engine problem....please help??!!

[britchie]

just wanting some opinions, please help!!??

The engine in my swb 2a 2.25l petrol was very very strong for a 2.25, never driven one better. However, it breathes quiet a lot of oil out the top, and has always had a fluffy exhaust note, but still pulls like a train.

driving the other day, all of a sudden it started detonating severely in one cylinder. I immediately pulled over. checked the timing.

Couldn't see anything untoward, but it was still pinging when i snapped opened the throttle at idle, so i retarded the dizzy a fraction. Completed my highway drive with very flat performance, then wound the dizzy back when i stopped. the timing is now back where it was, no pinging. Engine still revs out smoothly with no nasty noises.

Now performance is low, very fluffy idle. i pulled number 1 & 2 ignition leads off and neither one made a noticeable difference to the idle but the spark is very strong at both cylinders?? pulliing 3 & 4 leads make the difference you would expect.

Burnt exhust valve, broken piston rings, or something far more simple (points, cap, leads, timing etc??)

[JDNSW]

Could be lots of problems - difficult to tell without further tests.

First thing I would do is check compression for evenness by turning it over by hand. This will immediately show whether you have a ring/valve problem.

Pulling the plugs and keeping track of where they came from will usually show by colour, oiliness etc, whether there is a problem with one or two cylinder(s).

My guess is that you have valve or ring problems, but there are all sorts of other possibilities from a loose intake manifold, to a broken spring in the centrifugal advance in the distributor (or sticky weights) to a timing chain that has skipped a tooth (very worn sprockets or faulty tensioner).

John

[chazza]

just wanting some opinions, please help!!??

i pulled number 1 & 2 ignition leads off and neither one made a noticeable difference to the idle but the spark is very strong at both cylinders?? pulliing 3 & 4 leads make the difference you would expect.

Do a compression test to see if the head gasket has blown between numbers 1 & 2; this would also show up burnt valves and worn rings.

You can check the valve timing as John suggested, by removing the rocker cover and number 1 plug and turning the engine by hand until the piston is on top dead centre. Get a helper to put their thumb over the plug hole firmly to feel for the "little poof" of escaping gas; exact TDC can be found with a long thin screwdriver, while the person on the crank handle very slowly turns the motor. Inspect the rockers on the front cyl and make sure that both are loose and not depressing either valve. If one valve is down the piston is on the exhaust stroke and the engine needs to be turned another revolution. If the rockers are tight, inspect the timing chain and valve timing marks.

From your desription it sounds like the rings are worn hence the breathing from the "top".

Time for an overhaul I suspect,

Cheers Charlie

[Aaron IIA]

A better way of checking the valve timing would be to use the EP (exhaust peak) mark on the flywheel, and correspont this to the number one exhaust valve. The manual describes how to do this. I would conduct a compression test. Check the valve clearances. If one or two are significantly low, then that valve may be burnt. Let us know how you go.
Aaron.

[britchie]

thanks guys, all sensible advice. good to check i was on the same track. will let you know.

[dandlandyman]

A couple of years ago, I missed doing a valve clearance check on my 2a 4cyl petrol. By the end of the oil change period, it was seriously down on power and went through 45Ltrs of petrol just to go from Darwin to Katherine, using overdrive and all. I think it's valve seat regression, thanks to modern fuels.
Most people forget that those engines are an old design and therefore require a bit more maintenance than a modern engine. Even Holden sixes are easier, though their hydraulic lifters can mask the issue until it's well too late.

[isuzurover]

I have seen a few 2.25P engines (mostly x-military for some reason) where the compression rings on one or more cylinders have broken. When I pulled my 2.25P doen it still went like a train, but was getting a bit "breathy" - the top compression ring on #3 had broken into 7 pieces!!!! and EVERY top compression ring was broken.

[britchie]

blown head gasket between 1 & 2, compression was way down 60 psi in these two cylinders (should be 145psi when new) I would still expect 125psi from a reasonable motor. Has anyone got an tricky way to gauge the condition of the piston rings when the head is off, without taking the pistons out??

[mike 90 RR]

I have seen a few 2.25P engines (mostly x-military for some reason) where the compression rings on one or more cylinders have broken. When I pulled my 2.25P doen it still went like a train, but was getting a bit "breathy" - the top compression ring on #3 had broken into 7 pieces!!!! and EVERY top compression ring was broken.

I'ld think on these terms if your's is old & breathy
Broken rings can pace up the wear on the cylinders

How much lip do you have at the top of the bore? / This might help for a decision

[britchie]

will take the head off tomorrow and check the lip. I image it will have a fair mileage on it, however the head appears to have been off it not that long ago, so someone has been poking around in there before