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Burnt valve solution for g10; keeping the valve from burning in the g10
Topic Started: Mar 19 2017, 11:36 PM (811 Views)
trustyrusty90
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Hey guys, been a while since ive been on here but in the time i have been gone working on 9liter plus diesel engines in trucks i have come across a fix for my burnt valves in my old trusty metro. one issue i have found is the oil pressure releif valve in the oil pump. i have noticed that debris sticks this thing and over time it wears enough to cock in the bore and stick shut, therefore building an overkill amount of oil pressure in the cylinder head. keeping clean oil and changing the filter helps alleviate this as well as clean engine repair practices. but the main issue i have found is driving high rpms for extended periods of time with these cars. i used to put a head job in my car about every two months before i found this little mod. i drive it on the interstate about 60 miles a day. i found that when i would pull the head to change the valves the lifters would actually be pumped solid hard due to high oil pressure/debris mixture overcoming the return spring in the hydraulic lifter chamber. everytime the valves would be open with the cam lobes on their base circles. if i put it together and kept the rpms low i could make it last a lot longer. so the last time, which was about 65k miles ago i tried the oil restrictor mod. i took a 6mm allen set screw and drilled roughly a .104 hole in the center and tightened it into the oil feed in the cylinder head. its tapped to receive already and it fit really well. then i cleaned the lifters and kept clean oil and i can drive 80 on the interstate no issues with cold starts no lifter noise as before. just some food for thought. i tested this theory with stock style valves on the 96 i just bought and i didnt put the restrictor in the head but cleaned the lifters and clean oil. it lasted two weeks at that high rpm before the valves burnt yet again. im currently rebuilding this engine for a daily drive as it has ac and sway bars where my 90 base model does not. any input is greatly appreciated. i and a local machine shop guy have developed this theory to the burnt valve issue on these engines. and my car has also burned 3 qts of oil a month in this 65k miles so i know that wasnt the issue before. these engines are simple and easy and cheap so i have made mine into a test subject hahah
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trustyrusty90
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i would like to discuss this with anyone that has had the same issues
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Metromightymouse
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I would suspect the burning oil issue is contributing to your problem. I have driven a 95 Metro since 2000 and have always driven around 75 mph and am not afraid to go faster on occasion. I have never had burnt valves. 30 minute commutes, 2 hour commutes and some in between so extended time at high rpms. It's not a fluke of my engine either because I have lost 2 to other issues and none of the 3 have died from a burnt valve. TXJato also runs these engines extremely hard in AZ heat and he hasn't burnt any valves that I'm aware of.
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1DCGUY
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Don't be a "Richard"

Speed and high RPM's have nothing to do with burnt valves.
I have torn apart more motors than I can count, and the best motors that I find after tear down are the automatic motors.
They spin at high RPM's constantly, unlike the 5 speeds were most folks, but not all, like to lug them for better fuel mileage.
I personally rev the piss out of my 5 speed and see's 5500 to 6000 rpms quite frequently.
If you are burning valves that often, you have something else wrong with your setup.
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Coche Blanco
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Something someone proposed a while back (I think it was Geo Glenn? RIP) was the hydraulic lifters getting gummed up/overpumped and not allowing the valves to seat fully.

All I know is I wish we knew for sure what caused them.
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evmetro


1DCGUY
Mar 20 2017, 05:02 PM
Speed and high RPM's have nothing to do with burnt valves.
I have torn apart more motors than I can count, and the best motors that I find after tear down are the automatic motors.
They spin at high RPM's constantly, unlike the 5 speeds were most folks, but not all, like to lug them for better fuel mileage.
I personally rev the piss out of my 5 speed and see's 5500 to 6000 rpms quite frequently.
If you are burning valves that often, you have something else wrong with your setup.
This sounds right. I run my 3/5 metros hard, and I don't experience burnt valves. My '96 3/5 that I bought brand new, has about 250k on the clock now, and it is a virgin. I have never done anything to the engin besides the timing belt and oil changes, and it still runs strong. I have driven her hard for almost 22 years. Lots of high rpm driving, and pedal to the floor whenever I am on an interstate. I have driven it like I am racing the whole time.
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metro-mike
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Most of the burnt valves was from using the wrong grade oil.

