it actually runs better WOT than anything, no misses that i can tell of and it pulls pretty hard. You got any places to look for a leak that I might be missing or how to detect it?
i dont remember it early on, i have been building this car for 2.5 years, finally done, it has about 600 miles on it total since i drove it a little bit once it was streetable. But I do remember putting a fancy PCV valve in the valve cover from summit racing...it is in the passenger side valve cover and has a hose that runs into the base of the carbeurator. Is that supposed to run into the air filter instead?
PCV usually goes to the carb base or to the carb spacer between it and the intake manifold, if so equipped. Just for the heck of it, plug the hose and see what happens. The system is designed to work with the air from the PCV but the result might indicate a vacuum leak elsewhere. It won't hurt the engine.
Normally, in a closed system, there is a hose from the air filter housing to a valve cover breather/oil separator. Under vacuum induced by the engine intake process, fresh air is drawn into the engine and crankcase fumes are drawn out through the PCV valve and into the intake manifold, where they join the air/fuel mixture and are burned in the engine.
let me clarify this because i think we have found the problem...
A typical PCV valve for a normal car would probably expect to see about 20-22 inches of vacuum at idle, however, my cam is only expected to produce 12 inches at idle, which means that the spring in the valve would overcome the vaccum and open, creating a huge vacuum leak. That would also make a lean mixture in the intake and hard to idle cause a need for more advance. Now when i put it in gear, the load increases on the engine, vacuum drops even more, aggravating the situation and opening the PCV valve further, creating a larger vacuum leak and there is my problem.
That would make sense why it runs pretty good WOT because the valve would be open anyway to let the blowby back into the intake. That is what I get for buying the shiny universal PCV from summit.
Like I said, remove the PCV and try it. You won't break it
Here's what I do on the race car:
Two oil separators tied together into one hose going to a puke tank. Note the breather on the puke tank. In the old days people just ran breathers on the valve covers and vented to atmosphere. Stinky but simple.
Sometimes you have to get simple to find a problem. You should end up rich when you block the PCV. If you're not, I still think there's a vacuum leak somewhere.
kdillard21, do what Pat said and cap the PCV hose where it goes into the the back base of the carb and run it. Is it better or worse? This sounds like classic vacuum leak.
You might want to fill out your profile with the details of your car and engine set-up.
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**Never drive faster then your guardian angel can fly**
Hi Pat, and getting older every day. Dang, I can build a brand new 1965 Mustang from parts, how can I build a brand new old guy? Where IS that catalog? .....
OP, If it falls to an idle slowly then that points to a vacuum leak. Only problem with that is normally a vacuum leak wouldn't let the idle drop clear down like yours is aparently doing. Are you running a Pertronix ignitor in the distributor? I noticed you were talking about the coil as if it were replaced and many times people install those together and incorrectly.
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**Never drive faster then your guardian angel can fly**
As a matter of fact I do have a pertronix ignitor on the distributor and a flamethrower coil. How else can they be hooked up? I thought it was straightforward...
I never had a ballast wire, I am using a single wire alternator and a painless performance wiring kit, so everything was new, but the flamethrower coil didn't require a ballast resistor anyway in the instructions. And the PVC troubleshooting didn't change anything, idled the same after plugging it.
Already retorqued the manifold (a couple of times actually just to make sure) 20 ft/lbs. The brakes are manual and the transmission is an AOD, no computer or vacuum modulator (just a throttle valve cable that controls shifts). Ironically, whether I set the idle out of gear at 850rpm or 1050rpm, it drops to 650 rpm when its put in gear. That makes no sense to me.
Last edited by kdillard21; 11-03-2009 at 07:13 PM.
Since the issue wasn't apparent when the engine was new, something must have changed. We've eliminated nearly all of the easy stuff.
When you put the new carb on, how did you set the idle mixture? Also, out of curiosity, if you were to unscrew the idle speed screw until the throttle plates bottomed, how many turns would that be?
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