Setting Timing by Vacuum?
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,023
Likes: 2
From: TEXASTEXASTEXASTEXAS TEXASTEXASTEXASTEXAS
St. Jude Contributor
Setting Timing by Vacuum?
Found an old post by a member named AC. He said:
"You can also use a vacuum guage to see where you get your highest reading. I have found when you set the timing to the best vacuum reading, it is usually right on the money . I have used this method twice when the outer ring of my balancer had slipped slightly, and couldn't use a timing light correctly. Each time, when I got a new balancer and timed it...it was right on."
Whatchall think? I may have a slipped harmonic balancer & I need a quick way to set the timing so I won't miss an event this weekend.
JB
"You can also use a vacuum guage to see where you get your highest reading. I have found when you set the timing to the best vacuum reading, it is usually right on the money . I have used this method twice when the outer ring of my balancer had slipped slightly, and couldn't use a timing light correctly. Each time, when I got a new balancer and timed it...it was right on."
Whatchall think? I may have a slipped harmonic balancer & I need a quick way to set the timing so I won't miss an event this weekend.
JB
Le Mans Master
Joined: Dec 2000
Posts: 9,752
Likes: 0
From: Chattanooga TN
St. Jude Donor '08-'09
Re: Setting Timing by Vacuum? (JB)
I've heard that too. Usually what I do if I can't see the timing mark for some reason is set to where I think it's a little low, then start advancing it slightly. I shut off the car for about 30 sec. then try to restart it. When it becomes just slightly difficult to start (i.e. the starter seems to not have enough power to turn over the engine for about the first second) I leave it. If you don't like the sound of the starter there, you can back the timing up just slightly. It's a messy way to do it, but it's always worked for me.
:cheers:
:cheers:
Tech Contributor
Joined: Aug 1999
Posts: 14,356
Likes: 6,328
From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Setting Timing by Vacuum? (JB)
JB -
You can set the initial timing that way and get in the ballpark. This method, however, will not get you set up correctly for your total timing. Once you get the car running at idle and best vacuum, do a test drive and just make sure you don't get any "pinging" out of it. If you do, back it off a tad. In this configuration, the car will be drivable enough to get it to the tech session on Saturday.
If your balancer has slipped, it will make tuning the car with the curve kit this Saturday very difficult, since we need to know where 36 degrees is. We'll need to determine TDC and re-mark your balancer so we can get your timing set up. We can do this as part of the tech session - no problem - but I need you to procure a long (about 4-6") 14mm bolt that will screw into your spark plug hole and bring the bolt with you to the session. The last person who borrowed my 14mm bolt failed to return it to me, so you need to buy a bolt. With this tool, we can set up your TDC and get you accurately tuned in spite of a slipped balancer. Drop me an e-mail if you need any assistance:
V8FastCars@msn.com
You can set the initial timing that way and get in the ballpark. This method, however, will not get you set up correctly for your total timing. Once you get the car running at idle and best vacuum, do a test drive and just make sure you don't get any "pinging" out of it. If you do, back it off a tad. In this configuration, the car will be drivable enough to get it to the tech session on Saturday.
If your balancer has slipped, it will make tuning the car with the curve kit this Saturday very difficult, since we need to know where 36 degrees is. We'll need to determine TDC and re-mark your balancer so we can get your timing set up. We can do this as part of the tech session - no problem - but I need you to procure a long (about 4-6") 14mm bolt that will screw into your spark plug hole and bring the bolt with you to the session. The last person who borrowed my 14mm bolt failed to return it to me, so you need to buy a bolt. With this tool, we can set up your TDC and get you accurately tuned in spite of a slipped balancer. Drop me an e-mail if you need any assistance:
V8FastCars@msn.com
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Re: Setting Timing by Vacuum? (JB)
Remember, U-Haul rents drive-on trailers for $49 per day. As they say in the car commercials, push it in, pull it in, or drag it in! But whatever you must do, get the car there :smash:
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,023
Likes: 2
From: TEXASTEXASTEXASTEXAS TEXASTEXASTEXASTEXAS
St. Jude Contributor
Re: Setting Timing by Vacuum? (page62)
Lars--thanks, I'll start hunting up that bolt this afternoon.
Page--I'll be there, don'tcha worry. :D Car's actually running pretty good, though when I shoot the timing light onto the balancer, I can't even see the timing line at all. It's over somewhere on the other side of the balancer.
JB
[Modified by JB, 1:46 PM 6/19/2003]
Page--I'll be there, don'tcha worry. :D Car's actually running pretty good, though when I shoot the timing light onto the balancer, I can't even see the timing line at all. It's over somewhere on the other side of the balancer.
JB
[Modified by JB, 1:46 PM 6/19/2003]
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,443
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Setting Timing by Vacuum? (JB)
JB - Go get a new balancer and the seal ring. You can do it with the motor in the car.
My L-82 balancer broke between the inner and outer ring before the car had 50K miles on it. I'm lucky that nothing got tore up when it came appart.
I almost forgot I use a vacuum gauge to set the four corner idle screws. From what I have seen max vacuum is 6-8 degrees to high initial so your max advance unless you have some kind of modified ignition curve you will end up with to much total timing at higher rpm.
[Modified by gkull, 2:04 PM 6/19/2003]
My L-82 balancer broke between the inner and outer ring before the car had 50K miles on it. I'm lucky that nothing got tore up when it came appart.
I almost forgot I use a vacuum gauge to set the four corner idle screws. From what I have seen max vacuum is 6-8 degrees to high initial so your max advance unless you have some kind of modified ignition curve you will end up with to much total timing at higher rpm.
[Modified by gkull, 2:04 PM 6/19/2003]
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,023
Likes: 2
From: TEXASTEXASTEXASTEXAS TEXASTEXASTEXASTEXAS
St. Jude Contributor
Re: Setting Timing by Vacuum? (gkull)
JB - Go get a new balancer and the seal ring. You can do it with the motor in the car.
My L-82 balancer broke between the inner and outer ring before the car had 50K miles on it. I'm lucky that nothing got tore up when it came appart.
[Modified by gkull, 2:04 PM 6/19/2003]
My L-82 balancer broke between the inner and outer ring before the car had 50K miles on it. I'm lucky that nothing got tore up when it came appart.
[Modified by gkull, 2:04 PM 6/19/2003]
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: Setting Timing by Vacuum? (JB)
You don't have to pull the radiator. Just the fan and water pump. It isn't easy but then pulling a radiator and shroud is much worse. It really helps it you have air tools. There is a company out there that rebuilds balancers. I'll look for their web site. Actually Repairing my balancer wasn't THAT big of a deal. Just a little challenging ! But then again I like challenges.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
7 Bolt-On Upgrades From Extreme Online Store to Level Up Your C6 Corvette
Pouria Savadkouei
Le Mans Master
Joined: May 2000
Posts: 6,493
Likes: 6
From: Bloomington MN
Cruise-In II Veteran
Re: Setting Timing by Vacuum? (bluevetteman)
That was me in the original post. I don't actually tune the motor with just the vacuum guage, but it comes in handy when setting the timing at idle and also adjusting idle mixture screws. In the two cases where my balancer had slipped, I kinda had to use it. I would much rather have a balancer on the mark and a timing light. Your ear can tell you a lot about how the car is timed as well.
The one thing I learned about timing with a vacuum guage though, is that it was only the best timing at idle, not under load. I have 11:1 pistons, and on hard accelleration it was too far advanced and pinged.
AC
The one thing I learned about timing with a vacuum guage though, is that it was only the best timing at idle, not under load. I have 11:1 pistons, and on hard accelleration it was too far advanced and pinged.
AC
