Rocker Arm Problem
Printed From: TheAMCForum.com
Category: The Garage
Forum Name: AMC V8 Engine Repair and Modifications
Forum Description: AMC-made V8 engine mechanical, ignition and fuel from basic repair to high-perf modifications
URL: https://theamcforum.com/forum/forum_posts.asp?TID=96613
Printed Date: Apr/20/2024 at 11:21am
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Topic: Rocker Arm Problem
Posted By: Javelin360
Subject: Rocker Arm Problem
Date Posted: Oct/01/2018 at 5:00pm
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I'm having a bit of trouble with 3 sets of rocker arms I replaced. I had a collapsed lifer so I pulled the intake and replaced all of the lifter. I inspected the rocker arms and found three sets that had galling between the pivots and the rockers so I replaced them with Sealed Power units. The silver ones are the Sealed Power units and the move around A LOT when you wiggle them. The heat glazed units are what was in the motor when I got it and none of them have any movement. I measured the pivots between the old units and the SP units and they were within .002 of each other. I don't have a real way to compare SP rockers to the old rockers. The lifter rods do not appear to be bent or worn. I have swapped the position of the rockers to see if it changed anything but the movement problem persists no matter where the rockers are. One set of rockers I could get a .012 feeler gauge between the pivot and the rocker pivot surface. I removed .012 from the base of the pivots with my surface grinder and installed them back into the head. They still had movement. Any suggestions and can anyone identify the brand of the old rocker arms?     ------------- 69 AMX 401/727 74 Javelin 360/727 09 Mustang Supercharged 4.6 14 Wrangler Sport 4X4 18 GMC Sierra |
Replies:
Posted By: motorhead_1
Date Posted: Oct/02/2018 at 3:07am
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are the lifters pumped up? checking on the correct stroke? flat cam lobe? ------------- 69 SC/Rambler tribute 401/th400, 68 Rebel SST LSA, 66 F100 460/c6, 88 Merkur Xr4Ti, 71 Jaguar XJ6 LS1, 08 Supercharged Tundra |
Posted By: 304-dude
Date Posted: Oct/02/2018 at 6:53am
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Let's try something different... use a good used bridge with the new SP rocker set, and a SP bridge on a good used rocker set, and compare again. I have a feeling the SP rockers are not within OEM standards. This could be one of those instances. You may need to order a custom size push rod, or a set of adjustable push rods. Though, it can be expensive just for something so simple. ------------- 71 Javelin SST body 390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
Posted By: Trader
Date Posted: Oct/02/2018 at 8:31am
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I have used the SP rocker but you will notice that they are stamped V, VI, VII or none. I found slight differences between the V and VII and usually buy more then one set to get all with the same stamp. The VII had a larger diameter push rod recess and was overall longer then the V. Currently all VI on my 401. Have not seen the "none" but there are differences, and if the stamping is the indication, then I would tend to try and find a set and go from there.
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Posted By: SC397
Date Posted: Oct/02/2018 at 9:01am
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If you have replaced 3 sets of rocker arms and you are still having a problem then, the rocker arms are not the problem. Has the cam been replaced from the stock one? Has a valve job been done before you started having the problem? Why did the first lifter collapse?
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Posted By: 401MATCOUPE
Date Posted: Oct/02/2018 at 1:18pm
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The factory V-8 units had both T and V stamped in them over the years, what you do have to becareful of the 6 cylinder rocker looks the same but the oil hole is at different angle and other small differences. ------------- Ross K. Peterson 68X,GoPac,343,AT,52A(1stCar) 68X,GoPac,390,4sp,52A 69X,GoPac,390,4sp,64A 70X,GoPac,390,4sp,87A,8 70X,GoPac,390,4sp,BBO,8 70 Jav SST,390,AT,BSO 74MatX,401,AT,Prototype 74MatX,401,AT |
Posted By: SC397
Date Posted: Oct/02/2018 at 1:43pm
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Yea, I was thinking about the 6cyl rockers too. The 6cyl ones (top) are actually longer. https://flic.kr/p/2ag9Eg2" rel="nofollow">  https://flic.kr/p/2ag9Eg2" rel="nofollow - IMG_0806 by https://www.flickr.com/photos/149168736@N07/" rel="nofollow - Rick Jones , on Flickr https://flic.kr/p/2ag9EgH" rel="nofollow">  https://flic.kr/p/2ag9EgH" rel="nofollow - IMG_0807 by https://www.flickr.com/photos/149168736@N07/" rel="nofollow - Rick Jones , on Flickr https://flic.kr/p/2ag9Efk" rel="nofollow">
 https://flic.kr/p/2ag9Efk" rel="nofollow - IMG_0805 by https://www.flickr.com/photos/149168736@N07/" rel="nofollow - Rick Jones , on Flickr |
Posted By: Javelin360
Date Posted: Oct/02/2018 at 8:02pm
Yes the lifters are pumped up. I pre lubed the oiling system before I ever started the engine also. It's only the three new pairs of rocker arms that I am having trouble with. All the rockers that were not replaced have no slop. The cam appears to be fine.
I did try swapping the old pivots into the new rockers and the new pivots into the old rocker. It did not seem to make a difference. I have also moved the new pairs of rockers to several different locations and they are still sloppy and the original sets have no slop. I'm begining to think the SP pairs are out of spec as all three pairs have varied amounts of slop.
The three pairs all have the same stamping/slash marks. I spoke with a tech guy from SP and he said that the marks are put there by the manufacture. This implies to me that SP has someone else stamp these out.
