PVC not necessary...do this

Roger/Sacramento

Roger/Sacramento

Senior Member
Right now I am using an electric fuel pump and a mechanical fuel pump in line with each other. I want to eliminate the mechanical because it cannot pull the fuel thru the electric pump if I exceed 2000 RPM's. The fuel line from the mechanical pump to the carbs is a solid stainless setup. I have gutted a spare pump and blocked off the lower half with a stainless plate to allow the fuel to pass thru the gutted pump to the carbs. I have wanted to eliminate the stock draft tube so I have installed a brass fitting in the lower portion of the gutted pump to allow for a 1/2" plastic tube (PEX) to connect to a brass fitting in the passenger side exhaust pipe. The exhaust passing by the brass fitting with cause a vacuum which will pull fumes from the interior of the motor.This setup will solve two problems and still appear stock.
 

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Hi roger
Can you provide some more details of that idea?
I think the idea is very sound.
Thanks
Jim
 
I think I get it, wold like to see routing to the exhaust pipe please...seems like a short piece of tubing to reach?

And how does it do at idle?
 
What stops the exhaust gas going up that pipe and into the valve area?
I know these "exhaust evac" systems exist, it's not quite as simple as what you have explained. The exhaust system has to confer with the evac, they only work when the exhaust driven "vacuum" is stronger than the check valve in the breather pipe part. It has to pull it open. I believe this system also needs some real nice tuned length headers in order to create this vacuum or negative pressure through efficient scavenging to work as best as it can. The exhaust needs to be moving fast in the right direction to do this, The angle of the sucky pipe needs to be right. Street driven flathead, how often do you think this setup will actually pull from the crank case? Not sure it will do a proper job on any street driven engine. It's designed for all out high rpm race situations.
Martin.
 
Re: PCV not necessary...do this

WOW my head is spinning. The red tube shown is just a sample. I have a longer piece which will be cut to length. I have Fenton headers on my engine. The connection point will be south (depending on which direction I park) of the header flange. The exhaust will not be hot enough to ignite anything coming out of the engine. Also there is an internal pressure that will seek an outlet so the exhaust suction will go hand in hand to remove any smoke product from the valley. The red tubing is actually modern hot water piping that has replaced copper or galvanized in house construction. Who would have ever thought that would happen. What is next ? Plastic electrical wire ? I will have to install a plug at the draft tube opening to seal off the system.
 
Re: PCV not necessary...do this

Roger/Sacramento said:
WOW my head is spinning. The connection point will be south (depending on which direction I park) of the header flange. The exhaust will not be hot enough to ignite anything coming out of the engine.
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And do you really think that you can get it far enough back for an engine backfire not to effect it.??
 
My solution- removed the draft tube and plugged the hole with a frost plug, drilled the frost plug and installed a gromett to fit a pcv valve from a 283 Chev and connected the pcv valve to a vacuum port on the intake manifold.
 
There is no suction in the exhaust it's under pressure how do you think it gets out to the tail pipe.
Lawrie
 
rick r said:
My solution- removed the draft tube and plugged the hole with a frost plug, drilled the frost plug and installed a gromett to fit a pcv valve from a 283 Chev and connected the pcv valve to a vacuum port on the intake manifold.
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Better system .
 
I think Roger's setup would rely more on fairly weak exhaust gas entrainment than true Bernoulli vacuum. Accordingly, the tubing should be bigger and at least partly filled with stainless steel scouring mesh as a flame arrestor. Sealing off the road draft tube with such a system probably wouldn't be a good idea either.

Jack E/NJ
 
Re: PCV not necessary...do this

I too thought of going with the one way valve, but it can eventually fail and I don't like the idea of running smoke into either the carb or manifold. What I will do is simple and never wear out. It is a by product of solving the pump problem and only works on that basis.
 
Interesting, the effect of the Venturi at the port of entry should be measurable. Most Venturis are designed by speeding up,the air flow over the suction tube. Since the need is to remove a gas it makes sense. I'm not an engineer, will be interesting to hear more on theory.
 
CA Victoria said:
Interesting, the effect of the Venturi at the port of entry should be measurable. Most Venturis are designed by speeding up,the air flow over the suction tube. Since the need is to remove a gas it makes sense. I'm not an engineer, will be interesting to hear more on theory.
Click to expand...

Sort 'a like this---
 

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Re: PCV not necessary...do this

This system will have warm weak smoke meeting a hot weak exhaust. That should not need a flame arrester which is necessary when raw gas gets a spark.
 
51 Merc>>>Sort 'a like this--- >>>

Looks like your venturi diagram isn't sucking correctly. 8^)

Roger>>>That should not need a flame arrester >>>

Maybe not, but for 99 cents for a couple of scouring pads, why take a chance of a crankcase oil mist explosion.

Jack E/NJ
 
A PC valve works on throttle off ,max vacuum ,like carb heat risers you may get the reverse ,a flapper valve and temperature gauge to monitor may be needed .Ted
 
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