Dual Carb Tuning

[matt_s]

Hey, I helping my Mom get he MGB back on the road for the summer and all that is left is to get the dual carbs tuned and an alignment. Does any one know either a good link on how to do it or someone or a shop in Courtenay that will do it and not charge a arm and a leg?

Thanks
Matt

[stevo911_]

are they sidedraft (webber DCOE's, mikuni PHH's, dellorto DHLA's) or your run of the mill downdraft?

[matt_s]

Umm yea they are Side Draft. I think they are aftermarket carbs to, I would have to double check that one though.

[stevo911_]

If they're sidedraft pray that they're webers (WAY easier to find jets for), your best bet would to be trying to track down either a mechanic that works on old european cars or something along the lines of an Alfa-Romeo club. I've got a set of Dellorto sidedrafts i'll eventually be putting in my car and finding jets absolutely blows (unless you want to pay way too much or ship them from england)

[Fleemer]

you might be able to get away with just syncing them. Otherwise you're lookign at taking them apart and cleaning them depending on how long the car sat their for.

I'd take off the float bowl side and clean out all the jets etc with carb cleaner and put it back together. Easy. Then to sync them you need a tool or a homemade device. Theres a few good links on google for your homemade carb syncer

goodluck, and thanks for the rx7 parts :P

[matt_s]

Originally Posted by Fleemer

you might be able to get away with just syncing them. Otherwise you're lookign at taking them apart and cleaning them depending on how long the car sat their for.

I'd take off the float bowl side and clean out all the jets etc with carb cleaner and put it back together. Easy. Then to sync them you need a tool or a homemade device. Theres a few good links on google for your homemade carb syncer

goodluck, and thanks for the rx7 parts :P

The car has been sitting for YEARS but we try to start it every year. It hasn't been insured for probably 9 or 10 years now. So really it hasn't run much.

I'll find out what carbs are on it and take a look around town for shops who work on the old European cars.

No problem, hope everything worked out with the parts your got. I'm really wishing now that I didn't give up and part it all out HAHA...

Thanks
Matt

[m1ataman]

A good mechanic who does work on air cooled VW's should be good at dual carbs too if that helps you.

[oldskoolz24]

Try getting a hold of someone from the Old English Car Club branch in Courtenay, they would know who to talk to.

http://oecc-comox.com/

[Hondatech]

What the hell is a carb?

[Fleemer]

Originally Posted by Hondatech

What the hell is a carb?

ancient form of technology that introduced fuel into the cylinders without the use of any electronics of any kind

I think they use some kind of black magic... apparently all the wizards of the time died off and their secrets with them. now we are stuck with these fuel injector thingies.

[Black SC2]

Originally Posted by Hondatech

What the hell is a carb?

You're old enough to remember the steam engine. What do you mean "what the hell is a carb?"

[NashMan]

it's this box with littel elf's in that dump gas into a hole that feed's the motor

[snootworks]

What year is it? Early ones had SU's, and later ones had POS Strombergs.

[DragonsMaw]

Pray for the early SU's before they added coolant routing for the automatic choke.

They're pretty easy to take apart, when I rebuilt mine I think it was $25 worth of gaskets each plus a new set of jets. I'm on the mainland though and was really close to Octogon Motors. The only wear that I can think of that might need professional rebuilding is if the butterfly valve shaft has worn through the housing. Otherwise taking it apart and cleaning it real well should do wonders already. Assuming everything else is in order anyhow.

Oh, on top of jets you might want to replace the valve over the floats in the float bowl. Forget what it's called but the design of it changed over the years. It's basically a small tube with a ball bearing in it. When the fuel level rises in the float bowl the float pushes it and restricts the gas flow.

But yeah, what year is it and is it stock?

[matt_s]

Umm the car is a 1971... But like I said I'm pretty sure it has aftermarket carbs, I'll find out tomrrow and post up if it does.

Matt

[matt_s]

Umm so the carbs on the MG are "SU" carbs.

Matt

[DragonsMaw]

There's a section near the bottom of this page that details where the screws are for dual SU HS4's. I used this when I was starting but the rest is probably too much detail.

Details the whole process but doesn't have large images. Especially of the tools.
Personally I just took apart a stethoscope if I wanted to do a ballpark tune. Doing it properly means measuring how much the interior carb piston rises or drops in response to changes to the other carb.

Good articles but all text. Looks like most of the links are borked.

Same deal, bit more concise maybe. Sorta.


Z-Therapy used to have a fair number of linked articles and guides but it looks like they've taken them down.
Remember, that carb setup came on a lot of different cars, such as the 240Z even so searching for MGB specific resources might turn up dry while looking for Leyland or Triumph material might help a bit more.


Also most of those links came from the first page of 'tuning dual su carbs' on google.

Search for carburettor as well, limeys and their strange ideas on english.

[DragonsMaw]

Oh also, there's a tool called the unisyn. All it does is float some balls based on the airflow going past the throttle, measuring by venturi effect. If your carbs are balanced the idea is that they'll rise and fall in unison if the carbs are balanced.

Small picture here

Some discussion on it here.