I may have been unclear. I replaced three pairs of rocker arms not three entire sets. So the engine has 6 new rocker arms and 10 older rocker arms. I purchased the engine from another party. It had been rebuilt with a stock cam, bored .030. I assume it had a valve job done but can't be sure. The motor ran fine until the lifter collapsed. I don't know why it collapsed. The base of all the lifters had a very nice wear pattern and the cam looked good. I had a buddy that builds race engines inspect the surfaces for impropper wear. He said all the wear surfaces looked good. The only rocker arms that have slop are the 6 that I replaced. All the others have no slop.
As I mentioned earlier I spoke to a tech guy about the SP rockers. The part # R875 I have is supposed to be for an AMC 401 with bridged rockers. He is also leaning to the rockers not being made correctly. I purchased these things back in Jan of 2012 so I doubt that Summit or SP are going to replace them. I supose that 6cyl units could have been errantly placed in an 8cyl box but how would I tell? I was considering buying a set of Melling rocker arms but the pics on the Quadratec web site have the same stamping marks as the SP rockers that are giving me a problem. This leads me to believe that the Melling and SP brands are made by the same manufacture. Are there any other brands worth trying? ------------- 69 AMX 401/727 74 Javelin 360/727 09 Mustang Supercharged 4.6 14 Wrangler Sport 4X4 18 GMC Sierra |
motorhead_1 wrote:Posted By: SC397
Date Posted: Oct/03/2018 at 7:12am
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I still don't think that the rocker arms are the issue. I have seen some not-so-great valve jobs where they ended up with different valve heights on the same head. It makes a mess to deal with if you don't have adjustable rocker arms. You could lay a straight edge across the tops of the valves to see if they are the same height. Check all of your push rod lengths and let us know what they are and of coarse if they are all the same or not. |
Posted By: Boris Badanov
Date Posted: Oct/03/2018 at 11:52am
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How is the oil pressure? ------------- Gremlin Dreams |
Posted By: Javelin360
Date Posted: Oct/03/2018 at 6:09pm
60 on start up as engine warms up it drops to 40 at idle. ------------- 69 AMX 401/727 74 Javelin 360/727 09 Mustang Supercharged 4.6 14 Wrangler Sport 4X4 18 GMC Sierra |
Posted By: Javelin360
Date Posted: Oct/06/2018 at 2:15pm
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I spent a bit of time this morning determining the differences between the rocker arms and taking some measurements. The lifter rods are 7.8 inches long. The valve spring height is 1.8 inches. I know the push rods are the correct length. Can anyone verify that 1.8 inches is the correct height? Pictures of the rockers up close. The area that appears to be a shadow is the older rocker arm. It is considerably lower than the newer rocker.   ------------- 69 AMX 401/727 74 Javelin 360/727 09 Mustang Supercharged 4.6 14 Wrangler Sport 4X4 18 GMC Sierra |
Posted By: 304-dude
Date Posted: Oct/06/2018 at 2:29pm
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Donna, but the old rocker arm seems a bit more taller on the sides (wall height) at the push rod half, up to the stud. Maybe having some reason as to your issues. Like explained in an earlier reply, not all stampings are perfect. Actually the sides are not taller... After looking harder, the depth of the push rod end is a wee deeper, thus the taller wall height. If what I see is right, that would explain why the new rocker has some looser fitment again the push rod. ------------- 71 Javelin SST body 390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
Posted By: Javelin360
Date Posted: Oct/06/2018 at 2:37pm
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Yes there is a definite difference in the rockers. What I'm not sure of is if the problem is because the new rockers are incorrect or if the valves and the old rockers are the problem. I have ordered 4 sets of Melling rockers that should be here by the 15th. If they are also loose I'm guessing that the problem is the valves and old rockers. ------------- 69 AMX 401/727 74 Javelin 360/727 09 Mustang Supercharged 4.6 14 Wrangler Sport 4X4 18 GMC Sierra |
Posted By: Boris Badanov
Date Posted: Oct/06/2018 at 2:47pm
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In my AMC experience stock rockers are excellent. Aftermarket rockers SUCK. If you can not find a set of NOS rockers it is best you convert to aftermarket rollers rather than mess with the aftermarket stamped steel junk. ------------- Gremlin Dreams |
Posted By: Javelin360
Date Posted: Oct/12/2018 at 9:57pm
Looks as if it is going to be a valve/Rocker problem. I received some OEM rockers today and installed them. The looseness is still present.  As it is now I've got enough OEM rockers to replace them all and get some longer push rods. I've got a buddy coming over tomorrow to help me determine the length I will need. ------------- 69 AMX 401/727 74 Javelin 360/727 09 Mustang Supercharged 4.6 14 Wrangler Sport 4X4 18 GMC Sierra |
Posted By: Javelin360
Date Posted: Oct/13/2018 at 5:28pm
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Looks to be that there is about .040 difference between the height of the ball socket areas of the old and new rockers. Ordered some push-rods that are 7.900 inches. If that isn't quite enough I can remove another .025 from the bottom of the pivots on my surface grinder. Hopefully this gets things up and running decently. Some time in the future I'm going to have to yank these heads and get them reworked. ------------- 69 AMX 401/727 74 Javelin 360/727 09 Mustang Supercharged 4.6 14 Wrangler Sport 4X4 18 GMC Sierra |
Posted By: Javelin360
Date Posted: Oct/27/2018 at 5:19pm
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Spent two hours today with a hot rod buddy dinking with this motor. He feels the the valve train is functioning correctly and there is something else wrong. Looks as if I'm pulling this motor after I attend the SNAMC show next week and start tearing it down with him to figure out what is wrong. The upside is I will know what has been done internally after we are finished. ------------- 69 AMX 401/727 74 Javelin 360/727 09 Mustang Supercharged 4.6 14 Wrangler Sport 4X4 18 GMC Sierra |