PVC not necessary...do this

[Roger/Sacramento]

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.

[Kahuna]

Hi roger
Can you provide some more details of that idea?
I think the idea is very sound.
Thanks
Jim

[Roger/Sacramento]

Kahuna.....I am not sure what you need to know. The pictures should help with the explanation.

[Mike B]

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?

[51 MERC-CT]

Sounds like the tube to the exhaust pipe is like a 'wick' used to ignite blowbuy gas in the crankcase.

[scooder]

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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.

[Roger/Sacramento]

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.

[34PKUP]

Originally Posted by Roger/Sacramento

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.

And do you really think that you can get it far enough back for an engine backfire not to effect it.??

[rick r]

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.

[Lawrie]

There is no suction in the exhaust it's under pressure how do you think it gets out to the tail pipe.
Lawrie

[51 MERC-CT]

Originally Posted by Lawrie

There is no suction in the exhaust it's under pressure how do you think it gets out to the tail pipe.
Lawrie

Not necessarily true, think about how a home type grit blaster manages to suck grit out of the container.

[dude]

Originally Posted by rick r

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.

Better system .

[Jack E/NJ]

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

[Roger/Sacramento]

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.

[CA Victoria]

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.

[51 MERC-CT]

Originally Posted by CA Victoria

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.

Sort 'a like this---

[Roger/Sacramento]

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.

[Jack E/NJ]

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

[51 MERC-CT]

Originally Posted by Jack E/NJ

51 Merc>>>Sort 'a like this--- >>>

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

Duly noted and corrected, thanks
Probably should have named the first one, 'flame path to crank case'

[FlatheadTed]

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

[scooder]

Roger, the hole in your exhaust that you've fed the crank case vent into. Disconnect at this point and put your finger over both holes, the one in the exhaust and the breather pipe end, tell me the pressure at these points at idle, mid rage and high rpm. Apart from having a burnt finger, I'm purty damn sure the higher pressure will be the exhaust. Which way do you think the gases will travel? It won't wear out, I have to agree, but it won't work I'm sure. Like I said the proper evac systems rely on the scavenging action of high speed exhaust gas, they don't work at street rpm levels. And they must have a check valve of sorts, other wise you'll fill the crank case with exhaust gas, and only when/if you get the exhaust speed up to a point where it will pull from the breather pipe, will it have any chance of pulling the crank case gas out.
Think your barking up the wrong tree here. If you find it doesn't have the negative effects I talk of please let us know.
Martin.

[Roger/Sacramento]

Here is what I believe. There will be pressure from the exhaust to go out the tailpipe and there will be pressure from the engine to release out the pex tube. They will co-mingle and gleefully travel along until they release into the clean California air.

[Jack E/NJ]

Try the scooder finger test anyway. Just to be sure. 8^)

Jack E/NJ

[51 MERC-CT]

Originally Posted by Roger/Sacramento

Here is what I believe. There will be pressure from the exhaust to go out the tailpipe and there will be pressure from the engine to release out the pex tube. They will co-mingle and gleefully travel along until they release into the clean California air.

If you do install a tube in the tailpipe as you have illustrated, before hooking it up to the engine a way to check your theory is to connect a water column tube to see if in fact there is a vacuum.

[Mike B]

I think the exhaust tube would have to be dimpled, in order to create a venturi effect?...or would would the tube just have to be installed at a proper angle? In order to draw?

[Mike51Merc]

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A properly running engine (without much blowby) does not have pressure in the crankcase seeking an escape. This is why PCV systems rely on engine vacuum to pull the vapors out and also why draft tube systems rely on road draft to pull as well. Crankcase pressure is generally neutral, except that heat will cause the air to expand and seek an escape. Once the engine is hot and it escapes, the pressure is equalized and generally neutral again, except for blowby which is only significant if your engine happens to need a rebuild.

I think your device will only succeed in filling the crankcase with exhaust. If it does work, you'll be filling your exhaust with oil and water vapor.


Interesting concept, but perhaps an easier method is to buy a pulse fuel pump that allows fuel to pass through and do a typical PCV conversion.

[Diavolo]

As mentioned before, the draw needs to come from where the road draft tube is/was. There are air flow schematics that clearly show this. While I can see your point in scavenging, the whole purpose of a PCV is "positive crankcase ventilation".

IMHO, it is one of the only smog designs implemented before year 2000 that actually has a positive and useful effect on an internal combustion engine. It is certainly one of the best ideas. By actively sucking crankcase gases out of the engine, it not only actively keeps those gases and moisture out of the engine, it reduces or removes positive crankcase pressures, reducing oil seepage.

[Ol' Ron]

Man, I lov this Forum, Thood Ginking Guys.

[BILL WZOREK]

Work or not / I like the thought process / That is how things use to get solved
Talking over the pros & cons of something / sometimes it will let you see a problem that you may have over looked.