Question for those running hi rpm (7000+) and aggressive cams.

How often do you check or inspect your valve springs? Do you test for actual spring pressures or do you just do a visual inspection?

I'll pull the valve covers and check lash and then check spring seat pressure..
As long as there still 250# at the seat .. Lem says I'm ok.

He just told me not to turn it to 9000 Rpm's to much SO I've put my goal Rpm at 7500 to 7800..



ShaZam

Thanks for the input Shazam

We just had a friend drop 2 valves at about 7500 rpms so its very fresh in our minds.

Which spring tester do you use?

I have the Moroso Spring Checker Jeg's #710-62390 63.99 page 122 of there yellow camaro cover book .



ShaZam

So how much damage did it do to there motor ..
Last year it cost me a Sleeved cylinder and new piston, rings, pin and set of heads when I dropped a valve.

Hi guys
I am very curious. Over the years watching and fixin motors that dropped a valve we came to some conclusions that not many consider.
It is rarely a spring that broke first, or suddenly went weak.
More often than not it was too tight a clearance on the valve stems that causes the valve to bind sufficient in the guide that the spring was not capable of returning the valve to its seat.
In turn the piston slaps the valve and snaps it off.
On really rare occasions a spring might break, but there is not a way to tell if a spring is suspect for that by checkin pressure. Usually a spring breaks because the outer limits of clearance to bind have been succeeded and one is overstressin the spring by too much compression.
The other thing we saw lots of was extremely high combustion temps because of bad timing or fuel issues that overheated the valve which caused the head to pop off.
Now dont get me wrong - spring pressures do go away, but not as much as people think, and rarely bad enough to wreck a motor in one run.
There are many more reasons a valve may drop , but the spring bein suspect is rarely one of them in my experience

Just my .03

Im not 100% sure because I havent seen the results personally but this is what I was told.
Consensus is that his cam was pushing the limits of the valve springs (280+@.050,.740+ lift and 8000 rpms) and floated an exhaust valve to start the mess.

He did drop both the intake and exhaust on the same cylinder. He took a chunk out of the piston and cylinder. The chunk of piston made its way down to the pan making a nice hole in it. One of the rods was damaged, another suspect.

Overall I think he is going to get the head repaired (AFR alum heads), sleeve the block, new piston and rods...oh yea...new springs!

Ken..thats a good thought about the valve stem guide in bind.
When you inspected the guides did you see alot of premature wear on them to suspect that is what was happening?

I will ask what his guides looked like and report back to you.

We have seen galling in the other guides, being that the damaged one was destroyed.
We have seen premature guide wear on the order of being able to move the top of the stem almost 1/16" after just ten runs
We have seen guides so tight that you had to almost drive em out too after a run or two - no idea why
other than maybe the shop didnt even check? We saw too tight spring clearances , wrong spring retainers etc etc etc LOOOONG storey on several shops - to the point we started doin our own work as much as possible.

reaching higher hp numbers, an getting the rpm's out of it, I have seen a several broken springs. Got to where they were getting caught like Dan said, during the weekly checks. Engine builders agreed springs where right for the engine, dont know why, heads where checked too, all was fine, abd never the same cylinder, so we figrued it better to check and replace as neccesary.