Am I correct in saying that floating valves will cause pushrods to bend? Just pull my valve covers and have 3 bent pushrods. One is bent pretty bad. Looks like a banana. Just got my new chrome molly ones in yesterday going to change valve springs and install new pushrods this weekend.
Bent Push Rods...
- Thread starter 87gnguy
- Start date
Welcome!
By registering with us, you'll be able to discuss, share and private message with other members of our community.
joe_schindler
Living better with carbon
- Joined
- Oct 1, 2001
- Messages
- 842
No. Valve float will get the valve bent.
If you have bent pushrods, it is apparent your valves have impacted the top of the pistons. With this in mind, it would be prudent to do a compression test to verify the valves are seating properly PRIOR to installing your new moly push rods. A bent valve will require the head removal.
better take a good look at the cam and lifters too.
I can see the cam being flat. I know we installed the chain correctly. When doing this we drained the oil and it smelt burnt. I don't know when the guy changed it last. I know it did alot of sitting in the years prior to when I bought it. I also got a lot of receipts when I bought the car and the guy apparently LOVED Pepboys for some reason 
so I know he didn't put ZDDP in the oil. I've been looking for an excuse to do a rebuild. After all the car does have 162K miles on the clock.
so I know he didn't put ZDDP in the oil. I've been looking for an excuse to do a rebuild. After all the car does have 162K miles on the clock.turbofabricator
Well-Known Member
- Joined
- Mar 7, 2004
- Messages
- 4,261
Severe detonation will bend pushrods, too. Too much cylinder pressure to open against with stock (weak) push rods, and they bend. Typically it'll pop a gasket at the same time, too. So, do a quick leak-down on it and see if it is hissin' past a blown gasket.
joe_schindler
Living better with carbon
- Joined
- Oct 1, 2001
- Messages
- 842
I just can’t see a detonation circumstance where the cylinder pressures are high enough at the time of exhaust stroke to bend a push rod.
If detonation could do this; it would only bend the exhaust rods; and not the intake.
- Joined
- May 28, 2001
- Messages
- 16,684
Time to look deeper. As you mentioned........ A rebuild.
Well, I did a compression check tonight and all cylinders are at 160 exept the driver's side rear which is at 155. That cylinder was not the one with the severly bent push rod. There were two more cylinders that had slightly bent pushrods. It has had a timing chain replacement before I bought it. I'm wondering if the original stock on went out bending the push rods then and they didn't bother to replace them...? I know the timing we installed was done correctly. I'm not sure about the other one though.
- Joined
- May 28, 2001
- Messages
- 16,684
Sounds like a reasonable explanation....
As for the cam going flat, and bending them: I suggest that would be possible, but only if the cam lobes were so far gone, as to allow the rods to come out of the rocker cups..At that point the compression would be affected, and the noise would be easily heard...
But that's just my $.02..
As for the cam going flat, and bending them: I suggest that would be possible, but only if the cam lobes were so far gone, as to allow the rods to come out of the rocker cups..At that point the compression would be affected, and the noise would be easily heard...
But that's just my $.02..
Just a Six??
OK! Who Farted??
- Joined
- Jul 4, 2003
- Messages
- 3,574
Years ago before I worked on my car a mechanic/engine shop did my heads & used the wrong size keepers on the springs. Any boost & I bent pushrods. I had 12 spares in the trunk to get back to his shop. I dont know why they did it but I went thru a Lot of pushrods that week.
- Joined
- Aug 1, 2003
- Messages
- 9,713
x2 been there done that
you dont always have to hit the valve with the piston to bend stock pushrods
joe_schindler
Living better with carbon
- Joined
- Oct 1, 2001
- Messages
- 842
Like the detonation thing; I can’t imagine a way that a cam going flat could bend a push rod.
As the cam is being eroded away; the valve opens less and less. Once the cam is eroded to just below the base circle; there is no longer much pressure on the lifter/cam; and the erosion pretty much stops.
At that point; the valve doesn’t open; and the push rod just sits there. If the lifter was to erode away; and the push rod fell into the crank case; I guess it could bend there; but it won’t bend if it doesn’t move.
As the cam is being eroded away; the valve opens less and less. Once the cam is eroded to just below the base circle; there is no longer much pressure on the lifter/cam; and the erosion pretty much stops.
At that point; the valve doesn’t open; and the push rod just sits there. If the lifter was to erode away; and the push rod fell into the crank case; I guess it could bend there; but it won’t bend if it doesn’t move.
Well, when I pulled th pushrods out, they were all in the cup of the lifter. I agree with the flat cam theory. I don't see how a flat cam could bend pushrods since the valve wouldn't open. Therefore the valve and piston could never meet. With the mods in my signature, I'm am running 18-20 pound of boost with no knock plus the car has 162,000 miles on a stock motor. Maybe the pushrods are just old and weak having gone through so many heat cycles at stock boost level, then when I cranked the boost up they didn't like it? I'm used to working on Ford Mustangs, this is a whole new animal...
I will also add that as I was going through a stack of receipts the previous owner gave me, there is one in there for a timing chain done by what looks like a small no name shop, they did just the chain and I doubt they checked anything else since the car "seemed" to run ok. I'm changing out the valve springs and pushrods this weekend so I guess we'll see...
I will also add that as I was going through a stack of receipts the previous owner gave me, there is one in there for a timing chain done by what looks like a small no name shop, they did just the chain and I doubt they checked anything else since the car "seemed" to run ok. I'm changing out the valve springs and pushrods this weekend so I guess we'll see...
- Joined
- Aug 1, 2003
- Messages
- 9,713
do yourself a favor
replace the pushrods first and while its opened up do a compression test and leakdown if compression seems odd or leakdown fails you know your in for pulling the heads
if comp test looks good go and change the springs
just did the chain ? did it fail or was it just preventative? , the valves may have already been tweaked
replace the pushrods first and while its opened up do a compression test and leakdown if compression seems odd or leakdown fails you know your in for pulling the heads
if comp test looks good go and change the springs
just did the chain ? did it fail or was it just preventative? , the valves may have already been tweaked
Compression/leakdown was normal all cylinders were at 160lbs exept the one on driver's side rear was 155. We did the chain as preventative, when we opened the front cover we saw the job had been done. Whoever did the last timing chain, we don't know the reason for it. We went ahead and put a DR on it since we had it on hand and the one that was replaced was not. I'm guessing the bent rods might have been from original one going out (I hope). I'm going to check these pushrods after running it 1000 mile or and under boost. If they're still straight, I'm going to assume the bent ones were from the previous chain replacement being wrong or from original chain breaking. What does everyone think?
