Tdc
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 924
Likes: 0
From: Columbia South Carolina
Tdc
Hello everyone,
I hate to keep bugging everyone,but I'm kind of slow with this stuff.I'm trying to find TDC before pulling my distributor as I'm in the process of removing the heads on my '87 'vette. I did a search and there are varying techniques so I'm a little confused. I have the plugs out,I've turned the engine with my finger in/over the NO.1 spark plug hole until I felt pressure,and the rotor is pointing towards the no.1 cylinder,but the marks are not lined up at 6 degrees. Should I feel pressure only on the compression stroke,and do the marks have to be aligned? Thanks in advance.
tankman
I hate to keep bugging everyone,but I'm kind of slow with this stuff.I'm trying to find TDC before pulling my distributor as I'm in the process of removing the heads on my '87 'vette. I did a search and there are varying techniques so I'm a little confused. I have the plugs out,I've turned the engine with my finger in/over the NO.1 spark plug hole until I felt pressure,and the rotor is pointing towards the no.1 cylinder,but the marks are not lined up at 6 degrees. Should I feel pressure only on the compression stroke,and do the marks have to be aligned? Thanks in advance.
tankman
Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 196
From: folsom california
The finger over the spark plug hole is to get you in the ballpark; the only thing feeling compression tells you is that that particular cylinder is, or just was, on the compression stroke. There is no guarantee that it will stop at TDC; so after you remove your finger from the number one spark plug hole, look at the balancer timing mark and pointer on the timing chain cover and manually turn the engine over till the marks line up where you want them.
but for stabbing the distributor "close enough is good enough" since the final timing is done with a timing light while the engine is running.
any particular reason you're looking to set it at exactly 6 degrees ?
but for stabbing the distributor "close enough is good enough" since the final timing is done with a timing light while the engine is running.
any particular reason you're looking to set it at exactly 6 degrees ?
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
When you feel pressure in cylinder #1 with your finger or thumb over the hole....you know that you are on the compression stroke. Now turn the crank slowly until the timing mark lines up with zero "0" and stop. Leave it there and pull the cap off your distributor and note where the rotor is pointing. I usually tape some paper to the windshield and draw a circle to represent the distributor and then a line to indicate where the rotor is located.
When you drop the distributor back in, you will have to turn it back a little because the rotor will move as you pull it out of the block. You might have to try this a couple of times to get it where you want it by rotating the the shaft.
You are doing this (aligning #1 on the compression stroke) so it will be easier to drop the distributor back in to where it was and to be at the "start" to adjusting the valves.
-John
When you drop the distributor back in, you will have to turn it back a little because the rotor will move as you pull it out of the block. You might have to try this a couple of times to get it where you want it by rotating the the shaft.
You are doing this (aligning #1 on the compression stroke) so it will be easier to drop the distributor back in to where it was and to be at the "start" to adjusting the valves.
-John
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 924
Likes: 0
From: Columbia South Carolina
The finger over the spark plug hole is to get you in the ballpark; the only thing feeling compression tells you is that that particular cylinder is, or just was, on the compression stroke. There is no guarantee that it will stop at TDC; so after you remove your finger from the number one spark plug hole, look at the balancer timing mark and pointer on the timing chain cover and manually turn the engine over till the marks line up where you want them.
but for stabbing the distributor "close enough is good enough" since the final timing is done with a timing light while the engine is running.
any particular reason you're looking to set it at exactly 6 degrees ?
but for stabbing the distributor "close enough is good enough" since the final timing is done with a timing light while the engine is running.
any particular reason you're looking to set it at exactly 6 degrees ?
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 924
Likes: 0
From: Columbia South Carolina
When you feel pressure in cylinder #1 with your finger or thumb over the hole....you know that you are on the compression stroke. Now turn the crank slowly until the timing mark lines up with zero "0" and stop. Leave it there and pull the cap off your distributor and note where the rotor is pointing. I usually tape some paper to the windshield and draw a circle to represent the distributor and then a line to indicate where the rotor is located.
When you drop the distributor back in, you will have to turn it back a little because the rotor will move as you pull it out of the block. You might have to try this a couple of times to get it where you want it by rotating the the shaft.
