• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

74

Share this page

B

backyardmechanic

Freshman Member
Offline
74 MGB, So far I have replaced the distributor with a new one with electronics. It has a new weber conversion. I have replaced the spark plug wires. I drained the tank and put new fuel in it since the car had not been run for about 10 years. I have set and reset the timing and have gone through the carb tuning as described, I have installed a new fuel pump, filter and regulator and set the pressure to 3.5 psi. It is running a lot better than when I first took this project on but It still does not have any power when driving. It appears to idle ok but under load it sputters and sometimes backfires.
I bought a book on the Webber carb and am going to undertake the job of removing the carb and rejetting. There does not appear to be much information on how to determine the correct jets,etc. I can not seem to determine if it is running too rich or too lean so I am not sure what the appropriate jets, etc.I should be ordering. Is there anybody out there that can give me some advice about how to determine what selection of jets and other parts I should order? I suppose If I order two sizes over and two sizes under what I have now and just keep trying trial and error I may be able to hit the right combination. Seems like a lot of trouble.
Thanks for any advice Backyard Mech.
 
My first WAG is to pull th' Weber off and go thru it. Sounds as if it (backfire) is dumping fuel. It's not so easy to diagnose from just "backfire" as the descriptor but if it's "reporting" from exhaust you've got a fuel excess.

I'd be for pulling the carb off and insuring the thing has good seats and seals at all the jets and such. If it sat for that long you've got to be thorough with induction.
 
Some people say incorrectly that spitting back thru the carb is backfireing. If its doing that its probably too lean and if its a true backfire then go with what Doc is saying and consider it too rich. Thats if all else is really correct. Also is the mechanical advance working on the distributor? You should be able to grab the rotor and turn it a bit and then feel it return to its original position because of the small springs in there. Bob
 
I'd pull the Weber off & see if anybody needs a good door stop! & then, install the original carbs.
 
You dawg, Tony. :jester:
 
Thanks for the advice. I have gotten so frustrated with messing with this weber carb conversion that I have considered taking it off and going back to the stock stuff. I can't understand why I can buy a new carb for my old Ford truck slap it on and drive it away but the Weber seems to require all this special treatment.
It is indeed spitting back through the carb and not puking out the exhaust. I went through the initial set up as described by Pierce (the supplier of the Weber conversion)and this process indicates that the idle jet may be too lean. I am going to take the carb off and order new jets.
thanks again for the input.
backyardmech.
 
Teglerizer.com has good info on Weber jetting/setups you might find rewarding.

Now is it a downdraft or a sidedraft? Downdraft, if you can get the originals might be an easier application. Sidedraft, slug through it, when done it will reward you nicely.
 
Thanks for the reply. What I have on the car is a new Pierce manifold and down draft Weber 32/36 DGV carburetor conversion kit. I just got finished talking with a Weber tech at Pierce Manifolds and he is going to send me some new jets that are larger than what I have in the carb now. I will try the new jets and see if that works. If not maybe I will have some expensive door stops and the Irishman that owns the car will have a nice classic MGB lawn ornament after I tow it back over to his house.
Cheers
 
Back
Top