1927 Buda - Blow by - rings or valve guides

tvscum

Member
Hey guys,
I am getting blow-by with oil coming out of the oil filler tube and dipstick hole on a 1927 Buda HS-6. How do I tell if it's the rings or the valve guides? If the guides are bad, the pressure when the exhaust valves open would still go into the crankcase, I am pretty sure. See attached photos. Cheers!


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Very unlikely it's valve guides. They would have to be extremely bad and the exhaust restricted to cause any significant blow back into the engine.

Most likely there are stuck, or worn, or broken, or all 3, compression rings.

If the engine was improperly stored and condensation, or rain water, or coolant, sat in the cylinders, the rings are likely stuck. Minimal chance they will free up on their own, best go in now before further damage occurs. Possibly everything can be cleaned up, freed up and reassembled.

It is also possible the head gasket has blown internally, but that is not as common as stuck rings.
 
A leak down test will show lots of problems that a compression test will not, if you know how to do it properly. Worn valve guides
and stems will cause blowby also. If you don't believe me, rebuild the bottom end and don't touch the head and the problem will
still be there. I have a case engine in the shop right now that the valves,guides and seats were all worn out and the bottom end
has new pistons and rings. Puffed like a steam engine out the breather tube.
 
I agree, in this case the guides are not in a location that fosters oil loss. They could be worn, but certainly no a cause of blow by. If you pull the tappet cover as a first step, the simple act of using a little side to side in and toward pressure would show slop. The oil mist is enough to lube the guides, but not enough to flood the intake with oil to burn. If compression is uniforn, and above 80psi, I would make sure it is not loosing coolant, and probably run it for at least 25 hours or so to see if it changes blowby volume. If no change, and oil is consumed, probably rings. If more than .005" taper in the bore, then cylinders/pistons need service. Jim
 
98 percent it is the rings and cyl's worn way out of spec. those valve guides wont do that. unless you could move the valve stem 1/8 " either
way. blow by is related to cyl. wear. also you got to realize that the piston is pushing 125 psi at the top so you need a good set of sealing
rings. once its exiting out the exhaust valve there is no where near that pressure. its just blowing out in a flow out the exhaust pipe.
 
Sorry to say, I didn't look at the diagram to see it was a flathead. I am a fanatic when it comes to rebuilding engines. I do not do inframes, ring jobs or patch it up. We totally disassemble them and put them back as close as possible to factory specs. I tend to get side tracked if someone starts looking for a quick fix. We don't do those.
 
Thank you guys! I am a bit of a rookie on diagnostics but did some youtube research. :) I will try to get a loaner leak down tester. Also, I will take the cap off the oil filler tube and see if the blow by seems like it's coming from one cylinder. The truck sat in a junkyard for 30 years but the hood was closed. The engine runs but it may indeed need rings. Not even sure if one can find rings for a BUDA HS-6 anymore?

http://gotfredson.org/models/BUDA_HS-6.pdf
 
I tried the ATF/Marvel Oil soak. Compression got a bit better but the oil still blows out of the oil filler spout at higher RPMs. I hooked an air hose up to the lowest compression cylinder (at top of compression stroke) and I could hear the air coming out the oil filler spout. Strange, the engine does not smoke out the tailpipe at all. Just blowing oil out of the filler spout and dipstick.

Anyway..... when I dive in, what do I need to measure? The gaps between the rings and grooves? The gaps between the piston (without rings installed) and the cylinder walls? Do I put the old rings back into the cylinder to measure the ring end gaps? Rookie here :)
 

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