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

[Blknight.aus]

depending on how worn the bores are (and the pistons) you might be able to slide a piese of .7 or .5mm mig wire down the side and if you get further than the depth of the top ring then youve got top ring problems.

[Aaron IIA]

I wouldn't judge the wear by the lip to any great extent. Part of the lip will be carbon build up. Once the carbon has been removed, you can get an idea of how much the bore has worn.
Using feeler guages, measure the clearance between the piston and the bore wall. Do this front to back and side to side, at the top of the stroke and at the bottom. If the piston to bore clearance is tolerable, you may want to replace the rings only. To do this, drop the sump, undo the big ends and withdraw the conrods and pistons. Hone the bore, and fit new rings, after scraping the carbon from the ring groves. Assemble. This is assuming that it needs doing. What were the compression pressures of the other two cylinders?
You mention that the head has been off recently. Could the gasket have blown due to incorrect gasket fitting? When fitting a new gasket (any gasket in any location) always make sure that the surface is perfectly clean. I scrape both surfaces with a new Stanley knife blade until they are perfectly smooth. This means shinny metal. It does take a fair amount of time and effort to get it that way. Alternatively, you could use a brass wire wheel. Is it a copper or fibre head gasket? Did they use Hylomar? Was it re-torqued at the appropriate interval? If the two good cylinders have good compression, I would be inclined to just replace the gasket properly, and give it a run before deciding on what to do next. Head gaskets are quite cheap anyway.
Aaron.

[britchie]

Can't tell you what the compression on the good cylinders was because i had a ****ty compression tester that you push into the spark plug hole instead of a threaded one. The good cylinders were convincingly going past 100 psi when i couldn't hold the pressure anymore. the others were sealed and only registered 60psi.

the existing gasket is a copper one and at first glance (with the head still on) has no sealant on it. I have a replacement copper gasket to fit tomorrow.

Do people recommend using a sealant like hylomar or permatex copper gasket sealant etc on these engines?

[Blknight.aus]

Could the gasket have blown due to incorrect gasket fitting? When fitting a new gasket (any gasket in any location) always make sure that the surface is perfectly clean. I scrape both surfaces with a new Stanley knife blade until they are perfectly smooth. This means shinny metal. It does take a fair amount of time and effort to get it that way. Alternatively, you could use a brass wire wheel. Is it a copper or fibre head gasket? Did they use Hylomar? Was it re-torqued at the appropriate interval? If the two good cylinders have good compression, I would be inclined to just replace the gasket properly, and give it a run before deciding on what to do next. Head gaskets are quite cheap anyway.
Aaron.

Just a precaution on doing this there needs to be a "surface quality" to a head and shiney aint it. while the head needs to be nearly perfectly flat the very very minor abrasions help the head gasket do its job. Once youve got all the muck off of the head/block and confirmed that both are inside of tolerances then If you can get it (for an ally head) I swear by blank newspaper if you can get it (the stuff on a roll before it goes through a press) wrap a hand full of layers around a nice soft wooden block and in small circles gently massage the block and you should come up with a dull matt grey finish after you clean it all down with metho the same applies to a cast iron part but you use a very very fine wet and dry paper. Getting the surface finish wrong can lead to the gasket letting go.

If you get one of the composite gaskets that look like expensive cardboard you usually dont need a gasketing compound but the proper one piece metal gaskets do require the goop.

[isuzurover]

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??

You will most likely see vertical score/scuff marks in the bore(s) if the rings are broken.

[Aaron IIA]

Just a precaution on doing this there needs to be a "surface quality" to a head and shiney aint it.

What you say does make sense. What the main point of my post was, make sure that all of the old gasket was removed, and that the surfaces were flat. I am usually accustomed to dealing with people who would not remove all of the old gasket. So by saying shiney, I mean that you are looking at clean metal, and not rust or old gasket. I can fully understand that a polished surface will allow the gasket to blow more easily.

If using a copper gasket, I would recommend using a sealant that is suitable for head gaskets. One that comes to mind is Hylomar. I have used it in the past, and it works quite well.
Aaron.

[Aaron IIA]

Can't tell you what the compression on the good cylinders was because i had a ****ty compression tester that you push into the spark plug hole instead of a threaded one. The good cylinders were convincingly going past 100 psi when i couldn't hold the pressure anymore.

Push harder on the compression tester. If the others appeared to be going past 100 psi, I would suggest that the bores and rings will be servicable. The adjoining two being low would have to be a blown gasket. If it was my engine, and it wasn't too smoky, I would just replace the gasket. If you are going to do much more than this, it would pay to take the engine out and do everything. That said, when you have the head off, it won't hurt to lap the valves back in, and fit the new stem seals that will come with the VRS kit. Do you know if you have the cup or the O-ring stem seals? All the VRS kits that I have seen come with the cup seals. O-ring seals can be bought seperatly and do not cost much.
Aaron.