350 problems
Thread Starter
Pro
Joined: Jun 2007
Posts: 688
Likes: 1
From: Stevens Point WI
350 problems
I am helping a friend with his 350 and we are having some issues regarding the correct TDC in relation to setting the valves and where the timing marks are on his timing set.
First off its a hydraulic cam,
Now what we are seeing is the dots on the timing set are lined up next to each other, the #1 piston is at the top and the #1 lifters are both deep in there bores which should indicate TDC on the compression stroke right?
Now if thats right all the different info we have found states you can set the valves like this
set..
1 exhaust, 1 intake, 3 X, 5 I, 7 I, 2 I, 4 E, 8E then rotate 360 and do the rest.
Well when we come to #8 E at TDC on the compression stroke its not on the base circle its creating lift??
What step are we missing here?
I just do not want the timing set to be off and have to tear it all apart to restet it.
First off its a hydraulic cam,
Now what we are seeing is the dots on the timing set are lined up next to each other, the #1 piston is at the top and the #1 lifters are both deep in there bores which should indicate TDC on the compression stroke right?
Now if thats right all the different info we have found states you can set the valves like this
set..
1 exhaust, 1 intake, 3 X, 5 I, 7 I, 2 I, 4 E, 8E then rotate 360 and do the rest.
Well when we come to #8 E at TDC on the compression stroke its not on the base circle its creating lift??
What step are we missing here?
I just do not want the timing set to be off and have to tear it all apart to restet it.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
OK, there are a couple of things here - is this a new build where you just installed the cam? If so, note that not only do the dots need to line up, but the cam pin should be at 3:00 and the crank key at 2:00 when the marks are lined up - I have a pic I can post if this isn't clear.
The method you're talking about is the companion cylinder method which is based on two cylinders being at TDC at the same time but at two different points in their cycles. Great approach, one that I use, and I'll reproduce the sequence here although it appears you've got it right. You're correct that if both lifters on #1 are not providing lift you should be on the compression stroke #1.
No. 1 cylinder at TDC compression:
Adjust exhaust valve: 1, 3, 4, 8
Adjust intake valve: 1, 2, 5, 7
No. 6 cylinder at TDC compression
Adjust exhaust valve: 2, 5, 6, 7
Adjust intake valve: 3, 4, 6, 8
If this isn't working, then you're not on TDC compression, the cam is installed incorrectly, or TDC is located incorrectly.
The method you're talking about is the companion cylinder method which is based on two cylinders being at TDC at the same time but at two different points in their cycles. Great approach, one that I use, and I'll reproduce the sequence here although it appears you've got it right. You're correct that if both lifters on #1 are not providing lift you should be on the compression stroke #1.
No. 1 cylinder at TDC compression:
Adjust exhaust valve: 1, 3, 4, 8
Adjust intake valve: 1, 2, 5, 7
No. 6 cylinder at TDC compression
Adjust exhaust valve: 2, 5, 6, 7
Adjust intake valve: 3, 4, 6, 8
If this isn't working, then you're not on TDC compression, the cam is installed incorrectly, or TDC is located incorrectly.
Last edited by billla; Jun 28, 2009 at 10:21 AM.
Race Director
Joined: Jun 2000
Posts: 10,039
Likes: 668
From: FL
EDIT: REMOVED BAD ADVICE (DERIVED FROM BAD PHOTO)
Listen to Billa. Put the cam pin at 3 o'clock with marks aligned.
I usually set the valves at by putting each piston in turn at TDC on the firing stroke and then set the valves. Start with #1, turn crank 90 degrees and set the next in firing order. Read this paper for good info on setting valve lash:
http://www.corvette-restoration.com/...Valve_Lash.pdf
Listen to Billa. Put the cam pin at 3 o'clock with marks aligned.
I usually set the valves at by putting each piston in turn at TDC on the firing stroke and then set the valves. Start with #1, turn crank 90 degrees and set the next in firing order. Read this paper for good info on setting valve lash:
http://www.corvette-restoration.com/...Valve_Lash.pdf
Last edited by SteveG75; Jun 28, 2009 at 11:04 AM.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
I *think* you're just talking about finding TDC compression #1 and not for cam installation...in which case your guideance is fine...but I want to be sure we're 100% clear.
Last edited by billla; Jun 28, 2009 at 10:53 AM.
Race Director
Joined: Jun 2000
Posts: 10,039
Likes: 668
From: FL
Both dots should not be at 12:00! The cam dot will be at 6, and the crank at 12. The dots are supposed to be lined up right next to each other. You are correct that this is TDC compression #6 - which is why so many distributors get installed 180 out on new builds.
I *think* you're just talking about finding TDC compression #1 and not for cam installation...but I want to be sure we're 100% clear.
I *think* you're just talking about finding TDC compression #1 and not for cam installation...but I want to be sure we're 100% clear.
