390 engine tic
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390 engine tic
so i was out muddin and my truck poped outta gear, the engine wrapped up, dont know how high but it was momentary. After the incedent the the engine has a tic. I know it could be one of three things:
A. a bent pushrod
B. a bent valve
C. A lifter.
The truck runs on 8 and has plenty of oil.
I drove it 10 miles home with no change. I am at school and was wondering what the likleyhood of it being each of these? Ive had to change several bent pushrods on FE's. Is this a common problem? I am at college and have a limited number of tools and no garage to work in.
I hope it is a pushrod. any incite would be great.
thanks highrider
A. a bent pushrod
B. a bent valve
C. A lifter.
The truck runs on 8 and has plenty of oil.
I drove it 10 miles home with no change. I am at school and was wondering what the likleyhood of it being each of these? Ive had to change several bent pushrods on FE's. Is this a common problem? I am at college and have a limited number of tools and no garage to work in.
I hope it is a pushrod. any incite would be great.
thanks highrider
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Joined: Jul 2002
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From: Long Island USA
Either a lifter or a pushrod is my first guess...
You have to figure out where it is, used a stethoscope or screwdriver to the bone in front of your ear, placing it in various places to see where the ticking is loudest. Then, pull off that valve cover, and spin the pushrods (you might have to turn over the engine to get the valve all the way closed so you are able to spin it). If any are bent enough to tick, you'll see it. With the valve closed, push down on the rocker arm and see if the lifter collapses easy - you'll see a marked difference between the bleed down rate of a good lifter and the bad one(s).
Or, worst case, it's a rocker shaft that came loose - you might be able to just torque them down again, or not if it pulled the threads from the head or broke a bolt. Or broke a shaft... but you'll find it eventually.
You can try running the motor with the valve cover off to really get a sense of where it is, but there'll be a lot of oil coming off the valve train. I've been able to bend pieces of cardboard to keep the stuff from dripping onto the exhaust... but it still flies around a bit...
You have to figure out where it is, used a stethoscope or screwdriver to the bone in front of your ear, placing it in various places to see where the ticking is loudest. Then, pull off that valve cover, and spin the pushrods (you might have to turn over the engine to get the valve all the way closed so you are able to spin it). If any are bent enough to tick, you'll see it. With the valve closed, push down on the rocker arm and see if the lifter collapses easy - you'll see a marked difference between the bleed down rate of a good lifter and the bad one(s).
Or, worst case, it's a rocker shaft that came loose - you might be able to just torque them down again, or not if it pulled the threads from the head or broke a bolt. Or broke a shaft... but you'll find it eventually.
You can try running the motor with the valve cover off to really get a sense of where it is, but there'll be a lot of oil coming off the valve train. I've been able to bend pieces of cardboard to keep the stuff from dripping onto the exhaust... but it still flies around a bit...
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By the way, a bent valve can be found if there is slack in a rocker arm (you can move it back and forth) and the pushrod is not bent or rocker arm/shaft buggered.
I'm betting on a pushrod first, lifter second, bent valve third. But that's only because I'd hate to see it was a valve that was bent
I'm betting on a pushrod first, lifter second, bent valve third. But that's only because I'd hate to see it was a valve that was bent
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From: Purdue
yea I got stuck w/ my 79 w/ a 351 m and my friend decided to get me out while I was lookin for a tractor and racked it up past 8 grand for a few seconds and that definitely bent my pushrods,thats the first place I'd look.
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when it gets reved up it pumps oil out the main seal thats a different issue. so i stopped and had to add 3 or 4 quarts after the tick started the oil pressure looks fine and unchanged. I just havnt had time to pull the cover cause of classes. i should have time this weekend to getter done.
Last edited by highrider76; Mar 30, 2005 at 12:18 AM.
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pulled the valve covers the left bank appeared to have no play. The right bank had one valve that had a little less than a quarter inch of play. I pulled the rocker shaft on that side and checked the push rods but they all look ok. I am thinkin its in the lifter but havnt got the intake pulled off yet. do you think i am headed down the right track? How much more time would it be to stab a new cam iif i have to replace lifters anyway?
thanks highrider
thanks highrider
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Lead Driver
Joined: Oct 2004
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From: Central Oregon
Yes, you sound likr you are on the right track with the lifter. The spring in the lifter sounds like it broke. I have pulled lifters out of my FE with the intake still on. Had to replace one in my 65 F-100 about 2 months ago. Some say that you can not change a lifter without flatenning the cam, and it may yet, but I didn't want to pull the engine down in the middle of winter. So if it goes at lease I gained some time until it's warmer
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Tuned
Joined: Jul 2003
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From: Dudley, GA
OK, if Highrider bent a pushrod or two can he just replace them or does he have to replace lifters too? Where can a guy get a set of stock rocker shafts and rockers (whole assy) if those needed to be replaced?
Sounds like I've heard this tic before....
Sounds like I've heard this tic before....
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From: Purdue
When I bent my pushrods I just replaced the rods......but they bent again shortly after that so I don't know if not replacing the lifters was a bad idea or just trusting Summits lengths was the bad idea?
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From: Long Island USA
I've pulled apart only a few FE's, but each one, even totally bone-stock, had different length pushrods on some of the valves. So, if you don't use adjustable rockers, you need to go through the painstaking "adjustment" process even on an original motor, if you want things to last a long time.
My 390 with high-lift cam (.554") and double valve springs stayed together up through 6000RPM with stock rockers. But I had to used some VERY undersized pushrods, the block was decked and heads milled a bit
My 390 with high-lift cam (.554") and double valve springs stayed together up through 6000RPM with stock rockers. But I had to used some VERY undersized pushrods, the block was decked and heads milled a bit
Tuned
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From: Dudley, GA
After looking all over the net for rocker assy's, and seeing prices of $250+, I found complete rebuilt rocker arm shaft sets for $84.50 (for both assy's) ready to bolt in, just in case anyone was looking to replace them 
See: http://www.shastacounty.com/rockerarm/page5.htm
See: http://www.shastacounty.com/rockerarm/page5.htm
Fleet Owner
Joined: Jun 1999
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From: Creedmoor, North Carolina
Originally Posted by Purdue Offroader
yea I got stuck w/ my 79 w/ a 351 m and my friend decided to get me out while I was lookin for a tractor and racked it up past 8 grand for a few seconds and that definitely bent my pushrods,thats the first place I'd look.
You turned up a stock 351m to past 8 grand?? You must be running alcohol with a blower or something.
I had no idea that they would go to 6500.
John
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Joined: Jun 1999
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From: Creedmoor, North Carolina
Originally Posted by Purdue Offroader
yea I got stuck w/ my 79 w/ a 351 m and my friend decided to get me out while I was lookin for a tractor and racked it up past 8 grand for a few seconds and that definitely bent my pushrods,thats the first place I'd look.
You turned up a stock 351m to past 8 grand?? You must be running alcohol with a blower or something.
I had no idea that they would go to 6500.
John
Elder User
Joined: Sep 2004
Posts: 863
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From: Grain Valley Mo.
OK...this is probably a dumb ?...where do you get the odd length pushrods? And...say you want to install a new cam/lifters and new pushrods, do I need all different lengths? How do you tell? I bet the guys at my Napa store would have a stroke if I asked for anything other than a stock pushrod.
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