VR6 Intermittent Burning Oil Woes.....Page 3.

[Gti_Jamo]

So basically i bought a replacement engine for my high miler as its burning oil quite bad and down on compression on cylinder number 6. Now i bought it off another forum and was told it was a good engine but noticed oil deposits on a couple of the inlet valve stems (more so on cylinder number 1) so decided to whip the head off for a better look. Now the heads been off recently as its been skimmed, it has new chains also. The exhaust valve in cylinder number 1 was badly carboned up as was the spark plug that came out of it. Valve guides look good. Just in the process of cleaning the head up and removing the carbon from the valves, new stem seals and lap the valves back in and the heads good to go.

The pistons are in good condition. However what concerns me is that all of the cylinders have a bit of a lip at the top that I can feel with my finger. All pretty much the same. Should this be a problem. Was told the engine only done 80k but I doubt that very much. I'm not prepared to go getting it rebored with oversized pistons or have to do any work on the bottom end whatsoever and would try and just source another one if its a big issue. The last thing I want is to build it all back up and fit it only for it to burn oil like my current one. I sat an inch of oil in each of the bores on top of the piston and the levels barely dropped over the course of 3 days.

What do you think? I guess I should have done a leak test on the engine before I began stripping it.

[gazareth]

it all depends on how big the lip is. seen plenty engines with a lip on the bores but running fine. that thing your doing with the oil in bores will give you a good idea of how even your cylinder wear is. I would try it again with atf as it will drain through quicker. its not an easy thing to measure without a bore gauge. you should take it to an engine builder and get them to measure it up just to be sure.

[Gti_Jamo]

i wouldn't say is huge be can be easily felt, more so on outer edges but that would be normal i guess. I'll test the cylinders again and see what happens and take it from there. I'm hopeful that because its even wear I can put the oil on the valve stems down to the stem seals or the guides. I done a rough test on the guides by checking the latteral play in the valves and its not much but waiting on my digi gauge coming to get some accurate measurements.

[VW BUSH]

You have a lip you so you have wear.
Measure the gap with feelers at room temp, dia of piston and bore as well. you should be able to find the tolerances somewhere ont net, let that be your guide.
How much has it worn over 80k vs how much metal is left in the tolerance band between piston and bore.
I have got away with new rings before but that can be a can of worms in itself


I am not 100% on VR valve guides and geometry, but at about £100 a set it will give you piece of mind


What sort of gauge have you bought?

[gazareth]

yeah when you have a lip you have wear but you can get away with a little. all depends what your plans are with engine and what kind of mileage you want out of it. what I would do if I was you would be to take the head of the engine in the car(assuming it aint a daily ) and compare the bores to your new engine to see which is best. could be the head that's bad on the car. and if that's so then you could just put the head you cleaned up straight on to car engine. get a leak down test done on car engine and that will confirm if its bad cylinders or a bad head.

[Gti_Jamo]

Sorry for the delayed reply.

You have a lip you so you have wear.
Measure the gap with feelers at room temp, dia of piston and bore as well. you should be able to find the tolerances somewhere ont net, let that be your guide.
How much has it worn over 80k vs how much metal is left in the tolerance band between piston and bore.
I have got away with new rings before but that can be a can of worms in itself


I am not 100% on VR valve guides and geometry, but at about £100 a set it will give you piece of mind


What sort of gauge have you bought?

The gauge I got isn't suitable for measuring the bore wear unfortunately. I will check with feeler gauges though if i can find tolerances. Ive measured the valves and the lateral play in the valve guides and all appears to be decent enough.

yeah when you have a lip you have wear but you can get away with a little. all depends what your plans are with engine and what kind of mileage you want out of it. what I would do if I was you would be to take the head of the engine in the car(assuming it aint a daily ) and compare the bores to your new engine to see which is best. could be the head that's bad on the car. and if that's so then you could just put the head you cleaned up straight on to car engine. get a leak down test done on car engine and that will confirm if its bad cylinders or a bad head.

My car is currently a daily so have planned for a quick change over. Have already done a leak down test on the engine in the car and its definitely leaking past the rings on cylinder number 6 and is way down on compression on same cylinder. My plan is to more than likely sell or swap the car once the engine is changed and is running perfect as this is the last job on the long list I had when I first got it and will be worth decent money when finished. I have a Mk2 I want to get started.

[Len]

I would say thats  a rebore job mate!

[Gti_Jamo]

I would say thats  a rebore job mate!

Well that will not be happening lol....I might take my chances on it. Depending on what the feeler gauge test says. I must also add that the wear lip is more apparent on outer edges but i guess thats normal given the configuration. Will be a slight ovalisation in that case.

[gazareth]

I would get a second opinion from an engine rebuilder. the bores might not be past it yet. to measure piston to bore clearance you really need the rings out and you know what that means???

[Len]

There should be no leaking past the rings!
 = rebore