Burning oil but no smoke

[Andyman]

I'll try and keep this brief so folk don't look and think ''too many words'' and move on lol





Had a bottom end rebuild end of last year using stock ph2 14k mileage old pistons and matching rings.

Also had brand new cams fitted (428's) at the same time.

All mapped up, power was a tad down and quarter mile figures are also down. Disappointed with the performance if im honest. Also mpg isn't quite as good.


The car is loosing oil at a rate of roughly 5 litres to 2 thousand miles.


No oil leakage from under the car to speak, there is a bit of smoke when i boot it and also kicks it out when i start it but its black smoke not blue or white and its been compression tested at 150psi right across all 4 cylinders.


Valve seals, valves themselfs (cut 3 angles) and springs are original and have 130k miles under their belts.


Does anyone have any ideas what could be causing the problem?
I'm leaning towards the head although don't want to folk out for a head rebuild if theres something hidden going on with the pistons / rings.


Help much appreciated

 

[sideways danny]

i read that as using old rings? were the bores even honed first? If not there's just not going to be any hope the oil control rings are sealing anything

that compression result is also lower than I'd be happy with after a rebuild

 

[Fred@BTM]

5L in 2K?

 

[Andyman]

Yeah the block was honed. If there was any leakage then wouldn't the cylinders have different levels of pressure reading?

No smoke is confusing also other than the black smoke.

Yeah roughly 5 litres in 2k miles. Im filling up with Halfords stuff now. Waste of time putting decent quality stuff in.

Havent had chance yet but going to mix 10w 40 oil with forte and see if it plugs it a bit. Not really a fix tho

edited:

Sorry, yeah old rings but only had 14k on them. In hindsight i should have bought new rings i know

 

[sideways danny]

if it's kicking out black smoke it must be RIIIIICH. bit of a circle to which came forst though, rich running will cause ring/bore wear and poor sealing, but poor compression will make it run rich as it'll be losing power.

old rings would be nagging at me though, as would 130k old stem seals.

 

[Jonny1*2]

What was the reason for rebuilding bottom end?

 

[Andyman]

^^Lost a crank bearing. The crank, rods and pistons were all changed.

The car hasn't done many miles, (roughly 6k total guess, id need to check) since the rebuild so would guess this is two separate issues?

What really confuses me is no blue smoke.

Could the oil be somehow mixing with petrol causing the oil to escape in among the black smoke?

 

[Jonny1*2]

Unless the block got damaged and it's leaking into combustion chamber some how. Saying that the bores should have been checked when honed. Strange one. Not healthy to use that much oil though, unless they stuck a wankle under there

 

[Andyman]

Its a bit of a dilemma what to do. The head is getting on a bit but don't want to folk out for it rebuilding this if it turns out to be the bottom end thats the issue.

Wonder if a leak down test would be worthwhile ?