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quote:
Originally posted by PanteraDoug:
My difficulty at the moment is engineering in a PCV system with the Webers off of a vacuum manifold.

There isn't enough volume of vacuum left to pressurize the brake booster. Just getting the PCV system to work means finagling with internal restrictions in the line to the pcv and loosing 2 in-hg at idle.

Problem is there are no pcv valves that close 100% at idle. They are all open a little.


Doug, check out this product, http://mewagner.com
I also did not want to bleed off vac at idle because I have a large duration cam and I cannot find a "performance" pcv. I have bought quite a few, some have just a small hole and are rated at different vac levels. There are also people who threaded a screw on the top of a regular pcv valve to adjust it. I bought one of these valves but because of the cold weather and bolting on other parts, I am not sure when I will get to test it. Try it risk free for 30 days and you can get an inline adapter and it can be mounted in any direction / orientation.
quote:
Originally posted by bdud:
quote:
Originally posted by PanteraDoug:
My difficulty at the moment is engineering in a PCV system with the Webers off of a vacuum manifold.

There isn't enough volume of vacuum left to pressurize the brake booster. Just getting the PCV system to work means finagling with internal restrictions in the line to the pcv and loosing 2 in-hg at idle.

Problem is there are no pcv valves that close 100% at idle. They are all open a little.


Doug, check out this product, http://mewagner.com
I also did not want to bleed off vac at idle because I have a large duration cam and I cannot find a "performance" pcv. I have bought quite a few, some have just a small hole and are rated at different vac levels. There are also people who threaded a screw on the top of a regular pcv valve to adjust it. I bought one of these valves but because of the cold weather and bolting on other parts, I am not sure when I will get to test it. Try it risk free for 30 days and you can get an inline adapter and it can be mounted in any direction / orientation.


I already investigated this one. If you read the information you will note that they do no claim the valve to close 100% at idle. That is the issue for me.

What I currently have is an Allen set screw that is drilled with an orifice of .060" or so (maybe I used 2mm?) that is installed in line to the PCV valve.

What it does is instead of me having 14" at idle it reduces the leak to only 2". That leaves me with 12" at idle.


Considering that I have 74 degrees of overlap with this camshaft that is a very strong vacuum signal. Even 12" would be good.



IF there was a PCV valve that fully closed that would solve much of the problem. As far as I can determine there is not. These valves are $2 parts and the quality of the construction is as cheap as you can get. The design intent is there with them but the execution in building them is not.

The combination of low VOLUME of vacuum signal (not strength) created by the IR (individual runner) manifold and a 5/8" vacuum tube to the brake booster creates an issue that even a one gallon storage tank in line does not fix.

I am still in progress with this vacuum refinement. Too cold to run the engine right now. Got up to 18 this morning. Webers don't like that.

The issue was complicated by a non-functioning check valve at the booster. I've replaced that but still haven't pressure tested the booster itself to see if the internal diaphragm is shot (kaput). Considering this is the original booster to the car, that is a distinct possibility and if it is rotted out could be the problem right there?

I may have to take my own recommendation and send this booster to Harmon brakes and let him rebuild it?


At the moment, this is a very, very complicated issue and I need to backtrack to identify basic problems that I may have overlooked.

The availability of the vacuum pump is comforting and the fact that there is no one anywhere that I can find that has run a PCV system with a Weber set up makes me a trailblazer. That is a task which I detest but often find myself immersed in.

I thank everyone for the input. Hopefully I will be able to remember all of these options but I suspect that it may be just that scenario of the elephant hiding in the bowl of M&M's and everyone else sees it but me?

Confucius say, "never set a cannon to kill a mosquito!" Well ok, but he never said anything about a machine gun? Ask Ted Nugent.
I am not sure what vacuum the dual valve uses at idle, it talks about adjusting it with a gauge and reading 0-1", but this might be the port for setting the valve up and not what the valve will allow at idle. They designed the valve to allow some vacuum at idle and increased flow at cruise.
I did use a GM truck pcv at one time which is just a small hole, not sure it helped.
quote:
Originally posted by Detonator:
I have a hard time grasping the concept of needing to add a vacuum pump, is the engine not a giant vacuum/air pump, I would think a check valve and manifold pressure would be all you need? what am I not understanding?
I am being serious what did I miss?


In order for the engine to be the vacuum pump itself that will operate vacuum accessories like the brake assist booster, it must provide 1) pressure to the intake manifold (source of vacuum). That pressure is measured in inches of mercury rather that in pounds per square inch.

The reason is it is a negative number if stated in psi and that confuses too many people 2) the engine needs to produce the pressure across a large enough hole in the intake manifold. In the case of the stock Pantera that hole is 5/8" and the minimum pressure is 15in-hg.

