I was doing cam break in in a 65 289 and this happened
Any one seen this before?
Cam is Comp Cams XE256H
Springs are matching Comp Cams
All other push rods appear to be straight.
My best guess is that the rocker was over tightened. I’m going to put a straight edge on top of the adjustment nuts a give it a look
I’ve only experienced this because of an over rev. My guess is that the lash was set on the wrong part of the cam lobe.
Okay I put a non hardened push rod in to just move the car out of the bay and it bent it in no time at all. Maybe 45 seconds. WTF?
Too long? Something is off with the geometry.
To tight of a valve guide when you get some heat into the valve. The piston will force it shut but the push tube isn’t strong enough to force it open and bends. The non harden push tube bent sooner once the guide to valve clearance closed up. The piston could have also bent the valve forcing it shut. Something to check and make sure the guides were machined correctly. I gauge pin all guides and have found some rebuilders will use wore out reams and the guide tolerances will be to tight.
This is sort of a frankenengine. The previous owner is deceased so I can’t ask questions.
I have documentation of a rebuild that was done more than 10 years ago. It was running but poorly afterwards. It appears that it was rebuilt at a Chevy dealer where the owner worked.
It started out as a '65 289. The bottom end seems fine. They used a very aggressive cam with the stock rockers. They installed threaded studs. When I pulled the covers I found misalignment of the rockers and valve stems. I found the rockers and studs to be badly worn. I replaced the rockers and studs and everything seemed to line up well. The cam and lifters were also replaced. I found USA made lifters and used a mild comp cam.
I should add that the car mostly sat after the initial rebuild. So probably no more than a few thousand miles since the initial rebuild. Lifter valley was very clean. No residue in the heads.
Initial start and run sounded great. Running at 2000 rpm during break in for about 20 minutes I didn’t hear anything amiss. The radiator began to leak so I shut it down. There was a minor lifter tap that I could hear at idle. Temperature never went high.
After replacing the radiator I started it and heard the slight tap at idle. It went away as I increased engine speed. I brought it up to 2500 rpm and after a few minutes I heard a snap and then loud tapping and shut it down.
Pulling the cover revealed the broken push rod and the rocker off the valve.
lifter went solid
Is that something that happens? I guess I was thinking the opposite that it was bleeding down and letting the push rod get loose.
The rocker will usually turn when that happens and no bent pushrod. was the rocker bolt loose? Or is it a stud? Pressed in studs will pull out some.
I bet on a the lifter.
What did the push rod hit?
I think once it is out of the pocket it gets up on the edge of the lifter and may also hit the bottom of the rocker
Inspect your rocker arm and see if it is worn uniformly “straight” and not off to one side.
Since you know little about this engine, I would perform a full valve (lash) adjustment procedure… Look in the SMALL BLOCK engine rebuild book you should have in your collection… for the valve adjusting procedure… Check your firing order to see if you have the proper procedure…you don’t know if you have later (5.0 351W) firing order or early 289 302. Figure that out first.
Then proceed with manual rotation of engine and adjustment procedure. OR you can do it while engine is idling, but that can get messy fast…you’ll need cardboard oil guards, or a cut up SBF valve cover with an access slot cut in the top to access adjustment nuts.
If non- running choice is made, back off nut of valve in proper position of rotation, to loose…then snug it up carefully until slack is taken out…you can feel this point where it is in slight compression vs loose… You’re only working against the spring inside the lifter here…not oil pressure. Once you’re comfortable with the “no slack” setting, then tighten the nut 3/4-1 full turn. Tighten any jamb nut if so equipped, but you probably don’t have these…you likely have self locking nuts.
My take on this is likely an improperly adjusted rocker arm…once oil pressure arrived, the internal lifter piston hyper lifted the valve and may have contacted the piston as someone suggested.
If the rockers were adjusted too loose…you’d likely have clattering…
Hope this helps! Good luck!
Steve
You changed the rockers and camshaft, but did you match the valve springs?
Some great replies here. Thanks!
A bit more back ground. When i first tire into this thing I found a fairly radical cam that had been installed with the original push rods and rocker arms but on screw in studs. I found some pretty bad wear on the rockers fulcrums and the studs. There were also two different studs that were used. The springs looked to be very stiff to match the cam.
I decided to toss all of this stuff. I initially ordered the Comp Cams kit With cam springs keepers retainers and lifters. After much waiting and postponements I ordered the cam and was able to locate the correct springs keepers retainers but I had to look elsewhere for lifters. My recollection is that I found some made in the USA Elgin lifters that matched the spec for the engine. I reused the push rods as they were supposed to have been new from a previous rebuild.
When first fired all I had to do was set the timing and it ran great. Solid vacuum although a bit lower than I like, sounded great no clatter at all. Once I set the base timing to about 10 degrees I began the 20 minutes at 2000 to 2500 cam break in. Valvoline VR1 plus Comp Cams break in additive. For the first 12 minutes it ran great. No noise. I noticed the radiator was beginning to leak and returned it to idle. It sounded like I had one minor tapping lifter.
After replacing the radiator I began the next round of cam break in. The light tapping seemed to go away at about 1000 rpm and really sounded minor. After probably another 5 minutes I heard a snap and then loud lifter noise so I shut it down. In reflection the tapping may have been worse before the snap. I was more focused on the noise an idler pulley for the AC compressor was sounding. Mia culpa…
I pulled the rocker cover and the rocker arm was off to one side and the broken and bent push rod was obvious. I had an extra push rod that i used to push against the lifter and it seemed solid. The rocker adjusting nut was a bit lower (tighter) than the two to each side so I suspected that I had maybe over tightened it. I put the new push rod in and adjusted lash to zero plus 3/4 turn and set the poly lock. It bent this push rod in only a few seconds. I did check for srping bind and the coils were still open the valve appeared to move up and down normally.
I am of course pretty well depressed over having to tear this apart again but that is what must happen. Ugh.
There is so much going on with this motor that I am open to buying some ones nice 289 that is being pulled for a Coyote swap.
My current hypothesis is that the check valve in the lifter has failed so it collapses. The push rod starts banging around and gets bent.
By the way oil pressure has always looked good on this engine.
Ugh. It does sound like you may have a collapsed lifter. Hopefully you didn’t wipe a cam lobe. I would pull the top end apart and go from there. Good luck.
