ideas on what happened?

[raindriver]

Thanks G-man, good to hear my sizes are in the right ballpark.

I'll take readings with 2 decimals. My spiffy new digital meter seems a bit wonky, it sporadically jumps from numbers like 60.23 to -1459.59. I just have to repeat the measurements many times to get a good reading.

[G-Man]

What I meant to write is that you should be looking at a figure of 60.75 plus or minus the normal clearance.

G

[conbs]

Rain, A "wonky" measuring stick is no different than guessing. If it is not accurate there is no way to tell what you have. You need precise measurements to tell what to do.

[conbs]

Bill Silver has a note in his 305 Engine Repair Guide on page 109.

"The intake guides are drilled with small holes which break up the 'suction effect' of the oil film on the valve stem moving in the guides. The idea was to prevent excess oil from being drawn down the guide and into the intake port. If the passages are plugged or restricted, exhaust smoke and increased oil consumption can occur. There are no valve stem seals installed in these engines. If the valve spring seats are not installed under the springs, the valve guides can work loose in the heads, as the spring seats also serve to keep the guides in place"

Something to consider, though if this is the problem I would expect the smoke to smell of burning oil.

[LOUD MOUSE]

HONDA discontinued those vents on the head in 1967.
Lots of engines have them pluged with bolts or run a tubing from one to the other. ....lm

Bill Silver has a note in his 305 Engine Repair Guide on page 109.

"The intake guides are drilled with small holes which break up the 'suction effect' of the oil film on the valve stem moving in the guides. The idea was to prevent excess oil from being drawn down the guide and into the intake port. If the passages are plugged or restricted, exhaust smoke and increased oil consumption can occur. There are no valve stem seals installed in these engines. If the valve spring seats are not installed under the springs, the valve guides can work loose in the heads, as the spring seats also serve to keep the guides in place"

Something to consider, though if this is the problem I would expect the smoke to smell of burning oil.

[conbs]

HONDA discontinued those vents on the head in 1967.
Lots of engines have them pluged with bolts or run a tubing from one to the other. ....lm

Bill Silver has a note in his 305 Engine Repair Guide on page 109.

"The intake guides are drilled with small holes which break up the 'suction effect' of the oil film on the valve stem moving in the guides. The idea was to prevent excess oil from being drawn down the guide and into the intake port. If the passages are plugged or restricted, exhaust smoke and increased oil consumption can occur. There are no valve stem seals installed in these engines. If the valve spring seats are not installed under the springs, the valve guides can work loose in the heads, as the spring seats also serve to keep the guides in place"

Something to consider, though if this is the problem I would expect the smoke to smell of burning oil.

LM, I take Bill's quote to refer to the valve guides themselves and not the head casting. Is he wrong?

[LOUD MOUSE]

The data may be correct for what HONDA intended the guides to do. ???
"Draw clean air from the air filters".
However in 1967 it was deleted.
The statement Vents On The Head ment that was an easy way to see those heads no longer used the vents.
I've never seen data as to why HONDA discontinued the vents and can only assume they weren't really necessary. .............lm

HONDA discontinued those vents on the head in 1967.
Lots of engines have them pluged with bolts or run a tubing from one to the other. ....lm

Bill Silver has a note in his 305 Engine Repair Guide on page 109.

"The intake guides are drilled with small holes which break up the 'suction effect' of the oil film on the valve stem moving in the guides. The idea was to prevent excess oil from being drawn down the guide and into the intake port. If the passages are plugged or restricted, exhaust smoke and increased oil consumption can occur. There are no valve stem seals installed in these engines. If the valve spring seats are not installed under the springs, the valve guides can work loose in the heads, as the spring seats also serve to keep the guides in place"

Something to consider, though if this is the problem I would expect the smoke to smell of burning oil.

LM, I take Bill's quote to refer to the valve guides themselves and not the head casting. Is he wrong?