I found some very small vacume leaks and need some opinions.

Headlight actuator relays ,wiper door actuator and vacume can leak

Head lights go up & down very good, wiper door works well

My question is......... how adversly do these leaks affect the performance, do you guys think that with the small leaks the motor is running to lean.

I finished the tune up & added a new holly carb & set it up and disconected the vacume line and the car runs great. I have not tried it with the vacume line connected. I could only get 37 total advance.

Thanks for your help in advance

Butch

 

36 is the total with vac. line off at dist can.Read your plugs after you drive for awhile-your little leaks are probably OK until you want to spend the time and money to fix.

 

Thanks for your thoughts Roger, I checked the plugs and so far look good, I'll take another look after about 50 miles,

I was hopeing I could wait untill winter to change out what is leaking,
like I said everything run by vacume works good.

Butch

 

Small (4") wire ties can be used to snug up the vac hoses. For TOTAL advance, the vac needs to be ON & RPM brought up to 3000 or so.

 

I have no idea what year car your talking about as your profile isnt filled out...but

On my 73 I had a leak somewhere.
I pinched off the manifold vacuum line which controls the headlights/vents ect with a pair of forceps and the car idled nice and smooth again
The leak was coming from the manual headlight over ride valve
I replaced the valve and its fine now.

Basically what Im trying to say is
If you think its effecting your performance, pinch the line off on the intake manifold... just behind the carb and you will know instantly

 

---That would be maximum with vacumn on !!---for TOTAL (inital and centrifugal) leave vacumn off !!

 

Roger, total was 37 with vacume off.........Thanks

Bob, I did pinch the vacume hose & the idle smoothed out a little, that is what promped me to look for the leak. Like I said the leak seems very small, I was just thinking if it would lean the rear two cylinders during higher rpm's, I guess I'll have to pull the plugs and see

Oh by the way its a 70 350

Thanks guys

Butch

 

Buy a cheap vacuum pump,or (autozone will let you borrow one, give them a deposit and take it home) Hook the pump up to different locations and see if it holds vacuum....If it doesnt then your getting closer to finding the leak.

Just keep moving the pump to different locations untill you pin point the leak

 

That would be incorrect.

Base is the innitial timing. (at idle)


With the vacuum off you see the mech advance (when revved up)


Total advance can be seen with vacuum hooked up & engine revved up.

 

OK---I'm not sure what your saying.What do you call the combination of initial and centrifugal.-----initial + centrifugal = ? You say that is not what everyone on the forum refers to as "TOTAL" I think your a bit confused.If your telling him to set his total to 36 with vacumn connected your just flat wrong.Go back and read some more.

 

JBB--BarryK has a page on his website about timing that will help you.

 

With the advance disconnected you should see close to 35 degrees
With the advance hooked up you should be seeing about 48-53 degrees @ 2,500 rpm

 

Let's use your terminology, & set the "total" at 36-40 degrees. Now we reinstall the vacuum line, and we have too much advance when RPM is brought up.

 

Please tell me your kidding-you really dont understand this?Your avitar shows you are a master tech? If you will go to BarryK website he has some info from Lars that will help you understand this.On this forum it is understood that "total timing" is set with vacumn disconnected and plugged.I hope you will go to his website and get an understanding of timing so you wont confuse other forum members in the future. Thanks
Roger

PS-yes the timing will go higher with vacumn back on--it is suppose to!

 

Oh JBB go to the top of this forum and BarryK has a great article on timing-sorry I didnt see it before.

 

sorry, that is incorrect, I believe you are confused.

initial timing = also referred to as base timing. This is taken at idle rpm speed with the vacuum advance disconnected. Should be in the range of approx 6º - 12º normally although some people tend to run them higher up to apptox 18º

Centrifugal advance - mechanical advance that the distributor adds in based on engine speed

total timing = initial advance and centrifugal advance added up with the vacuum advance DISCONNECTED. This is typically in the 34º-36º range, again with the vacuum advance disconnected.

The vacuum advance cannisters typically add in 15º - 16º advance over and above what the previous numbers listed above are so if your total timing is set for 36º (usually the most optimum setting on most cars) and than you reconnect the vacuum advance your total timing with vacuum advance will be about 52º.

52º of total timing (without vacuum advance) is WAY too high as it should be at 36º but with the vacuum advance connected 52º is usually just about perfect to shoot for.

keep in mind that the vacuum advance decreases based on load so as you accelerate (under load) and your rpms comes up, the mechanical advance will add more in but the vacuum advance will decrease. That 52º you measure while setting and checking timing while the car is sitting in the garage will not go above 52º - that's the MAX, all it can do is be at 52º or less. Under load it will never even get to the max of 52º

 

Oh, I understand just fine. You appear to be confused, I will try to elaborate.

Take that # + subtract base & you get the mech advance.

Clearing up your confusion now.

Yes, that is why it is called TOTAL advance. Base + Mech+ Vac= Total.

 

that's correct - with the vac can disconnected.


TYPICALLY, Total timing is referred to as the initial + mechanical = Total timing - with the vac advance disconnected.

With the vac can connected it's referred to Total Timing with vacuum.

you ask anyone on this forum and anyone that I know that does their own work and you say "Total Timing" 99.9% of them are going to assume you are referring to the initial + mechanical WITHOUT the vacuum connected.

 

OK JBB I guess we'll have to let you have it your way.But if you set total to 36 your way it won't have any initial and run like a dog.It will be lucky to have 5*initial.

 

That is how I learned it & how our old Bear Analyzer did it. Didn't mean to get everyone riled up, just didn't want someone accidentailly running too much timing.