I have a /6 with hydraulic lifters. One of the lifters was stuck in the up positions. I have removed it and purchased a new one. The new lifter push rod seat is easy to depress and of course comes right back. However, the old lifter seats will not depress under considerable force. Should I replace them or is this normal behavior for hydraulic lifters that have miles and miles on them?

You can't just replace one lifter on a non roller camshaft. That is a good way to wipe out a lobe(s) on the cam. You have to change the camshaft and all of the lifters.

Have you tried disassembling and cleaning the bad lifter?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Other way around, Jeb. You can't put old lifters on a new cam, but you can put new lifters on an old cam. You can reinstall old lifters on an old cam, as long as the lifters stay on the same lobe they had been run on before. No problem to replace just one lifter.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Ooops, guess you learn something new everyday.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

simply curious....why does it ruin the cam to put old lifters on a new cam..old lifter on a different lobe? Also, should I be able to depress the old lifter rod seat?

BTW, thanks for the help.

I may just be talking out of my rear on this.
But I would think due to the worn state of the old lifter, the new lobe it contacts would wear unevenly. If the natural wear between the old parts was biased to one side somehow, you would incread the pressure and wear to the new lobe in the same spot. Think of it this way, you don't put old break pads on a new rotor. Unless you're my dad.

Basicaly, like icetitan said. it has to do with wear pattern. Putting an old lifter on a new cam, will not definatly mean a wiped out cam, but it increases to odds, greatly. It is cheap insurance, to replace the lifters. As for the lifter: an old lifter, with oil in it, will seem almost solid. If you hold pressure on it for awhile, it should, slowly bleed down. A new lifter, without oil, will be able to be depressed, easily. This is for hydraulic lifters, not solids.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

If you put a straight edge across a new lifter you will find that it is slightly domed. Likewise the cam lobe is grounf at a slight angle to the axis of the shaft. The result is that when running the lifters spin in their bores assuring even wear. If you pull and old lifter and put a straightedge on it you will likely find that it is slightly cupped. The wear pattern will exactly match the wear on the cam lobe from which it wasw taken. If you put it on a different lobe it won't match resulting in rapid and excessive wear and often the destruction of the cam itself.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.