Vaccuum Advancement on the Distributor

[vettepilot]

GerryLP,
Excellent post! What more can we say.

vettepilot

 

[GerryLP]

Thanks! I hope that TR and others find it usefull.

 

[Stallion]

Thanks a lot for that post! Very informational and now I have a good idea of what's done and the process. I really appreciate that.

Unfortuneately, we just got a bad snow storm so it looks like I can't take out the Vette to this Vette guy down the street. Now I'll have to wait until the snow clears up and only God knows when that'll be.

This sounds like a fine idea for me to take it to this guy. He's nice and I'm sure he'll let me stand right there while he does it and I'm also sure that he'll explain everything he does. He's really into Vettes and his job.

TR

 

[Skyguy007]

You can get a "dial back to zero" timing light at most any Sears store that has a decent tool department. This kind of timing light has a knob on the back end. You turn this knob until the timing mark on the harmonic balancer lines up with the "zero" or top dead center mark on the timing bracket that's attached to the engine block. When the marks are lkined up you can read the degrees of advance from the scale under the knob's pointer.

The biggest problem with the light is that it requires a 12 volt source and the battery on my '69 is behind the driver's seat, like may Vettes are. I think I clipped the positive lead to the output on the alternator and the negative clip to the alternator bracket, which is grounded. Clip the spark plug lead onto the #1 plug wire (front spark plug on the driver's side) and start the engine. The light will pulse every time the plug fires.

I started the timing process by temporarily disconnecting the vacuum advance (remember to plug the hose to the intake manifold with a golf tee), and removing the mechanical advance springs so I could get a read on total advance. I discovered this process via an Internet search. If you can't find it, write me and I can probably dig up the source.

Good luck.

 

[Stallion]

I'll definitely go look for that source, thanks. You wouldn't happen to know a key word of the source, would you? That would probably make searching a whole lot easier. But I'll just do a general seach on timing lights. Thanks!

TR

 

[Stallion]

So, GerryLP, pretty much summed up this timing light tells you the amount of degress before the piston reaches the top that the distributor sends out the spark? If the advancement is working correctly, than as the revs go higher the distributor should be sending out the spark more often, but still at a constant amount of degress, rigth? Do I have that theory right? And thanks again for that post!

TR

 

[vettepilot]

You got it half correct... The ignition pulse does increase in frequency (speed), but it should also advance as the engine speed increases. This is because the mechanical advance, (centrifugal) advances the ignition timing as the engine speed increases in order to give the mixture time to burn as completely as it can. Your a good study, catching on quick. We will have you wearing a Mr Goodwrench shirt by the end of next week.
vettepilot

 

[GerryLP]

That would be cool! You can be a certified mechanic and help us with the cars...:L

(however, If you plan to go to college, then stick with that!!!! You can always choose mechanical engineering or something like that!!!)

 

[Stallion]

You hit the nail right on the head, I want to go into mechanical engineering. And then if I get good enough I can work on the Corvette team designing C6s (depending on how long that generation lasts, it might be C7s or C8s before I get on the team ).

Anyways, I don't think I'll need to take it down to that Vette expert down the road. It turns out my father knows exactly how to use a timing light and he has been working with them for quite some time. So it'll be great me and him in the Vette with this timing light figuring this problem out! I really can't wait. I'm all excited. We even have a timing light to use, he says. So we won't need to buy one.

I'll keep you guys updated on how it goes, I'm not sure when we'll be able to work on the Vette. Hopefully Sunday if Dad is not too busy.

And here's a picture of the vaccuum hose not attached to the actuator on the distributor. Just in case you wanted to see a picture. Ever since I got the Vette I just want to take pictures of her!

TR

 

[vettepilot]

It's been many years since I was under the hood of the C3 generation Vette, but I clearly remember the distributor being about 30 degrees counterclockwise from what I am seeing in the photo. Unless I am misinterpreting the photo, it looks to be on the right hand side of the engine. The vacuum fitting on the vac. advance is normally facing or pointing towards the vicinity of the left rear runner of the intake manifold.
Say Vig, tell me, am I looking at the photo correctly?
I just got in from a fast run back home from Clearwater today, so my eyes may be playing tricks on me.... LOL
vettepilot

 

[JohnZ]

Distributor position is correct - all Chevy V-8 distributor vacuum advance cans are in the same position as shown in the photo; any further toward centerline and it will hit the intake runner, any further outboard and it'll hit the plug wire support bracket.

 

[vettepilot]

JohnZ,
Thanks, now that I have been home for a while and had a cup of java, I can see now that it is correct. For some reason it just didn't look right when I first looked at the photo.
vettepilot

 

[Jack]

I had an earlier impression the vacuum can may've been removed. After seeing the pic, it's clearly attached & in proper position. At this point I would pull a vacuum on it (hook a hose to it ... suck on the other end & seal w/ tip of tongue) ... observe if unit did advance ... AND if it is holding position. If either not happening then go to NAPA store & get a replacement vac can ... then reconnect can & hose properly ... then reset ignition timing.
JACK:gap

 

[81NMVETTE]

TR
Go to the Knowledgebase and do a search for timing . There are at least 2 great spots that deal with just the very topic you are talking about. I read them and they are just the ticket for you.
Earl
Hey Gerry did you get my E-Mail ? I will be headed to Lubbock on Saturday morning to get the Vette !!:Twist
I will be back in RR on saturday evening. Lets meet on sunday .

 

[Stallion]

I did the search and this is what I came up with. I just put in "timing". What two topics are you referring to? Thanks!

TR

 

[Jack]

I did the search and this is what I came up with. I just put in "timing". What two topics are you referring to? Thanks!

TR

http://corvetteactioncenter.com/kb/category.php?catId=95

http://corvetteactioncenter.com/kb/question.php?qstId=440

http://corvetteactioncenter.com/kb/question.php?qstId=453

http://corvetteactioncenter.com/kb/question.php?qstId=447

Any article authored by Lars is worth your time & study.

 

[81NMVETTE]

TY Jack,That is where I wanted to send him.

 

[400hp_76]

Im not stating facts or anything, but ive heard that the vacuum advance can be harmful, especially at high rpm driving. I was also told that it is basically a fuel economy device. I have noticed that my vette felt like it was dying at higher rpm so i diconnected the vacuum advance and if feels better now. Im not sure if the vacuum advance was pulling the timing around so far that it was detonating or close to detonating. maybe. any opinions

 

[MoeJr]

400 if your engine is of say 9.5 or higher CR then it is possiblt you were getting too much vacuum advance and would cause the car to be close or detonating and losing performance. You can get an adjustable vacuum advance can and dial in what ya need. Vacuum advance is not just for fuel economy. It helps lower CR engines make the most of their HP. Just my.02

 

[400hp_76]

Thats a good .02. I wanted someone to say it could be doin that. I didnt wanna be makin stuff up in my head. well im over 10.1 comp. , so it is very possible. when i had a light put on the car i forgot that i had advanced the cam this time. ill figure it out tho..thanks