Discussion
Hi there am getting my piston rings valve stem seals and shells replaced on a 2.5 noble m12 as having a blow by issue.Car is very low on 1 cylinder on compression.Just a thought will I notice an improvement on performance once I've had thos work done ? and what is the running in process after having this work done ?.
Are you doing the work yourself, Chris?
I presume that there is insufficient bore wear to justify a rebore, or leave a ridge at the top that might damage a top ring.
You should hone the bores before fitting to allow the new rings to bed in. You can use a classic three arm hone, or the Flex-Hone device with lots of abrasive balls on spring arms, but slow speed and dip it in oil often.
Running in; drive the car accelerating in as high a gear as posisble to maximise bore pressure and promote bedding in, followed by coasting in gear and slowing with the throttle closed to minimise bore pressure and draw up oil onto the bore walls to lubricate them and prevent glazing. You need to choose the road where you do this with care, else anyone following you will be confused!
JOhn
I presume that there is insufficient bore wear to justify a rebore, or leave a ridge at the top that might damage a top ring.
You should hone the bores before fitting to allow the new rings to bed in. You can use a classic three arm hone, or the Flex-Hone device with lots of abrasive balls on spring arms, but slow speed and dip it in oil often.
Running in; drive the car accelerating in as high a gear as posisble to maximise bore pressure and promote bedding in, followed by coasting in gear and slowing with the throttle closed to minimise bore pressure and draw up oil onto the bore walls to lubricate them and prevent glazing. You need to choose the road where you do this with care, else anyone following you will be confused!
JOhn
Edited by tapkaJohnD on Sunday 21st November 17:05
Initial bedding in of the rings happens after startup. A few revs will help. After that I'd drive it at different loads and rpm's. Drive under some load for say 5 seconds and then lift off so the bores get oiled. Repeat and over time increase the load and rpm's. Don't labour the engine and don't nurse it. It needs to do some work to bed the rings.
coolchris said:
Hi there am getting my piston rings valve stem seals and shells replaced on a 2.5 noble m12 as having a blow by issue.Car is very low on 1 cylinder on compression.Just a thought will I notice an improvement on performance once I've had thos work done ? and what is the running in process after having this work done ?.
Depends whether any of those parts are the actual cause of your problems or not and whether they need changed or more work was needed.I'd want a proper diagnosis before changing parts at random, valve stem seals will make zero difference to compression.
What was wrong with the rings ? What condition are the pistons/bores in ? Head gasket etc ?
Edited by stevieturbo on Sunday 21st November 17:25
The blow by was established when I noticed smoke coming from the pipe that vents to atmosphere from the oil catch tank.I personally did a compression test all cylinders were between 100 and 110 but one of them was just under 80.Ive kept oil topped up performance wise car still pulls pretty well
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