car was going great but i only drive it every few weeks so anything can happen i guess. it generally doesnt idle until slightly warmed up but on this occassion wouldnt idle well at all. got it to 180 after taking it for a drive and when i back of throttle there was a ticking noise. get home and told the gf to play the throttle while i look around enging bay. yep there it is the hose from pcv to manifold is collapsing. i pull the valve and blow in it and it operates fine . it rattles when i shake it so it seems ok but ill get a new one tomorrow and see what happens.the noise seems to come from the maifold vacum T rather then valve itself but its hard to tell..... if the problem is still there when i get a new one tomorrow what would you think it is?

 

My PCV valve ticks too. It alarmed me at first , but every one that I put in did the same thing, so I am assuming that it is normal.......As far as why it is not idling correctly, that could be anything from bad gas, gas filter, plugs, a loose power wire , dirty carb, etc, etc, etc.....You get the picture.....Start wit a tune up and go from there...

 

thanks jeff. good info. it did seem a lil low on power so i will check those plug leads in the morning. im going to replace vacum hose as well .

 

check your crankcase breather, where ever it is, valve cover etc. if you are running those baffled rubber grommets, that could be your problem as some of them are actually sealed shut because of the rubber not having an open slot.....there is sometimes flashing over of the vulcanizing process that leaves them plugged almost solid....if there is no flow through in the breathing process it will collapse the vacuum hose...good luck.....

 

It may be, that you need hose designed for vacuum. Some fuel hose used in a hi vacuum situation will colapse. Just a thought.

 

Shane
Where is your PCV valve plumbed to? The reason I am asking in your original post you said the noise seems to be coming from the vacumn T rather than the valve. Are you using the port on the carb that the PCV valve goes to for anything else?

 

Almost all carbs have a port for a pcv that is balanced to all cylinders.
Tick can occur if installed in just 1 runner.

 

The hose that came off would have continued to run to the base on your carb. That's how the engine fumes (coming from the valve) get burned off. With that hose loose, the fitting on the carb base just created a big vacuum leak. You need to buy the correct type of (non-collapsing) hose for PCV system use; then hook it up properly and your idle problem will disappear.

 

update
-got new pcv today . no difference so can rule it out
- bought new thicker hose that wont collapse
-cant set timing or idle as it fluctuates. for 5 seconds its fine sitting on 700rpm then it will quickly rise to 1200rpm.that i would tghink is a vacum leak but i sprayed carby clean around everything and it didnt make engine pick up.
- my pcv is routed air gap manifold.demon 750 only has 3 points. 2 small forward ones which i use for kickdown and vacum advance and the large one at rear im using for my brake booster.
-im now going to garage to do all jeffs tips on fuel filter,clean bowls etc etc
-midyear breather is all clear. valve covers have built in plate underneath that are non restricting.

 

Here is a pic of the underside of a Holley similar to yours.
You can see how the large 3/8 port is channeled to both sides of a split plenum so that the pcv vapors will be distributed evenly to all cylinders.

I like to connect only the pcv to this port and the brakes can be connected anywhere on the manifold separately, they don't care.

Sound like you may have a vacuum leak in addition.

 

update
-i agree noonie. been looking for a leak like crazy but cant find it.
- i have just returned from garage. pulled carb. stripped and cleaned it. fuel was clean( poured bowls in to dish to check)
- timed it again and it seemed a lil easier after the carb clean. i find my timing is very sensitive.th tiniest of movements and its all over the place.
- i reset my plates to .020 or at least pretty close.
- one thing i noticed is if i hold carb to the sun i can see around the plates as they dont sit perfectly around the edge. check out the pic.
- on my way for a drive now and some fresh fuel. will report back soon.

 

Could the HEI control module have 'bit the dust'?

 

possible something in my ignition has bit the dust 7t1 but its a msd ready to run with external coil ( master blaster or whatever they call it). only 2 years old and only driven every few weeks so i havent heard of any failures in that short time but who knows.

 

im back from my little drive. its running ok but something is off. idling on about 700 in gear. put it to neutral or park and it goes up to 1200. it never used to do this. it would only be maybe 200 rpm difference between in gear and out of gear.

 

everyone i just wasted 3/4 of a nice saturday . i have now found the problem or should i say problems( i think) it wasnt just 1 and without all your help i could not have done it so thankyou. i could take pictures but now after all this i just cant be F*** so ill just write it up ....
1) found that vacum leak, wouldnt believe it kickdwn vacum had the smallest little rupture in the hose. wasnt making any noise at all but spotted it on the bend where it comes out of the carb vacum port.
2) throttle cable was not adjusted correctly. was ever so slightly pulling on the throttle not allowing the carb throttle springs to return all the way giving me that erratic idle.
3) my aircleaner has the fitting on the underside for a breather. im normally always carefull in my positioning of the aircleaner but in my lazyness i was allowing it to cause clearance issues on the ( correct me if im wrong but is it the squirter pump) on the opposite side,rear of the throttle connection.

it seems to be going fine now and it might take some fine tuning but not today. the footy semi final is on here and i plan on getting a carton and getting on it !!!
thanks again.

 

It usually turns out to be the simplest, least expensive things..That's we we love the SB's !