Engine dead?

[VitesseEFI]

Opinions Gentlemen please,

1972 2.5 PI.
I've had it since last October, but not done much driving of it until recently due to it having been standing for many years, needing recommissioning and then needing just about everything mechanical fixing. Mileage shown is 38K - more likely 138K.

I've converted it to electronic management, so fuel and sparks are now controlled by Megasquirt. Haven't done alot to the engine mechanicals - just dropped the sump and changed bearings due to rather large end-float plus a quick reface of the oil pump end faces. Oil pressure is now good with 25 - 30 psi hot idle rising to 60 by 2000 rpm. Compressions appear good at 190- 200 psi throughout (hot cranking, throttle closed). It runs pretty well and pulls hard through the rev range.

However:
Since day one the engine has been a heavy breather. I initially put this down to high petrol content oil (knacked PI!). It's had a couple changes now and the sump cleaned out, but hasn't made much difference. Smoke from the exhaust when revved was put down to knacked PI and borewash plus an external rocker feed now removed. It still smokes pretty heavily on the over-run (visible in mirror) and has used about 1 litre of oil (20/50) in 4 - 500 miles. Crankcase pressure is also an issue, forcing leakage from the (new) crank oil seals and filler cap.

Due to the long standing period I'd wondered about stuck rings and have done a couple of engine flushes plus leaving the bores with ATF soaking in them for 4 days. It's also now done nearly about 650 miles with me so I'd think they'd have freed off by now if they were going to...... Amount of smoke and oil consumption seems too high to be down to valve guides.

Will try an additional breather (from fuel pump blanking plate) and some Wynns, but suspect it is time to admit it going to need rings and a hone at least?

Any bright ideas anyone? Good source for reasonably priced pistons?

Cheers

Nick

[TedTaylor]

The smoke from the exhaust is very likely due to due to worn valves - only cure for this is replace guides and if valve stems are out of specification replace those as well.

Also smoke and crankcase pressure problems point towards towards worn/stuck rings even though your cylinder compressions seem good. I don't consider you are doing your compression check correctly because you imply that you are spinning the engine over when hot with the compression tester in place which will simply pump up the pressure in the gauge and give false readings.

You should turn the engine over cold with the tester in place just once to get a reading which I expect will be much lower than you are getting at the moment. Then with the cylinder at TDC leave it for a short while and recheck the pressure - if it has a built in valve to hold the pressure then pressure the release button and see if it drops. If it does it indicates worn rings which you can double check by putting a little engine oil in the bores to seal the rings a little and repeat your compression test which if higher does indicate worn rings.

Soaking in oil as you have done to free the rings is a good procedure but only if it does it effectively and releases all the rings. I suspect you have only done the top one (compression ring) a little which has improved things but not enough. If the rings are slack in their grooves this can cause them to act like a pump and either pump air into the crankcase or oil into the combustion chamber depending upon the nature of the wear and other circumstances like the position the piston on compression or exhaust stroke.

You will have to get the pistons out if the revised compression test shows low cylinder compression (may be advisable anyway). You will then very likely find the pistons a bit coked up in the ring lands which can be cleaned of carbon (WITHOUT removing metal) as well as on the piston crown ...... but DON"T rub off polished wear patches on the sides of the piston which should be there if the piston is nicely run in. If the ring lands are burned the piston is scrap but otherwise it can probably have new rings fitted after checking the side clearance of the rings in the grooves for excessive wear.

Where in the country are you based in case any one is local to you and can give personal help?

Ted

[VitesseEFI]

Ted,

Thanks for your reply. I'm near Yeovil in Somerset.

Not come across your method of compression testing before. My normal method is done hot, with all plugs removed, throttle held open (though not in this case) and turn on the start for 10 compression strokes. While it's turning I'm watching the gauge closely to see how quickly the pressure builds, and in this case I was getting something like 60% of the final pressure on the first stroke and that was consistent across all 6, which is indicative of pretty decent compression ring performance in my experience. I've edited my original post as in fact the the cylinder pressures were 190 - 200 psi and where so high and consistent that I didn't follow up with a wet test. No cold (or hot for that matter) engine I've ever owned holds pressure at TDC for more than a few seconds when turned by hand, but none of them have used as much oil as this one.

As to guides - well, they probably are worn, I just find it hard to reconcile the amount of smoke and oil loss with the relatively small amount of oil flow to the top end. Also when I did the guides on my Vitesse (which now have stem seals as well) it made no difference to oil use at all, even though the old guides were absolutely shot.

I reckon you are right about some rings being free (at least one compression ring) but others stuck. Also, some pistons (not sure about these) have drain holes in the oil-ring groove which could be blocked?

Anyway, it's looking like it needs to come apart to be dealt with properly - everything else on the car was shot, so I shouldn't be surprised the engine is tired too I suppose!

Cheers

Nick