My BB smokes a liitle, and worse after accellerating. Did compress. test, 170-180 all around. I suspect valves seals. Could it be a carb? Some of the plugs were fouled pretty bad. What the best way to test valves while motor is on the car (leak-down?)? Should I be looking else where?

Thanks

Does the smoking get worse when you are decellerating? If so, then it's probably worn valve guides / seals. When you let off the throttle after accellerating, the engine vacuum goes WAY up, much higher than it is at idle. If your valve guides / seals are getting worn out, the vacuum will suck oil through the valve guides. It typically doesn't happen during accelleration because the vacuum drops during accelleration. Now, if it smokes while you're on the throttle, and gets worse the more you stand on the gas, then it'e more likely to be worn rings. (Blowby)

Hope this helps!

Craig

Seems to be happening on deceleration, failtly at idle or when I'm just sitting there revving the heck out of it graemlins/thumbsup.gif

Vince
The leak down test is great for spotting a blown head gasket, cracked cylinder/head, bad rings, holes in pistons, burnt valves - anything that would allow pressure to leak out of the combustion chamber. It won't identify bad valve guides or valve stem seals (assuming the valves themselves are sealing).

Like kctransplant said - smoking on deceleration is usually valve guides. You might want to pull a valve cover & have a look - you might find little bits of hard rubber inside or around your valve springs. If so, that's what's left of your valve stem seals - they get hard and crack due to heat & age.
Apparently you can change them without pulling the heads - air pressure in the spark plug hole and a special spring compressor. Never tried doing it that way myself, but I've heard of it being done...

Chances are if the car is smoking quite a bit, you've probably got a build up of burnt oil on the valve stems on the top side of the valves. I've seen it built up 1/2" thick all the way around. Can't be too good for the flow rating of the head...

Hope this helps
Wes

Great Info Thanks!!!!!

Sounds like valve guide or seals.
You can purchess the adp. to pressurize the cyl. and the tool to compress the springs at most auto parts stores.Gm oem seals are not the best, go with a set of after market ones,also ford has a red colored seal that works good.

When you break down the valves,check the guides they could be worn,they are replaceable.

HTH
Good Luck,
Troy, graemlins/thumbsup.gif

Vince, you can brake the springs down as Beau and Vince said. I would add that the adaptor that I used to do mine, I had to make because the one I bought from the parts store didn’t have enough thread depth to work. I made one out of am old spark plug. When you pressurize the cylinder, have a plastic mallet handy to tap the spring retainer loose from the keepers or you will just open the valve when you try to compress the spring. Have a magnet handy to catch the keepers so they don't fall down where you can't get them. I did mine with the engine out, it will be a bit of a pain with the engine in the car. You will need to bend the tool to get the springs near the brake booster.

Will

Will - funny you mentioned that part about the valves opening when trying to compress! Thats what was happening to me. :( I just gave up. I was using a lever type bar to compress the spring. How do you tap the retainer when the compressor is on the spring?

I'm going to get the overhead spring compressor at PepBoys I think.

Before you put the spring compressor over the retainer, use a plastic mallet and give the retainer a good rap. You should be able to feel/see the retainer move relative to the valve stem. Then try the compessor.
Tapping it with the mallet "unseats" the retainer as they kind of get seized.

Try this & hopefully it works - it does work for the compressors you use when the heads are off anyway...

Good luck.
Wes

Well fellas your all right on the $$$ graemlins/hurray.gif

That little "tap" was all that was needed to get those pesky keepers off those retainers. When I pressurized the cylinders, I actually used log needle-nose pliers as my special tool to compress the springs and get the keepers out. I was kinda surprised that there wasn't much tension on the springs.

Next question(s). What type of seals should I use? I just popped of these white seals that looked like plastic actually (Teflon?) They had a large retaining ring on bottom and a smaller wire retainer up on top. My engine has dual springs, and what lookes like brass guides. I'm looking through my PAW catalog and (actually they are same seals as the catalog shows!!) and wondering what to get. Also, valves seem to be pretty tight in the guide - I can wiggle ever-so-slightly is this good?


Thanks fellas graemlins/thumbsup.gif

Vince. It's been years since I rebuilt heads myself. Can't remember what the guide to valve stem clearance should be. 0.003" to 0.005" comes to mind, but DON'T take that as gospel - it might be double that. Just can't remember. In fact 3 thou does sound a little tight..

I do know that you shouldn't be able to rock the valves back and forth (so much that you can feel it anyway). The guides (and likely the stems as well) are worn. The seals may help a bit, but it's not going to solve your blues problem for long. The white seals sound like after market items. The originals I've seen (on 70's and earlier GM's) were typically black rubber. Between those & the bronze guides, I'd say the heads have been rebuilt before.

As far as what to use for seals - I've always liked the ones you're taking off - the teflon ones with the spring. They don't seem to harden and crack like the original rubber ones. But they might wear and not seal. Teflon (and other plastics) aren't elastic like the rubber - so they would slowly relax away from the valve stem. The spring is there to counteract this cold flow. Hopefully someone with more recent head rebuilding experience can offer some insight.

Sorry I can't be more help.
Wes