EDIT: Removed bad info derived from flipped photo. (I hate the Internet at times
)For fun, read the whole info about swapped photos and timing marks here:
http://www.hotrodders.com/forum/edel...ng-145746.html
Most people forget that the crank does two revolutions for one cam revolution, that is where confusion starts.
Last edited by SteveG75; Jun 28, 2009 at 11:06 AM.
Race Director
Joined: Jun 2000
Posts: 10,039
Likes: 668
From: FL
New post to correct my earlier info.
Timing marks next to each other and cam pin at 3 o'clock is the right orientation. If the OP has #8 already off the base circle, then the cam may be too large in duration to do the companion cylinder method. In that case, I would recommend trying the 90 degree crank method that Lars talks about in the poster I posted earlier (repost here to keep info together).
http://www.corvette-restoration.com/...Valve_Lash.pdf
Timing marks next to each other and cam pin at 3 o'clock is the right orientation. If the OP has #8 already off the base circle, then the cam may be too large in duration to do the companion cylinder method. In that case, I would recommend trying the 90 degree crank method that Lars talks about in the poster I posted earlier (repost here to keep info together).
http://www.corvette-restoration.com/...Valve_Lash.pdf
Thread Starter
Pro
Joined: Jun 2007
Posts: 688
Likes: 1
From: Stevens Point WI
New post to correct my earlier info.
Timing marks next to each other and cam pin at 3 o'clock is the right orientation. If the OP has #8 already off the base circle, then the cam may be too large in duration to do the companion cylinder method. In that case, I would recommend trying the 90 degree crank method that Lars talks about in the poster I posted earlier (repost here to keep info together).
http://www.corvette-restoration.com/...Valve_Lash.pdf
Timing marks next to each other and cam pin at 3 o'clock is the right orientation. If the OP has #8 already off the base circle, then the cam may be too large in duration to do the companion cylinder method. In that case, I would recommend trying the 90 degree crank method that Lars talks about in the poster I posted earlier (repost here to keep info together).
http://www.corvette-restoration.com/...Valve_Lash.pdf
That cam has somthing like 290 degrees duration that would explain the #8 issue
Yes the the cam is new and was installed cam gear at 6 oclock and crank at 12 oclock having the cam pin at 3 oclock
The book we were following just confused us as it says at TDC you should set #8 exhaust and we kept seeing it allready on lift
So with both #1 valves closed and piston at top with timing dots at 6 and 12 we should be good to go on adjusting the valves right?
Race Director
Joined: Jun 2000
Posts: 10,039
Likes: 668
From: FL
I never thought about the duration
That cam has somthing like 290 degrees duration that would explain the #8 issue
Yes the the cam is new and was installed cam gear at 6 oclock and crank at 12 oclock having the cam pin at 3 oclock
The book we were following just confused us as it says at TDC you should set #8 exhaust and we kept seeing it allready on lift
So with both #1 valves closed and piston at top with timing dots at 6 and 12 we should be good to go on adjusting the valves right?
That cam has somthing like 290 degrees duration that would explain the #8 issue
Yes the the cam is new and was installed cam gear at 6 oclock and crank at 12 oclock having the cam pin at 3 oclock
The book we were following just confused us as it says at TDC you should set #8 exhaust and we kept seeing it allready on lift
So with both #1 valves closed and piston at top with timing dots at 6 and 12 we should be good to go on adjusting the valves right?
Now, here’s the trick:
What’s the firing order for a GM V8?
1-8-4-3-6-5-7-2
How often does a cylinder fire in a V8?
Every 90 degrees
That means we can now rotate the crankshaft 90 degrees at a time, and go right to the next cylinder in the firing order for the valve adjustment, with confidence that both of the valves for that cylinder will be closed and ready to adjust.. So rotate to your next chalk line, and adjust #8 as described above.
Rotate to the next line and adjust #4. After you’ve rotated the crankshaft twice over (using the starter and “bumping” is the easiest way), you’ve finished your valve adjustment! No oily mess, no worrying about if you missed a valve. Just a nice, simple, structured procedure!
What’s the firing order for a GM V8?
1-8-4-3-6-5-7-2
How often does a cylinder fire in a V8?
Every 90 degrees
That means we can now rotate the crankshaft 90 degrees at a time, and go right to the next cylinder in the firing order for the valve adjustment, with confidence that both of the valves for that cylinder will be closed and ready to adjust.. So rotate to your next chalk line, and adjust #8 as described above.
Rotate to the next line and adjust #4. After you’ve rotated the crankshaft twice over (using the starter and “bumping” is the easiest way), you’ve finished your valve adjustment! No oily mess, no worrying about if you missed a valve. Just a nice, simple, structured procedure!
Last edited by SteveG75; Jun 28, 2009 at 12:35 PM.
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