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Adding an evap system

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Blairsville Ed
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Adding an evap system

Post #1 by Blairsville Ed » Sat Jul 18, 2020 7:57 pm

1968 F100 240, Weber 38. 2 barrel carb

Is it possible, practical , beneficial to add an evap system to control gas vapor loss?

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THE FRENCHTOWN FLYER
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Re: Adding an evap system

Post #2 by THE FRENCHTOWN FLYER » Sat Jul 18, 2020 8:11 pm

Blairsville Ed wrote:1968 F100 240, Weber 38. 2 barrel carb

Is it possible, practical , beneficial to add an evap system to control gas vapor loss?


Does that Weber have an evap port on the Bowl? It would be beneficial to add one from a standpoint of a cleaner planet but don't expect any difference in mileage or performance.
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

Blairsville Ed
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Re: Adding an evap system

Post #3 by Blairsville Ed » Sat Jul 18, 2020 8:17 pm

There is a carb bowl vent port.
Summer heat leads to a gas smell in my garage. That’s what I would like to correct.
I’m not sure how it is designed to work.
Gas fill tube needs to be vented?
How does the canister purge? And when does it purge?

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Re: Adding an evap system

Post #4 by Lazy JW » Mon Jul 20, 2020 1:48 pm

I'm pretty sure you would have to address the entire system to be effective.
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THE FRENCHTOWN FLYER
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Re: Adding an evap system

Post #5 by THE FRENCHTOWN FLYER » Mon Jul 20, 2020 2:46 pm

Typical modern day evap systems connect any sources of evaporative emissions - the fuel tank(s) vent(s), the carb bowl vent, the EFI manifold - to a charcoal canister where the vapors are collected. Then, when the engine is in an operating mode, i.e., warmed up, not at idle or WOT, it releases the fumes by applying a vacuum to the canister and drawing them into the intake manifold in a fashion that is not detrimental to the point that a customer would notice it.

It would not be too hard to imagine a home built system that would do the lions share of collecting and burning off those vapors.Fords did this in various ways which included PVS valves, electric solenoid valves, PCV tees, etc.
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Re: Adding an evap system

Post #6 by BigBlue94 » Tue Jul 21, 2020 10:50 am

I would just scrounge the parts off an 80-86 f150 with a 300 in it.

Most importantly is the canister and CanP (canister purge) valve and solenoid. Though im not sure how you will control the CanP valve. The rest is just tubing. Might check Gary's Garagemahal website for a diagram on how the 80s carb systems worked with the CanP system.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

Blairsville Ed
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Re: Adding an evap system

Post #7 by Blairsville Ed » Wed Jul 22, 2020 7:43 am

I think I’m starting to understand the system.
I need a charcoal canister which seems to be easy to buy.
I need to vent the gas tank. Currently I’m using a non vented, 1969 Mustang tank. I’ve read that the vent should have a very small orifice so that only vapor can pass easily and not liquid.
I connect the tank and carb vent to the canister.
Purging could be done using the carb ported vacuum fitting.
It should have a purge valve that does not allow purging when the motor is cold.

Should the purge line use a small orifice? .040?

Am I missing anything?

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Re: Adding an evap system

Post #8 by MechRick » Wed Jul 22, 2020 10:36 pm

Nope, you've got it covered.

When I megasquirt a vehicle, I'll lose the canister purge solenoid. I typically route the hose from the canister to filtered air (always in a partial vacuum because of the restriction of the air filter). Once upon a time, I thought I was breaking new ground, but some older Fords are set up that way.

Running off the ported vacuum port is even better. The only possible hitch is really warm days might make the engine run rich. A restriction in the ported vacuum line should fix that.
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block, stock pistons, ARP rod bolts
Stock cam, aluminum cam gear
Hedman header, full mandrel bent duals, crossover, super turbos
http://fordsix.com/forum/viewtopic.php?f=2&t=73244
Bronco II with a 2.3L swap http://fordsix.com/forum/viewtopic.php?f=13&t=72863
1988 F250 2x4, 460 ZF 5 speed.

Blairsville Ed
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Re: Adding an evap system

Post #9 by Blairsville Ed » Thu Jul 23, 2020 11:10 am

Venting the tank:

I was considering removing the steel filler neck and welding a threaded bung to it.
Would that suffice for the gas tank vent?

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Re: Adding an evap system

Post #10 by MechRick » Thu Jul 23, 2020 11:17 am

Can you use one of the factory rollover/vent valves? It would be much safer in the event you ever turn turtle...

They have to be mounted horizontally, but many of them just use a round hole with a rubber grommet.
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block, stock pistons, ARP rod bolts
Stock cam, aluminum cam gear
Hedman header, full mandrel bent duals, crossover, super turbos
http://fordsix.com/forum/viewtopic.php?f=2&t=73244
Bronco II with a 2.3L swap http://fordsix.com/forum/viewtopic.php?f=13&t=72863
1988 F250 2x4, 460 ZF 5 speed.

Blairsville Ed
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Re: Adding an evap system

Post #11 by Blairsville Ed » Sat Jul 25, 2020 10:03 am

I’m shopping for the charcoal canister and I have a few concerns.
I have a sealed gas tank with a gas cap that has a vacuum valve and an over pressure release. When the outside temp rises there’s a pressure build up in the tank. If the charcoal canister has a port for the tank and the carb bowl, could the pressure from the tank go through the canister and then to the carb bowl vent, effectively venting the gas tank through the carb bowl vent?
Or, does the charcoal canister have one way valves. Vapor goes in but cannot go out.

