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66 mustang vaccuum idle problem
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cameron c
Novice
Apr 11, 2009, 7:17 AM
Post #1 of 2
(1444 views)
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66 mustang vaccuum idle problem
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66 ford mustang
6 cyl
lots and lots of miles
My question/problem involves my Mustang coming off idle and progressing to 1/4 throttle. Currently it stalls or tries to stall every time. I have put a carb kit in it, new points, plugs, fresh gas, oil, air filter, new gas tank ( old one had rust in it). I have tried to fix carburator type issues and reset it from the manual and the settings don't seem to make a difference. I have come to the conclusion that it might be a vaccuum issue. When I take out the chrome breather on the valve gasket and place my hand over it it sucks my hand into the hole and the car runs better, idles better and doesn't hesitate as normal when speeding the engine up. Does anyone know what this could mean, or whether a 66 mustang should have a breather or should it be a sealed system. ( it does have a return line from the back of the valve cover to the carburator area? What could happen if I seal the filler whole with a newer style valve cap that seals?
I haven't checked my compression yet I need to buy a tester but i think the car needs rings at least it uses oil regularly. I just want it to run smooth at all speeds at this point.
Thanks
Cam
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 11, 2009, 7:33 AM
Post #2 of 2
(1443 views)
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Re: 66 mustang vaccuum idle problem
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All kinds of things possible of course but it's fairly basic.
It should have a PCV and there should be slight vacuum on anything crank case - barely measureable but a good engine will have some because of the PCV. I really thought PCVs were mandated by 1963 or at the latest 64.
At any rate - that's too much vacuum from the crankcase - which include the items on valve cover.
Fuel etc: If this has just the small fuel filter right into carb or right near it consider a larger one before that one as well.
The accellerator pump should be adjustable if you need to make it work earlier in the throttle motion. Find out about the excessive vacuum in crankcase before making adjustments.
You also need to watch the vacuum advance that all is within spec for the engine. Many times it will run consistantly ok with it plugged off and if so there's an issue with it or when it gets vacuum from what source.
Trick: Rust mud in float bowl will usually pick up with a magnet! I would use the screw holding pen type things for installing screw(s) for points and condenser which comes with a nice small magnet at the other end. Just saw those sold new still at Sears by chance so they are still out there. Neat to have for lots of stuff.
If you find the PCV - car should run with it OUT and change idle when you plug it with a finger. If that can draw way too much it's faulty. I don't think they've changed much in many years after that so consider a new one even if it's new I think there's a problem there,
T
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