What causes valves to stick?

[SavageC20]

I rebuilt my 454 in my 72 last summer. Ran the engine for about 600 miles and then started getting a lot of valve train noise. Pulled valve cover and the tips of several pushrods were worn down/galled. Replaced pushrods that were worn and fired it back up only to hear a horrible noise in the top end after about 20 minutes of running. Pulled valve cover again and discovered stuck intake valve . Pulled intake and 7 or 8 lobes of the cam were pitted, but the bottoms of lifters were fine. Pulled engine out and paid machine shop go through it again and I also had them break the engine in this time. They said the valve hit the piston and put a nice ding in it , but they were able to reuse it. I go to pick up the truck and two miles down the road I hear the same noise and now a different valve is stuck. Keep in mind they went through both heads and installed new seats, valves, and springs the first time I rebuilt the engine. I'm not sure if it's the same head this time.

Engine is 454 bored .40 over, fresh 049 heads, .478/.501 cam, flat top pistons

What can cause a valve to stick?

[Wrenchbender Ret]

If you are running gas with ethenal in it & it is old gas it can gum up the guides & stems & cause them to stick.

[SavageC20]

Originally Posted by Wrenchbender Ret

If you are running gas with ethenal in it & it is old gas it can gum up the guides & stems & cause them to stick.

I did not realize that. When the event occurred the gas that was in the truck did contain ethanol. However, the gas in the truck was less than one week old.

[toolboxchev]

I am wondering about your machine shop buddies???

I can rebuild a top in my driveway and have less problems. If you have bronze valve guides the ethanol can be an issue, not to the point that you are describing. I have not seen that. Every car on the road would have problems.

You have other issues happening most likely a compound issue. How about some pics?

[SavageC20]

Originally Posted by toolboxchev

I am wondering about your machine shop buddies???

I can rebuild a top in my driveway and have less problems. If you have bronze valve guides the ethanol can be an issue, not to the point that you are describing. I have not seen that. Every car on the road would have problems.

You have other issues happening most likely a compound issue. How about some pics?

Yeah that's the thing, its not like this is a one off custom engine, its standard stuff that has been around for years.


Machine shop went with hardened one piece pushrods and roller rockers the second go around. They also thought there was an oiling issue because a couple of the rockers had oil burned/baked onto them, but were unable to determine a cause...

Here is a pic of the pitted cam and pushrods the first go around, keep in mind that the bottoms of the lifters were perfect. Also, I am not 100% sure if I have bronze valve guides , but I believe I do.

[toolboxchev]

Unfortunately that Cam does not look like it will make it. Comp Cams come nitride hardened now.

Second thing comes to mind is what did they use for oil. 99 percent of what is on the market will not do anything but destroy a new camshaft.

Vavloline VR1 is the only thing I use in my small block chevy with a hyd flat tappet cam.

Read up on motor oil below it is anything but the same. Even diesel oils have changed dramatically.

https://540ratblog.wordpress.com/

With the metal debris in it, I personally would do a complete tear down, disassembly and rebuild again.

[SavageC20]

Originally Posted by toolboxchev

Unfortunately that Cam does not look like it will make it. Comp Cams come nitride hardened now.

Second thing comes to mind is what did they use for oil. 99 percent of what is on the market will not do anything but destroy a new camshaft.

Vavloline VR1 is the only thing I use in my small block chevy with a hyd flat tappet cam.

Read up on motor oil below it is anything but the same. Even diesel oils have changed dramatically.

https://540ratblog.wordpress.com/

yeah I know the cam is toast, as I stated in the original post the engine has been completely gone through since this happened. I run high zinc oil exclusively in flat tappet engines (driven or torco).

[Mike C]

On a rebuild my guess would be the guide clearance was insufficient on the valves.

On an older engine, stuck valves happen usually because of excessive buildup on the valve stem of oil and then sitting for an extended period, or it can happen when running an engine on varnished gasoline and then shutting it down. The varnished gas may run, but it doesn’t all burn and then when it cools on valve stems it glues them open.

A bent valve can stick as well but that again is on the shop if that happened on a rebuild.

[geezer#99]

when was the pic taken of your motor with the cover off showing the roller rockers?
Was the motor hot tanked?

[RodnRudy]

I'm not an engine guru but I had a thought. Is the rocker ratio too much causing a valve to hit the piston like in your first post? Rocker in pic shows 1.72 is that the ratio? Combined with cam lift you may have an interference problem even with flat top pistons?

[HO455]

Are the pictures from the first incident or the second time? I would look very hard at the oiling system. Inspect the oil pump and its relief valve. Pull the filter and cut it apart to see if it is plugged. Check the filter bypass. Pull the galley plugs and rod the passages if necessary.
Low oil volume will cause the valve train to overheat. The oil that flows from the push rods down over the rocker arms valve springs and the down to the valve guide is what cools those components. If the volume of oil is not enough then heat builds up. The heat causes the guide clearances get tighter which in turn makes more heat. Worse case is the valve siezes and it is hit by the piston.
The gauling on the push rods in the photo look to me to be oil related.

[SavageC20]

Originally Posted by geezer#99

when was the pic taken of your motor with the cover off showing the roller rockers?
Was the motor hot tanked?

this picture was taken after the second rebuild. I put this engine in last weekend and towed the truck to the shop for them to break it in. after they broke it in I was driving it home and a valve got stuck again. they hot tanked the motor.

