Valve guide moved

Phillybo · 2025-09-07T16:54:44-0400

sgkent said:
manual say replace head if it overheats and damages guides. Ne factory kit per head is $200 - $220. What is your time worth? Or lets say you fix it, it lasts 10 hours, guide moves, a valve sticks open, takes out the piston, valve, connecting rod, scores the cylinder wall ... what then?

Guess guides were good. Should have did leakdown first. Bad rings. Massive air from oil dipstick

Phillybo · 2025-09-07T16:56:02-0400

Auto Doc's said:
Hi Phillybo,

The manuals do not give the exact design specification for the installed height of the valve guides.

If this head has a pushrod guide plate mounted below the rocker arm retainer bolts, be sure to check them for excessive wear in the area that pushrod comes through. These are often overlooked.

Thanks

Auto Doc's · 2025-09-07T16:56:34-0400

How did you determine bad rings? Are the cylinder scored?

Phillybo · 2025-09-07T16:58:24-0400

Auto Doc's said:
How did you determine bad rings? Are the cylinder scored?

Did a leakdown test and massive air from distick

Phillybo · 2025-09-07T16:58:39-0400

Phillybo said:
Did a leakdown test and massive air from distick

Auto Doc's · 2025-09-07T17:10:19-0400

What was your leak down test gauge showing? I ask because you cannot always trust what the dip stick fill tube is indicating.

Was this engine a "smoker" before the pushrod incident?

Was the head releveled by sand with fine sandpaper on a true flat surface, and a new head gasket used during reassembly?

Phillybo · 2025-09-07T19:11:13-0400

Auto Doc's said:
What was your leak down test gauge showing? I ask because you cannot always trust what the dip stick fill tube is indicating.

Was this engine a "smoker" before the pushrod incident?

Was the head releveled by sand with fine sandpaper on a true flat surface, and a new head gasket used during reassembly?

Test guage was building virtually no pressure with almost 100 psi going in.Not sure about the mowers past. Guy just brought it by and asked me to check it. Put new plugs in and they were getting oily immediately.
Runs perfectly for couple minutes and then starts pouring white smoke.

sgkent · 2025-09-07T19:36:39-0400

if the head has not been off, do a visual inspection with a bore scope on the piston. You may find that the pushrod was bent when the piston and the valve met. That can be because the piston cracked and broke into a top and bottom, or a valve hung open. The leak can be either the hole in the piston, cracked piston or a broken guide and bent valve where air is leaking past the guide. Usually that will also show up in the intake or the exhaust.

Auto Doc's · 2025-09-07T19:38:15-0400

I would suspect head warpage and compression pressure blowing past the head gaskets into the valve pushrod area. (That goes straight into the crankcase) Rings are a seldom failure unless they are smoking badly and have scored cylinders due to excessive dusting and poor oil changes.

sgkent · 2025-09-07T19:41:26-0400

Auto Doc's said:
I would suspect head warpage and compression pressure blowing past the head gaskets into the valve pushrod area. (That goes straight into the crankcase) Rings are a seldom failure unless they are smoking badly and have scored cylinders due to excessive dusting and poor oil changes.

example of warped head

Valve guide moved

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