Engine problem, need experts advise.

Few miles after rebuilding my engine, it start to burn oil, it happened to me long time ago for short time, so i decided to use the car and see if it was the same thing but this time problem became worse, and decide to remove head and check for problems. When we did that, piston # 1 from flywheel, was covered with oil and look like new, others 3 pistons were black covered with normal combustion residues. However, all the cylinders was marked on the back side like if the rings were doing more pressure there. The mechanic said the rings was the problem and we change them for a new ones, cylinders were polished to recover the normal surface appearance. Head got new valve seals and engine was built again. When we started, few minutes later it started to smoke again, blue smoke came out from the exhaust, we did a compression test and cylinder # 1 was at just 95 psi while # 2,3 and 4 was at 110-115 psi. Again the piston #1 was covered with oil at the top. Engine was opened again and cylinders have the same mark on the back like if the rings are pushing harder to the back of the cilinders.is going out again but I can´t afford more mistakes, moreover I have to buy parts in the USA and bring them to my city in South America which make prices even higher. If any of you know or had this same problem, i'd be glad to receive your help. Thanks.

pd: i'm using now 7:8:1 standar compression pistons, 1.00 overbore.

 

[SouthCaliVR4]

is there a matching wear pattern on the front of the cyl? if yes I would say the pistons are not getting up to temp as they are cam ground & come to full round at temp, running under temp (no stat) will cause wear marks on opposite sides, if there is no similar pattern on the front I'm not sure, piston skirt clearance perhaps? as for the oil, check that the valve seals & guides where done properly on that cyl. I have seen several cars where the guides where loose & just dumped oil into a given cyl just like that.

 

[ApexHunter]

Considering the location of the marks on the cylinders i'd check bore diameter going across the deck vs. the length of the deck. Cylinder could be out of round still even if overbored. Cylinders tend to wear in a tapered fashion with more wear towards the top, plus there is a lot of load on that wall during the power stroke.

 

[mitsuturbo]

Whoa..that is some SERIOUS scuffing. What do the pistons look like? What was the ring gap set at?

 

[broxma]

Wouldn't those scuff marks be made during the minor thrust angle? They would be pulled into that position if I am thinking correctly, or more appropriately pushed by the other pistons.

Looking at three ways for engine oil to enter the cylinder to that degree, eliminating a straight up crack in the piston, I'd have to believe it has something to do with the out of bore of the cylinders. Even with no valve seal at all I don't think it would pull that much oil in, however if the bore is totally out of round and the ring doesn't seal well, you would still have compression, albeit limited and suck oil up from the bottom at idle. Other than that, the oil passage in the headstudd would have to have a broken path to the cylinder. I cannot verify that from the picture.

Did you have the motor bored 1.00 over personally?

/brox

 

[ApexHunter]

Those marks are on the major thrust side- we are looking at the left side of the engine.

Andres, what are those marks? Scuffs? Carbon?

 

[SouthCaliVR4]

On the oil in the cyl, just to clarify. I'm not talking bad seal I'm talking bad guide, where oil is running down between the guide & the head not the valve & the guide. Mazda b2000's had a major issue with this & you'd be freaking amazed how much oil can run down the guide. It puddles just like that, along with smoking like mad. when the oil is hot it just gets sucked in by the manifold vacuum I would guess on a turbo car it would reverse & pressurize the crankcase under boost.

At any rate it is a distinct possibility.

 

[broxma]

Quoting ApexHunter:
Those marks are on the major thrust side- we are looking at the left side of the engine.

Andres, what are those marks? Scuffs? Carbon?



Thanks. I can't differentiate the orientation very well from the pictures. It almost appeared the image had been flipped vertically.

I am curious as to what the marks are as well. Judging from the location and the uniformity in each cylinder I assumed piston to wall contact.

Valve guide. Certainly could produce oil in those quantities provided it were adequately destroyed. Seems like it would have to be damn near split up the length of the guide and on the intake side if so. My logic tells me it would be more pronounced as the car warmed up as well and the burn would decrease with cylinder pressure. Looking at the amount of oil on the piston though, it seems like it isn't burning any of it and has possibly fouled the plug to a point of failure.

Under vacuum. Liquid oil present. Possible piston-wall contact. Did you try and idle the motor for a long time or rev the motor, or possibly drive it in this condition? Maybe the oil fouled cylinder is essentially dead and throwing the other piston against the wall due to imbalance? Maybe the bore/piston/piston ring combo is not all set for the 1.00 overbore?

/brox