1990 Other Toyota Models Should I do a valve job or a rebuil

DOCWEATHERS

MEMBER
1990 TOYOTA

Engine Mechanical problem
1990 Other Toyota Models 6 cyl Two Wheel Drive Automatic 74K miles

I have a 90 Winne 3.0 V6 auto with 74k. Just before I bought it at 62k it burnt a valve on the right bank. The prior owner did a valve job on the right. Now, 12k later I have a burnt valve on the left bank. It burns no oil. Compression test is about 150 on all cyliners except the bad one, which is 25 lbs. It still has quite a bit of power but runs a little rough at idle. I am being told by my mechanic that the extra compression created by a valve job risks damaging the lower end, such as throwing a rod. They are recommending a rebuilt engine instead. Almost half a century ago I was a car mechanic. I did valve jobs all the time with no problems with the lower end. I am told that modern engines are different, but they look the same to me. What is the reality here? Can I do a valve job safely or are the telling me the truth?

Also, it is my conjecture that the fuel injection running lean is causing it to burn valves. It that accurate and what needs to be done to the FI to solve this? If not, what else could be causing it to burn valves

Thanks Larry

3 Replies

MHPAUTOS

MECHANIC
31,938 POSTS

Hi there,

If the lower end is getting tired and you have already got some blow by, this is when doing a valve job will over stress the bottom end, not to the extent of breaking a rod, but you can get an increase in oil consumption due to the extra stress on the worn rings, if the comps are ok and there has been no history of oil consumption, I would not have a problem with doing the valves, as for why it has failed, yes a lean mixture will cause the engine to run hotter and valves can suffer, you can get a exhaust analyzer reading this will confirm if it is lean, also as there is no lead in the fuel the seats do tend to get a bit more of a pounding, even if stelite seats are used, so a regular dose of upper cylinder lube or set up a flash lube drip system won't hurt at all.

Mark (mhpautos)

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Monday, August 24th, 2009 AT 8:00 PM

DOCWEATHERS

MEMBER
2 POSTS

Thanks. I think I need a new mechanic.
Since it burns 0.0 oil, I will get a valve job.

The motor never runs over mid way on the temp gauge, even on the steepest, longest hills. Under most conditions it is only about 1/3 of the way up.

If the fuel injection were not running lean and causing overheating, what else could cause it to burn valves?

Larry

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Monday, August 24th, 2009 AT 8:10 PM

MHPAUTOS

MECHANIC
31,938 POSTS

Hi there,

Good luck with this, I am sure that you won't have any problems, just don't use synth oil keep the mineral oil in it, it is a shame that so many mechanics these day are more interested in spending large amounts of your hard earned $$$ than giving the correct advice!

Mark

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Monday, August 24th, 2009 AT 8:35 PM