finding TDC to set valves?
Thread Starter
Burning Brakes
Joined: Feb 2012
Posts: 1,047
Likes: 43
From: Longview Texas
finding TDC to set valves?
New cam is in and now I need to find TDC to adjust the valves. If I'm not mistaken you turn the engine over by hand until you get the exhaust to come out of cylinder #1. When this happens will the dot on the cam sprocket be down at the 6:00 position and the dot on the crankshaft sprocket be up at the 12:00 position? I understand you adjust half of them to 22 ft. lbs. of torque (I have the list of which ones) and then you turn the engine over 360 and do the rest. However, from some research that I've done one post said that both dots will be at 12:00 which didn't sound correct to me.
Thanks.
Scott
Thanks.
Scott
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Unless you have adjustable rocker arms, there is no adjustment on the OEM rockers. You control lifter pre-load with the length of the pushrod.
The trunnions of the rocker arms are torqued to 22 ft-lbs ... period. No adjustments unless you are using aftermarket rockers where you can adjust lifter per-load.
There's a page out of the service manual that has been posted a 100 times on this board over the years that shows where the crank needs to be when torquing the rockers to 22 ft-lbs. Object is to torque them down when the valve is closed.
The trunnions of the rocker arms are torqued to 22 ft-lbs ... period. No adjustments unless you are using aftermarket rockers where you can adjust lifter per-load.
There's a page out of the service manual that has been posted a 100 times on this board over the years that shows where the crank needs to be when torquing the rockers to 22 ft-lbs. Object is to torque them down when the valve is closed.
Last edited by ZeeOSix; Jun 19, 2013 at 04:14 PM.
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
Unless you have adjustable rocker arms, there is no adjustment on the OEM rockers. You control lifter pre-load with the length of the pushrod.
The trunnions of the rocker arms are torqued to 22 ft-lbs ... period. No adjustments unless you are using aftermarket rockers where you can adjust lifter per-load.
The trunnions of the rocker arms are torqued to 22 ft-lbs ... period. No adjustments unless you are using aftermarket rockers where you can adjust lifter per-load.
Thread Starter
Burning Brakes
Joined: Feb 2012
Posts: 1,047
Likes: 43
From: Longview Texas
That's the post I'm questioning. How would the dot be up at 12:00 when the dowel for the cam pin is at 3:00? When I reinstalled my cam sprocket the dot is down and the dowel is to the right. I'm using the OEM chain and sprockets.
By the way, I've never understood why people take the time to post "it's been discussed 100 times ... look it up". I had the post and knew what it said but was questioning it. I believe the old saying goes if you have nothing good to say don't say anything at all. You folks without anything helpful to add get old and make using the forum to do research frustrating. Just my 2 cents.
Scott
By the way, I've never understood why people take the time to post "it's been discussed 100 times ... look it up". I had the post and knew what it said but was questioning it. I believe the old saying goes if you have nothing good to say don't say anything at all. You folks without anything helpful to add get old and make using the forum to do research frustrating. Just my 2 cents.
Scott
Advanced
Joined: Aug 2001
Posts: 99
Likes: 0
From: Cincinnati OH
That's the post I'm questioning. How would the dot be up at 12:00 when the dowel for the cam pin is at 3:00? When I reinstalled my cam sprocket the dot is down and the dowel is to the right. I'm using the OEM chain and sprockets.
By the way, I've never understood why people take the time to post "it's been discussed 100 times ... look it up". I had the post and knew what it said but was questioning it. I believe the old saying goes if you have nothing good to say don't say anything at all. You folks without anything helpful to add get old and make using the forum to do research frustrating. Just my 2 cents.
Scott
By the way, I've never understood why people take the time to post "it's been discussed 100 times ... look it up". I had the post and knew what it said but was questioning it. I believe the old saying goes if you have nothing good to say don't say anything at all. You folks without anything helpful to add get old and make using the forum to do research frustrating. Just my 2 cents.
Scott
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
By the way, I've never understood why people take the time to post "it's been discussed 100 times ... look it up". I had the post and knew what it said but was questioning it. I believe the old saying goes if you have nothing good to say don't say anything at all. You folks without anything helpful to add get old and make using the forum to do research frustrating. Just my 2 cents.
Scott
Scott
Last edited by ZeeOSix; Jun 19, 2013 at 06:55 PM.
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Thread Starter
Burning Brakes
Joined: Feb 2012
Posts: 1,047
Likes: 43
From: Longview Texas
Thank you and again I apologize.
Thread Starter
Burning Brakes
Joined: Feb 2012
Posts: 1,047
Likes: 43
From: Longview Texas
I see what you saying. That picture is kind of misleading. With the crank dot at 12 and the cam dot at 6, the cam dowel should be at 3 o'clock. Rotate 360 degrees and the crank dot should be at 12, the cam dot should be at 12, and the cam dowel should be at 9 o'clock.
So where is TDC? With the cam dot at 6 and dowel at 3
OR
with the cam dot at 12 and the dowel at 9?
That picture from the service manual doesn't seem correct to me.
Scott
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
TH - I'd go by the crankshaft key at the 1:30 position as the SM described in Step 6. Forget about the dots on the crank and cam sprockets in the SM figure at this point.
To verify, put the pushrods in the lifters on Cyl #1 and watch the intake pushrod go up (intake valve would be opening), then back down (intake valve would be closing) as you rotate the engine. The piston is on the compression stroke after the intake pushrod stops moving downwards. Bring the piston to TDC and you are there. The crank key should be at 1:30 then if the SM is correct.
To verify, put the pushrods in the lifters on Cyl #1 and watch the intake pushrod go up (intake valve would be opening), then back down (intake valve would be closing) as you rotate the engine. The piston is on the compression stroke after the intake pushrod stops moving downwards. Bring the piston to TDC and you are there. The crank key should be at 1:30 then if the SM is correct.
