Tight Rockers
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Cargo Master
Joined: Dec 2004
Posts: 3,362
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From: Florence, SC
Tight Rockers
I took off my passenger's side valve cover of my 302 to investigate some valve noise I had. I discovered my rocker arms to be extremely tight. Two were so tight they were actually cocked to the side! What does this condition do to my engine? It has less than 1000 miles on the rebuild.
Will the tight and cocked rocker arms cause a rich condition? I have dual exhaust, and I also seem to have a problem with my passenger's side exhaust pipe (the same side as the tight/crooked rockers) running slightly richer than the driver' side, even with my carburetor adjusted. Would this be related?
Will the tight and cocked rocker arms cause a rich condition? I have dual exhaust, and I also seem to have a problem with my passenger's side exhaust pipe (the same side as the tight/crooked rockers) running slightly richer than the driver' side, even with my carburetor adjusted. Would this be related?
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Cargo Master
Joined: Dec 2004
Posts: 3,362
Likes: 22
From: Florence, SC
Hmmm...I don't know. That is a good question. I don't know enough about engines to know. I am actually having someone else take a closer look this weekend.
What would be the effects of too-tight and cocked intake rocker arms?
What would be the effects of too-tight and cocked exhaust rocker arms?
What would be the effects of too-tight and cocked intake rocker arms?
What would be the effects of too-tight and cocked exhaust rocker arms?
Senior User
Joined: Sep 2009
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In the case of the 302, the exhaust ports and valve springs will be a direct line from each other.
Edelbrock 60259 - Edelbrock Performer RPM Cylinder Heads - Overview - SummitRacing.com
Off the top of my head, I'd suspect premature valvetrain wear to be the highest-probability effect, especially the valve tip.
I'd take the rocker arms in question off and look at the tip of the valves for wear.
Is your valvetrain original? Have the heads been milled? There's also a chance that the rockers were installed properly, but have worn a groove to one side and cocked the bolt tight.
Edelbrock 60259 - Edelbrock Performer RPM Cylinder Heads - Overview - SummitRacing.com
Off the top of my head, I'd suspect premature valvetrain wear to be the highest-probability effect, especially the valve tip.
I'd take the rocker arms in question off and look at the tip of the valves for wear.
Is your valvetrain original? Have the heads been milled? There's also a chance that the rockers were installed properly, but have worn a groove to one side and cocked the bolt tight.
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Joined: Jan 2001
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From: Virginia
Your setup is not stock, so with a Ford you have to be careful about the valvetrain geometry. Are you running the stock valve train with that different cam or did you convert to adjustable rockers?
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Cargo Master
Joined: Dec 2004
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From: Florence, SC
Originally Posted by Franklin2
Your setup is not stock, so with a Ford you have to be careful about the valvetrain geometry. Are you running the stock valve train with that different cam or did you convert to adjustable rockers?
*stock Ford cast iron heads found on the 1987 - 1996 Ford F150/Bronco and 1987 - 1993 Ford Mustangs with the 5.0 and 5.8 engines
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From: Virginia
The base circle of the cam could be different also, requiring an adjustable valve train. You can somewhat tell what is going on by turning the engine till a particular set of valve's cylinder is a TDC, and then do the same method as a chevy with an adjustable valve train, and tighten the bolt holding the rocker while wiggling the pushrod. It's the same principle, except with a chevy you stop when the slack is taken up, and then turn the adjustment 3/4 to 1 turn and then leave it. In your case with the Ford, you are going to do the same thing except you are going to keep going till the bolt stops, you can't stop in the middle like on the chevy. So if you take all the slack out of the pushrod(with the cylinder at TDC) and then count the number of turns till the bolt bottoms out, and it's way over 1 turn, then yes your valve train is adjusted too tight. If you are 1/2 turn or less, then it's loose and you will get a lot of clacking.
Posting Guru
Joined: Oct 2010
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From: Missouri
Since our trucks use hydraulic lifters you should be able to push the rocker arms on the pushrod side and make the lifter "plunge?" with the specific cylinder at top dead center. In the event that the rockers are tight and you can't then their is excessive preload and you could be holding a valve open a fraction.
The previous owner of my truck installed an aftermarket cam and fully adjustable erson rocker arms.
The previous owner of my truck installed an aftermarket cam and fully adjustable erson rocker arms.
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On the newer heads the rockers 'bolt down.' They should be torqued when not on the lobe. So if all the components are present they should be 'square' with the head.
I like to set them up when the lifter is empty of oil. That way you can see the pre-load of the lifter.
To get the most performance out of a stock hydraulic roller lifter you will put only enough preload as needed. That way the lifter will stay pumped up at rpm. You can usually feel the push rod begin to get snug as you tighten, after you take it to zero lash.
On a bolt down rocker you adjust 'up' with shims.
I like to set them up when the lifter is empty of oil. That way you can see the pre-load of the lifter.
To get the most performance out of a stock hydraulic roller lifter you will put only enough preload as needed. That way the lifter will stay pumped up at rpm. You can usually feel the push rod begin to get snug as you tighten, after you take it to zero lash.
On a bolt down rocker you adjust 'up' with shims.
Cargo Master
Joined: Nov 2010
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I swear to goodness that you guys are speaking Arabic or something lol. I love learning about mechanics but much of the internal engine stuff is way over my head. Don't want to dog your thread, but just wanted to say that boy you guys sure are awesome on this forum!
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