99a Flathead Setting up Valve Clearances

Phil Gillespie

Phil Gillespie

Well-known member
First time for everything and so here it goes.


I'm playing around with a spare 99a Flathead engine. On setting the valve clearances to specs of 10 thou inlet and 12 thou exhaust. I noted that on turning engine over the valves on a few cylinders were sitting off valve seats by approx 10 to 15 thou. Still plenty clearance between lifter and valve.These are the mushroom ended valves with the split guides. A light tap on valve head and valve sits on valve seat. So maybe spring tension on valve springs suspect.
Got a new set of valve springs noted uncompressed length longer than existing ones. Guess what similar senario on some valves on 1 to 4 cylinder bank.
Maybe some valve shims would assist. Nope. THe valves sitting oof the seats all had clearance between follower and valve foot. A gentle tap and valves seat well as not able to slide a feeler between valve and seat. The valves are all free in guides. At this stage I am open to all ideas and suggestions.
Thanks in advance.
Phil NZ
 
Measure installed height of valve spring. Spring pressure should be around 40psi at this height. Installed height is usually around 2 1/8 to 2 1/4"
 
They are standing off the seat. But with no spring pressure? There should be some spring pressure. Are they standing off the seat due to tightness in the guide?
Are the guides and springs assembled correctly with the horseshoe clip in the groove in the guide? It is possible to fit the clip above the spring and the guide can sit higher than normal.
Careful inspection, disassembly and reassembly ought to show what is wrong.

Mart.
 
Mart said:
They are standing off the seat. But with no spring pressure? There should be some spring pressure. Are they standing off the seat due to tightness in the guide?
Are the guides and springs assembled correctly with the horseshoe clip in the groove in the guide? It is possible to fit the clip above the spring and the guide can sit higher than normal.
Careful inspection, disassembly and reassembly ought to show what is wrong.

Mart.
Click to expand...

Yep Mart understand about fitting clip above the spring,They are not tight in guide as a gentle tap seats the valve. As suggested a complete disassembly and go from there, Appreciate your assistance,
Phil NZ
 
If it was mine, I'd pull those split guides and mushroom valves and put in a later 49-53 set - so much better on all fronts. ;)

With even a very light-pressure assembly spring, they should all come right back to their seats.

You must be hanging up in the guides - did you put lubrication in them prior to assembly? I put some good heavy assembly lube in them when I put them together. I used to run the 5/16 split guides (first engine - almost 50 years ago), but have not used them since.
 
Id check for burs or irregular valve stems . Check diameter in a few spots and rotate valve making sure theres no bend . Just a little could mess up . Are the valves and guides lubricated ?
 
Mart said:
They are standing off the seat. But with no spring pressure? There should be some spring pressure. Are they standing off the seat due to tightness in the guide?
Are the guides and springs assembled correctly with the horseshoe clip in the groove in the guide? It is possible to fit the clip above the spring and the guide can sit higher than normal.
Careful inspection, disassembly and reassembly ought to show what is wrong.

Mart.
Click to expand...

So been and checked my handiwork on these valves.
Yep I did it . Horseshoe clip was fitted above the spring instead of in the correct groove in guide. Clearly verified. And now getting it sorted. Appreciate all advice on this one. Its now back on track.
Phil NZ
 
Phil Gillespie said:
So been and checked my handiwork on these valves.
Yep I did it . Horseshoe clip was fitted above the spring instead of in the correct groove in guide. Clearly verified. And now getting it sorted. Appreciate all advice on this one. Its now back on track.
Phil NZ
Click to expand...

Excellent! It's great when the culprit is easily identified. I bought a flatty that had a couple like that.
 
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