Advanced
Joined: Aug 2001
Posts: 99
Likes: 0
From: Cincinnati OH
Ok, now I'm really confused. I'm a HS math teacher and am off for the summer so I must have my "summer brain" working now.
So where is TDC? With the cam dot at 6 and dowel at 3
OR
with the cam dot at 12 and the dowel at 9?
That picture from the service manual doesn't seem correct to me.
Scott
So where is TDC? With the cam dot at 6 and dowel at 3
OR
with the cam dot at 12 and the dowel at 9?
That picture from the service manual doesn't seem correct to me.
Scott
Drifting
Joined: Jan 2012
Posts: 1,341
Likes: 8
From: Hopatcong New Jersey
Ok, now I'm really confused. I'm a HS math teacher and am off for the summer so I must have my "summer brain" working now.
So where is TDC? With the cam dot at 6 and dowel at 3
OR
with the cam dot at 12 and the dowel at 9?
That picture from the service manual doesn't seem correct to me.
Scott
So where is TDC? With the cam dot at 6 and dowel at 3
OR
with the cam dot at 12 and the dowel at 9?
That picture from the service manual doesn't seem correct to me.
Scott
There are two top dead centers. One on compression stroke, and one on exhaust stroke. You want to start the process from the FSM at TDC compression stroke, which is cam sprocket and crank sprocket dot 12 o'clock.
Thread Starter
Burning Brakes
Joined: Feb 2012
Posts: 1,047
Likes: 43
From: Longview Texas
Thanks guys. I think I have it now. How does this all sound?
1. The OEM cam sprocket has a small "half circle" on it and is also stamped "12" at that spot. When you install the cam this "dot" will be at 6 (making the stamped "12" upside down), the crank dot is at 12, and the dowel pin is at 3.
2. To get to TDC rotate the "12" to the top putting the dowel at 9. This is always the compression stroke. Both #1 valves are closed.
3. After you install and torque the proper rockers (including both #1s) turn the CRANK 360, which will bring the "12" on the cam sprocket to 6, and do the rest (including both #6s).
Sorry to be so confusing and ask so many questions but I enjoy learning new things and this is the first time I've done a cam in a LS1. Other than having someone install the ring and pinion (after we took them the differential), we've done everything on our own on this including a converter, cam, header, etc. install in our 2-car garage.
Scott
Thread Starter
Burning Brakes
Joined: Feb 2012
Posts: 1,047
Likes: 43
From: Longview Texas
TH - I'd go by the crankshaft key at the 1:30 position as the SM described in Step 6. Forget about the dots on the crank and cam sprockets in the SM figure at this point.
To verify, put the pushrods in the lifters on Cyl #1 and watch the intake pushrod go up (intake valve would be opening), then back down (intake valve would be closing) as you rotate the engine. The piston is on the compression stroke after the intake pushrod stops moving downwards. Bring the piston to TDC and you are there. The crank key should be at 1:30 then if the SM is correct.
To verify, put the pushrods in the lifters on Cyl #1 and watch the intake pushrod go up (intake valve would be opening), then back down (intake valve would be closing) as you rotate the engine. The piston is on the compression stroke after the intake pushrod stops moving downwards. Bring the piston to TDC and you are there. The crank key should be at 1:30 then if the SM is correct.
Drifting
Joined: Jan 2012
Posts: 1,341
Likes: 8
From: Hopatcong New Jersey
Drifting
Joined: Sep 2009
Posts: 1,719
Likes: 4
From: cinnaminson n.j.
St. Jude Donor '14
I just did this job. One thing nobody mentioned was pushrods length/lifter preload. It's very important. You could have lifter damage, valves hanging open or at minimum a noisey engine. I did a lot of Internet searching and got conflicting specs so I called Texas speed and they told me .035-.085 preload is acceptable. .050-.070 is preferred.
I used a comp cam adjustable pushrod to check it on 2 valves per head. I also checked with a dial indicator. I was at .095 preload with the 7.400 pushrods. I had tsp overnight me a set of 3.375's and rechecked, .070 good to go. It took me a while but I would rather be safe and didn't want to take it back apart.
The car should be all completed early next week. I'll let you know the final results.
I used a comp cam adjustable pushrod to check it on 2 valves per head. I also checked with a dial indicator. I was at .095 preload with the 7.400 pushrods. I had tsp overnight me a set of 3.375's and rechecked, .070 good to go. It took me a while but I would rather be safe and didn't want to take it back apart.
The car should be all completed early next week. I'll let you know the final results.
Thread Starter
Burning Brakes
Joined: Feb 2012
Posts: 1,047
Likes: 43
From: Longview Texas
I just did this job. One thing nobody mentioned was pushrods length/lifter preload. It's very important. You could have lifter damage, valves hanging open or at minimum a noisey engine. I did a lot of Internet searching and got conflicting specs so I called Texas speed and they told me .035-.085 preload is acceptable. .050-.070 is preferred.
I used a comp cam adjustable pushrod to check it on 2 valves per head. I also checked with a dial indicator. I was at .095 preload with the 7.400 pushrods. I had tsp overnight me a set of 3.375's and rechecked, .070 good to go. It took me a while but I would rather be safe and didn't want to take it back apart.
The car should be all completed early next week. I'll let you know the final results.
I used a comp cam adjustable pushrod to check it on 2 valves per head. I also checked with a dial indicator. I was at .095 preload with the 7.400 pushrods. I had tsp overnight me a set of 3.375's and rechecked, .070 good to go. It took me a while but I would rather be safe and didn't want to take it back apart.
The car should be all completed early next week. I'll let you know the final results.
