18 replies to this topic

[dotmatrix]

hello.

one of my engines that was recently rebuild with a rebore, new pistons and rings, and a rebuild cylinder head with guides and valve seats have started using oil and it does not seem to be leaking out, I think cyilnder 3 uses it.

 

The question is then. Is there any way to test or deduce whether the oil is being sucked up past the piston rings or down the valve guide before I take it apart and check the guides?

 

thanks

[KTS]

a compression test may help identify if the rings are an issue i would think.

[Northernpower]

Does it emit blue smoke on overrun?

[Fast Ivan]

a leak down test will give you more information

[dotmatrix]

a compression test is easy and quick to do so have thought of doing that, but will not test the oil rings.

 

I haven't noticed any smoke on overrun, but have on start up.

 

yes of course. I can put air pressure on the cylinder and check how much air comes out where.

[JXC Mini GT]

Carry out a compression test as planned, then squirt some oil into each cylinder and check compression's again, if compression increases it's likely to be rings.

[Steve220]

a compression test is easy and quick to do so have thought of doing that, but will not test the oil rings.

 

I haven't noticed any smoke on overrun, but have on start up.

 

yes of course. I can put air pressure on the cylinder and check how much air comes out where.

 

When the cylinder head was rebuilt, did you have valve stem seals installed? The latest ones?

[dotmatrix]

 

a compression test is easy and quick to do so have thought of doing that, but will not test the oil rings.

 

I haven't noticed any smoke on overrun, but have on start up.

 

yes of course. I can put air pressure on the cylinder and check how much air comes out where.

 

When the cylinder head was rebuilt, did you have valve stem seals installed? The latest ones?

 

yes new valve stem seals (4x)

I believe this is the type: http://minispares.co.../LJQ101160.aspx

[dotmatrix]

Carry out a compression test as planned, then squirt some oil into each cylinder and check compression's again, if compression increases it's likely to be rings.

will do. but will be surprised if this reveals problems.

[Steve220]

 

 

a compression test is easy and quick to do so have thought of doing that, but will not test the oil rings.

 

I haven't noticed any smoke on overrun, but have on start up.

 

yes of course. I can put air pressure on the cylinder and check how much air comes out where.

 

When the cylinder head was rebuilt, did you have valve stem seals installed? The latest ones?

 

yes new valve stem seals (4x)

I believe this is the type: http://minispares.co.../LJQ101160.aspx

 

 

Yeh, thats them. 

[carbon]

In my experience if you're running without exhaust valve stem seals this can cause higher oil consumption.

 

Typically will smoke slightly on restarting a hot engine (leave sitting engine off for about 5 minutes, then restart and watch exhaust)

[dotmatrix]

A Quick update.
I had the cylinderhead off and renewed the guides and stem seals, relapped the valves and changed one exhaust valve that Was badly pitted.
The guides were a bit worn but not much.
What wories me more is that All 4 pistons had significant piston slap which i did not expech after 15k miles or so.
The next thing i Will do is to change a leaking driveshaft seal and see how much that helps because the 8 new valve stem deals havent done any difference.

[Spider]

It may appear that there's a lot of clearance between the piston Crown and the bore when cold and I wouldn't at all be concerned about that.

 

It may well need a fresh hone and new rings.

 

How much Oil is it burning?

[dotmatrix]

It may appear that there's a lot of clearance between the piston Crown and the bore when cold and I wouldn't at all be concerned about that.

 

It may well need a fresh hone and new rings.

 

How much Oil is it burning?

 

so the running clearance of 0.0025" stated for this piston is in hot conditions? http://www.minispare...-STN100-20.aspx

 

it uses about half a litre every 400 miles.

 

I must say I expected the new pistons and rebore to last about 3-4 times what it has currently done before starting to use oil at this rate.

[cal844]

It may appear that there's a lot of clearance between the piston Crown and the bore when cold and I wouldn't at all be concerned about that.
 
It may well need a fresh hone and new rings.
 
How much Oil is it burning?

 
so the running clearance of 0.0025" stated for this piston is in hot conditions? http://www.minispare...-STN100-20.aspx
 
it uses about half a litre every 400 miles.
 
I must say I expected the new pistons and rebore to last about 3-4 times what it has currently done before starting to use oil at this rate.

What was the engine rebored to? Was it checked for bore ovality and any deviation from vertical?

How was the engine initially set up(fuel and timing?)

Half litre to 400 miles is excessive imo, however you say there was also a driveshaft seal leaking, are there any others?

Edited by cal844, 05 April 2018 - 09:40 PM.