All Small Six Large Log Cylinder head questions

[marquis83]

My engine makes blue smoke for about 30 seconds when I start it up.

It's not immediate, more like within the first minute or two of a cold start.

Based on my research I'm thinking it could be the valve seals.

Trying to get the car ready to do some longer trips.

We did a 45 minute drive last night, and it went mostly great.
It did develop a low rpm miss getting off the freeway at the end.

When I started it this morning it still had the miss, but it cleared itself up after driving around the block a few times.

Then made another 45 minute trip back home.

I plan to check the condition of the spark plugs tomorrow morning.


If I take the head off and have a machine shop do the valve seals, what else should I have them do besides a valve job to increase performance/durability?

 

[Kritas]

Others will chime in, but I'd have them see if the head should be milled to give more compression. My engine is a 78 200 and I'd also like to boost performance, so I plan to pull the head to find out if it's stock at some point. Porting is also an option.

 

[aussie7mains]

Others will chime in, but I'd have them see if the head should be milled to give more compression. My engine is a 78 200 and I'd also like to boost performance, so I plan to pull the head to find out if it's stock at some point. Porting is also an option.

Please do a compression test before you do anything. Lifting the head isnt necessary to valve stem seals, but I doubt that is the only problem.

 

[bubba22349]

My engine makes blue smoke for about 30 seconds when I start it up.

It's not immediate, more like within the first minute or two of a cold start.

Based on my research I'm thinking it could be the valve seals.

Trying to get the car ready to do some longer trips.

We did a 45 minute drive last night, and it went mostly great.
It did develop a low rpm miss getting off the freeway at the end.

When I started it this morning it still had the miss, but it cleared itself up after driving around the block a few times.

Then made another 45 minute trip back home.

I plan to check the condition of the spark plugs tomorrow morning.


If I take the head off and have a machine shop do the valve seals, what else should I have them do besides a valve job to increase performance/durability?

X2 yes on Aussie7Mains recommendation of doing a full on Compression Test First. How many real Miles does that 200 Six have on it? But if after that the head dose come off be sure to have them check out the Valve Guides too for excessive clearance there is a good chance that is were your Blue Smoke is likely coming from.

 

[Kritas]

Please do a compression test before you do anything. Lifting the head isnt necessary to valve stem seals, but I doubt that is the only problem.

I have, thanks. I'm uncertain as to why your comment regarding valve seals was directed to me.

 

[Invectivus]

I want to say the rule of thumb is if it smokes on acceleration, it's oil coming up through the rings, and if it smokes on deceleration, it's oil coming down through the valves. Definitely check compression before tearing off the head so you have a baseline.

When I had my large log head done (poorly), I CC'd the chambers which came to 62, then had it shaved to lower it to 49 I think. 3 angle/backcut the valves, machined for nitril seals, and I was in the process of setting up my mill to bore the carb hole for a BBD when I lost my workshop. I'm transitioning to a Carter RBS until I build my own workshop and can unpack everything again.

 

[marquis83]

Today I started it and it didn't smoke at all. It doesn't smoke during driving that I notice

When it misses it sounds like my mustang did when I had the wrong size pushrods in it. Like a pop, incomplete combustion happening in one of the cylinders.

When I get on the gas it smooths out, sitting at a stop light with my foot on the brake it sounds crappy.

It was sitting for almost 3 months recently due to a catastrophic breakdown.

X2 yes on Aussie7Mains recommendation of doing a full on Compression Test First. How many real Miles does that 200 Six have on it? But if after that the head dose come off be sure to have them check out the Valve Guides too for excessive clearance there is a good chance that is were your Blue Smoke is likely coming from.

The odometer says 96k. The car is a 1983. Interior is pretty clean, so i'd say either 196k or 96k.

I didn't get around to checking the compression today but I will do it soon. Got hand pain from replacing the control arm last week.

 

[Frank]

Today I started it and it didn't smoke at all. It doesn't smoke during driving that I notice

When it misses it sounds like my mustang did when I had the wrong size pushrods in it. Like a pop, incomplete combustion happening in one of the cylinders.

When I get on the gas it smooths out, sitting at a stop light with my foot on the brake it sounds crappy.

It was sitting for almost 3 months recently due to a catastrophic breakdown.



The odometer says 96k. The car is a 1983. Interior is pretty clean, so i'd say either 196k or 96k.

I didn't get around to checking the compression today but I will do it soon. Got hand pain from replacing the control arm last week.

Oil coming down the valve stems is pretty common on that vintage engine, and will happen to all eventually. The oil pulled into the combustion chamber is relative to manifold vacuum. With high vacuum -idling and deacceleration- the suction moves up the intake valve when it's open and pulls the oil that's in the valve guide into the incoming air/fuel charge. More vacuum=more smoke. Also, oil will dribble down the valves by gravity when the engine is off, especially a warm engine. A puff of blue smoke on start up, or after idling a while is 100% valve guide induced.
A misfire can be associated with this: the oil fouls the sparkplug. I have a truck that has a broken valve stem near the head. It's JB welded, and oil consumption is light, but every 5000 miles #6 plug has to be pulled and cleaned. Know it's time when there's an intermittent miss at idle and light load, or after slowing from a hard load.
Now a miss associated with a popping noise is from (usually exhaust) valve not opening much, or in time. Can be caused by a wiped cam (would be doing it constantly), loose rocker arm or bent pushrod (would also be continuous, and clicking valve), or a lifter that is failing to pump up, this would be intermittent.

 

[78_200_C4]

Replace the valve stem seals with the head on.
ENGINETECH S9241 Premium Umbrella seals are high-temp Silicone with garter springs to retain stem interference.
Rockauto sells them for 41 cents a piece in a package of 20.