[SavageC20]

Originally Posted by HO455

Are the pictures from the first incident or the second time? I would look very hard at the oiling system. Inspect the oil pump and its relief valve. Pull the filter and cut it apart to see if it is plugged. Check the filter bypass. Pull the galley plugs and rod the passages if necessary.
Low oil volume will cause the valve train to overheat. The oil that flows from the push rods down over the rocker arms valve springs and the down to the valve guide is what cools those components. If the volume of oil is not enough then heat builds up. The heat causes the guide clearances get tighter which in turn makes more heat. Worse case is the valve siezes and it is hit by the piston.
The gauling on the push rods in the photo look to me to be oil related.

The pictures of the pushrod and the cam lobe are from the first time. They rodded the oil passages when it went in for the second time. engine has melling hi-volume oil pump. they were unable to find any issue with the oiling system. filter was cut open and was clean.

[SavageC20]

Originally Posted by Mike C

On a rebuild my guess would be the guide clearance was insufficient on the valves.

On an older engine, stuck valves happen usually because of excessive buildup on the valve stem of oil and then sitting for an extended period, or it can happen when running an engine on varnished gasoline and then shutting it down. The varnished gas may run, but it doesn’t all burn and then when it cools on valve stems it glues them open.

A bent valve can stick as well but that again is on the shop if that happened on a rebuild.

I was thinking the same thing, but I don't know why it keeps doing it if they went through the heads twice. Maybe their guy that does the heads needs to find another job lol?

[HO455]

I think your right. Time to have a serious conversation with the shop owner and get some satisfaction for your misery.

[El Dorado Jim]

sub'd

[SavageC20]

Once the machine shop finds out what the issue is I will update everyone in case someone runs into a similar problem in the future.

[Myoldtruck]

May sound stupid on my part, but did they check the clearance from the pump pickup to bottom of the pan.

I guess I would pull the distributor and install a priming tool and check the oil flow in the valve train.

[SavageC20]

Originally Posted by Myoldtruck

May sound stupid on my part, but did they check the clearance from the pump pickup to bottom of the pan.

I guess I would pull the distributor and install a priming tool and check the oil flow in the valve train.

I had them set the pickup tube and braze it to the pump. Should be correct, but I don't know for sure. I'll mention it to them if they can't find the issue. I actually did try a priming tool on it and the valve train looked like it had adequate flow. Also ran it with no valve covers and had oil at every rocker.

[Wrenchbender Ret]

Maybe the valve seals are not letting enough oil get to the guides.
George

[SavageC20]

Originally Posted by Wrenchbender Ret

Maybe the valve seals are not letting enough oil get to the guides.
George

Is that a relatively common problem?

[special-K]

Getting coolant into combustion chamber with cause a sticky valve. That's exactly what happened to my '72. It would have one stick after sitting more than a week or so when I first started it till warm up. Never smoked, no noticeable coolant loss, no milkshake on oil cap. It was this way for a few years or more. Ran great, plenty of power, oil looked fine with each annual/semi-annual oil change. It was burning what little leaked in

Went to pull headers to change front brake hoses. One plug broke off. Went to remove the base and it wrung off. Pulled the head and one cyl didn't look too good. Had magnafluxed and a hairline was found.

[Wrenchbender Ret]

Originally Posted by SavageC20

Is that a relatively common problem?

Not really. Just a thearedical possibility. Being it just had a valve job, the machinist may have put positive seals on top of the guides & are wiping the stems to thin.
George

[cleszkie]

I had an AMC 360 small block that spun the rear cam bearing just enough to impact oil flow to the entire engine. I'm not exactly sure how the oil flow is routed in a BBC, but this is something to consider. It would be easy for an engine builder to miss if they were not looking for it. Just a thought.

[AussieinNC]

You dont mention the year of the 454 so this is a generic response.

Cam wear pics you posted point to excessive valve seat pressures....maximum seat pressure in a race engine running a flat cam is around 135 lbs....
I always keep street flat am seat pressures around 100 max...ask the shop if they even measured the seat pressures...did they provide you with a build spec card?

Anything higher and the followers end up galled up destroying cam lobes...plus push rod ends gall out just like your pic.

Your pic of the cam lobe showing a widened run mark tells me the cam is also floating back and forth in the engine....making me wonder if the cam was installed correctly...I have seen later cam gear sets installed on early engines and the cam walks back and forth an 1/8"...

Finally...valves sticking....if the heads have had the valve guides knurled the guides may now be too tight on the valve stems..a valve can also "stick" if the valve head has contacted a piston and bent the stem....you list a .501 lift figure...that combined with a 1.75 ratio roller gives you 0.089 lift into that chamber...depending on where your cam is set and the lobe centers....flat top pistons would be running very close to those valves....deck clearance and head gasket thickness come into play....but this seems a little risky to me...

As mentioned previously...flat tappet cam engines MUST be run in on an oil specially designed for flat cam engine run in...products like Lucas 10627 oil or Royal Purple Break in Oil contain high zinc components to protect the rubbing surfaces during break in. Some modern oils have some zinc, but nowhere hear enough to do the job correctly.

As always...the above is just my opinion...