Removed Timing Cover: Picture
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Removed Timing Cover: Picture
This is what I found. The builder advanced the cam 4 degrees so the mark on the crank sprocket circled is the triangle and the mark on the cam sprocket circled is the circle. The motor is at TDC on the compression stroke in this picture.
The chain is not slack or loose, however if you look at the cam dowel it looks like it tried to break out of the retainer. I'll probably remove the cam tomorrow to see if it's damaged in any way.
I believe I remember reading in some posts that at TDC, compression stroke both alignment marks should be at the 12 o'clock position which they are. Anyone see anything suspicious?
The chain is not slack or loose, however if you look at the cam dowel it looks like it tried to break out of the retainer. I'll probably remove the cam tomorrow to see if it's damaged in any way.
I believe I remember reading in some posts that at TDC, compression stroke both alignment marks should be at the 12 o'clock position which they are. Anyone see anything suspicious?
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Help me out now. I know the motor isn't in my Vette but it may be one day. Are both marks supposed to be at the 12 o'clock position with the motor at TDC on the compression stroke?
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
I assume that you checked the pressure (compression on all cylinders)
If the pressure is ok, the timing chain is ok and the carb is ok...and the rocker arms move.. and if I remember correctly, you also tried another distributor... then I think that somehow the cam gears (where they meet with the distributor) could be worn down which would also explain that it jumps timing...
If the pressure is ok, the timing chain is ok and the carb is ok...and the rocker arms move.. and if I remember correctly, you also tried another distributor... then I think that somehow the cam gears (where they meet with the distributor) could be worn down which would also explain that it jumps timing...
Last edited by GrandSportC3; Oct 7, 2005 at 10:42 PM.
Pro
Joined: Oct 2004
Posts: 663
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From: Honolulu Hawaii
Originally Posted by mandm1200
I prefer to look at the marks when the cam is at 6 and the crank is at 12. The marks are easier to align and it has no affect on the cam timing.
this is the way I always did it
Pro
Joined: Aug 2005
Posts: 613
Likes: 2
From: West Central Florida
you have got it on the exhaust stroke according to the marks.
START- marks are (cam at 6 o'clock crank at 12 o'clock) top of compression stroke
Stroke 1- (combustion) crank goes to bottom and cam to 9 o'clock
Stroke 2- (exhaust) crank goes to 12 o'clock and cam to 12 o'clock
Stroke 3- (intake) crank goes to 6 o'clock cam to 3 o'clock
Stroke 4- (compression) crank goes to 12 o'clock cam to 6 o'clock and start over agian 4 strokes per cycle (2 revolutions of crank and 1 on the cam)
vic
START- marks are (cam at 6 o'clock crank at 12 o'clock) top of compression stroke
Stroke 1- (combustion) crank goes to bottom and cam to 9 o'clock
Stroke 2- (exhaust) crank goes to 12 o'clock and cam to 12 o'clock
Stroke 3- (intake) crank goes to 6 o'clock cam to 3 o'clock
Stroke 4- (compression) crank goes to 12 o'clock cam to 6 o'clock and start over agian 4 strokes per cycle (2 revolutions of crank and 1 on the cam)
vic
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Pro
Joined: Aug 2005
Posts: 613
Likes: 2
From: West Central Florida
The cam gear only goes on ONE WAY
the crank gear can (on aftermarket performance timing gear sets) be set at 4 deg before TDC, 0 deg TDC, and 4 deg after TDC
Before TDC gives you more high rpm performance.
TDC gives you neautral torque/HP curve.
After gives you more bottom end (low rpm) torque.
vic
the crank gear can (on aftermarket performance timing gear sets) be set at 4 deg before TDC, 0 deg TDC, and 4 deg after TDC
Before TDC gives you more high rpm performance.
TDC gives you neautral torque/HP curve.
After gives you more bottom end (low rpm) torque.
vic
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Originally Posted by VETTEVIC
you have got it on the exhaust stroke according to the marks.
START- marks are (cam at 6 o'clock crank at 12 o'clock) top of compression stroke
Stroke 1- (combustion) crank goes to bottom and cam to 9 o'clock
Stroke 2- (exhaust) crank goes to 12 o'clock and cam to 12 o'clock
Stroke 3- (intake) crank goes to 6 o'clock cam to 3 o'clock
Stroke 4- (compression) crank goes to 12 o'clock cam to 6 o'clock and start over agian 4 strokes per cycle (2 revolutions of crank and 1 on the cam)
vic
START- marks are (cam at 6 o'clock crank at 12 o'clock) top of compression stroke
Stroke 1- (combustion) crank goes to bottom and cam to 9 o'clock
Stroke 2- (exhaust) crank goes to 12 o'clock and cam to 12 o'clock
Stroke 3- (intake) crank goes to 6 o'clock cam to 3 o'clock
Stroke 4- (compression) crank goes to 12 o'clock cam to 6 o'clock and start over agian 4 strokes per cycle (2 revolutions of crank and 1 on the cam)
vic
THis is what I thought too, meaning it is firing on ( TDC ) the number 6 cylinder in this configuration
Race Director
Joined: Feb 1999
Posts: 16,978
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From: In Dreams There Is Truth Ohio
Originally Posted by nastee383
This is what I found. The builder advanced the cam 4 degrees so the mark on the crank sprocket circled is the triangle and the mark on the cam sprocket circled is the circle.
