Doing valve stem seals on SBC in car:

speeder · speeder's Garage

Or more accurately, "in truck". I posted before about my old Chev truck and rich running, (and got some good and appreciated advice), now I need to plan out doing the valve stem seals. I may just take the heads off and have everything checked, (guides/valves), since it's an easy job but want to know if the option of changing just stem seals in the vehicle is a big PIA? Someone told me that it is, now I can't remember why...

I know the basic drill of pressurizing the individual cylinder with it @ TDC and compressing the spring somehow to remove keepers and springs, not sure what tool I need to compress spring with head on engine? I have a big valve spring compressor but it's used with head off--it wraps around the bottom for leverage.

i know that there are some domestic vehicle techs on here, (as well as just good old gear heads with a lot of general knowledge), is this a PIA job? Should I just pull the heads? TIA.

speeder · speeder's Garage

Oh yeah, it's a 1988 Chev K1500 with 5.7 TBI.

VincentVega · 09-03-2013, 10:15 AM

I've done it with one like this

Not on a that truck though, but I would think this is room.

Zeke · 09-03-2013, 10:23 AM

Valve seal Replacement - YouTube

Newer model with the 5.3, but the process is much the same with the 5.7 (350)

RANDY P · RANDY P's Garage

It's not a big deal with a valve spring compressor (rent it at autozone), compressed air, and a stick magnet. drop the fan and shroud and rotate the crank to put the cam on the flat spot for each cyl.

At that miles, honestly you might want to just swap heads- they're tired and most likely will need valve stem guides and could be cracked- those are lightweight castings, a major overheat will cause failure.. You can get replacement heads all day long for $200 / Pr anywhere. Had we had this conversation 6mos ago I would've had some heads for you- fresh, sold 'em tho.

If you do the replacement heads, make sure you stay away from Vortec castings or aftermarket, no EGR provision, which is what you need to stay smog legal.

One last thing- when you reassemble the rockers and need to adjust prelash, BE VERY CONSERVATIVE with the preload. It's easy to overdo it. slowly tighten the rocker arm while you wiggle the pushrod back and forth (cam on heel, not on lobe obviously) - when the pushrod and rocker literally have zero slop (the moment they touch), go maybe 3/8 a turn more, and that's it. It's pretty sensitive. If you overdo it, you'll hang valves when the engine warms up.

RANDY P · RANDY P's Garage

El cheapo. Use with rocker arm bolt and pull...Shouldn't be too bad, not like those are badass springs on that head. Someone ripped and buff might even be able to compress by hand

RANDY P · RANDY P's Garage

87 up chevy tbi heads for 5.7 motor

I have a set of rebuilt chevy tbi heads for sale , asking $225.00 for the pair the heads are completly rebuilt ready to be slaped on , hit me up if interested ill post some pick when I get home , ask for Jose 562 303 3726

casting # should end with "193"

asphaltgambler · 09-03-2013, 12:00 PM

My experience is it is a colassal waste of time because I have done it trying to band-aid a customers car years ago. The real problem is the guides wearing badly in those years. And the amount of time spent replacing these on the motor is @ equal to swapping the complete cylinder heads with new / rebuilt.

chapo · 09-03-2013, 10:31 PM

waste of time. Did it in my 73 Blazer, one month later I overhauled the whole engine.

RANDY P · RANDY P's Garage

Pulled one head off and cyl 7 gone- blowby. Stopped me dead in my tracks- got a new crate and slammed it in instead

speeder · speeder's Garage

My truck only has 98k original miles and runs like new, only problem is the smoke on start-up and for a short time after. Pretty sure it's the valve stem seals. Obviously, if an engine is completely worn-out, replacing those seals is waste of time. I don't think that my situation is the same.

speeder · speeder's Garage

Quote:

Originally Posted by RANDY P

87 up chevy tbi heads for 5.7 motor

I have a set of rebuilt chevy tbi heads for sale , asking $225.00 for the pair the heads are completly rebuilt ready to be slaped on , hit me up if interested ill post some pick when I get home , ask for Jose 562 303 3726

casting # should end with "193"

Thanks, Randy. I might pull mine and let my very trusted machinist take a lookie, the advantage of my heads is that I know they've never been off, shaved, etc... I'f they're bad for some reason, I may call that guy.

VINMAN · 09-04-2013, 02:39 AM

Denis, the only issue Ive ever run into doing it that way is, having a valve that didnt have a good seal on the seat, and the commpressed air not holing it. Ive done it a bunch of times, using the tool Randy P posted, I think the one I have is made by Lisle

Willem Fick · 09-04-2013, 05:42 AM

I didn't have access to compressed air when I did it years ago and got advice from someone to remove the plug, thread a good length of soft cotton string into the combustion chamber, and then to manually turn the piston to TDC. The ball of string compresses against the valve allowing you to compress the spring. Worked a charm!

Zeke · 09-04-2013, 08:22 AM

Might want to do a compression check before unbolting the heads. You can eliminate rings and the valves on each cyl as you go. Find something bad and you know what direction to take w/o speculation.

RANDY P · RANDY P's Garage

98K changes the game. Wasn't aware the miles were that low.. If it wasn't using water or drinking oil so far, maybe the seals would be worth a shot. Would save a ton of cash- and no bull**** like draining coolant, oil change, new head gaskets, etc. etc. I'd rather do that than tear the top end off and all the accessories off the front- as would be required for head swap. That "Horseshoe" on the front of the engine (holds the accessories) is a PITA to deal with.

Mine was 268K when it finally bit the dust, didn't even use much oil..

rjp