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Discussion Starter · #1 ·
I know they work well in in drag race applications, but what about a street car?
 

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I agree with RC Man. You won't really see a benefit of reduced crankcase pressure and ring sealing at street rpms.
 

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Discussion Starter · #4 ·
well i have a set of headers with the valves and pipes in them, willl have any trouble runnign this system?
 

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1) you need to replace the check valves at least every year

2) If you have a complete exhaust system, you will pressurize the engine....

Cranckcase evac systems are designed for high rpm, high cylinder pressure engines,,,,WITH NO EXHAUST !!!

the backpressure caused by the mufflers will cause the engine to pressurize just like trying to fill yer gas tank with a 3" hole in it. The gas will run out as fast as you pump it in. But if the hole is only 1". it will slowly fill up.
 

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That is not true, i have good vacuum thru mine with my good motors. Yes you can use it on the street, and especially you should use that style evac system when using a manifold with the vac plug out of 1 intake runner unless you like leaning out 1 cylinder (air gap intakes included in this)
 

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Well they are doing something wrong then, all my motors use a full exhaust with mufflers and pull at idle as well as under full throttle, exhaust is more than just stick these on there and weld this in like that, if they put the tubes in the collector wrong then it won't pull at any rpm
 

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Matter of fact im using the same evac on the trucks motor, since i don't want that 1 cylinder running out of balance do to that single runner vacuum port in the air gap
 

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how do you figure single runner vacuum port ?? it is connected to 4 ports, not 1.

Explain this to me....as I am running the air gap too.

The only diff I see between this and the M-1 dual plane OR factory cast iron is the vacuum port on the airgap is on #8 cylinder runners, and the other two are on #5 cylinder runner.

# 3, #2, #8, & #5 runners/ports all all connected, so if vacuum is pulled off one, it is equally pulled off all 4....that's basic physics.

And I fail to see how a vacuum port location will have anything to do with a crankcase evac system....or how it will lean out any cylinder........unless that vacuum port is open to the atmosphere, then you have a vacuum leak, which is a whole other story.
 

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Evildriver-3 said:
Well they are doing something wrong then,
Well, Ed, I have seen them run.......I'd say come down here and prove them wrong, but if yer not running faster than 8's in the 1/4, you'll get yer feelin's hurt.
 

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Think about it, your pulling from 1 runner not the plenum, how can it be equal pulling off 1 runner.

I know guy's running 6's that make mistakes, just because they run 8's doesn't mean they put the evac tube in correctly.

If they want they can come here and pull the hose while it idles, or they can put a piece of paper/cardboard over it and wait to see if falls off.
 

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go look at your intake ed. the runners are all connected for one side of the carb. If you were to turn the intake upside down, put tape over the carb mounting surface, and pour water in the #8 runner, it would fill the runners for #2, #3, #5, & #8, because they are all connected under the carb.

OR, go find or borrow a dual plane intake (off the engine), and hold your hand over the port for the for #2 cylinder, and put an air hose on the port for #5 cylinder, and you will feel the air thru the intake, or better yet, put the hose in the vacuum port...same thing.

This is why when you flow test the intake, you bolt it on to the head, and you have to block off the other 3 runners or you will suck air in thru them and get false readings. A dual plane intake has 2 plenums...and each plenum connects for of the runners. All the air has to go thru the carb mounting surface, or you will not be flowing the intake correctly.

If you really think that the 4 runners aren't connected, then explain to me the reason for a dual plane intake ??

4 runners are connected to one side of the carb (plenum), and the other four are connected to the other side of the carb (plenum). If they are all individual and not connected, then you don't have a dual plane The reason a dual plane is more effective on the low end, is BECAUSE these runners are seperated from the other half (carb too). If they weren't, you'd have a single plane intake, or an individual runner intake.
 

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Evildriver-3 said:
Think about it, your pulling from 1 runner not the plenum, how can it be equal pulling off 1 runner.
Because the plenum connects the 4 runners......

Just like if you could measure it....you pissing in the atlantic ocean will raise the water level in the pacific ocean too.

Even IF the vacuum tree was connected to only 1 runner, it would still be impossible for it to lean out that cylinder, unless that tree is open to the atmosphere. When you draw a vacuum on something, you remove the air from inside it, but you do not KEEP removing air, as long as the system is closed.