Camshaft timing, most specifically the overlap of the camshaft, i.e., the amount of time both the intake valve and the exhaust valve are open, effects how high the manifold pressure will be.

These engines when new and "stock" produced about 16 or 17in-hg.



When you change to a longer duration camshaft with more valve overlap, the pressure produced in the intake manifold drops. Almost always under 15. Sometimes as low as 7 or 8in-hg at idle.

That isn't enough pressure for the accessories to operate on.


In my case, the design of the intake manifold does not have a common plenum. Each runner to an intake manifold has it's own. It's own carburetor as well.

In order to get a reading of the combined vacuums being produced by each cylinder, the intake runners need to be connected together to each other in some way. Sometimes that connection of plumbing to which they all connect is called a vacuum manifold.

In the case of independent runner manifolds using carburetion, not fuel injection, you have to minimize the amount of pressure lost into that vacuum manifold to insure that you can still tune the strength of the fuel mixture, or more correctly stated, minimize the amount of leaning out of the mixture due to the interference of the leak of cylinder pressures into the vacuum manifold.

The vacuum manifold on mine, as with many with Webers is made from 1/4" od metal tubing, and is strung together in series like a Christmas Tree light bulb set.

So the pressure can be read accurately now with a vacuum gauge because of the vacuum manifold, but the quantity of vacuum (negative pressure) does not add up to the amount you get from the 5/8" inside diameter hose that would be connected to an intake manifold with one common plenum under one carburetor that would supply the entire engine with atomized fuel.

I've also introduced a PCV valve into the equation by connecting it to the vacuum manifold which equates to a 2in-hg loss, AND I had to restrict that to keep it at only a 2in-hg loss at idle. So now I have 12in-hg at idle. This is not enough pressure, and not enough volume of pressure to operate the brake booster.

So one possible solution is to use a vacuum pump to supply the accessories, in this case just the power brakes because it is not dependent upon the engine itself to produce the vacuum. It is a self propelled vacuum pump producing up to 22-23in-hg on demand.

Get it now at all?
quote:
Originally posted by Detonator:
Yeah for me the V8 NA carbureted concept is somewhat new, spent most of my life building high HP 4cyl turbos, completely different concept with standalone ECU and boost.


My son built a SC Contour SVT. 3.0Liter. Quite a handful to keep running at full boost. Supercharger keeps breaking. Very quick to 140. Dynos only at 285.

Never did turbos. Always wanted to do a Covair Spyder. Factory limited to 6psi. Had a '63. Car had other issues. Two piece flywheel riveted together. Came apart on me at about 100.

Probably what really got me interested in the mid-engine concept of the Pantera though.

Son #2 has an '02 Audi TT 1.8 Turbo. 6 speed. Very very quick under boost. Probably over 300 hp. Great straight line car. Quatro makes it go straight but not through the curves.

Can't handle though. Only good for 35-40 mph on an off ramp whereas my Taurus SHO (275dyno) is good for almost 70 and the Pantera spun out at 90. The SHO handles. The Pantera is just plain filthy. Pantera with Webers.

Two more stablemates. 68 Shelby GT350 347, 5 speed, 2x4 Holleys. 67 Shelby GT500.

6 cats. One retired Greyhound racer. Two outside cats. All interesting toys. Keeps me busy.

I probably learned the most by breaking them all (the cars) at one time or another and having to fix them all by myself. Some things come hard but you NEVER forget.
quote:
Originally posted by Detonator:
Cool stuff, yeah my last project was 91 turbo mr2 300whp fun at the auto cross.


Sounds a lot like the Audi TT. Quatro keeps it from spinning the tires but doesn't help it handle until it's doing 90 to 100.

It's ironic though. Center of gravity is as low as the Pantera's and corners flat. It just doesn't bite in the turns.

I don't drive it enough and know that each car needs to driven one way to make it handle. The TT is still a mystery. Haven't found the secret yet.
Way off-topic, Detonator, but superchargers may not be your best choice for a stock 351-C block due to the thin cylinder walls that flex under high boost- for a while. Then they crack, and good blocks are getting scarce. Nitrous is a little better since it's only a momentary overload, much like Corvair turbos which were originally meant as a sort of 'passing gear'. If big power with decent vacuum for brakes is what you want, I'd look at a big-block conversion in a Pantera. There are quite a few around. Some will pass smog tests while delivering scary power.
quote:
Originally posted by Detonator:
I still have two 351c blocks n heads I am going to rebuild, one is the Australia block so that one for sure, nope no boost on this car the 351w made 500hp on the engine Dyno so I am good with that, I hope not to have vacuumed issues when everything is said and done, got STI for boost lol.


You need to have the Australian block sonic tested. Apparently many of the cylinder bores are too thin to make them worthwhile to use.

That could be a reason someone along the line sold the thing to begin with. In my opinion from feedback I've heard on them, that is very likely.

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