Found the problem, but not the cause. Broken rocker tips - both push rod end. I had a friend take some pictures but since I don't do pictures, is there anybody that I can e-mail these to that will post them for me. If there is please send me your e-mail so I can send you the pictures to post. After finding this problem I do have lots more questions and how I can fix it so it doesn't happen again. I will most likely need replacement parts, hopefully an upgrade. I will be checking the lift on each lobe to make sure it's within specs. As soon as anyone can help me, I will send you the pics.
Thanks guys, Fritz
This message has been edited by 65slick on Aug 3, 2012 1:13 AM
At the bottom is my July 30 post with information about the motor in question. If you thumb through that you'll know a little bit about what I was looking for. I had lots of suggestions which I followed up with and found to rocker arms broken at the push rod ends. I have pics but do not know how to post them here. I was hoping I could send them to somebody and have them post them for me. You know what they say a picture is worth 1000 words. I was getting on and off compression out of number eight and then nothing. After pulling the valve cover on the left side, I discovered a broken rocker arm on #8 and one on #6. Both of these were on the push rod end. The rocker (push rod end) on #8 was broken off enough that the push rod was no longer making contact - thus the reason no compression and number eight. The rocker end on #6 was also broken off but not enough for the push rod to come loose, still had good compression in that cylinder. My question is how this could happen all of a sudden and what kind of parts are available so this will not happen again. I was not racing the motor, I haven't really pushed it in quite some time and as stated below it doesn't have much more than 10,000 miles on it. It started running rough after I went to the store came out and started it up - two blocks later it started running rough. I guess maybe if I was really pushing it but I wasn't. Now that I know what's happened I really need to find the cause so this doesn't happen again. This motor build is about 15 years old - guess you can tell I don't drive it much. Could it be the TRW rocker assembly was just a bad casting from when it was new. Very strange that all of a sudden two rocker tips would break off.
Any and all help I can get from you guys in finding the cause and parts to replace the damaged ones. I'm assuming an upgrade in rocker assembly might be needed but then I see so many motors going thousands of miles on more or less stock parts. If you check the July 30 posting one motor specs, the cam is nothing special... ???
Sorry for the long postings.
Thanks for any help, Fritz
July 30 post
Ok, before I pull the valve covers off and destroy a a perfectly sealed motor I need some advice from the motor experts out there. Let me lay it out for you. Took one of my trucks out for a ride and to do some errands. On the way home, I started the truck and heard one of the lifters tapping away. This is happened before but usually stops right away. This time it did not, and then the motor started running rough. Got it back to the house and noticed smoke coming out of the left exhaust, so I shut it off and pulled the plugs on the left bank. Number five and seven looked wet. I'm thinking its unusual for two plugs to go bad at the same time, at least it would be unusual, so it must be a loaded up distributor. Sure enough, after pulling the distributor cap And looking, all the brass poles were caked in corroded. I cleaned them and replace the cap.
Since I had the plugs out, I decided to do a compression test. I rebuilt this motor about 15 years ago and it only has around 10,000 miles on it.
So this is what I found and some info about the motor:
390 motor +10 over
new rocker assembly (TRW if I remember correctly)
Chet Herbert cam 275/285 215/225 @ .50 500/525 lift.
300lb springs (Chet Herbert)
lifters (Chet Herbert)
C4AE 6090 G heads (ported and polished)
Edelbrock manifold with 870 3310 Holly
Mallory uni-light distributor with multiple spark unit
I have almost the exact same set up, on a 428 motor in another truck. Both ran perfect up until yesterdays problem with the 390.
Now back to the 390. After cleaning up the distributor contacts which I felt caused the Miss in the motor, I decided to go ahead and do a compression test. All plugs were pulled but I only had time to do the left bank this is what I found in 5,6,7,8
6 = 150lbs and no leak down for ten mins.
7 = 150lbs and no leak down for ten mins.
8 = 150lbs and no leak down for ten mins.
9 = this one was acting very weird. Rechecked 3 times to make sure the tester was tight in the hole. BUT, this is what happened. When I first pulled a starter trigger it would not pump up past 30 pounds. I released the air and tried it again. This time 90 pounds. So instead of releasing the air this time, I just bumped the trigger without having it spinning around and around and it jumped up to 110. I bumped it one more time without having it spin around and it jumped up 10 more pounds to 120. This all seemed a little strange, so I release the air, rechecked to make sure the tester was tight, and spun the motor up six or seven turns and it would only pump up to 60 pounds. I again just bumped it once to get one revolution and it jumped to 90. I again bumped it once and it jumped up to 120. I repeated this same thing over and over again five times and got the same results. It would only jump up to a higher compression if I just bumped it and stopped and bumped it again. But every time I try to spin it up five or more times it would not pump up higher than 30 pounds. By the way, this cylinder, no matter what pressure it has in it is also never leaked down. I waited 10 full minutes at each one of those pressures to see if it would leak down - never did. The last pressure in there before I stopped for the evening was 90 pounds, and this morning, after a bout 10 hours time, it had only lost 2 pounds.
SO, This is very strange -never had this happen to me before. Any ideas on what it might be before I pull the valve cover off a perfectly sealed motor. This motor has never leaked in the 10,000 miles it has on it, so pulling this valve cover is tough. But I'm sure it's going to have to come off.
So, any thoughts to what it might be? Broken valve, collapsed lifter not pumping up each time. I have both inner and outer springs - so maybe inside one or the outside one could have broken and the valve is bouncing around? Whats your thoughts guys. Anything like this happened to you GURU motor builders. Thanks in advance.
shafts available if you find a broken one at the hold down bolt. Make sure the oiling holes are positioned down, new rocker arms on the broken ones, and when you bolt the rocker arms down, screw them down in steps, making sure the shaft does not bend. Take each bolt down a couple of turns in sequence. This assures you don't crack the new shaft at the bolt hole. Joe-JDC.
Big question, why did two of them break with just a start up after so many start-ups? They seem to be oiling, there was oil in the lower part of the head and rocker ass had oil on it. Guess I could check the oil pump. I think my air drill should turn it fast enough or does it really need to turn that fast to see oil pumping through the rocker ass ? I got the TRW rocker ass from my local Machine shop. The owner was and still is a goof friend. Never asked at the time if it was a HD set. Whats the difference between standard and HD? Could I tell just by looking at them? Are TRWs ok quality? Are there other brands at the about same price that are better? Sorry for all the questions but you guys LIVE these FE motors and I'm very happy your out there.
Are the oil holes on the bottom of the shaft with it
August 4 2012, 2:55 PM
assembled and installed on the head? If not, you are starving the last arms. Sometimes folks inadvertantly pick up an assembly, and switch it in their hands, and when they set it on the engine, everything is opposite of what it should be. Shafts are then positioned with oiling holes up, which is wrong. Joe-JDC.
I'm pretty sure the holes are pointing down. This motor has around 10,000 miles on it. I think it would have gone south way before this - BUT, I will check when I pull them off. My schedule has been wacky and haven't had much time to really spend on the motor but I've got some time off coming up. I'm thinking that if the left side is questionable, perhaps the right side assembly could also be. If the oil pressure is good, and I will check, I'm thinking maybe a bad run the TRW rocker assembly. I've always trusted TRW, but then you guys may know more about that.
As always any thoughts are appreciated.