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Discussion Starter #1
I recently changed from a stock 2BBL manifold and carb to an Edelbrock setup. I decided to plumb the pcv directly into the manifold like this:
http://141.217.51.5/dave/pcv.jpg
The first time I started it up I realized I had a pretty major vacuum leak because of the size of the opening on the manifold. I made up a restrictor to drop into the hole and it improved things somewhat. The problem is that I still don't have a real smooth idle, the engine shakes pretty hard, and it stumbles a little just off-idle. There is also a tendancy to backfire through the exhaust when decelerating. Above 2500 RPM it runs very well.

My questions are;
1)is there any difference between the vacuum port on the front of the carb and the port I used on the manifold?
2)how do I determine what size the pcv port should be?

I guess I should just bite the bullet and use the port on the carb, but I would have to figure out how to adapt the different sizes of hose to each other and I wanted to hear some opinions first.

As an aside, the first time I toook the car out and romped on it both of my old glasspacks blew! Sounds like crap now. What is the optimal size of exhaust pipe for this setup? I am thinking 2.25 would be right, 2.5 is probably overkill for what I've got. The cam is an edelbrock performer, besides the carb, manifold and headers all else is stock c code.

Thanks as always for any advise.
 

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Hi Dave,
Opinion varies but I prefer to plumb the PCV into a carb spacer or carb baseplate because that way all the engine vapors and air is spread amongst all cylinders, not just one.

Betcha #4 is running way lean...

BTW, IME, the PCV does not need any restriction if installed correctly.

In your situation, I'd recommend a 1/2" or 1" phenolic carb spacer and drill and tap the spacer in the middle for a pipe nipple of the appropriate size to fit your hose. That's what I did on the D-coder, although I had to make a 1/2" spacer to allow the stock air cleaner to clear the hood....it works fine.

Hope that helps!
 

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Discussion Starter #3
I had thought of going with a spacer but I plan on switching to a taller air cleaner element and it will be pretty tight space wise. I didn't want to use the port on the carb because it is on the wrong end of the engine, I had wanted a cleaner looking installation but in the interest of running good I will switch it.

Any feeling on exhaust pipe size Pat? Keeping in mind that my exhaust system runs only to the rear axle with turn downs. I have pretty much decided to go with the cheapest turbo mufflers I can find (for the time being).

Thanks for your time.

I want to check the plug from cyl#4. I will report any interesting results. It helps to look at things from a different perspective sometimes. I honestly never thought of any troubles that might arise from my setup.
 

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I don't think the PCV is your problem although I would change the way you have it. Run down to your local NAPA and look at their plastic water hose connectors. Your going 1/2" to 3/8" or something like that I think.

It does sound like you have a vacuum leak. The very first thing I'd do is torque the manifold down again. Be sure to follow the Ford pattern and run through the sequence until all the intake bolts are at torque when you try to tighten them.

Then look over the carb and intake and make sure there is not an open vacuum connection.

There is more you could do, but maybe this will take care of it.

Good Luck,
 

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I ran 2 1/4" on the D-coder, with Dynomax ST's, but that system goes over the axle...

You could run 2 1/2" but I don't know that it's necessary with your combo...that's what I run on the race car

I fabbed up some X-pipes for both and everything clears nicely....I made the systems from mandrel bends and straight tubing and coated it with some of that Hirsch stainless steel brush-on goop...the system on the D-coder still looks fine after 8 years...

BTW, the #4 plug reading will depend on your blow-by...if substantial it may become oil fouled; otherwise, I'm betting it's lean...we'll see...*G*

Have fun!
 

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Did you remember to install the round pipe plug into the back of the carb? The one that the instructions say is for a power brake booster? Did you use teflon tape on it? In any case, since you don't have power brakes, and you want the PCV valve in the back, put a 3/8" pipe nipple in there, and run your PCV hose off it. That will also distribute the blow by to all the cylinders.

Edelbrocks will tend to run well straight out of the box. However, in my application, I found it ran WAY too lean. But all that comes after you get the vacuum leaks resolved.
 
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Just wanted to add my $.02. Instead of using adaptors to step down the hose size off the PCV, get one (PCV) that has the same size outlet as the inlet port on the carb baseplate. Then get the matching size hose. That's the way I did it when I installed my Holley Street Avenger 570. It turned out nice and neat. /forums/images/icons/smile.gif

Jason
 
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