Purging the canister.......could the tank pressure vent through the ported carb vacuum line causing a flooding condition?
Thus the need for a purge valve, perhaps ported vacuum actuated.

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Re: Adding an evap system

Post #12 by MechRick » Sat Jul 25, 2020 10:27 am

In addition to a purge port, the carbon canister will be vented to fresh air. No pressure buildup should ever occur in a properly operating system.

A good rollover/vent valve will prevent liquid fuel from getting to the canister.
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block, stock pistons, ARP rod bolts
Stock cam, aluminum cam gear
Hedman header, full mandrel bent duals, crossover, super turbos
http://fordsix.com/forum/viewtopic.php?f=2&t=73244
Bronco II with a 2.3L swap http://fordsix.com/forum/viewtopic.php?f=13&t=72863
1988 F250 2x4, 460 ZF 5 speed.

Blairsville Ed
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Re: Adding an evap system

Post #13 by Blairsville Ed » Sun Jul 26, 2020 8:15 am

Pardon my ignorance....

So, the way the system operates is that vapors coming from the carb and tank pass THROUGH the charcoal canister to open air with the HC’s attaching to the carbon grains. Ported vacuum draws air through the canister and picks up the HC’s and burns the air and HC mixture. In a computer controlled engine there’s a purge valve controlling the purge. In a carburetor motor is there a need for a purge valve or will a reduced diameter orifice tied to ported vacuum work? It would be a constant vacuum leak.

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Re: Adding an evap system

Post #14 by MechRick » Mon Jul 27, 2020 12:39 pm

Pass into the canister would be a better word choice.

The old school carbon canisters had a vent with a dust cover on the top. After shutdown, vapor from the fuel tank and carb would push into the carbon granules (from the top) where they were stored. Vapor purge happened either with a duty cycle-controlled canister purge solenoid or a vacuum-controlled canister purge valve, that used EGR vacuum to operate if I remember correctly. During a purge event, fresh air enters the vent, works it's way through the carbon picking up vapor, then enters the carb vacuum nipple. Excess vapor from the tank and carb gets purged also.

Those old vacuum-controlled systems used ported vacuum switches, delay valves, one way valves, etc. Those were the dark days of emission controls, and a nightmare to diagnose and fix.

I would think a system set up to run off the ported vacuum port could be tuned with a restriction to keep it from having a cold startup or hot running rich condition.
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block, stock pistons, ARP rod bolts
Stock cam, aluminum cam gear
Hedman header, full mandrel bent duals, crossover, super turbos
http://fordsix.com/forum/viewtopic.php?f=2&t=73244
Bronco II with a 2.3L swap http://fordsix.com/forum/viewtopic.php?f=13&t=72863
1988 F250 2x4, 460 ZF 5 speed.

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Re: Adding an evap system

Post #15 by THE FRENCHTOWN FLYER » Mon Jul 27, 2020 1:21 pm

I would just start with a simple system using one of these as Rick suggests.

https://www.428cobrajet.org/id-dist-vac-valve

A two port PVS is all you would need but a three port could be used.
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Blairsville Ed
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Re: Adding an evap system

Post #16 by Blairsville Ed » Sun Sep 06, 2020 7:03 pm

Update:

It took a while to get it installed but the system works well. No more gas smell in my garage, however, purging through the ported vacuum line caused the vacuum advance to stop working. I used a .045 metering hole but it still dropped the vacuum signal to the distributor. Next I’ll try a metering hole of .020 on a T fitting on the PCV line. I’m trying to keep the purge as simple as possible. I’m just not sure how much purge flow is needed.

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Re: Adding an evap system

Post #17 by THE FRENCHTOWN FLYER » Sun Sep 06, 2020 8:36 pm

Do you use a ported vacuum signal to the dist or full manifold vacuum? I prefer ported.
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Re: Adding an evap system

Post #18 by sdiesel » Sun Sep 06, 2020 11:28 pm

Fascinating conversation thank you for posting this Ed
a long love affair with the 300 six.
my lastest and final fling is a fresh 300 in an 88 ford f350 dually 4X flatbed

Blairsville Ed
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Re: Adding an evap system

Post #19 by Blairsville Ed » Mon Sep 07, 2020 8:31 am

I use ported vacuum for the distributor advance. I’m guessing that the ported vacuum signal is weak so a split in the signal weakens it to the point that the advance diaphragm will not pull in.
I’ve seen port vacuum switches that open the purge line to manifold vacuum but for now,
I’ll try a direct line to manifold vacuum to purge the canister with a metering device in line. Maybe a .020-.030 Orifice.

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Re: Adding an evap system

Post #20 by Blairsville Ed » Wed Sep 09, 2020 7:03 pm

All is working well.
I picked up a 3/8 brass T and put it on the PCV hose. The 90 degree side of the T went to the purge port. For metering, I put a 1-1/4 long piece of 1/4 brass round round in the purge side of the T. The T bore is .265 that leaves .015 clearance around the brass round to meter the vacuum going to the purge port of the canister.
I also turned down 1/4 inch of the brass round So that it wouldn’t obstruct the pvc feed.
It pulls a light air Flow through the canister but doesn’t affect the idle Rpm.
And... no gas smell in the garage.

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Re: Adding an evap system

Post #21 by THE FRENCHTOWN FLYER » Wed Sep 09, 2020 9:25 pm

congrats
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