vacuum advance

When I step on the gas pretty hard, my engine pings pretty bad.  If I just ease on my gas it speeds up just fine.  A friend at work suggested I check my vacuum advance coming off my distributor, he said that it may not be working. I looked at my distirbutor and the "diaphram" (not sure what you call it, where the vacuum hose connects) looks pretty rusty.  Also, the vacuum hose runs from the distributor to the passenger side of the carburator (holly 650).  Is this correct?  If not, where should it connect to?  To replace the vacuum advance thing on the side, do I just pop the distributor off and bolt the new one on?  I don't want to get into something that is above my head.  Thanks.

Hi again and Happy Holidays.
If the engine pings when you step on it you might have to much timing.
Warm the motor up and disconnect the vacuum line where it connects to the vacuum can and plug the line.
Now loosen the distributor hold down bolt and set the timing to whatever the book calls for, lets say 8*.
Then reconnect the vacuum line and check the timing again, if the can is working you should read about 16* more.
Initial timing             = 8*
Vacuum advance adds 16*
Total=                       24*
 
The vacuum advance line should be connected to " Full Manifold Vacuum", if you have a vacuum guage you can connect it where you disconnected the hose at the vacuum can.
When you step on the gas you loose Manifold vacuum untill you get to a steady speed and for these few seconds the vacuum can does not add any timing.
The next thing that happens is as the engine speeds up the Centrifugal advance weights inside the distributor spin out and they ad more timing. 
If the vacuum can is no good you will have to pull out the distributor to change it. PG.

another way to test ;engine running,remove vac hose from dist and feel for vac. at hose if none raise idle to 1200 and recheck for vac. if ya got vac raise dist. 'door' while looking inside connect vac hose. you will see the plate move if advance is good.check basic timing first.YOU DO NOT HAVE TO REMOVE DIST TO R+R ADVANCE.ill tell ya an easier way but i doubt this is the trouble unless its is bad and someone jacked the timing up to compensate.this just start doing this

I checked for vacuum and did not have any.  I am changeing out the vacuum can and I will let you know the results.  Thanks for the help.

Whoa, no vacuum?
Did you check the hose "from" the carb, or did you check "from" the can? No vacuum does not mean the can is bad.
Disconnect the hose from the can to find out if you have vacuum from the carb. If no vacuum, you have a plugged line or the line is not connected to the right place on the carb.
You can watch the vacuum advance linkage at the dist. If it moves while running engine at different speeds, the can is O.K.

I guess I mis understood the whole thing.  The can was ok.  The guy at advance told me to install a valve into the vacuum line (to hold the vacuum I guess) and it helped a little.  I think the timing must be out of wac.  Don't have the tools (timing light) to do this so I guess I have to take it to the shop.
 
Thanks

Ya might think about getting a timing light. They are cheeper than takin' it to a shop, and with a little practice, you can do just as good a job of setting the timing. There is an amount of satisfaction in doing your own work, and ya save a few bucks too.
I've developed and "ear" for tuning my engines. With the engine running I can set timing, adjust points, and tune in the carb. (and never use a light) All it takes is practice.

Did this problem come "over time" or "all of a sudden?"   

The Corvette sat for about 2 years before I bought it in July of this year for 7800.  The interior is all new and the outside is in real good shape with a few cracks in the paint.  I had to put a new carb on it when I bought it (the old one was beyond repair) and replaced the transmisson pan gasket because of a leak.  The engine has always started pinging when I step on the gas real hard.  I know I have a transmission problem, it does not down shift when I get on it either.  That was my next project.  Well I was out driving it last night to see if the valve on my vacuum hose helped (it did a little) and started smelling burnt tranny fluid.  Brought it home, jacked it up and it looks like the front seal on the tranny is in need of replacement. It is leaking real bad up at the front of the transmission.  I guess that will be my christmas present (that is definetly out of my league).  I will go out and get a timing light since I plan on keeping the vette.  Know of a dependable transmission guy in Virginia Beach Virginia?
 
