What causes valves to stick?

[Grumpy old man]

I'll bet a donut they never measured pushrod length ? It would explain a lot , Like why it happened twice .

https://www.youtube.com/watch?v=OmzbHgVY3cI

[SavageC20]

Originally Posted by 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...

The block has a 1979 date code on it and it is a 2 bolt main truck block w/ 2-piece rear main. Bored .40 over.

They didn't provide build spec card nor do I know what the seat pressures are, but I will ask them.

In regard to the timing set it has an engine pro double roller in it.

The roller rockers are 1.72 ratio, the block has been decked and so have the heads but I am not sure how much they took off. This is what concerns me the most. I am running regular fel-pro head gaskets. I will have them look into this.

I run high zinc Joe Gibbs (Driven) break-in oil and then their HR series after the break in was completed.

[SavageC20]

Originally Posted by Grumpy old man

I'll bet a donut they never measured pushrod length ? It would explain a lot , Like why it happened twice .

https://www.youtube.com/watch?v=OmzbHgVY3cI

I am not sure if they did or not. Will check on this as well.

[SavageC20]

Originally Posted by 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.

When they tore it down the second time they inspected all of the cam bearings and said that they looked fine. They went ahead and put a new set in to be safe.

[SavageC20]

So I picked up the truck from the machine shop. The intake valve seized on cylinder number 8, the stem was severely galled. They also pulled the other head and found another intake valve starting to gall so it probably would have seized if the engine would have ran a bit longer. We thought it was extremely odd that the intake valves were the ones with the issues, NOT the exhaust. They installed guide liners in all of the intake valves then honed the liners out to allow for an extra thou of clearance. They told me that they rarely install liners on intake valves. So far so good after 150 miles on the engine. Only time will tell if this was the permanent solution. If I don't update this thread consider it fixed.

I was able to view the cam lobes when the engine was torn apart and they all looked perfect.