Exhaust smoke and oil consumption

[51_Meadowbrook]

So now that the weather is getting cooler I think it’s time to fix the smoking issue my ‘51 Meadowbrook has. It uses about a quart every 100-150 miles, depending upon if I go about 40mph. I can use a quart if I go 55-65 for about 15 minutes. At those speeds I get a faint smoke out of the tail pipe. During deceleration I get it too. I was going to replace the seals but i can’t find any and don’t see them in the book. Does this engine not have seals? I have been told it’s the oil ring on the pistons. I have been told it’s the valve guides. Is there a way to definitively know prior to taking off the head? My dry compression test was around 95 across the board. I didn’t do a wet compression test, mainly because I’m new to a lot of this and didn’t know I was supposed to do it. 

[greg g]

Do you have active oil leaks? Is so where?  How much oil is in the pan when you add oil? If adding oil is actually is over filling the pan , the engine will  tend to purge what is extra.  This question because there were three different styles and lengths of dip stick.  If your car has an incorrect dip stick, it may be over full.  Next time you need to add oil according to the stick, drain the pan and see how much is in there. Does the car smoke after sitting at a light or after making a sharp turn? If so that might suggest worn valve guides. What type of oil are you using?

[kencombs]

IMO, the chances of valve guides causing excessive oil use in our flatheads in almost nil.  There is no oil delivered to the valve / tappet chamber other than a small amount of mist from the crank.  So, the guides and stems are not flooded with oil like an overhead valve would be. 

 

Smoking on deceleration is usually due to worn oil rings not properly wiping the oil from the cylinder walls and the vacuum above the piston sucking it into the chamber.  Or, more accurately, the air pressure in the crankcase pushing it up. 

 

I'd pull the head and measure the cylinder size and taper.  It may be possible to just hone and ring, but don't be suprised if it needs more.

 

I recently tore down a 56 Ply engine that had been 'overhauled' sometime in the not to distant past, at least recent in terms of miles.  The piston crowns still showed scratch marks from decarboning, but were covered with a thick layer of soft, wet carbon.  .010/.010 crank, good bearings, but the cylinders have at least 15 thou wear.  I didn't even bother to measure taper/egg shape wear when calipers revealed that much wear . They must have reamed out a huge ridge and put in standard rings!

[51_Meadowbrook]

A retired mechanic around town was listening to my explanation of things and said he was pretty positive it was the rings. The engine has 48k on it. I got it 4 years ago said 43k on it and it had sat since 1973. I believe what he said but every time I tried to look this up it always said the valve seals. So a quick search for those and I didn’t find anything. 

 

 I’m pretty new to engine rebuilding so I need a quick education on ring sizes. Where do I find the measurement sizes that I need? Are they in the book or is it based on measuring the piston? Are the  .010, .020, etc numbers the actual numbers I’d see on the tool? For example, 4.010?

Edited March 27, 2019 by 51_Meadowbrook

[Plymouthy Adams]

37 minutes ago, 51_Meadowbrook said:

A retired mechanic around town was listening to my explanation of things and said he was pretty positive it was the rings. The engine has 48k on it. I got it 4 years ago sigh 43k on it and it had sat since 1973. I believe what he said but every time I tried to look this up it always said the valve seals. So a quick search for those and I didn’t find anything. 

 

 I’m pretty new to engine rebuilding so I need a quick education on ring sizes. Where do I find the measurement sizes that I need? Are they in the book or is it based on measuring the piston? Are the  .010, .020, etc numbers the actual numbers I’d see on the tool? For example, 4.010?

don't believe everything on the internet...get your factory repair manual and back that up with a good Motors brand manual if  you can find.  Ring size is based on the piston bore of the block..they will be fitted to the very piston but when fitting you should do an end gap just to ensure.  Your book will  have the base bore listed and the plus sizes .020 , .030 etc will be the bore oversize.  you will need to first establish where you are at in the older engines to see if stock or bored and if bored to what oversize and then do a cylinder taper test to see if you can clean the block with the next available oversize piston and ring set...there are no valve stem seals in this engine...the guides as explained above is going to have a negligible effect on consumption...most oil consumption is worn rings accelerated by the very ring blow by that will pressurized the crankcase and with increase likelihood of gasket blow by in the misting oil will also be pushed out the draft tube at a great rate with higher internal pressure....