You are doing this (aligning #1 on the compression stroke) so it will be easier to drop the distributor back in to where it was and to be at the "start" to adjusting the valves.
-John
When you drop the distributor back in, you will have to turn it back a little because the rotor will move as you pull it out of the block. You might have to try this a couple of times to get it where you want it by rotating the the shaft.
You are doing this (aligning #1 on the compression stroke) so it will be easier to drop the distributor back in to where it was and to be at the "start" to adjusting the valves.
-John
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 924
Likes: 0
From: Columbia South Carolina
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
Just make sure it is back to zero on the compression stroke when you reassemble to avoid getting the oil pump key off. Also note how the rotor moves as it comes up and the distributor gear twists out of the cam gear.
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Le Mans Master
Joined: Oct 2008
Posts: 9,758
Likes: 49
From: Houston Texas
When the distributor is going back sometimes it will not drop into place with the rotor pointed in the same place. this happens because the oil pump drive has a slot that lines up with the bottom of the dizzy. I take a long screw driver ans turn the oil pump shaft where it will line up. GL
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 924
Likes: 0
From: Columbia South Carolina
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 924
Likes: 0
From: Columbia South Carolina
When the distributor is going back sometimes it will not drop into place with the rotor pointed in the same place. this happens because the oil pump drive has a slot that lines up with the bottom of the dizzy. I take a long screw driver ans turn the oil pump shaft where it will line up. GL
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
When removing the dist, I use a simple method with dist orientation using a black marker:
-remove the dist cap
-make a mark on the intake base & 1st one on the dist base
-note where the rotor is pointing with a 2nd mark on dist base
-slowly lift the dist, observing where the rotor comes to rest and make a 3rd mark of the dist base.
-diagram these meaks and their meaning
To install the dist, I reverse the process:
-align the dist base 1st mark to the intake base mark
-align rotor pointer to 3nd mark on dist base
-lower dist into position, observing that the rotor now points to the 2nd mark on dist base.
This method works well so long as you do not rotate the crank and/or the cam.
NOTE: If you intend to clean the intake base, simply scribe the mark into the Al.
-remove the dist cap
-make a mark on the intake base & 1st one on the dist base
-note where the rotor is pointing with a 2nd mark on dist base
-slowly lift the dist, observing where the rotor comes to rest and make a 3rd mark of the dist base.
-diagram these meaks and their meaning
To install the dist, I reverse the process:
-align the dist base 1st mark to the intake base mark
-align rotor pointer to 3nd mark on dist base
-lower dist into position, observing that the rotor now points to the 2nd mark on dist base.
This method works well so long as you do not rotate the crank and/or the cam.
NOTE: If you intend to clean the intake base, simply scribe the mark into the Al.
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 924
Likes: 0
From: Columbia South Carolina
When removing the dist, I use a simple method with dist orientation using a black marker:
-remove the dist cap
-make a mark on the intake base & 1st one on the dist base
-note where the rotor is pointing with a 2nd mark on dist base
-slowly lift the dist, observing where the rotor comes to rest and make a 3rd mark of the dist base.
-diagram these meaks and their meaning
To install the dist, I reverse the process:
-align the dist base 1st mark to the intake base mark
-align rotor pointer to 3nd mark on dist base
-lower dist into position, observing that the rotor now points to the 2nd mark on dist base.
This method works well so long as you do not rotate the crank and/or the cam.
NOTE: If you intend to clean the intake base, simply scribe the mark into the Al.
-remove the dist cap
-make a mark on the intake base & 1st one on the dist base
-note where the rotor is pointing with a 2nd mark on dist base
-slowly lift the dist, observing where the rotor comes to rest and make a 3rd mark of the dist base.
-diagram these meaks and their meaning
To install the dist, I reverse the process:
-align the dist base 1st mark to the intake base mark
-align rotor pointer to 3nd mark on dist base
-lower dist into position, observing that the rotor now points to the 2nd mark on dist base.
This method works well so long as you do not rotate the crank and/or the cam.
NOTE: If you intend to clean the intake base, simply scribe the mark into the Al.