Take a hand vacuum pump, and put a hose on it, and plug the hose real good. Now, pull a vacuum on that hose. Once you get to 20", stop. Does the vacuum stay there (it will if the hose and your plug is good). Do you have to keep pumping on the hand pump to hold it ?? NO !!!! So, once you draw a vacuum on all the lines from that vacuum tree, then you will hold vacuum there, and no air will move , so it will not lean out the cylinder.

If you still don't understand, take a old milk jug, put yer mouth over the end, and suck the air out of it until it collapses. Then hold it (your breath) and do not move. As long as you do not breathe in or out, it will stay collapsed. But when you breathe out, it will no longer be collapsed.

As long as the other end of that vacuum line on that vacuum tree is closed, or goes to another diaphragm that is good, it will not add any air to the intake runner at all. BUT, if it has a leak, it will.

Regarding the evac system:
The exhaust flow thru the collector is what draws a vacuum on the evac system. If you have an exhaust system, which induces backpressure, you will not have a lot of vacuum, and definitely not as much as no exhaust system would be. If you had vacuum and no back pressure with a full exhaust system in place, then how can you have header collector gasket leaks ??? If it's a vacuum as you say, it would suck air in, not blow it out. it's not, so you can have a collector gasket leak. The same pressure that causes this, will cause the evac system to fail if the check valves do not seal perfectly.

Yes, it CAN work, if you have perfectly working check valves, and a very free flowing exhaust. Otherwise, the chances of problems with it are much greater. One piece of trash on the check valve seat, and it wil not seal, and will no longer work.

Here in the real world, most things don't work perfectly.

Ed, at this point, you're really causing me to doubt your understanding of physics and how an intake, exhaust system or even vacuum works if you think the runners of a dual plane are seperate, and if you think a vacuum line (with no leaks) will cause a cylinder to lean out, and if you think you can produce enough of a vacuum on an exhaust system with mufflers to not have any collector gasket leaks due to pressure in the collector (yes, I know, you never have gasket leaks) and a bad or loose gasket.
 

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Problem is you are pulling after the plenum, so when you already start down that runner and add something to it it isn't balanced, the 4 runners are connected to the plenum on 1 side, but the vacuum port is on 1 runner after the carb after the plenum effecting only 1 runner to 1 cylinder not all 4 equally so in turn actually even doing it in the plenum you only effect those 4 cylinders a reason why you would use a plate beneath the carb and install the pcv or brake booster to that, why would you want to make an effect to only half of the motor or 1 cylinder.

You are sucking thru the pcv valve to 1 cylinder not 4, unless you know of a theory that when the # 8 cyl sucks thru the pcv valve it equals the other 3 cylinders.
 

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You can have all the doubt in the world about you and your friends exhuast systems, but not mine, i have no exhaust leaks in any part of my exhaust.

As the exhaust and it's pulses pass the evac tube which is installed to make a low pressure point and draw or suck out the psi in the motor, so if you don't have it installed correctly then you have a problem.

The check valves are only for back fires in the exhaust nothing else, they do absolutley nothing for helping the evac system.

So you are saying to me that sucking wasted crankcase oil fumes into 1 cylinder through 1 runner is good and is balanced on cylinders 3 - 5 - 2 and are all experiencing that loss, you do know that the dual plane is set up to work with the firing order and each side of the carb works that set of cylinders in that sequence.

So you think that when cyl 3, 5 or 2 draws in it sucks runner 8 into them, and when cyl 8 draws the runner 8 vacuum port is adding to help that cyl fill evenly and as balanced as the other cylinders.


Try this, get a straw put a hole in it's side add another straw and connect it to something with positive pressure and then suck in see what happens at the straight end that would be your plenum. Then lose that positive psi side of the straw and see how it works

Your plenum is where everything is equal, adding a positive psi crankcase with junk spewing from it past the plenum into the # 8 cyl runner where it would be negative psi for a moment and would draw all this crap in is not equal.

