I believe 70 or 71 A-bodys went to charcoal canister and no cap venting. I wonder if a vent with a one-way valve would work?

You are talking about the pump pulling enough volume to collapse the tank, so not as much flow needed to exhale gas fumes.

Seems like this would only be a problem with really high flow of fuel where you are actually burning the fuel and not recirculating it back to the tank via the return line. Likely not a problem with a 300HP or less motor unless you are full throttle all the time. My guess is a vented cap would work.

Lou

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Home of Slant6-powered fun machines since 1988

I have just a stock vented cap on my 73 Suburban EFI....it can burn $500/day fuel....or $40/hr if you prefer while towing at 75mph.

The 3 gal fuel cell on my bogger has a tiny vent......

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Sam, please send pics of the tank when you get it. I would love to see how they modify the tank and the efi pump design the use.

I will be happy to take a few photos, and share them. I don;t know how to post a photo myself, in spite of the photo in my signature. But I can send them to anyone else who can post them.

Comments and questions, Does the charcole canister take the place of the vent in the cap? It seems like the have different functions, and as if the flow is in the opposite direction. I don;t know. Does the cap vent flow in and out? Is the cap vent for relieving internal pressure as well as vacuum? It seems as if the charcoal canister is only for relieving pressure. I am just generating a theory here that is not grounded in technical knowledge. Otherwize known as BS. Once the external surge tank is gone from under the hood, I will be able to put the charcoal canister back in its place.

This car has always smelled like gas. What ever venting I end up with, I want to get rid of the gas smell, if possible. The smell is strongest with the window open just a crack. So I suspect the smell is coming mostly from the trunk, as opening the window a crack creates a low pressure system inside the car.

I would love to see a diagram of the GM system. I would suspect their concern is mostly emissions compliance. In Maryland, they test the sealing of the gas cap in the emissions test.

Sam

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I also would love to see photos of an A body tank with Internal EFI pump. At the moment I am running a surge tank under the front guard/fender of my '61 Val, this has a GM pump fed buy the mechanical pump as per Sam's. This system works well but is a bit noisy when stationary, an in tank pump would be much quieter.
Mal

That all looks really neat. It must be a race car, or it never rains in your neck of the woods. It always shocks me to see the brakes on the "Wrong" side. You must have had this all down for a restoration, as clean as it is. What did you do with all the EFI wiring clutter that usually goes with MPI?

Sam

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I am unable to find clear diagrams to post but here is the reply from my brother:

The diagrams just show lines drawn. But a talked to a couple other guys here and we all agree, the primary amount of air would come through the canister vent solenoid and the charcoal canister. There is no way the stock cap will vent the volume of air needed. I highly doubt that it will collapse the tank, most likely it will just slow the pump down and you will loose fuel pressure.

I’d suggest welding a bung on the top for a rollover valve, like a fuel cell has.

He also stated that the factory vents are controlled by the ECM. A solonoid adjusts the amount of "venting".

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Chris'
Autobody
Restoration
Service

Hi Sam

It's not a race car we use it as a second road car and tow a caravan on trips. It doesn't rain much here 10" per year if we are lucky. The wiring etc. is all there compare it to when I had the SUs only.

The SU's are cool too. I remember tuning up my friends Austin Healy back in the sixties by listening to the sound of the exhaust. Did that car run strong with the SU's?I see what you mean, but you have been very efficient, and very neat with your wiring. You should see the mass of wires running around under the hood of my car. Congratulations.

What are you using for a throttle body? Are those heater lines running to it?

Sam

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It ran well with the SUs on a cool day. They don't like the heat here in Central Aust, I had vapour lock problems and our ULP does not have the additives the old fuel had to stop vapourisation. So I have gone the fuel injection road for reliability.

I used mainly GM parts from our local V6 Commodore which is similar to your 3.8 litre Buick engine. Throttle body, injectors and all the sensors are from the GM range. ECU is Delco 808 with Kalmaker programmable chip.

http://www.kalmaker.com.au/page2.html

I ground out a 2 barrel manifold and fitted the Commodore throttle body.

It runs a MAP system.

Fuel rail is a modified Australian Ford Six they are steel so easy to cut and shut. I have made a complete new one since the photo but it looks the same only a bit neater.

I'm planning something similar to what Sam is getting except strictly diy and thought I'd take a minute to explain my plans and reasoning.

First off I'm going in tank for three reasons their quieter, they run cooler, and if properly placed they have a slight reserve capacity in those little sock filters they use meaning that if temporarily run dry (think sloshing) the full filter will collapse allowing the pump to suck up that tiny amount of fuel before sucking air then refill as soon as its wet again.

I don't plan on adding any sort of sump but do plan on some sort of baffles or a small tray possibly with a trap door or two. The stock one in my jeep cherokee appears to hold about a quart and is baffled to keep bubbles from the return away from the pickup. I'll probably go just a little bigger but thats already close to 15 seconds or so at 255lph(walbro)

As for fuel pumps I haven't decided yet whether I'll use a GM pump from a syclone/typhoon or the slightly larger LT1 pump (ep381) which is probably the "vette" pump Sam is getting, or a Walbro unit which are said to be a little loud.

I guess I need to read the emissions control section of a newer factory service manual to have a good answer to the venting issue but I do know newer cars run a slight vacuum in the tank and get mad (check engine light) when they check for it and it's not there.

Also for anyone doing this themselves be sure to use efi hose rated for in tank use.SAE 30R10 its hard to find but alot of the people who sell pumps have it. DON'T USE R9 (or r7 for that matter) it will turn to mush in the tank and eventually burst.

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1970 Vitamin C Duster 225 2bbl 904 eventually turbo efi r154 5 speed

1969 B5 blue roadrunner 383/727 soon to be turbo slant (JK)

1972 Barracuda was green 318 who knows?