Dan

quote:

ORIGINAL: riley6riley

The Corvette sat for about 2 years before I bought it in July of this year for 7800.  The interior is all new and the outside is in real good shape with a few cracks in the paint.  I had to put a new carb on it when I bought it (the old one was beyond repair) and replaced the transmisson pan gasket because of a leak.  The engine has always started pinging when I step on the gas real hard.  I know I have a transmission problem, it does not down shift when I get on it either.  That was my next project.  Well I was out driving it last night to see if the valve on my vacuum hose helped (it did a little) and started smelling burnt tranny fluid.  Brought it home, jacked it up and it looks like the front seal on the tranny is in need of replacement. It is leaking real bad up at the front of the transmission.  I guess that will be my christmas present (that is definetly out of my league).  I will go out and get a timing light since I plan on keeping the vette.  Know of a dependable transmission guy in Virginia Beach Virginia?

Dan

Hi again, We all had to start where you at today, with a Corvette that needed a lot of work and no clue about how to fix it. Get a Haynes repair manual at the parts store, it shows you step by step how to do the repair.
Timing light -costs about $60. Get a Dial back, its got a knob on the back and it makes timing a piece of cake.
Vacuum guage-very usefull, theres lots to check on a Vette.
Everyone on this forum will help you every step of the way, so if you need help just ask.
When I first got my Vette every time I wen't for a ride something else broke or needed some work.
I took a ride one day and nothing broke, then I put my turn signal on to turn into my block and it broke.
Happy Holiday! PG.

Here's some good info on timing: http://www.lbfun.com/Corvette/Tech/vettetech_files/Timing101Article.pdf
 
http://www.lbfun.com/Corvette/Tech/vettetech_files/MAPPING%20ADVANCE.pdf
 
http://www.lbfun.com/Corvette/Tech/vettetech_files/How%20to%20Set%20Timing.pdf
 
If you decide to get a timing lite, recommend getting one that has an adjustable timing knob on it like this one: http://www.sears.com/shc/s/p_10153_12605_00921023000P?keyword=timing+light
 
Eliminates need for timing tape on balancer.  Yeah it's expensive but you get what you pay for.  I know as I bought several cheap ones and threw them away.    Besides if your engine ain't timed right,   nothing else performance-wise will be 100%. 
Just my $0.02  Good luck.  Don't hesitate to ask questions as there are a lot of wise heads around here.

Here's a link to Holley's website and the instructions for the 650. Look at illustration 7 for the vacuum advance port, this is where your vacuum line should go, from the distributor to here.
 
http://www.holley.com/data/Products/Technical/199R8020-3.pdf
 

 
 

I have only received excellent help here the whole time I have owned the vette.  I am going shopping!  Thanks for everything and hopefully I get to drive it soon.
 
Merry Christmas

borrow a t light ,its the only time [no pun] you will ever use it

   Are you using "regular" gas?  Go to the next higher octane, if you already haven't.  I use mid-grade as regular, depending on what brand gas I use, gives me alittle bit of a rough running.
  Yes, the vacuum gauge as already spoken about can also be used to set the timing.  Vacuum readings can tell mucho stories about your vehicle, if you know how to use it, and a good one comes with good instructions/info sheets.  With the year 'Vette you have, it should be easy to get rid of the pinging; with what gas you use, the timing/carb adj.(over-all good tune-up.)  With some messing around and getting to know the engine and it's compartment and surroundings, you'll beable to work out most things on your own w/ alittle assistance from the members here.
   I always feel great reading all the good replies that the site members contribute.  Out of all the auto sites that I frequent, and that's quite afew, this place is the friendliest where people here are most likely to jump right in feet first with all the help. In other sites, there are quite afew really sharp auto techs w/ mucho experience, but who also can be ****ty and super insulting to beginners.  This place is the opposite.

Ya know, text book mumbers are a great start.
But to get the most from a time and tune, ya need to concider some factors regarding where ya live.
For instance, A car tuned at sea level will not perform as well at higher elevations. So, ya got to tune for the area where you will do most of your driving. Temp comes into play also. I tune dif for hot summer weather than I do for cold winter weather. Lean 'er out a little when it's hot, go richer when it's cold. A timing light is not a "use once and forget it" item. I'll use a light to get close, then "ear tune" to my preferred "feel" of performance. 
Dwell meter, vacuum guage, and timing light are all good to have on hand. And if ya have points, add a feeler guage to the list. You should have one to set your plug gaps anyway.
 
A little trick I stumbled on......
A match book cover is about .019 thick. You can use it to set your points.
Double it over, and you have around .038 to set the plug gap.  

Well, I bought the timing light and discovered the timing was way off.  It runs 100% better and no pinging.  The front seal on the tranny is the next project. Thanks for all the help.