390 pushrod/rocker question
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From: Steilacoom, WA
390 pushrod/rocker question
I have a 390 with about 20k on it. The rockers are pretty evenly, excessively worn on all rockers. The engine ran fine no issues. What are the main reasons for this wear? Valve stems look good. I compared he pushrods from the 390 with the ones from my 352. The 390 pushrods are noticeably longer. Is the problem too long pushrods or possibly valve springs? The oil pressure has always been good.
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How do you know it only has 20k miles?
Bad rocker geometry can cause problems. If it has been rebuilt, the design of the particular rockers in use, a bigger cam, a bad valve job, longer or shorter than stock valves, and to a lesser degree with shaft rockers, milling either the heads or block can have an affect on the geometry.
Bad rocker geometry can cause problems. If it has been rebuilt, the design of the particular rockers in use, a bigger cam, a bad valve job, longer or shorter than stock valves, and to a lesser degree with shaft rockers, milling either the heads or block can have an affect on the geometry.
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From: Deep River, CT.
Just to let you know push rods are/were available in standard, .060 longer and .060 shorter. There is a shop manual procedure that involves a tool you put on the rocker and press down toward the lifter to compress all the oil out of the lifter. Then you measure the gap between the rocker and the valve stem. There is an allowed spec and if not within you would then choose a longer or shorter push rod to get you in spec. Of course you need to follow the procedure to make sure the valves are completely closed. Your 390 should be in the family of engines this applies to.
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From: Steilacoom, WA
I got the engine with receipts about 20 years ago to put in my moms 76 F250 and she put right around 20k miles on it. She didn't drive it much after I swapped it and didn't drive it at all after 2004.
All of the wear on the rockers are even and flat on all rockers. Are valve springs color coded for spring rate? With this much wear what is the likelihood of excessive cam wear also? Like I stated before the engine ran great. Before I pulled the motor and junked the truck I started it after not running for 5 years and it ran perfect. When I pull the intake I'll look at the lifters and see how they look. This is a C6ME block with D2TE-AA heads
All of the wear on the rockers are even and flat on all rockers. Are valve springs color coded for spring rate? With this much wear what is the likelihood of excessive cam wear also? Like I stated before the engine ran great. Before I pulled the motor and junked the truck I started it after not running for 5 years and it ran perfect. When I pull the intake I'll look at the lifters and see how they look. This is a C6ME block with D2TE-AA heads
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Were the rockers new or used? Used rockers would explain an appearance of excess wear on a low mileage motor.
If new, then all the causes I mentioned about rocker geometry are still possible and you'll need to check those.
I don't know about color coding for the spring rate.
Regarding cam wear, if it runs well, then it's probably ok. A compression check would help to verify and if you want to take it further, and have the tools available you could measure the lobe lift of several cylinders to make sure there is no significant variance.
If new, then all the causes I mentioned about rocker geometry are still possible and you'll need to check those.
I don't know about color coding for the spring rate.
Regarding cam wear, if it runs well, then it's probably ok. A compression check would help to verify and if you want to take it further, and have the tools available you could measure the lobe lift of several cylinders to make sure there is no significant variance.
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