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Burned Exhaust Valves on 1.0L G10 Engines; GM technical notes regarding Geo 1.0L G10
Topic Started: Nov 22 2011, 09:33 PM (4,846 Views)
MonTex
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Santa Clarita, CA
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Ref URL:

http://www.rebuiltautoengines.com/geo-metro-articles.html
_________________________
Burned Exhaust Valves On
GM 1.0L Geo Engines

The AERA Technical Committee has received calls concerning repeated exhaust valve burning on GM 1.0L engines used in the Geo Metro. One reason for this type of failure may be caused by a restriction in the exhaust system.

After repairing a cylinder head with a burned exhaust valve, instruct your customer to perform an exhaust system backpressure check. After the engine has reached normal operating temperatures, this test should be performed at 2,500 rpm. A value of 2.8 psi or higher indicates a restricted exhaust condition.

An exhaust restriction may be due to a collapsed header pipe, internal center pipe failure, internal muffler failure, a damaged tailpipe or a plugged catalytic converter.

The AERA Technical Committee
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Memphis metro


They said this also,

(The following list are engines that AERA is currently aware of that have exhibited interference.)

(1986-95 1.0L Geo Metro)

Thats a bunch of :shit


Also this is not GM documentation.

Just keeping it honest. Welcome to the forum.
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Johnny Mullet
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Fear the Mullet

Retarded timing to meet Emissions cause carbon buildup and the lifters have been redesigned 3 times because they stick due to carbon. The stuck lifters do not allow the valves to close completely causing them to burn

:bananaburn
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MonTex
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Santa Clarita, CA
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Good to have the forum members weigh-in on this stuff for verification. Others may run across this information outside of this forum too. The subject URL at http://www.rebuiltautoengines.com/geo-metro-articles.html has other Geo information that may also require verification.

If you order a set of lifters, how may a person tell which version of lifter you are ordering? New old stock vs. new stock parts? Are the less expensive lifters new old stock? :'(

:scared

Do the Geo parts gurus know about configuration management (CM)?
Edited by MonTex, Nov 22 2011, 10:40 PM.
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mwebb
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FOG

lifter related problems are always related to
lubrication
oil
usually because the wrong oil was used and the oil change interval was incorrect , too infrequent .

timing , ignition or cam , can not cause lifter related problems .

overly ADVANCED cam and or ignition timing can cause elevated exhaust gas temperature s
due to incomplete combustion
and
will lead to burned valves

incorrect oil coupled with overly advanced ignition timing
will lead to deposits in the EGR passages which will restrict EGR flow or completely block EGR flow
and
will lead to deposits on the exhaust valve stems which will cause exhaust valve s to stick or bind open -

excessive exhaust back pressure in a speed density system like Geo metros use will increase MAP by decreasing intake vacuum
which can result in elevated exhaust gas temperatures because of overly retarded ignition timing under load which will lead to
incomplete combustion
you should expect 2psi back pressure at WOT measured at the EGR back pressure transducer center tap on a "normal" stock metro system

as always
dogshnit oil is the primary cause of the problem

and
your systems are designed to maintain peak combustion pressure at 14 degrees after TDC under all loads and driving conditions except DFCO and idle - until you learn why that is important , it is something you should not tamper with --- after you learn why it is important you will never tamper with it .
study and learn

use ACEA A3 B3 - A3 B4 oil s only or at the very least , use the minimum spec oil recommended for your systems by GM
DEXOS1 , as long as the oil meets the specifications , brand is unimportant
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Woodie
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enginedoctorgeo
Nov 22 2011, 09:55 PM
They said this also,

(The following list are engines that AERA is currently aware of that have exhibited interference.)

(1986-95 1.0L Geo Metro)

Thats a bunch of :shit


Also this is not GM documentation.

Just keeping it honest. Welcome to the forum.
That's just as accurate as the other proclamation. (not at all)
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Woodie
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mwebb
Nov 23 2011, 01:12 AM

which can result in elevated exhaust gas temperatures because of overly retarded ignition timing under load which will lead to
incomplete combustion
At least you got this part right. Overly retarded ignition timing (such as the 5° spec forced by the EPA, contrary to what the engine designers wanted) helps cause burned exhaust valves because the chrge does not have enough time to complete its burn. Still burning when the valve opens, superheating the valve seat area and increasing carbon production in the exhaust and EGR systems.

Suzuki's findings vis-a-vis the lifters was that the early lifters had too small a drain hole, and the original recommendation of 10W-40 oil were conspiring together to overpump the lifters and not allow the valves to close firmly at high speeds. That's why nothing thicker than 5W-30 should ever be put into a G engine.
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Johnny Mullet
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Fear the Mullet

I have seen rebuilds die after a year because of the lifters alone. Three different cars. Two were rebuilt by the owners and one was a replacement used head. All had the same issue of stuck lifters and all had burnt valves..
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wayn
Really fresh fish
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Johnny, are you trying to give us all nightmares???

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bogs
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Duct tape heals all wounds

wayn
Nov 23 2011, 05:09 PM
Johnny, are you trying to give us all nightmares???

:ahh
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Coche Blanco
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Troll Certified

For 58 dollars you can get brand new lifters.
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Memphis metro


:mokay
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3tech
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Retarded timing, absolutely. There is no question in my mind. Lifters? I'm not convinced. 3 other motors shared lifters with the G10 and have no valve burning problems. At this point, I don't know if anybody has seen more of these heads than I have, and I think the problem is a combination of things. The right series of events has to occur to toast a valve, and it starts with late timing. I doubt that oil quality or viscosity has anything to do with it. I believe that was an early attempt to explain it away, and think it's wrong, based on my experiences, and what I've seen in my own, and customer's motors and heads.
Edited by 3tech, Nov 24 2011, 10:40 PM.
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mwebb
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FOG

3tech
Nov 24 2011, 10:37 PM
Retarded timing, absolutely. There is no question in my mind. Lifters? I'm not convinced. 3 other motors shared lifters with the G10 and have no valve burning problems. At this point, I don't know if anybody has seen more of these heads than I have, and I think the problem is a combination of things. The right series of events has to occur to toast a valve, and it starts with late timing. I doubt that oil quality or viscosity has anything to do with it. I believe that was an early attempt to explain it away, and think it's wrong, based on my experiences, and what I've seen in my own, and customer's motors and heads.
http://geometroforum.com/topic/4593450/1/
read what is above
this is not the first example of this in this very forum , do not imagine that the oil pump described above was shipped from the factory with the problem that was located and repaired by the OP

the problem was oil related

this problem , while rare , does happen and is almost always attributable to incorrect oil that is thicker than specified
it can effect all engines with hydraulic lifters

so anyone
who
doubts that
"oil quality or viscosity has anything to do with it"

needs to study and learn and get some real time in fixing real cars in the real world
imho
again
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mwebb
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FOG

Retarded timing, absolutely. There is no question in my mind.

here
you will need to define
"retarded timing "
if you describe following original specifications for setting base ignition timing to 5 degrees BTDC
which results in
peak combustion pressure occurring around 14 degrees ATDC under all driving conditions with the exception of idle and DFCO

as "retarded timing"

then you are entitled to your opinion
but you should know that the facts disagree with it

the facts show that
in Geo Metros with stock ECMs
advancing base ignition timing before 5 degrees BTDC causes peak combustion pressure to occur
before 14 degrees ATDC which raises exhaust gas temperature and robs power and increases emissions
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