Flathead rebuild

K

keviny

Junior Member
Is it feasible to do a ring and valve job on my flathead? What’s the chance the babbet would still be ok?
 
In order to do the rings, you'll have to pop the pistons out. That will give you an opportunity to examine the babbit, plastigage and adjust, or pack all the parts back into a box and take to a rebuilder. Check the center main and look for broken babbit in the pan, often from main bearing thrust surfaces. Valves are easier. Remove the manifolds, side cover, and head.
As far as "whats the chance" the babbit is OK. Impossible to know without understanding a lot more about your engine. Are you needing valves and rings because of age, wear, running too lean, etc. Are the cylinders scored?
I am assuming you did a leakdown test to determine that rings and valves are suspect?
 
the opinion of "OK" depends a lot on the intended use.
does it make noise?----why do you think you need rings and valve job?
 
I’ve only heard it run for a few minutes. No knocking but she be a smoking and leaking some oil. I’d like to try doing the work. I have rebuilt quit a few engines but not a flat head unless you count small engines.
 
In our neck of the woods you will pull a part several blocks to find good babbet that isn't all cracked and might fall apart. You can replace exhaust valves and do a re-ring and you'll get by with some blow by for short trips.
 
Taking up the bearings is a maintenance thing on old engines. That is why there are shims in there. Replacing the rings and lapping the valves should be accompanied with adjusting the bearings. Plastigauge is the best method. There are plenty of instructions on the internet but I found the instructions in the Model A Mechanics Book, Vol. 1 to be most helpful.
 
You didn't say where you are leaking oil from, but rear main leaking is common and could be caused by too much oil, too much crankcase pressure, blocked oil return line, or worn rear main bearing.
You stated you've only heard the engine run briefly - sounds like perhaps it has been "sitting" for an extended period.
You could have stuck rings. Before tearing into it, I might suggest dropping the pan and cleaning it out. Open the side valve cover and remove any sludge - be careful that no sludge blocks the oil tubes to the main bearings. Clean the oil pump screen. Check the bearings while you're at it and if all looks good, add some top-oil (such as Marvel Mystery Oil) to your gas to help unstick any valves and rings.
 
Marvel Mystery Oil in the cylinders will loosen crud between pistons and rings. A person can put MMO in the fuel to loosen up valves and rings after a long time setting. It may get the rings working again or they may just be worn out. A compression check will tell.

It takes a while for the oil pump to fill up the valve chamber on an engine that has leaked down due to a long slumber. I usually pull the distributor and pour a quart of oil in there before starting it up. I do this before refilling the sump after a complete drain of old oil. This keeps a fresh supply of oil down in those mains for an initial start.
 
I did mine in the car, in the garage, by myself, like you I was concerned about my babbet, but it turned out to be all good, so it was just a quick refresh...so to speak.
No reason you could not do the same if you have even minimal mechanical skills, takes a few days, but not all that hard.
I put in new pistons/rings, valve guides, adjustable lifters.

NOTE: Keep rod caps and shims for each pistons marked and separated, put the shims back in the same place they were removed. And make sure rod caps are facing the correct way. When doing your valve seats make sure you get "ALL" the grinding compound out of the engine. And since you're there clean your oil pump and give it an ops check.
 
I had the same problem after purchasing a used engine. It went through a quart of oil every 200 miles. Such a disappointment...
I disassembled the engine in the car. I inspected the mains. The were all good so I adjusted them. I removed the pistons with the rods. The bore was still within specs so I honed the cylinders to clean them up. I ordered a set of rings and a balanced set of babbitt connecting rods. I also replaced one bent valve and all of the valve guides.
I reassembled the engine. It no longer burns any oil. I have put 6,000 miles on the rebuild without any issues. Best of luck to you!
 
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