I am having a bit of a problem with my latest 2 liter build. Basically, valves are colliding with pistons after warm up during break in. A valve got stuck and the pushrod actually fell off the rocker.

The heads were redon by RIMCO. After the problem happened, I pulled the heads, and there was clear indication of valve collision, and I had a valve stuck open. The head with a problem was sent back to RIMCO.

Reinstalled. What happened this time is the engine start up from cold, runs fine. But then I can hear the taping of collision again. The taping is accompanied by a chirping sound that sounds like something is dragging. I think it must be the valves dragging and closing too slow.

I have a deck height of .065.

This is essentially a stock build, stock camshaft, etc.


Any ideas? Is this perhaps a valve stem lubrication issue?

I thought if the valve gets stuck or struck the engine instantly destroy s itself ?

Deck height at the top of the barrels is one thing, but it sounds like maybe the shop cut the shoulders (where the top of the barrels slip into the head(s) too deep

You may need to install shims between the base of the barrels and the case, or get another pair of heads

The first thought is what did Rimco do when building the heads. They have a poor reputation for quality work.
Is this a basically a stock build?
How much lift is on the cam, what size valves are you running ? Aluminum or steel pushrods ?

Maybe you need pistons with a valve relief ?

Deck height as measured is not a direct measurement of the clearance from an open valve to piston due the valve angle and diameter.
That distance can be measured using clay ( or other formable material ) on the top of the piston, turn the engine over by hand slowly. After removing the head you can slice the clay to see the minimum distance that the edge of the valve to piston.

Regarding valve to guide clearance, should be correct as the guides come out of the box. Were the guides checked and replaced if needed ?
Since Rimco had the heads twice and the problem persists I would be looking for a better place to identify the problem.
Or pull the heads, remove the valve springs and check for clearance. If you have worn guides the valve can deflect at the tip.
.065" desk height should be more than enough if all other things are correct.
I am not an engine expert but I did once sleep at a Holiday Inn Express.

Basically a stock build. But with 96mm
Pistons with valve relief.

So, one head was sent back to Rimco.
This problem is on the other head.

See photos. Definitely a stuck valve. Pushrod
Fell out of rocker as result.

Stuck intake valve

Once the valve is bent, it is going to stick. Maybe a result and not a cause.

Possible causes:


Guides not sized/reamed/honed correctly after install, guides tight, valves sticking. Since you are saying it happens after warm up this is suspect. If this is the issue if you remove the springs you should feel drag on the valve even cold. I agree bent valve, but they usually bend at the tulip, not the stem.
Done right the valve should have no drag or sticky spots, it should slip like it's running in butter.

Same vein, when driving the guides in the tool is leaving a burr at the top (spring side) of the guide, again this is not sized/reamed/honed correctly after install issue.

Cam gear off by one tooth.

Lifter sticking in bore, unlikely but possible.

Bad or broken spring, weak spring should only show up in higher RPM's

Chirping sound, a fast squeak-squeak-squeak can also be a head sealing issue but you should be able to see (head off) carbon tracing or if using head gaskets a definite damage to the gasket. In extreme cases this will cut right into the aluminum head like a cutting torch.

I often see this when a seat is falling out.

Take the head off and look at that valve, if it is a seat it will be sitting cocked in it's bore. If it sits back down take the valve off and either knock the seat around a bit or heat it to 375-400 in an oven (chambers facing down) and see if the seat falls out.

The valves move in the same direction of the pistons, they are not canted or at an angle relative to the piston top so if you get lucky they just get pushed back straight if they contact a piston.

pistons put in upside down?

Photo of the stuck valve. When this happened to
the other head, I removed the spring,
and gave the valve a little tap and it came right
out. I then put it back in the guide and it was smooth.
There was some evidence of fine brass flakes, but on a
different valve spring.

Someone suggested possibly lifter catching. I checked them all,
and if you press down on the lifter when pulling you can feel
a small catch, but I think this is because the lifter is crossing a chasm in it’s travel in the case. I will probably replace them all. Cam off by one tooth? I usually triple check, but at this point anything is possible . I don’t know maybe I should just tear the whole case apart.

Looking over the sales receipt from Rimco, they reamed the guides on both heads originally. When I sent the other head back, they replaced the guides rather than reeming. So perhaps there is something with their reaming process ?

top end oiling problem ?? no lube

I'd check the clearance of the guides, most shops use a Go-No Go gauge, but it as simple as feel for an experienced machinist, if it catches before the spring goes on it will seize when hot.

Another cause for this is bad gas, varnish, new engine always use brand new gas.

This could just be caused by your issue, but that is lean city, brown exhaust valve, bright white electrode.

Maybe you should get your injectors checked/cleaned and flow tested.

Gotta give you major credit for turning your own wrenchs
But man this just affirms the fact rebuilding you're engine takes a certain amount of skill that i dont have.

Will do. The engine didn't run for very long, so I am not sure if I have a lean condition. I understand that valve guide lubrication occurs from the rocker side oil. Someone on the phone at the machinist was telling me it is also lubed by gasoline spray. I can't see how that would work. In any case, does someone have the specs so I can measure for myself if the valve guides were reemed properly?

So, after sitting on the workbench for a few hours, I noticed that the
valve sprung back closed on its own. So I got the spring compressor
and removed thr spring. Gave the stem a little tap with a rubber hammer: Valve was tight! It came out with a few taps. I immediately noticed the fine
Brass shavings again. Here I point to one...

Most likely issue is the guides are too tight.

Brass shaving found mid stem

It is hard to make a good photo of this, but looking
down the guide, there are areas that look non uniform. Like
the way wood looks when you have lightly run a chisel over it.
Again, cause or effect? I’m leaning towards imperfect guide reeming.

Next time, send them here. http://www.europeanmotorworks.com/

They used the wrong size reamer ?
Roll that valve stem on a piece of glass and see if it is bent.
How much did they cut/deck the heads?
Are you using stock length pushrods?

Hard to see, but definitely tight and a poor job.
When you drive guides in they collapse slightly, so they have to be reamed and honed back to spec.
This is just common procedure, part of the job.

I had this exact same problem once and it was the new valve guides that were not reamed to the correct size. That's why you see the small pieces of brass and gulling marks on the valve stem. Pull the heads and remove all the valves then have someone ream all the new guides to the right size. Ray

I won't be posting more about this until I have my head back. But sufficed to say, I'm very frustrated with RIMCO. I have been asking them for a week to work with me to get this resolved, as all the evidence points to a quality control issue starting with an improper inspection and work done on the valve guides. I have been asking the owner to call me since the middle of last week.