Hi guys….. looking for some opinions and advice on the below issue I’m experiencing with my M20.
Engine started to blow blue smoke during acceleration and start up in the morning so I decided to take her out and have the head rebuilt and the rings changed.
During the build process I sent the head off to a reputable company to have it completely reworked; Pressure testing, cleaned, new guides, new stem seals, lap vales and a minimum skim. Was told that the original stem seals were in a bad way.
As per the block I had the crank re-grinded/polished, block honed, new big end/main bearings and new piston rings.
I rebuilt the block myself ensuring the pistons were the correct way up and spaced at 120 degrees…. Etc
I had the engine back in the car last year and covered around 4k miles but I was still burning oil around 1qrt for 600miles - things started to get bad as the spark plugs fouling, back fire during start up etc.
A couple of weeks back I carried out a compression test which resulted to Cylinder 3 and 5 having compression low as 135psi and the rest at over 200psi. Spark plug on cylinder 3 was really fouled with oil similar to spark plug 5.
I also carried out a cylinder leak down test which did not prove anything as for all cylinders the leakage was around 10% max.
So this weekend end gone I ripped the head off to inspect what could be causing this and here are my findings:
With all the above checked I am a little stumped of what could be causing the oil consumption/ spark plugs fouling on 3 and 5?
As I have spent a lot of time, effort and money on this engine so fat rim not looking to replace it as I would like to resolve the issue.
Any feedback would be appreciated!
Engine started to blow blue smoke during acceleration and start up in the morning so I decided to take her out and have the head rebuilt and the rings changed.
During the build process I sent the head off to a reputable company to have it completely reworked; Pressure testing, cleaned, new guides, new stem seals, lap vales and a minimum skim. Was told that the original stem seals were in a bad way.
As per the block I had the crank re-grinded/polished, block honed, new big end/main bearings and new piston rings.
I rebuilt the block myself ensuring the pistons were the correct way up and spaced at 120 degrees…. Etc
I had the engine back in the car last year and covered around 4k miles but I was still burning oil around 1qrt for 600miles - things started to get bad as the spark plugs fouling, back fire during start up etc.
A couple of weeks back I carried out a compression test which resulted to Cylinder 3 and 5 having compression low as 135psi and the rest at over 200psi. Spark plug on cylinder 3 was really fouled with oil similar to spark plug 5.
I also carried out a cylinder leak down test which did not prove anything as for all cylinders the leakage was around 10% max.
So this weekend end gone I ripped the head off to inspect what could be causing this and here are my findings:
- 1. Inspected the cylinder head for any damage/cracks etc and all seems fine.
- 2. Nice seal around each cylinder chambers on the head as the head gasket had sealed nicely.
- 3. Nice carbon build up on all valves and pistons apart from cylinder 3 and 5 – carbon was wet (oily).
- 4. Stripped head and checked play on inlet/exhaust vales on cylinder 3 and 5 which was minimal comparing it to cylinder 1 (good cylinder).
- 5. Checked whether the valves were lapped correctly by putting the head upside down and having all valves closed and pouring water to see any leakage – this was all fine, no water leaked through proving the valves were lapped correctly.
- 6. Next I slowly took out piston 3, 5 and 1(good Piston) ensuring that there was minimal movement on the rings. All rings were intact and identical to piston 1 which is the good piston.
- 7. On cylinder 3 the spacing of the rings were quite close approx. 20degrees – I'm assuming that the rings spin during combustion.
With all the above checked I am a little stumped of what could be causing the oil consumption/ spark plugs fouling on 3 and 5?
As I have spent a lot of time, effort and money on this engine so fat rim not looking to replace it as I would like to resolve the issue.
Any feedback would be appreciated!
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