Pro
Joined: Aug 2005
Posts: 613
Likes: 2
From: West Central Florida
Originally Posted by GDaina
The cam sprocket and the crank gear have the triangle, o, and square markings. The crank gear is set on the triangle, the cam sprocket should also be be on the triangle, not the O. I think I mentioned that in an earlier post in this thread.
vic
Burning Brakes
Joined: Sep 2004
Posts: 1,167
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From: Ft.Worth Texas
Originally Posted by nastee383
I believe I remember reading in some posts that at TDC, compression stroke both alignment marks should be at the 12 o'clock position which they are. Anyone see anything suspicious?
Holy molie nastee, I hope you don't have a cam ground for a counter rotating marine engine.
Race Director
Joined: Feb 1999
Posts: 16,978
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From: In Dreams There Is Truth Ohio
Originally Posted by VETTEVIC
This is true, BUT you can only install the cam gear one way, you just line up the different marks. tha crank has to be installed in a different position for each timing change, ie: keyway in slot that corresponds to the mark you are wantin to line up. Good point though, I was assuming that was understood, sorry.
vic
vic
Le Mans Master
Joined: Oct 2004
Posts: 5,269
Likes: 54
From: Orlando Florida
St. Jude Donor '05
I've had this problem, too.
When piston #1 is on comp stroke at TDC the mark on the crank sprocket is at 12 o'clock and the mark on the cam sprocket, too.
I watched the valves opening and closing while turning the crank with a wrench (all spark plugs removed, paper towel in #1 spark plug hole to verify comp stroke).
I was sooo sure that it was wrong, I turned the crank, watched valves opening and closing for hours.... couldn't believe it was correct
I have both marks at 12 o'clock and the engine runs fine
As said above: it works only one way
Maybe it depends on the timing gear manufacturer where they mark the sprockets ???
When piston #1 is on comp stroke at TDC the mark on the crank sprocket is at 12 o'clock and the mark on the cam sprocket, too.
I watched the valves opening and closing while turning the crank with a wrench (all spark plugs removed, paper towel in #1 spark plug hole to verify comp stroke).
I was sooo sure that it was wrong, I turned the crank, watched valves opening and closing for hours.... couldn't believe it was correct
I have both marks at 12 o'clock and the engine runs fine
As said above: it works only one way
Maybe it depends on the timing gear manufacturer where they mark the sprockets ???
Pro
Joined: Aug 2005
Posts: 613
Likes: 2
From: West Central Florida
Originally Posted by RedBad1979
I've had this problem, too.
When piston #1 is on comp stroke at TDC the mark on the crank sprocket is at 12 o'clock and the mark on the cam sprocket, too.
I watched the valves opening and closing while turning the crank with a wrench (all spark plugs removed, paper towel in #1 spark plug hole to verify comp stroke).
I was sooo sure that it was wrong, I turned the crank, watched valves opening and closing for hours.... couldn't believe it was correct
I have both marks at 12 o'clock and the engine runs fine
As said above: it works only one way
Maybe it depends on the timing gear manufacturer where they mark the sprockets ???
When piston #1 is on comp stroke at TDC the mark on the crank sprocket is at 12 o'clock and the mark on the cam sprocket, too.
I watched the valves opening and closing while turning the crank with a wrench (all spark plugs removed, paper towel in #1 spark plug hole to verify comp stroke).
I was sooo sure that it was wrong, I turned the crank, watched valves opening and closing for hours.... couldn't believe it was correct
I have both marks at 12 o'clock and the engine runs fine
As said above: it works only one way
Maybe it depends on the timing gear manufacturer where they mark the sprockets ???
Pro
Joined: Aug 2005
Posts: 613
Likes: 2
From: West Central Florida
My Appologies
OOps, just reread the first post, you did ask about #1 being at TDC COMPRESSION. Sorry! Anyway, you have all the info you need to get it right, A Haynes, or Chilton manual should be able to give you all the info you need. If you dont have one ill try to scan a pick of the sproket align in a few and post it.
vic
vic