Engine Rebuild question about rocker arms and push rods
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Intermediate
Joined: Jan 2007
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Engine Rebuild question about rocker arms and push rods
I'm doing a top end rebuild on a 2002 Heritage Softail EFI. I was following the manual line by line. During the rebuild while installing the rocker assembly I followed the directions to find TDC by rotating the wheel while we had a finger on the spark plug hole. We stopped rotating as soon as the air flow through the hole stopped right before it started sucking in. As we started installing the rocker assembly it didn't lay completely flat. We had to ratchet down the rocker assembly and we could feel tension as the rocker assembly was becoming flush. The manual stated that the push rods should spin freely. They weren't able to spin at all. After we torqued it down and rotated the wheel a full revolution back to TDC the push rods would spin freely. Obviously we ran the risk of potentially bending the push rods. The fact that we were able to rotate the tire and get everything at rest to where we could spin the rods, I'm wondering where I went wrong. The piston was most definitely at TDC. We were able to shine a light through the spark plug hole and verify. Ive finished the first cylinder and will be starting on the second in the coming week. Id like to have the second one come together correctly. Any advice would be greatly appreciated.
Elite HDF Member
Joined: Nov 2010
Posts: 3,846
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From: Simi Valley, CA
It sounds like you were at TDC of the exhaust stroke. You actually need to be at TDC of the compression stroke to install the rocker arms without any preload.
Probably no damage done. The pressure you were feeling was simply valve spring pressure as the valves were being opened during the torquing process.
When you rotated the engine to the next TDC, now you were on the compression stroke and that is why you could now rotate the pushrods.
TDC exhaust stroke - exhaust valve is closing and intake valve is opening, but neither is closed completely.
TDC compression stroke - both valves closed.
Probably no damage done. The pressure you were feeling was simply valve spring pressure as the valves were being opened during the torquing process.
When you rotated the engine to the next TDC, now you were on the compression stroke and that is why you could now rotate the pushrods.
TDC exhaust stroke - exhaust valve is closing and intake valve is opening, but neither is closed completely.
TDC compression stroke - both valves closed.
Elite HDF Member
Joined: Nov 2010
Posts: 3,846
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From: Simi Valley, CA
TDC of the compression stroke gaurantees both valves are closed.
There are several degrees on either side of TDC (compression stroke) where both valves are closed, but once you pass TDC and the exhaust valve starts to open, both valves will not be closed at the same time again until you're approaching TDC of the next compression stroke.
Does that answer your question?
Tourer
Joined: Feb 2010
Posts: 420
Likes: 202
My two cents worth....
I think the hydralic lifters get "pumped" up when they have had the pressure off of them for a while. Assuming the oil was not allowed to drain out of them.
I noticed this event occuring when I changed my cam chain tensioners. The lifters were left in the engine with oil in them. Then I finished the job and noticed the stiffness when I reassembled the rods. It was a little tight at first but when I finished I rolled the pistons around right back to TDC and the rods were spinning with no problems.
I think the hydralic lifters get "pumped" up when they have had the pressure off of them for a while. Assuming the oil was not allowed to drain out of them.
I noticed this event occuring when I changed my cam chain tensioners. The lifters were left in the engine with oil in them. Then I finished the job and noticed the stiffness when I reassembled the rods. It was a little tight at first but when I finished I rolled the pistons around right back to TDC and the rods were spinning with no problems.
Road Warrior
Joined: Mar 2011
Posts: 1,378
Likes: 2
From: Macon, GA USA
After installing did you wait till the lifters bleed down before seeing if the push rods spun? It can take up to 10 or 15 minutes for them to bleed down. You should not turn the motor over till the bleed down.
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