This an off topic question remove it if you wish you be the judge. I have a 1990 Chevy 350 with only 70K miles. More then 75% times it blows out clouds of blue the exhaust pipe on 1st start up. Should this job be done with heads on the engine or not. My local shop said leave alone another guy said he does do that type of repair. What are the thoughts of fellow HAMBer's out there.
Its easy enough to do on an earlier engine, dunno about getting to everything on a 1990 model, have to get to the sparkplugs and insert an air hose to put the cylinder under pressure.
It'll be fine that way for years...but if it bothers you, change the seals on the ends of the valve stems. Kind of up to you, if you think the work and bother is worth the results.
Doing them with the heads off is the easiest way, but then you will have to remove them from the engine, which can be a pain in itself. I've done them with the heads on. It's not really that hard to do. I use a compression tester hose with an adapter to put air pressure in the the cylinder you are working on through the spark plug hole to keep the valves from dropping into the engine when you take the springs off the valves. Just make sure the piston is at top of the cylinder you are doing. I've heard of using a piece of rope stuffed into the cylinder to hold the valves up, but never done it that way.
You can replace the seals with the heads on by,as OJ said putting air pressure into the cylinder when it is at TDC compression so that the valve spring can be removed.My question would be is the car a beater or something you plan to keep? If it is a beater let it smoke,if not pull the heads, do a valve job and have the guides cut for positive seals-JMO.
In a bean counters decision, one of many, GM had bad valve seals on some of their V8's in that time frame, have OT 89 305FI that puffed blue out when new on start up, GM did nothing as they monitored it and 1 QT in 1500 miles is acceptable oil use, went up the ladder, no fix, still after 27 years and 70000 miles, oil consumption is the same, I got used to it. I have done this job w/ heads on, on a friend's 350 Nova, pain in A$$ to get everything out of way to insert air fitting @ TDC used 100# , bought a tool to compress springs, carefully remove keepers, springs, replace seals, reassemble. You need to mark the degrees on your front dampener @45 deg steps , I bought a stick on degree wheel, Summit or Jegs, after #1 follow firing order around at 45 degree steps and you got it, not that bad, like I said, everything is in the way, But be careful. My 2 cents today.
If the plugs don't foul, why bother? My 84 Monte has been that way for as long as I can remember, 178,000 mi and the plugs have never fouled. I think I lose more oil from the pan gasket than anywhere else.
Thx a bunch guys. Yes I would have left it the way it was. However, it first started as a small puff earlier this year when I bought the car. I drove it home in April added 1300 miles to the odometer and the only thing I did had the water pump replaced, History, the car did a lot of sitting over the last 20 yrs from what I am told. I other day I had a caregiver drive for me for to my treatment center I could see where the car was in the parking from all the BIG plume clouds of blue smoke..............LOL. To make a longer story shorter it is getting much worse. I'm at the mercy of my local garage mechanic and wants to pull the heads. In my mind that has to be more expensive. Oh well. what to do?
You can't change the guides with the heads on the engine. You can change the seals but if the guides are loose, the seals won't help much. My other thought is has anyone actually pulled the valve covers and looked at it? maybe it is sludged up and need to be cleaned out and have the oil returns opened back up. I once ran across a Ford van that would blow smoke only when you turned left. The oil returns were plugged on the left head from broken valve seals and oil would flood the valve guides when you turned and the oil sloshed over. Turn right, no smoke. Turn left and it would belch blue.
Just some thought starters.......that motor in my opinion just really doesn't have valve seal problems.......with modern oils, and catalytic converters, it is really hard to get that kind of smoke.......as onetrickpony said, check for plugged drain back holes in the front and back of each head.......some vehicles have computer programming to "light up" the converter on cold start in order to handle emissions while the engine runs cold/rich......are you somehow accumlating coolant in one or several cylinders overnight......check coolant....... do you have a leaking intake manifold gasket situation.........are there any smog pump/divertor issues. I would NOT just jump at valve seals.......our family has had over a dozen GM 305/350 engines in vehicles in that same model year window.......many with 200,000 plus miles and never had an issue with valve seals.
Invest 70 bucks in a cylinder leak down tester to determine the condition of the valves, and rings before you disassemble anything.Because of the age of it- may be just the seals have gone hard and not doing their job any more-i have had two older sbc engines in the last year or so- a 1989 and a 1996 that were blowing blue smoke- one at start up and one more continuously that tested well with a leak down tester and stopped smoking immediately when the seals were replaced with new style positive lock style seals - the old valve seals were hard and cracked causing the oil to be pulled into the combustion chambers Sent from my iPhone using The H.A.M.B. mobile app
Yes . I will have the covers removed. This is a little of a puzzle mechanics have look at this car , one in Fl. and found how well she was maintained. She was a garage queen for the 17 yrs. The owner started to loose his eyesight and eventual went total blind. My local mechanic here in NY was correct on removing the heads what onetrickpony said.
Is this a TBI ? Those had head cracking problems on some. Maybe better to pull the heads and upgrade them.
The damn oil pan rotted on my 85 elcamino Wtf Mine used to belch a bad cloud of smoke on first start up. Sort of embarrassing at times.
Man Excessive Oil smoke on cold start up only is text book 101 valve seals. Chevys are notorious for them. Catalytic converters are inanimate and unalterable by computers, they cannot be "lit up" by the ECM or anything else. Heated 02 sensors are heated to reach closed loop sooner. Computer programs run on an open loop fuel delivery map until the ECM sees what it wants needs or is told to see - Then it switches to closed loop control.
This is the one I use. I did shorten it up and added some more bend so it would work in tighter places.
As mentioned, this is a text book problem with the 4.3-305-350-400 sbc engines.. Valve seals. ..The video, old but interesting, is not for chevy engines as the valve guides are not removable.. The air pressure to the cylinder, is the on vehicle standard method. Beware! If you bring the piston to TDC and hit it with air pressure. It will go down, NOW! The piston has to be at the bottom of the stroke.. Strike the spring/retainer at a slight angle with a small hammer before trying to compress the assembly to remove locks. This will break the "set" of the locks. The modified, rocker stud mounted "over center" bar tool is the best way to change seals.. Valve guides are already cut for a positive seals on these engines. Simply remove the factory seal and replace with a Fel-Pro blue positive seal for the engine year. The O-ring seal, if equipped, is not required with the positive seal, tho GM did use them, to use up inventory for a couple of years, after the change to positive seals. While compressed air is in the cylinder, you can listen for excessive pressure loss by the rings. I drag raced in the late sixties-seventies and changed many a valve spring between rounds. In the pits, with a Co2 bottle regulated to 100 psi and a modified KD over center spring compressor. Been in the machine shop business since 1969..
Another option stuff 2 or 3 feet of soft rope in the spark plug hole and turn the piston up toward TDC to change the seals.
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