top dead center issues
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Senior User
Joined: Oct 2013
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From: wentzville MO
top dead center issues
so i am getting ready to start putting everything onto my rebuilt engine. i have the harmonic balancer on and before putting the valve covers on turned the engine to what I thought was top dead center. the only issue is the groove in the balancer is 180 degrees off from where it should be. it is sitting in the 5 oclock position and the little pointer I stole off the 302 points at about the 11:00. I could have sworn this thing is at the top of the compression stroke. the oil pan is off so I can see it is all the way up. any thoughts??? how do I time this thing or even find exact top dead center
Fleet Owner
Joined: Oct 2005
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From: Kentucky
The crankshaft rotates twice for every revolution of the camshaft. You have cylinder #1 at TDC but it is on the exhaust stroke, not the compression.
http://en.wikipedia.org/wiki/Four-stroke_engine
http://en.wikipedia.org/wiki/Four-stroke_engine
Lead Driver
Joined: Aug 2006
Posts: 5,670
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From: Sand Lake, MI
You have the valve cover off, piston starting down intake valve opens. Piston starts up intake valve closes, both valves closed through piston travel TDC (tdc mark lines up, you can see both rocker arms are "relaxed" valves are both closed), piston goes back down exhaust valve opens next.
If the exhaust valve just closed? it was the exhaust stroke.
Talking about #1 cylinder naturally.
Or take out #1 plug, put your finger over hole rotate main shaft until compression blows finger off, blows air out plug hole finger can't stop it. That'd be the compression stroke, no other stroke will do that.
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Senior User
Joined: Oct 2013
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From: wentzville MO
so I tested it and I am on the compression stroke with the piston to the top but the mark is off 180 degrees on the balancer. if i turn the engine to where the line matches the pointer then the piston is in the full bottom end of its stroke (I can see the crank). do I have the wrong balancer? wtf?
Fleet Owner
Joined: Oct 2005
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From: Kentucky
Trending Topics
Fleet Owner
Joined: Oct 2005
Posts: 20,785
Likes: 1,751
From: Kentucky
The crankshaft rotates twice for every revolution of the camshaft. You have cylinder #1 at TDC but it is on the exhaust stroke, not the compression.
Four-stroke engine - Wikipedia, the free encyclopedia
Four-stroke engine - Wikipedia, the free encyclopedia
Sorry about that
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Lead Driver
Joined: Aug 2006
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From: Sand Lake, MI
Hard to say wrong one or timing change not installed correctly?
Dots on gears need be toward one another, just to review, cam gear dot "down", crank gear dot "up" dead in line with shafts center lines.
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Senior User
Joined: Oct 2013
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From: wentzville MO
Sure is. I just can't figure it out. Very strange as well that it's exactly off by 180. What should the diameter of the balancer be? Just to double check that it's right
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Senior User
Joined: Oct 2013
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From: wentzville MO
ALL ABOARD. lord knows i belong on here. This entire things falls right in line with some of my other issues.
The deep groove on these balancers is not 0. its just a mark. would be a GREAT place to put the timing marks but those are actually extremely faint and ill be damn about 180 degrees away from the deep groove. so yeah I am dead on. i need better lights in my garage ... that's my excuse for this one
The deep groove on these balancers is not 0. its just a mark. would be a GREAT place to put the timing marks but those are actually extremely faint and ill be damn about 180 degrees away from the deep groove. so yeah I am dead on. i need better lights in my garage ... that's my excuse for this one
Logistics Pro
Joined: Mar 2005
Posts: 4,698
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From: Mexico, Missouri
I feel dumb, but, what if you put the old balancer on and see what it shows when the piston is at TDC on compression stroke. Can you post a pic of the problem you are having when its lined up?
Did you or another company assemble the engine? I'm very baffled as are others here. This is a mystery to me as well.
Did you or another company assemble the engine? I'm very baffled as are others here. This is a mystery to me as well.