Remove spark plug and pressurize. Some people stuff rope through the plug hole.

Steamdriver's rope trick would work, but most mod a spark plug and hook it up to an air compressor.

Cambridge is still a ways, look up Brimacombe ski hill, I'm about 10 minutes down the road.

well looks like i'm in for more fun ... I like the rope trick .. but I have a compressor and now i'm intrigued with the project.
waiting for my powder coating to get back anyway .

The rope trick Steam Driver mentioned earlier in this discussion at post 15! I'd call it the string trick, but you get the idea.

Another way to keep the valves in place is to use compressed air, but that requires a fitting to screw into the spark plug hole, and the air is going to try to move the crank, and you probably would not want to leave it that way over night if you received a summons you had to obey to come in from the garage while you had a retainer off, and so on.

For that matter, if you have the piston up at TDC, the valves can't fall far enough that the stems don't still stick pretty far out. You can pull them back with fingers, or a magnet. But holding them in place while you maneuver the keepers into place might call for more ingenuity than you'd want to summon up.

But first check - taking off four valve covers with the engine on a stand is a snap compared with doing something like that later, and the spring test is quick and definitive. Just don't expect to be able to see anything broken visually - you have to do the push test (unless you see a retainer cocked at an angle, and maybe find a loose keeper half or something else no one has brought up which doesn't look right).

thanks Walt, I will update after the check

No compressed air used in the process......
 

I was able to remove and inspect the 12 valves springs without using compressed air. Make sure you are at TDC for each cylinder. A magnetic pick up tool comes handy getting the valve keepers out. You could have these tools (P7E & P7I) for less than $150. Use the right tools and re-sell them later. The time you spent building tools and the using them awkwardly is not worth the inconvenience. It is not how hard you work but how smart you did the job. Just my two-cents.

Tony

ironically I just had the same sound happen while I'm installing my rockers into 1-3 and setting the lash. Popping sound startled the heck out of me.

Doesn't sound good at all, so I'm taking my head off, I think. :(

I'm pretty certain the chain must have popped. I can turn over now and there are no odd sounds. I suppose it's still possible a spring broke. but they are brands new dual eibach springs.

Loose camshaft locking nuts........
 

In my case, the culprits were the camshaft locking nuts. They were not sufficiently tightened after cam timing procedure and the problem was observed during valve timing. It took someone who is mechanically knowledgeable but has not done an engine rebuild to call my attention about these fasteners. To my surprise, he was right. Thanks Andy.

Tony

any updates as to what happened here? I still need to performs a valve spring check on my build after this happened to me. I'm still a bit concerned as to what happened, I doubt a new spring broke, but I guess you never know.

I could not find anything so just moved on ( maybe not the best approach ) did you find anything with yours ?