Heated argument
Thread Starter
|
Senior User
Joined: Apr 2001
Posts: 321
Likes: 1
Heated argument
Hi,
This weekend I was working on my 79 F100 w/351M. My father-in-law stopped by to see what I was doing, and I expained to him that I was advancing the initial timing to make more power.
To make a long story short, he stated, over and over again, that I needed to retard the timing to make more power. He also said that the vaccum advance (that he called a dashpot?) is supposed to retard the timing to make more power. Needless to say I thought the opposite and we had a *heated* debate.
I always thought that you "advanced" the timing to make more power, and that the vaccum advance "advanced" the timing to make more power when the ported vaccum increases. The only time the vacuum advance would retard the timing is when the ported vacuume falls off (under W-O-T, for example)
If I am wrong I will gladly applogize to him and admit I was wrong, but if I am right I will show his this post and any responses.
Thanks,
-Brents
This weekend I was working on my 79 F100 w/351M. My father-in-law stopped by to see what I was doing, and I expained to him that I was advancing the initial timing to make more power.
To make a long story short, he stated, over and over again, that I needed to retard the timing to make more power. He also said that the vaccum advance (that he called a dashpot?) is supposed to retard the timing to make more power. Needless to say I thought the opposite and we had a *heated* debate.
I always thought that you "advanced" the timing to make more power, and that the vaccum advance "advanced" the timing to make more power when the ported vaccum increases. The only time the vacuum advance would retard the timing is when the ported vacuume falls off (under W-O-T, for example)
If I am wrong I will gladly applogize to him and admit I was wrong, but if I am right I will show his this post and any responses.
Thanks,
-Brents
Posting Guru
Joined: Aug 2000
Posts: 2,416
Likes: 4
From: PacNW
Heated argument
You are correct. You always advance the timing to make more power. Obviously too much advance can cause detonation which is harmful to the engine and you don't make too much power when your pistons melt.
The vacuum advance works only at part throttle. At idle the ported vacuum port is covered so no vacuum reaches the vac. adv. diaphragm. At WOT there is virtually no vacuum and the mechanical advance has taken over anyway. At part throttle the vac. adv. advances the timing to increase fuel economy and performance.
For some basic information on automotive ignition and timing show him this link: [link:www.tpub.com/basae/46.htm|Basic Ignition Info]
The vacuum advance works only at part throttle. At idle the ported vacuum port is covered so no vacuum reaches the vac. adv. diaphragm. At WOT there is virtually no vacuum and the mechanical advance has taken over anyway. At part throttle the vac. adv. advances the timing to increase fuel economy and performance.
For some basic information on automotive ignition and timing show him this link: [link:www.tpub.com/basae/46.htm|Basic Ignition Info]
Posting Guru
Joined: Jul 2001
Posts: 1,613
Likes: 2
From: Gainesville, FL
Heated argument
Brents,
There were some distributors that had both advancing and retarding "dashpots"/vacuum servos. They were designed to operate inconjuction with a pneumatic emission system. They are obvious to the eye due to two vacuum lines coming off the vacuum canister. The previous post states that there are actually two ways to get timing advance. 1. vacuum advance - carb vacuum 2. mechanical advance - centrifugal weights. If you are wide open throttle (WOT) you can still have vacuum during acceleration. This will decrease as the motor reaches the top if its power band and the engine "tops out". This is how your auto trans knows when to shift.
Good Luck, Have Fun,
KingFisher
There were some distributors that had both advancing and retarding "dashpots"/vacuum servos. They were designed to operate inconjuction with a pneumatic emission system. They are obvious to the eye due to two vacuum lines coming off the vacuum canister. The previous post states that there are actually two ways to get timing advance. 1. vacuum advance - carb vacuum 2. mechanical advance - centrifugal weights. If you are wide open throttle (WOT) you can still have vacuum during acceleration. This will decrease as the motor reaches the top if its power band and the engine "tops out". This is how your auto trans knows when to shift.
Good Luck, Have Fun,
KingFisher
Thread
Thread Starter
Forum
Replies
Last Post
Jon351m
Ford Inline Six, 200, 250, 4.9L / 300
7
Jan 26, 2015 01:50 PM
76BIG/ORANGE
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
8
Dec 30, 2005 10:14 PM
Sedric
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
2
Jul 18, 2002 09:52 PM
