RE:BENT PUSHROD(S):

[Stewart G Griffin]

Please list any and all possible reasons for bent pushrods as it pertains specifically to small block chevys starting from most likely to least likely.

b) Is a completely stock crate 350(and for that matter small block chevys in general) an interference engine?  That is, is it possible at any time for the valves to come in contact with the piston in case of timing chain jump or failure or other mechanical failure?

[choptop]

The only time i have seen bent push rods is timing chain jumped,overtightening of the rockers, and floating the valves due to excessive rpm ( most commonly caused by led footed teenagers that think they can shift manually better than the automatic can)
The most likely cause is determined by the history of the engine
1) I got it from a young guy who said he never raced it, it just started running weird (floated the valves)
2) I just adjusted the valves a week ago and its runnnig funny (improperly adjusted)
3) Truck has alot (200K plus) of miles on it  (timing chain may have jumped)

Oldyellers truck had 275000 miles on it when we pulled the 350 out, and the chain was loose.but not dangerously bad.

[VileZambonie]

non interference engine.

The rocker improperly adjusted, stuck valve most likely cause.

[choptop]

non interference engine.

The rocker improperly adjusted, stuck valve most likely cause.

Oh yeah, he did say stock engine. Duh me

[TexasRed]

Do you still have warranty on that engine (not that GM would actually pay up anyway)? I know you don't want to hear this, but I'm glad I didn't buy a GM crate motor now.

[Blue 82]

I saw the pics on pg #9 of the "new problems" thread
Is the any reason why the EGR valve is off or not blocked off?

Since it's only one (so far)
Since it was an exhaust valve, and the piston chases the exhaust valve
I would say it would be to a sticking valve or lifter

Valves stick for a few reasons

Lack of lubrication
overheated valve (exhaust leak, retarded timing or running lean)
bent
loaded with carbon
insuffient valve to guide clearance
or any combination of the above and can be aggrivated by a weak or broken valve spring.

Since it was #4 exhaust
using an intake manifold bolt that was too long will bend it also
us a flashlight to make sure the bolt is not too lond (look down the pushrod hole to the lifter)

Improper adjustment and over-reving are the two most likely causes
but since it's only one (so far)
I think you are lookin at a stuck (and bent) valve

You might have had a sticking lifter
but since you don't have a bunch of sludge in your engine
I don't think a stuck lifter is the cause.

I'm giong to rule out valvetrain geometry also since it's a stock motor

[Stewart G Griffin]

1) Warranty:   It's way out of warranty---the Prev owner (bless him) bought it in 96.  i still think GM crate motors are ok;  There is a good,  at least 50% chance it was my fault.  Will explain fully in a sec.

2)EGR removed:    The main reason why the egr valve is removed is due to the fact that i can't get the valve cover off unless the egr is also removed.   i have previously tested the egr valve and found it and the associated vacuum tubing to be good.

3)"sticky" valves:
i'd like to discuss the concept of "sticky" valves in greater detail because i'm not sure i get it completely.  If the valve somehow gauged itself into the head or valve guide, thus causing a binding i could see the valve not moving----"sticking."  If, however, the valve is not moving smoothly in travel----due to say  varnish or not getting enough lubrication, then wouldn't the turning force of the engine overcome this, if the valve is "stuck" closed?   If the valve is "stuck" open, then hopefully the spring would close it?


What happened as i was turning the engine by hand was that i observed (to the best of my present mechanical ability/knowledge) that all 16 valves have normal travel and return.  This is including #4's exhaust valve;  i did not realize the pushrod was bent until i actually tried to adjust/tighten it.   This leads me to believe that the spring is good and that, hopefully, the valve itself is ok and not binding/sticking.

4) i checked with a flashlite and it looks ok and the lifter looks ok.

5) improper adjustment, over-reving as the most likely causes:
i would like to add that this engine rarely sees more than 3000rpm.  OK, last summer i did make a 1/4 run just to see what it could do but even then it was doubtful that the engine went past 5000.  And plus, it was last summer and surely the problem would have surfaced back then, not in december?

Improper adjustment:
After doing some thinking about it, and this is really getting deep into it.  What happened[and this is yet another long, out-to-lunch, neurotic post(do we see a pattern here?) dealing with a separate problem] was, and i don't know if i had posted it here.  But i definitely posted at this site:
http://www.chevelles.com/forums/showthread.php?t=141929

What happened in this case was when i first got the truck, there was white smoke coming out of the right side tailpipe only.  It turned out that the vacuum modulator on the trans was leaking and causing this.  Due to my poor diagnoising ability (i will address this when this present problem is done and taken care of) one of the things i did, among others before i found out what the real problem was, was to replace the right side head gasket----the same side cyl #4 or on---do you see where i am going with this?  This was 2 yrs ago.

i surmize that when i put the right side head back on i may have probably not adjusted #4's exhaust rocker correctly.  i did notice some backfireing after this "repair" was made but i discounted that to ignition wires.  The backfire was not there before the gasket change was made.  Then, occasionally there would be a miss at idle.  i did not think this was a big thing.


i guess what we could do is inspect the rocker the nut and that half-round nut thing, the stud and if possible the valve and valvespring.   But other than that i'm thinking i may have caused it by not getting the adjustment right.  And it took several thousand miles for the rocker to work itself loose?

[HAULIN IT]

Stewart, I have a couple questions & suggestions. 1) How many miles are on this engine? By the looks of the #3 plug ("others are similar") it looks to me that you have allot of oil in the cylinders. 2) I know we discussed this before & I'm guessing I know the answer but...Have you done a compression check or leak-down test yet? My interest now is if that valve is seated/sealed when closed.
 One concern at this point needs to be the lifter may not have been able to spin smoothly & could have "gone south"
 Not to rip on you, but I'm having trouble following the plan here...You had the engine on the test stand (your truck! It had all the things you needed...fuel, battery, wiring, ect.) & you took the engine out without TESTING. After reading your post on the Chevelle board, it would seem to me you would want to avoid the same type of plan (not saying I blame you for how that went...White smoke, only Right bank, I can see how it happened) Why pull an engine for a loose rocker arm nut? What are you going to learn with the engine out that you couldn't learn with it in the truck? Keep us posted, we'll help you through it, Lorne     

[Stewart G Griffin]

1) i have no idea.  Let's say at least 10,000.   i would estimate at least 50-60,0000.

2)No, i have not done compression yet because i feel it needs to be done on a warmed up and run engine.



Yes, i somewhat agree (to all others feel free to rip----this is how we learn);  An engine already installed in a car already has a test stand----the car!  But i did alot of thinking and i wanted the engine to be 100% kosher----there are other things on the engine i wanted to adress;  I.e.,  clean it up, fix or replace exhaust sheilds, install distributor tab, install "t's" for gauges etc.   And i felt it would be physically easier for me to do this outside of the truck.   i think next time i will leave it in the truck.

i've done some thinking and have decided/declaired that if A/c can be eliminated (let's face it: we don't use a/c that much around here), the fan shroud and fan replaced with and electric fan, and most of the vacuum lines can be eliminated, then the underhood is really not that cluttered and complicated.  i've recently realized that 70-77 monte carlos and grand prixes have really loooong hoods and thus lots of surplus underhood space.  But this is a topic for another post which we will get into only after this present problem is done and taken care of.