Valve Guides

[zeitgeist57]

My '86 Chebby sat for 7yrs, and despite decent compression numbers across all 6 cylinders in the 4.3L, it has what seems to be terrible blow-by ONLY when the breathers are covered up on the valve covers.

 

People I have talked to almost universally claim that the valve guides are probably all shot to shit...how tough are they to replace? What special tools do I need? Do I need to remove the valve springs? PLEASE HELP!

[nurkvinny]

Valve guides can't be changed without pulling the heads. I would start with changing valve seals . Pretty quick and easy with the right tools. Plus, they're less than 10 bucks.

 

First, loosen the lock nut that holds on the rocker enough to move the rocker out of the way.

There's a tool that screws into your spark plug hole that is on the end of an air line. This fills your cylinder with compressed air. This holds your valves up.

Take a valve spring compressor and compress the spring. Remove valve locks (holds spring retainer on). Remove spring.

You may have o-ring seals, umbrella seals, or both. Replace the seal(s). Reinstall spring, reinstall locks / retainer, uncompress the spring.

It's a good idea to GENTLY tap the top of the valve to make sure everything is seated correctly.

Reinstall rocker.

The toughest part is readjusting the valve lash. This might be tough if you have never had to do this, but it's not that bad.

 

Hope this helps.

 

[ 10. September 2003, 11:30 PM: Message edited by: nurkvinny ]

[Guest stevil]

I have the sparkplug/air fitting, let me know if you want to borrow it. They only cost $3 or so from a parts store. I also have a 90 degree fitting on it as well, which helped to actually connect the air hose in the tight space I had to work with. I bet your truck is a bit wider with more room, not sure.

 

AutoZone rents out the valve spring compressors, I found the turn style easier to work with than the stud type. I also used a long snake magnet to grab out the valve spring locks, as well as fish for parts I dropped.

 

It's fairly easy to do, just time consuming. Let me know if you need any help. You'll also need to loosen the rocker arms or take them off to get access to the valve spring. You won't have to remove the studs.

 

Here's a pic of the tool to use. Just put the arms on the bottom of the spring. Then compress it, and it will sort of pop when it's loose. Then you have to pull out the locks, you can see one on the magnet. Another pic. Here you can see the valve stem and seal.

[zeitgeist57]

Great info...thanks guys! I may take you up on someones' help...especially since I have no air compressor!

[Dave1647545494]

Originally posted by zeitgeist57:

My '86 Chebby sat for 7yrs, and despite decent compression numbers across all 6 cylinders in the 4.3L, it has what seems to be terrible blow-by ONLY when the breathers are covered up on the valve covers.

 

People I have talked to almost universally claim that the valve guides are probably all shot to shit...how tough are they to replace? What special tools do I need? Do I need to remove the valve springs? PLEASE HELP!

your not suposed to cover up the breathers if your blocking them off, you have blow by because the excess crankcase pressure has nowhere to go.

 

if you do need to do valve seals you can use rope instead of compressed air to hold the valve up you have to take the sparkplug out and feed rope into the cylinder until its full, then when you pull the spring off the valve will rest on the rope while you change the seals.

 

hth

[desperado]

I am in agreement that you are not suppost to cover the breathers. Unless you have a PCV system on the motor. If the car sat for seven years was it started from time to time or did it just set. Reason I ask is that the cylender walls could have easily rusted, bothe above and below the pistons, and when you started it it would have eated the rings up real quick. Actually as I am sitting here thinking about it more. I figure that is what is going on. When I hear blowby I thing combustion gasses blowing down past the rings. And coming out he breathers. If you cover then and has a PCV system, the inside of the engine will go into a vacuum state, which is what it should to except if your rings are hosed then the vacuum will help even more gasses get by. I assume that the car is smoking from the exhaust. But specifically when. At startup, and after idleing for a time. Like at a light. Or does it smoke all the time?

Knowing this would help to better understand the problem.

[zeitgeist57]

VERY difficult to start, and smokes BLACK smoke like crazy until it warms up. Then, it runs very rich (smell it) but no black soot from ass pipe.

 

Thanks for the rope reminder...I remember that trick from Auto Shop in high school smile.gif

 

If I found a carb'ed 4.3L or 5.7L, I'd try to put it in and break apart the original motor, but I don't have that luxury right now.

[Dave1647545494]

ahh did you fix the vacum hoses yet? bring the truck out one weekend the carb may need adjusted again to

[zeitgeist57]

No...but I can almost SWEAR there are no other vacuum leaks.

 

Now when it's running, a little puff of blue comes out...I am convinced the valve seals are shot.

[zeitgeist57]

Alright...new compression check and spark plug inspection:

 

After 500 miles, all the spark plugs are in PREFECT condition visibly, with the exception of the fact that they are BLACK. Not wet black, and not with little particules and globs on the electrodes...just signs of a RICH condition.

 

All cylinders between 140-150psi. No more, no less. Most are btw 145-150.

 

I tuned the truck by hand (grabbed the distributor and turned till I heard pinging one way, turned till I heard pinging the otherway, and then tried to find a sweet spot and I was AMAZED at the difference. Still bogs when I slam it in third gear, but much better.

 

Dave? Still think it's a vacuum leak? smile.gif I think the carb setup you gave me would be great if I had 2 extra cylinders, brah!