago.. and balancing the carbs on that was an utter, utter, UTTER pain in the arse. Jag V12 with 6 downdraught Weber 45s.

I'm proud to say I've not balanced a single carburettor since :-D

Not after having been roadie on a college disco that did support for Dire Straits, Toyah, The Motors and everyone else on the college circuit in the late 70's early 80's. Not after having been in the paddock for 5 seasons vintage racing on open pipes and megas.

I have a huge hole in my audio spectrum, I think it is centered just at the pitch of the female voice.

Place I work for takes on apprentices at 16, gives them hearing tests and they get perfect results. Others are taken on from uni at 21, 18 months later after grad training they get full time posts and a hearing test. Result - hearing shot to hell in 6 years of nice quiet studious living.

-- Peter Hill Spamtrap reply domain as per NNTP-Posting-Host in header Can of worms - what every fisherman wants. Can of worms - what every PC owner gets!

So how do you do that then? :-)

"Pete M" realised it was Fri, 07 May 2004 18:58:20 GMT and decided it was time to write:

FYI: single carbs don't need balancing.

In news: snipped-for-privacy@newsfeed03.glasvezel.net, Yippee decided to enlighten our sheltered souls with a rant as follows

Er, thanks for that!... learn something new every day

Right, I'm off to do the tracking on a Reliant Robin.. spose I'd better fit this new thermostat to that '71 Beetle while I'm at it. After that I'll fit the rear seatbelts to a TR7..

LOL - I'll be thinking of you while I'm rustproofing the front wings on my Delorean and changing the cambelt on the girlfriend's Mk1 1300 Escort. It's probably the hydraulic tappets causing all the bloody noise anyway but doing the cambelt first is easier and I'll get to the potentially expensive stuff once I've tried that. Hopefully that'll leave me free tomorrow to change the spark plugs on the Passat Tdi if it ever stops effing raining.

Dave Baker - Puma Race Engines

I'm not at all sure why women like men. We're argumentative, childish, unsociable and extremely unappealing naked. I'm quite grateful they do though.

Lucky man.

Geoff MacK

In message , Pete M writes

The worst I've done is balancing the individual butterflies on a PI TR6.

Not a hope. if you think that, you don't even understand how a stethoscope works.

Some people manage with a length of hose _and_ a home-made bracket. It's important to place the hose end back in the same position relative to the throat on each venturi. Most people just don't have the ears for this though.

Best flow measure that you're likely to find (with some difficulty and searching of autojumbles or eBay) is the Crypton swinging plate device. Another useful flow-measuring gadget that you might find S/H is a Velometer - two pitot heads and a differential manometer. The Gunson thing is rubbish though.

Colourtunes are wonderful. Get one per venturi and you'll save a lot of time. If you have a carb Rover V8, the cross-over inlet manifold means that you can;t sniff per-carb mixtures from the tailpipe, even with twin exhausts. You could drill a sniffer port in each branch of the exhaust manifold, but 4 Colourtunes will set one up in no time.

An Alfa with DCOEs is an easy car to balance the carbs on. Just check there are no air leaks and away you go. _Much_ easier than balancing multi SU or Stromberg setups.

Thank you kind sir. And I've been using one for all the years I had cars with carbs. You live and learn. Did anyone tell the stethoscope it can't be used for listening to things?

BTW, how do you get a different flow through a venturi without it producing a different sound?

In article , Pete M writes

Err beetles *do* have thermostats ;-)

Or at least, my combi did