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Valve seat contact width
06-23-2017, 06:54 AM
Post: #1
Valve seat contact width
Hello all,
I am inquiring about the valve seat contact pattern width spec in the 96 GEO Tracker FSM on page 6A1-32. The spec for both intake and exhaust is 1.1 to 1.3 mm. I had low compression in all cylinders. Ranging from 90 psi to 135 psi. I found leakage out the exhaust valves. I removed the head and the only problem I can find is the valve seat contact width is 1.75 mm on the exhaust valves. The owner I bought the car from 8 years ago said he had a reman head installed. I'm guessing they cut or lapped the valves to wide. Would the 1.75 mm contact width have caused the premature leak by on these valves? Thank you for any advice someone can provide.
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06-23-2017, 10:30 PM
Post: #2
RE: Valve seat contact width
what was the compression, on all 4, exactly, done wet and dry, done Wide open throttle. (about) done spark plugs all out,, ive only questions... many,
was the lash at spec?
is/was the cam timing set right using only the "E" marks and never 'I" marks.
is the head removed? still now?
take it to any machine shop, and get it tested?

ever do a home method of test? head upside down,
using a safe solvent. put that in the chambers and see if it the solvent leaks to ports? (kerosene is pretty safe) or paint thinner. if does lap them in, now. if fail , Machine shop time.
unseen , I'd say 1.75 is ok, but most shops do 2 or 3 angle cut, so , do so? but margin and concentric sealing is top of list.

the 1.32mm max is really what we call margin, the too wide cut results in to much recession, and the edge of the valve, is now like knife, this causes it to glow red hot and burn
this margin rule is what matters most.
why not get the heat fully tested in a real machine shop. or since its all ready out, get it rebuilt. end the worry?
lots of premature causes, EGR dead, lash wrong, over cut super bad, now edges burned,
many valves dont like excessive cuts, as the harness is not as hard deep inside.
Engine ping.(& age)
20year old heads can be hard to rebuild.
water flow problems i the head. hot spots,at seats.
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06-24-2017, 07:13 AM
Post: #3
RE: Valve seat contact width
Compression Dry with wide open throttle, all plugs out. I did the compression testing in accordance with your instructions and recommendations on your fixkick site. Great guidance by the way. Thank you for providing it. #1-130, #2-110, #3-90, #4-135. The wet test showed no difference.

Lash was good and timing was good. I did do the solvent test to determine them leaking. The head is off and torn completely apart. I speced out all parts to the FSM and everything is good except the 1.75 contact width on the exhaust valves. It does look like the head was machined and new seats put in. The seats look really good just needing a good lapping. I just don't understand why the machine shop would have made the seat contact width that wide if FSM spec is 1.1-1.3. Of course I don't recall ever seeing a spec that narrow on a exhaust valve.

The seat is a 2 angle cut. 15 and 45 degrees. If the 1.75 was going to be a issue I was going to order a 15 degree cutter and narrow it up. But if you feel the 1.75 is ok I'll save my money on the cutter and just lap them then test.

Taking it to a machine shop is still a option on the table but my first thought was to have some fun and check it out.

Thank you for all the good advice and information on the website.
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06-24-2017, 07:45 AM
Post: #4
RE: Valve seat contact width
the question is not that.
but what parts were used, china clones?
The cause of the leaking is not known.
1: burned valves.
2: non concentric how.
6: same with seats.

if you grind the valves, the bent ones are obvious, or from heat CAUSED warpage

a valve runs cooler the more contact there is on the face.
IIRC, the 2 angle cuts are for flow, a compromise to above.
they make 1 angle valves for 100 years with no problems.

finding quality parts today is not easy, and Suzuki dont help there either. It's no Honda/Toyota.
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