Trying to set TDC
Thread Starter
Racer
Joined: Jan 2004
Posts: 251
Likes: 9
From: Franklin KY
Trying to set TDC
I have installed a new cam and know there are bunches of threads on this but here goes. Set the new cam to where marks line up as per instructions (Summit cam). Everything is lubed up. All components back on engine, engine out of car. Was trying to find TDC with my son. Didn't want to rotate the engine as much as I have but unsure of TDC. My son is holding his thumb over #1 while I turn engine clockwise. Finger is blown off and line on balancer is prior to reaching timing tape by about 1/4 turn. Do I rotate to 12 BTDC at this point or do I rotate counterclockwise? All of the videos I have seen are with someone cranking the engine and it usually stops at 0 or TDC. Vette is a 76 with L48. Should I now add some additive? I have rotated the engine about 3 times now including setting lash. Afraid of removing all of the cam lub for break in by rotating the engine too much.
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
Rotating the engine is not such a big deal until you put the lifters in. Get the motor set to TDC then put one cylinder of lifters/pushrods/rockers in at a time and set the valves. Then, turn the crank a 1/4 turn and set the next cylinder in the firing order.
If you havent already, go ahead and mark your balancer in quarters. At TDC you set valves for #1 and then each quarter turn brings the next cyl in firing order to its TDC.
If you havent already, go ahead and mark your balancer in quarters. At TDC you set valves for #1 and then each quarter turn brings the next cyl in firing order to its TDC.
Melting Slicks
Joined: Aug 2008
Posts: 2,200
Likes: 3
From: Lehigh county Pennsylvania
The only accurate way to find top dead center of the #1 piston is by using a piston stop screwed into the spark plug hole. Then you can adjust your timing pointer to the mark on your balancer.
Thread Starter
Racer
Joined: Jan 2004
Posts: 251
Likes: 9
From: Franklin KY
Lifters and pushrods are already in as well as timing chain, cover, and waterpump. just trying to get it ready to put back in the car and put the distributor on. Just wanted to get it set up so I can break the cam in as soon as it starts.
Instructor
Joined: Jan 2012
Posts: 201
Likes: 0
From: some hole in the ground town- camp verde:) arizona
seems every1 has covered findin tdc so as for additives, when i got my car it had sat for 9 yrs. i pulled each spark plug n used a plunger for givin medicine to dogs, cats etc, n shot 2 squirts of oil in each cylinder for some pre-startin lubrication. blew a lot of white smoke at first but i'm sure it helped save the engine from possible damage. it also showed any exhaust leaks haha
Thread Starter
Racer
Joined: Jan 2004
Posts: 251
Likes: 9
From: Franklin KY
Think I have the lash set from what I thought was TDC when I installed the cam. Used the procedures sent with cam. Went to verify TDC by getting my son to put his finger over the hole of the number one plug and it blew his finger off short of where I thought would be TDC. Think I have it figured out now. I just rotated the engine another 1/4 turn to where it is about 12 degrees before the 0 mark. Am planing on setting the dist up and marking everything and pulling it back off before reinstalling the engine...a little practice!
Last edited by Hawkdriver; Jan 15, 2012 at 09:59 PM. Reason: picture
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Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
I like to look at the valves to determine TDC. Assuming that your balancer is good and the timing mark hasn't shifted you can observe:
On the intake stroke the intake valve will be open (piston going down)
On the compression stroke both valves will be closed (piston going up) When the timing mark gets to 0 this will be TDC
On the power stroke both valves remain closed (piston going down) Timing mark will be going past TDC
On the exhaust stroke the exhaust valve will be open (piston going up)
On the intake stroke the intake valve will be open (piston going down)
On the compression stroke both valves will be closed (piston going up) When the timing mark gets to 0 this will be TDC
On the power stroke both valves remain closed (piston going down) Timing mark will be going past TDC
On the exhaust stroke the exhaust valve will be open (piston going up)
Thread Starter
Racer
Joined: Jan 2004
Posts: 251
Likes: 9
From: Franklin KY
Thanks my 76. This is basically how I found it the first time after cam install, plus just rotating the cam to both marks at12 oclock. Afterward I set the lash. After setting the lash is when I started second guessing myself and trying new things! Think I have it set now. Getting the bay cleaned up and hopefully will drop the engine back in soon. Just trying to get everything set right to make sure I can try and get it started to break the cam in correctly.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
The finger over sparkplug hole method should get you close enough to set lash, but the piston stop method allows you to verify the balancer is indexed properly. They have been known to move around with age.
