Setting timing by vacuum reading
Thread Starter
|
Senior User
Joined: Jan 2004
Posts: 166
Likes: 0
From: Masontown, WV
Setting timing by vacuum reading
I just set the timing on my 400 using the vacuum gauge method. I then checked what I had with a light and it's about 15 deg. I ran it and it runs stronger than ever with no pinging.
I had never heard of this untill the other day. Anyone else set their timing using vacuum? What do you think about 15 deg timing? Too high?
I had never heard of this untill the other day. Anyone else set their timing using vacuum? What do you think about 15 deg timing? Too high?
Tuned
Joined: Jul 2003
Posts: 455
Likes: 3
From: Berkeley
does this simply mean setting timing to where one gets the highest vacuum at idle (with vac advance d/p)? is it done in drive or park? thanx.
Last edited by packlet; Dec 10, 2004 at 01:18 PM. Reason: 'nother ?
Elder User
Joined: Sep 2002
Posts: 615
Likes: 1
From: Smithville TX.
Originally Posted by towtruck
I just set the timing on my 400 using the vacuum gauge method. I then checked what I had with a light and it's about 15 deg. I ran it and it runs stronger than ever with no pinging.
I had never heard of this untill the other day. Anyone else set their timing using vacuum? What do you think about 15 deg timing? Too high?
I had never heard of this untill the other day. Anyone else set their timing using vacuum? What do you think about 15 deg timing? Too high?
Michelle
Chelle's 56 Hauler
Thread Starter
|
Senior User
Joined: Jan 2004
Posts: 166
Likes: 0
From: Masontown, WV
I advanced the timing to the max vacuum and then backed it off by 2". The highest was 20. After I reached 18" I checked it with light and then set the idle trying to keep the vac steady and at 18. This worked well on my motor.
I live at about 2000 feet and run my truck weekly from 900 to 3500 feet. I never heard of running more advance at higher altitude.
I live at about 2000 feet and run my truck weekly from 900 to 3500 feet. I never heard of running more advance at higher altitude.
Elder User
Joined: Sep 2002
Posts: 615
Likes: 1
From: Smithville TX.
I live at about 2000 feet and run my truck weekly from 900 to 3500 feet. I never heard of running more advance at higher altitude.
Most engines will run fairly well with specified timing until they get to about four to five thousand feet. It is mostly people in higher altitudes, five thousand feet and above that will start bumping their timing up and tuning their engines for altitude. If your truck is running well and your not getting any preignition knock, I would leave it where it is. I once knew a guy in my car club that was running his timming at twenty two degrees and not getting any knock. At that time I was living near sea level. I had questioned him about it and he swore that it ran good. One day while he was visiting me, I ask him if I could check his timing out. I brought the #1 pistom up to top dead center by removing the number 1 spark plug and manually checking it. Then checked his timing marks. I found that the outer part of the harmonic balancer had moved on the rubber insulater by about 8 to 10 degrees. So in reality he was running 12 to 14 degrees of timming. The only way to know for 100% sure is to check it when you are building your engine by using a dial indicator to measure top dead center on your #1 piston and then check to see if TDC on the balancer is right on the mark.
Michelle
Chelle's 56 Hauler
Trending Topics
Posting Guru
Joined: Dec 2002
Posts: 2,003
Likes: 2
From: chicago burbs
a vacuum gauge is a vacuum gauge. a timing light is a timing light. what does the vacuum gauge tell you your total advance is?
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
You can use a piston stop threaded into the spark plug hole and a degree wheel to find TDC also. A degree wheel is also required if you use a dial indicator during engine building. It is difficult to accurately find TDC by itself since the piston moves so little for several degrees around TDC. There is also some "slop" in the bearing and wrist pin that will cause errors when trying to observe piston motion at TDC.
Elder User
Joined: Sep 2002
Posts: 615
Likes: 1
From: Smithville TX.
I have to agree with you Eric on the degree wheel. I always use a degree wheel and a dial indicator to dial in my cams when I buid an engine. When I checked my friends timing I didn't have the room to install a degree wheel with out removing a lot of components. The estimation of TDC was an estimate with in a few degrees at best. But close enough to find out that his timing mark was way off. He soon replaced his harmonic balancer and his timing was more in line with what it should be.
Michelle
Michelle
Thread Starter
|
Senior User
Joined: Jan 2004
Posts: 166
Likes: 0
From: Masontown, WV
Thanks for the good info everyone. I just replaced my harmonic balancer and found I was only running 12 deg with it. The old one was wobbling and I thought I should change it.
The reason I tried setting my timing with the high vacuum reading was to see if it worked or not. I read a post on timing older engines or engines that have had mods done to them and they said this was the best way. What I found is that its a good starting point and like Eric said it will most likely be to advanced and will need retarted some.
Any recommendations on timing an engine that wont run at max performance on factory specs?
The reason I tried setting my timing with the high vacuum reading was to see if it worked or not. I read a post on timing older engines or engines that have had mods done to them and they said this was the best way. What I found is that its a good starting point and like Eric said it will most likely be to advanced and will need retarted some.
Any recommendations on timing an engine that wont run at max performance on factory specs?
Posting Guru
Joined: Dec 2002
Posts: 2,003
Likes: 2
From: chicago burbs
it may be interesting to find a correlation between vacuum, timing setting and how the engine runs, but it's only a correlation. i remember a few posters that have set by vacuum and ended up with extremely high inital settings, and did not make any adjustment or modification to control or even find out what the total advance was. a little more interesting would be to find out what the vac reading is at cruise rpm and see if you can tweek it within a few degrees to find highest vacuum at cruise, where it is pertinent. the dynamics of an engines' ability to draw an intake charge varies through the rpm range, starting with being the best at idle and getting worse as the engine reaches redline. many use a vac gauge to set idle mixtures to highest vacuum, and many more set by ear. there is a tool for the job, a gas analizer. while 99.999% of us can't afford and/or don't have access to a gas analizer, the vac gauge idle mix setting is widely accepted. but you can't dyno your vehicle with a volt meter, and IMO, you can't set timing with a vac gauge.
Postmaster
Joined: Jul 2003
Posts: 2,544
Likes: 2
From: okc
a couple years ago i came across a vacuum guage/fuel pump pressure tester, that shows timing on it, it shows
1-10 mmHg=late valve timing/intake or heat riser leak
10-18 mmHg=late timing
18-23 mmHg=normal range
ive found i can alter my timing up to 4 degrees and it still be in the normal range, but my truck will run different, 10-12 degrees will get me better economy but less power,i put it at 14 when i want more power, much more than that and it backfires out of the carb when u gas it......but i have the stock cam...........the gauge will get it close, but having a good harmonic balancer, a solid timing chain, and a timing light is the way to go......then just keep test driving until you find what setting suits you best....
1-10 mmHg=late valve timing/intake or heat riser leak
10-18 mmHg=late timing
18-23 mmHg=normal range
ive found i can alter my timing up to 4 degrees and it still be in the normal range, but my truck will run different, 10-12 degrees will get me better economy but less power,i put it at 14 when i want more power, much more than that and it backfires out of the carb when u gas it......but i have the stock cam...........the gauge will get it close, but having a good harmonic balancer, a solid timing chain, and a timing light is the way to go......then just keep test driving until you find what setting suits you best....
Thread
Thread Starter
Forum
Replies
Last Post
Argess
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
6
Jul 9, 2009 07:11 PM
LFDavidson
1973 - 1979 F-100 & Larger F-Series Trucks
8
Nov 6, 2006 01:51 PM
