Sticking Flathead Valve, Part II

I posted last week about what I thought was a sticking valve on my 59A flathead. To recap, I finally started my rebuilt flathead after about 8 years of it sitting waiting for me to get the car done. It fires, runs strong, and sounds good except for what I thought was a sticking valve in the rear cylinder on the right side. I took the Marvel Mystery oil suggestion and squirted Marvel Mystery Oil in the noisy cylinder while the valve was open, let it soak, and then ran the engine. I did this five or six times; each time, the engine was quiet for the first 10 to 20 seconds after firing, then the noise would gradually return.

I drove the car about 15 miles, hoping that it would get the oil hot enough to circulate and cure the problem, but so far the noise remains.

What makes me wonder if I really have a sticking valve is that I ran both a compression check and a leakdown on all eight cylinders. The compression was consistent in each cylinder (including the noisy one) and the leakdown showed 10% or less in each cylinder (including the noisy one.

My question, do I really have a sticking valve or is it something else? If a valve was sticking, wouldn't the compression and leakdown test results be different? If it's not a valve, any ideas on what it could be? If it is a valve, is my next step to pull the head and the valve, clean the valve, and replace it? Also, it may be a coincidence, but I'm getting a fair amount of smoke (on acceleration only) from the right side exhaust, but none from the left. Thanks for any thoughts on this.

 

Well with what your tests are showing I don't think it is a valve seating problem. Do you have adjustable lifters? If so maybe the adjuster backed off? Pull intake to check that . You may be just burning off oil in the exhaust system from all the MMO you have poured in there. Don't think pulling a head is indicated at this point.

 

And also...pulling the manifold and watching while engine cranks might help. That's easy and free, unless you tear your gaket.

 

The engine does not have hydraulic lifters. Any other thoughts as to what the problem is or what I should do next? The "sticking valve" noise (if that's what it is) is fairly pronounced and hard to ignore.

 

fuel pump rod maybe?

 

It's not the fuel pump rod. The car has an electric fuel pump. I removed the stock pump and rod.

 

check and make sure you have the horseshoe clip on the right part of the valve guide. Hard to get enuogh light and big hands in there sometime.

 

I DID NOT say hydralic lifters !! Stock flaties had NON-adjustable lifters, you could get ones with a screw in the topend so you could set valve clearance without grinding the seat deeper or grinding off a bit of the stem. That screw has been known to back off , as it is a self-locking one.

 

Sorry about misreading your reply. The engine has non-adjustable lifters.

 

Really? That's hard-core in today's day & age. Not many shops or mechanics who can/will set the valve lash by welding & grinding anymore. Might be worthwhile to check valve lash anyway...