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Discussion Starter #1
Il try keep this short but it wont be easy.

The engine it self is the rb20det long block and was running 170psi on all bores but the head needed the stem seals changing due to smoke, so the engine has had stem seals, port and polish, valves lapped, new gasket set, skimmed and put back together it's now giving me 120psi wet and dry compression all the same on a warm engine and 100psi on cold

Leak down test shows between 0 and 5% in the safe set range on the gauge no leaks yet I can hear the air when I place a tube on the dipstick but no pressure is coming up just noise?

After a warm run I remove the spark plugs and what looks to be smoke coming from 2 and 6 bores also smoke on idle and lots when revving like a old steam train white smoke

Bare in mind engine has been sitting a year so may partly be condensation in the exhaust due to weather as well

Turbo has been replaced with a new unit

Timing is perfect I've checked it so many times only thing I don't get is when setting TDC there a flat spot at TDC where the piston stops at the top I can move the crank a few mm back and forth but piston stays still is that normal.

Ecu is a auto stage 1 oem, engine was removed from a auto and converted to manual 88km

I'm completely stuck now and no idea what to do next any experienced rb guru out there able to help out

Thanks in advance

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So was 170psi but after head refurb and skim and sitting for 12 months its now only showing 120psi......first where both compression gauges reliable? second how many miles did it do once you used it again? third where the people who did the head reliable ...although leak down indicates valve seating is good and fourth is the turbo good ? if seals are gone it will smoke mostly on idle at first.....as for smoke when plug is removed is it just after a run? pretty normal.

Having said that allthough you wouldent normally loose compression it does sound like you have broken an oil ring or two...have you had any problems with over fueling since using again?
 

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So was 170psi but after head refurb and skim and sitting for 12 months its now only showing 120psi......first where both compression gauges reliable? second how many miles did it do once you used it again? third where the people who did the head reliable ...although leak down indicates valve seating is good and fourth is the turbo good ? if seals are gone it will smoke mostly on idle at first.....as for smoke when plug is removed is it just after a run? pretty normal.

Having said that allthough you wouldent normally loose compression it does sound like you have broken an oil ring or two...have you had any problems with over fueling since using again?
I've used three different comp gauges all give the same results and car was driven for only 5miles before being parked up for a year, engine was done by myself I've been building engines for many years with no issues and I use a local rep machine shop.

Leak test says valves are good. And I've tried 3 turbos one being brand new so definitely nothing wrong there, the smoke in plug hour was after a hour off idling just to warm the engine up for a leak test. Car has not been driven since incase it makes it worse.

Overfueling was happening before head was off had no overfueling since rebuild.

I hope it's not oil rings as leak test doesn't say and compression was done with all plugs out and wot.

Just don't understand how compression can be 120 on all 6

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I meant was the fist 170psi reading correct as it seems the only likely culprit by what your saying,
If the previous over fueling was server enough it could have worn the rings evenly ....but unlikly its is a bit odd that all cylinders read the same figure before and after...i think i would be inclined to just drive it for a bit and see how thing progress since other than the compression change and a little smoke there seems little wrong...but that's just me.
 

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Discussion Starter #5
The first ever comp was when I brought the engine conversion for mine and I done the comp test myself the readings where all with in 10 percent off each other range from 160 to 175psi across the board.

I would drive the car if the smoke coming out wasn't so bad it feels the drive you can't see anything.

This weekend I'm going to recheck the timing again, remove the downpipe and run the car to see if it's just condensation in the exhaust or the engine itself.

Any thing else I should check for

Fueling is much better before I had black smoke from the exhaust but car was only run for 10mins about 4 times throughout so I can't see any damage being done to the rings.

Another thing to add is when the head was off I filled each bore with the same amount off oil and they stayed the same over night hence why I can't see it being rings I just need to figure out how to get the compression up

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Re done the comp test with another tester see pictures dry and wet

Also removed the exhaust and started it and the smoke is definitely from the engine but with the results off the compression I'm starting to believe the head is knackered

Thoughts


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With the added oil (how much?) its come up 10 psi which is not a lot but you said the leak down test was not conclusive to and valve leakage but that figure is low but not terrible just looks worn to me and as you where suffering bad over fueling my thoughts are that the rings/bore are worn,
As i said personally i would just drive it for a few miles (not hard) and see if the compression changes but i would say your going to have to open the motor at some point.
 

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Discussion Starter #8
There is no way I could drive it not even gently I would end up causing havoc and getting pulled over its like a fog machine as well as no mot anymore.

I just used a 5ml syringe off oil in each barely a tablespoon

I'm just going to have to the engine out and strip it down to find the issues



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I hope you find the solution. FYI, not very relevant, but my RB25 was sitting for 5 years in my garage until last year when I fired it up. A little smokey to start with but it cleared fairly quick, and ran no worries. Then drove it (gently) for about 80 miles direct to the garage for a complete service. Sounds like you've got a fairly serious issue. Good luck.
 

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Actually done this the other day I let it warm up for 30mins with another 30mins revs at 1500rpm the white smoke finally cleared up but then the grey smoke started but not as bad but still enough to fill the road.

Shut down the car and noticed oil treakling from just below the manifold onto the floor I've not looked any further but it's ether from head gasket (warped head) or the exhaust ports are filling with oil again as I don't have all the manifold nuts on at the moment so faulty stem seals or cracked head?

But previous issue was every exhaust port was caked in fresh oil even tho stem seals have been done

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