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#16
10-30-2009, 04:37 PM
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FWIW I am sure 60PSI would be more than enough. It sounds like someone applied an extra 0.
__________________
Current: 2021 Charger Scat Pack Widebody "Sinabee" 2018 Durango R/T Previous: 1972 280SE 4.5 2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi" 1999 Chrysler 300M - RIP @ 221k 
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#17
10-30-2009, 04:46 PM
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I'm with tomguy. 60psi will hold the valve very secure. I've changed valve springs using that method. Frankly, changing a valve guide sounds a but far fetched. Perhaps MythBusters or Snopes can clear this one up.
__________________
"If it's in the newspaper it must be true." Dudley Do-Right
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#18
10-30-2009, 04:50 PM
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Boy, this Internet is an amazing thing....
I found where a guy did his Dodge V-6 like this and posted the whole thing online. The entire operation cost him $200 and took him four days, but he wanted everyone to know it could be done. The important thing here is that he was able to make the valves stay up with only 100 psi of air. This seems much more in reach of the average shop or home mechanic. Could the 600 psi I remember be typical Mercedes overkill of if some is good then taking it to the limit is better? Another thing I found people doing was inserting a length of nylon rope into the spark plug hole and then rotating the engine to cram the piston up against the valves to make them stay up, but even those that did this said it was risky in that the rope might get hung up and be impossible to get out. I don't know that anyone should try this, I just wanted to mention it since it was out there. You know, with only 100 psi necessary, this might be something you can try at home.....
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#19
10-30-2009, 05:33 PM
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Pooka,
I think that my reply may have been a bit hasty. The air to the spark plug hole can also be used for changing valve guide seals. Could that be what you ment in your 1st post?
__________________
"If it's in the newspaper it must be true." Dudley Do-Right
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#21
10-30-2009, 08:12 PM
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I never used more than 35 psi. If the car has an automatic trans, there's no easy way to keep the engine from turning when more pressure is used.
I doubt that guides can be successfully changed with the head in situ. I did replace a loose guide once without removing the head, but it was pure luck the valve was still on center with the seat.
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#22
10-30-2009, 11:08 PM
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60 PSI would surely do it if the valves weren't leaking severely. But, the rest of the stuff sounds like an incredible job. Probably only justifiable if it needed to be done on one cylinder only.
Sparky
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#23
10-31-2009, 12:28 AM
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An old boss of mine did valve seals in a 4.3 GM V6 that way. Worked well for him.
__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar. 83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles 08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles 88 Jaguar XJS V12 94,xxx miles. Work in progress.
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