Oil burning 4.3

[Taco Jeff]

Howdy! This is my first post so I'll try to get it right... I just bought an 89 shorty S-10 with 85,000 on it for dirt cheap. 4.3 with overdrive, clean as can be, but it burns about a quart in 300 miles( more under load ). Compression is 135 to 150 per cylinder( cold ), and it fouls #4 plug with nasty gunk! It actually passed emissions this way at the hollidays!

Do you think it might just be guides, or would it have to be a ring thing to use this kind of oil? It puts out black gunk rather than blue smoke. What should the compression be for this thing? I'm hopin that it might just be a heads-up thing.

Sorry for the long text and if this has been covered before...

This site rocks! Taco Jeff

[1993blazerlt]

do you have a made in mexic block? if so they are known to warp the cylinder walls pretty easy, i have seen this before

[Taco Jeff]

How can I tell where the block was made? A serial # or casting or something?

[Hammer Head]

Try some merv's mystery oil additive. The stuff will seal up most any leak.. if this stuff doesn't work then you problably need to pull the heads & look in the engine. Maybe you've got a cracked head gasket or head that seals itself when you're doing the compression tests & opens up like a flood gate when you're driving around. I would think that the valve guides are pretty worn, too.

[Taco Jeff]

The prior owners had a GM dealership try putting in new valve seals without pulling the heads at 75,000, ($2500) but it didn't seem to help. That was seals of course, not guides. So I'd be looking for Merv's mystery oil additive? Big stores like Auto-zone or smaller places..

[Sparky2263]

$2500 to put 12 seals in? Nah, it's like a 4 hour job at most, if you're slow.

First, ck. the pcv valve. Make sure it's the right one. When you stop flow with your finger, rpm's should drop no more than 50 rpm's. Aftermarket valves are notorious for high flow rates. Also, make sure the valve is in a baffled hole. Unbaffled they'll suck oil like crazy.

#4 cyl by itself could burn a qt. in 300 miles, so let's zero in on that cyl. You can't ck. for a bad oil scraper ring w/o pulling the piston but we can verify the valve guides. You'll need an overhead valve spring compressor and some 1/4" nylon rope (or similiar).

Pull the valve cover and remove the rocker arms for #4 cyl. Feed the nylon rope in the spark plug hole and turn the motor 'til the piston squeezes the rope against the valves, stopping them from moving when you remove the springs. You'll need to pop the retainer with a hammer to break it free (they stick pretty good) before compressing the valve spring and removing it. A small magnet comes in handy for removing the keepers.

Now you can ck. the valves for movement in the guide. You'll need to turn the engine back slightly to allow movement. Also, what kind of seal was installed? Old school mechanics would've installed an umbrella seal where a positive seal really needs to be. Might as well put 2 positive seals back in as they'll hold for a little while even on worn out guides.

[Taco Jeff]

thanks, I'll check those out and keep you posted... Any way to check if it's a mexican block?