 

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Evildriver-3 said:
Problem is you are pulling after the plenum, so when you already start down that runner and add something to it it isn't balanced, the 4 runners are connected to the plenum on 1 side, but the vacuum port is on 1 runner after the carb after the plenum effecting only 1 runner to 1 cylinder not all 4 equally so in turn actually even doing it in the plenum you only effect those 4 cylinders a reason why you would use a plate beneath the carb and install the pcv or brake booster to that, why would you want to make an effect to only half of the motor or 1 cylinder.
ED, have you ever heard of flow reversion ??? It will cause all 4 cylinders on that plenum to flow equally (in so far as how they would be affected by a vacuum leak), no matter which intake valve is open. When the flow is going to #2 cylinder because it's intake valve is open, the flowrate thru the other 3 cylinders on that plenum will stop, same as when #8's intake valve is open, it's flowrate goes up, while the other three stops. There is NO FLOW thru the runner for a cylinder if the intake valve is not open. Sorry, it's just physically impossible for air to flow thru a shut valve. Just like there is no flow thru the straw you are sucking on if the end of it is blocked with ice, or the bottom of the cup.

You are sucking thru the pcv valve to 1 cylinder not 4, unless you know of a theory that when the # 8 cyl sucks thru the pcv valve it equals the other 3 cylinders.
Why the heck do you have your pcv valve connected to the vacuum tree ??? It is supposed to be connected to the vacuum port on the bottom of the carb, so that it's fumes get dispersed evenly to all 8 cylinders. If you have the pcv connected to the vacuum tree on #8 cylinder, your causing your own different set of issues.
 

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TRCM i never said it flows thru all the runners, you said there all connected and are equal, does it matter if it's the pcv or whatever is connected to it, either way that runner is different and not equal to the rest that aren't having anything branched off it.

You are totally missing what im saying
 

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Evildriver-3 said:
You can have all the doubt in the world about you and your friends exhuast systems, but not mine, i have no exhaust leaks in any part of my exhaust.
I have no doubts about their exhaust, or mine...because they follow the laws of physics. Your trying to tell me yours doesn't. That's where the doubt comes in.

I also fully expected you to say you have no exhaust leaks, because I knew you would not understand what I said.

Ok, so you have no exhaust leaks. Good boy! Now, go out and loosen the bolts that hold your collector to your exhaust, and break the seal on the gasket, so that you CAN have an exhaust leak. Then start your engine....you WILL have an exhaust leak now because there is a path for exhaust gases to take that is shorter than the rest of the exhaust system. Every time the exhaust valve opens, it PRESSURIZES the exhaust system, and since it is easier for the gases to come out there than thru the remainder of the system, it will.

If I believe what you are saying, about the exhaust system not being pressurized, then YOU won't have a leak there, and YOU don't even need gaskets to seal the collector housing, but everyone else in the real world does.

If the check valves are only in the evac system for engine back fires, and since your engine runs so well it NEVER backfires, then take the check valves out of your system, and see if it works.

As the exhaust and it's pulses pass the evac tube which is installed to make a low pressure point and draw or suck out the psi in the motor, so if you don't have it installed correctly then you have a problem.

The check valves are only for back fires in the exhaust nothing else, they do absolutley nothing for helping the evac system.
I agree that the tube is positoned to allow a vacuum to be developed, and that if it is installed wrong, it will not work correctly. I DO NOT agree that the check valve is there for exhaust back fires.

Every time an exhaust valve opens, it increases pressure in the exhaust system. This pressure is what closes the check valve. If the check valve was not there, that pressure would go into the crankcase. This is NOT a back fire..this is normal engine operation. The check valves help the evac system by ensuring flow is in one direction only.

So you are saying to me that sucking wasted crankcase oil fumes into 1 cylinder through 1 runner is good and is balanced on cylinders 3 - 5 - 2 and are all experiencing that loss, you do know that the dual plane is set up to work with the firing order and each side of the carb works that set of cylinders in that sequence.
Yes, I know this, and I understand it and how it works with the laws of physics. It is you who seems at this point to have your pcv in the wrong place, and who does not understand fluid dynamics and flow, or flow reversion, or the fact that if you draw a vacuum, or put pressure on any closed system, ALL portions of that system feel the vacuum or pressure (the runners and plenum are a closed system for all intents and purposes). Read the previous reply.

So you think that when cyl 3, 5 or 2 draws in it sucks runner 8 into them
Yes, it does...no way around it, unless you have a way to change the laws of physics. It won't draw the complete runner volume in, but it will draw some of it.

and when cyl 8 draws the runner 8 vacuum port is adding to help that cyl fill evenly and as balanced as the other cylinders.
Well, on your engine, it will draw air off the cranckacse, which is basically a vacuum leak, and a dirty one at that. It should be drawing off the brake vacuum booster, which is sealed, hence no vacuum leak, and no change in intake charge dilution.