A lot of people were using 10/40 and the oil was to thick for the oil to bleed down the lifters in colder climates/cold engines.
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LesCrapp
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Not sure where I heard or read it but seems like it was something to do w/ the wonderful EGR system clogging that had something to do with the exhaust valves burning not sure just trying to help...
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sphenicie


trustyrusty90
Mar 19 2017, 11:36 PM
i used to put a head job in my car about every two months before i found this little mod. i drive it on the interstate about 60 miles a day.
YIKES, really?

I put on 200 miles a day, mostly hwy, 80 mph..........200k + on a head job, never have a problem with valves. although, I find them in cars I have purchased.

I would have to guess, valves not lapped in properly? Are you running used diesel oil?

there is no reason that a properly done head should be redone so often, period. 210k on my xfi, NEVER been opened. 634k on 'Barney', one rebuild, never a valve problem.

maybe luck?

maybe good maintenance!

I blame Mobil-1, changed every 5k. Or, maybe, just doing a proper head with NEW valves, sealed power lifters, and springs.

once again.......DO IT RIGHT OR DO IT TWICE, or every couple months.
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Woodie
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I've seen a hundred theories as to why G10's burn valves, they're all just wild guesses. "EGR clogging, that's why it's always cylinder 3." "PCV feeding oil into the intake, that's why it's always number 2." Those two prove each other wrong, it's not always anything, in my experience it could be any one of the three. Most of the MK2 cars didn't have EGR and they had the worst valve burning problems, although Suzuki figured that one out. It was too thick oil and too small drain holes in the lifters. I think the late ignition timing probably contributes some, that sooty exhaust pipe proves that the charge is still burning when the valve opens. No question that a sticky oil pressure dump valve would overpump and hold the valves off their seats a little bit, but tonnes of these engines burn valves and a new head fixes it, so that's only a once in a while type of failure, not the norm. There is also no question that burning oil will burn exhaust valves, as oil burns hotter and slower than gasoline. Maybe 150K miles is when the rings start to leak a little, causing most G10's to have burned valves around 160K.

None of this explains why automatics, which run at much higher rpms, seem to go MUCH longer without burning the valves.
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evmetro


Woodie
Mar 22 2017, 09:52 AM

None of this explains why automatics, which run at much higher rpms, seem to go MUCH longer without burning the valves.
I don't know for sure if the higher rpms is the answer to this question, but my 5 speed Metros do see high rpms like the auto's do. Never had a burnt valve in my last 22 years of Metros.
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sphenicie


Burnt valves ARE caused by(most prevalently) a bad seal between the valve and the seat. Hot gases blow thru, during compression, as hot as a cutting torch, thereby melting the valve.

Gaps are caused by a few conditions, such as, poor initial fitment, poor quality parts, and carbon build up. Bogging your engine adds to the problem because, in a bogging condition, you add unburned fuel to the equation. Unburned fuel adds to the temp of the gas passing thru the gap and speeds the degradation of the valve.

If you have so much gunk in your oil, that you feel the need to drill out the relief, YOU have a problem with basic maintenance. YOU, or anyone concerned with the life of your engine should NOT allow their engine to accumulate that much gunk.

Maintenance 101.........
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sphenicie


evmetro
Mar 22 2017, 11:54 AM
Woodie
Mar 22 2017, 09:52 AM

None of this explains why automatics, which run at much higher rpms, seem to go MUCH longer without burning the valves.
I don't know for sure if the higher rpms is the answer to this question, but my 5 speed Metros do see high rpms like the auto's do. Never had a burnt valve in my last 22 years of Metros.
Yes, it does, CARBON BUILD UP. Bogging adds to carbon build up. Higher rpms, in general, burns off carbon. Less carbon on your vale seats/ valves prevents leakage. Once a leak starts, valves begin to burn.
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Highwayman
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I wonder if the automatics were assembled at a different plant so different engine supplier ?
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freegeo
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Highwayman
Mar 23 2017, 07:35 PM
I wonder if the automatics were assembled at a different plant so different engine supplier ?
No, don't think so. Same engine.
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