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Fuel tank question

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Greg G.

Freshman Member
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Hey Guys,
I need to replace my fuel tank, and in the meantime all the emissions devices are coming off my 79 MGB. I will be switching to either the Weber downdraft or some SU carbuerators too.

Questions:
Should I get a vented or non vented tank?

If the answer is vented, where should I run a vent line remembering that the vapor collection system will be gone.

Thanks.
 
You can go with the standard newer style vented tank and leave the vent/vapor lines intact (including the vapor separator in the trunk), then just leave the vapor line open in the engine bay as a vent without going to a carbon cannister (then the whole system can be easily restored if need be later) - that's pretty much the way mine is except I still have the carbon can in the engine compartment (although it's empty and merely is a vent). That sort of answers your question - you already have the vent lines in place, I suppose if you insist on removing the vapor separator you can put a piece of fuel line in it's place.

If you don't want to retain any of the hardlines under the car to the engine compartment then you can always use a vented tank but plug the vent fitting and use a vented cap (or make one from a non-vented by putting a vent hole in it).

If you go with an older non-vented tank then you'll just need to get a vented fuel cap. Tony or someone might be able to say for sure, but I suspect the only difference in the later style tanks (between vented and non) is one has the vent fitting on top and the other relies on the cap.

[ 01-09-2004: Message edited by: aerog ]</p>
 
I can't advise re the gas tank but have a definite opinion on carburetion. I installed the Weber downdraft carb and wasn't real pleased with performance & have since switched to dual SU's. Much better in my opinion.
Brian
 
later non vented tanks are a bolt in replacement for the vented tanks and do require a vented gas cap, which can be made by drilling a 1/8 in hole in the mounting flange of your non vented cap. early strap hanger tanks won't work
 
I must ask why one would not use a vented tank and keep the evaporation recovery system??? I know you want to "desmog" your car, but the gas evaporation recovery system does not rob the engine of any performance, nor does it "clog up" the fuel system, but it does help to limit the amount of gasoline and additive gasses that polute the atmosphere. I am not a "tree-hugger" but let's do our part when it doesn't hurt, at least! for our kids and their kids!

That said, I would also recommend the SU's for your use. I think most LBC's look, run and sound much better with that set-up...and the connection to the gas cannister is simple and effective
grin.gif


Bruce
patriot.gif
 
On my V8 car, I took everything off to clean up the engine compartment...plus, needed to move everything from under the car anyway to route the passenger-side exhaust & the return line was in the way...am using the stock vented gas tank but have modified it & will just drill a small hole in my gas cap
 
Thanks for the advice guys. I already ripped out the lines, the canister in the trunk and the canisters under the hood, but I still have them all. My car had the Zenith and it had already been half assed desmogged. So no air pump, many capped off lines, ect., even the breather from the engine block was capped off. It ran like crap. So I really want a new carburetor set up. If it is easy to hook up the vapor collector to the SUs then maybe I'll do it. I really want to keep it simple though. Also the vent line from the tank to the canister in the trunk was broken and I could smell gas while driving. Are there any smells from the drilled gas caps?

Can you run a line from the vapor canister in the trunk to the carburetor without the carbon canisters under the hood?

I appreciate the comments on the carburetors too. I have been going back and forth on this. I really want the car to run reliably.
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Greg G.:
Can you run a line from the vapor canister in the trunk to the carburetor without the carbon canisters under the hood?
<hr></blockquote>

Yes... thats essentially how mine was because the carbon canister is empty, I just left it in there, vented to the engine compartment.
 
I think you misunderstood me a little. I was asking about running the vent into SU carburetors without the carbon canister.

Using an empty canister to vent the tank under the hood like you did is definitly an option but like Bruce74B said why not run it into the carbs and save the earth a little. My question should have been:

Do I use the vapor collector and the carbon canisters to run the vent line into the SUs?

Thanks guys.
 
I wouldn't run the vent directly to the carbs - what if the fuel bowls overflow? you'll be sending fuel directly back to the tank? that could be interesting! the reason for the carbon cannisters was that no fuel would head to the rear & hopefully the fumes wouldn't be strong
 
Greg, Ill skirt the vent line and carbon cannister questions and reply to the carburation. A Weber downdraft carburetor might be attractive for an owner that doesnt understand British SUs or ZSs but the Weber really under carburates The MGB engine. I have also encountered Webers that get problems, they are not foolproof. You do lose significant performance. A side draft Weber is much better over a downdraft for performance but twin SUs have to be the best option. I also would prefer a single Zenith over the downdraft Weber. I currently have a twin side draft carburetor of Japanese origin that I am impressed with for performance but still like the twin ZSs for all around performance and serviceability. If you are interested I will provide the details of the Japanese option.
 
Jack, I agree the side draft Mikuni is a better choice than the side draft Weber - but I also prefer dual SU's!
 
Well live and learn! I thought the purpose of the cannister was to contain the fumes from the tank and direct overflowing fuel from the carbs to the tank, or at least to evaporate it so that it could be sucked back up by the carbs as fumes, hence, a closed system.
 
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