Try this, get a straw put a hole in it's side add another straw and connect it to something with positive pressure and then suck in see what happens at the straight end that would be your plenum. Then lose that positive psi side of the straw and see how it works

Your plenum is where everything is equal, adding a positive psi crankcase with junk spewing from it past the plenum into the # 8 cyl runner where it would be negative psi for a moment and would draw all this crap in is not equal.
ED.....your example is actually a good one, but, at the rpm the engine runs, the flow you are talking about would never make it thru the straw, it would oscillate back and forth....hence the term flow reversion.

The reason you put the pcv on the carb base vac port, is so that it is constantly being sucked on by the flow thru the carb....constant mind you, as long as the engine is running, because the carb throttle plates are always open feeding the engine. Flow in a single runner is NOT constant.

If the engine is turning 3000 rpm, the carb has constant flow thru it to allow the engine to run. At this same 3000 rpm, the runner for #8 cylinder only has flow thru it 3000 times a minute. That is not constant.

Or better yet, for an engine to run, the carb has to supply all the air/fuel to it..right ??? OK, the carb is supplying 8 cylinders, so each cylinder see 1/8th the flow the carb does at any given second, since you are only filling one cylinder at a time (and yes, I know sometimes more than one valve is open at once, but that would complicate this far beyond what is needed). Do you understand that ??

So, by having your pcv on the vacuum tree on #8 runner, you are only gettign 1/8th the flow thru the pcv that you would get if it were at the carb base, like it should be.

You have your pcv on a runner, which is NOT constant. Flow thru the runner is only happening when that runner's intake valve is open. So that flow oscillates with the opening and closing of the intake valve. I would not be surprised if you have oil residue in your #8 runner, because as the flow oscillates in the pcv tube, the oil in the fumes can drop out of suspension, and you will get oil fouling on # 8 cylinder, since the weight of the oil will not allow it to get to the other 3 cylinders on that plenum, because the rpm of the engine will be too high. Air, on the other hand, can move that fast.

Flow can only exist if there is an open flow path. So, you can only have flow thru #8 runner when #8 intake valve is open.

The reason you can read vacuum on the intake manifold from any runner, no matter which intake valve is open, is flow reversion, and the simple fact, that I have been trying to show you, that if 4 runners are connected, and only one has an open flow path, air will go thru that path.....no matter what.

So, when you have #2, #3, #5, & #8 runners on the same plenum, flow will thru which ever runner's valve is open at the time, no matter which runner you are reading. And because of this, a vacuum port on one of those runners will provide flow to which ever of the connected runners has it's intake valve open, even if it is only a slight flow increase due to the length of the runner and the extremely short time the valve is open.
 

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Evildriver-3 said:
TRCM i never said it flows thru all the runners, you said there all connected and are equal, does it matter if it's the pcv or whatever is connected to it, either way that runner is different and not equal to the rest that aren't having anything branched off it.

You are totally missing what im saying
No ED, I fully understand what you are saying. The problem is, you either are refusing to understand/consider/think about what I am saying, or you aren't able to (I don't think it is the last part).

What you are saying is correct to a point. If the engine rpm is high enough, the flow thru that vacuum tree will not fully make it to all the other 3 cylinders, but it WILL make it to the plenum, which will get it to where everything is mixed up, and it WILL eventually get to the other cylinders on the next rev of the engine. At low rpm, the distribution is equal, at high rpm, is when it becomes like you are saying, but it is NEVER completely like you are saying. So, unless you run your engine above 5000 rpm ALL the time, it won't matter.

I am basing what I am saying on the laws of physics and math.

I canprove what I am saying is correct, and if you want to drive down here, I'll be glad to show you using pictures and reference material, and even on a flow bench.

But if you can't look at this with an open mind, and consider that you may not be correct, typing it in here won't do anything but make our fingers tired.

And if what you are saying is true, then there is no reason to have anything but single runner intakes for any engine. All engines would have a single runner for each cylinder, and no plenums would be needed. Since things aren't that way, there has to be a reason.

If you were to look at the percentages (on a street engine), what you are saying happens is correct .01% of the time, and what I am saying is correct 99.9% of the time (regarding these issues). ON a race only engine, it is more like 50/50. I'm not saying your always wrong and I'm always right, because we both know that ain't true, but on these issues, I can prove what I am saying, and there is no physical way for you to prove your point. It's just not physically possible.
 
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