Thread: Low compression engine ?

Yes they are the ones blowwing lots of smoke as they drive along deffinately low compression

This is the period following running in.

Mark, I'm interested in what compression is usual for such an aged motor. I checked mine and got varied readings and the situation was difficult to read.

Plugs show no oil and are all equal colour light Brown.

There is a little smoke from rocker cover cap vent and filler tube.

The previous 'pumping' of oil from the rocker cover has abated since I found that the Banjo fitting at the top was the same as the bottom one, rather than the smaller aperture. Fitted correct and seems much better.

The timing chain could be a tooth out causing valve overlap. In the end it starts and goes well and is reliable. It can cruise at 80-90kmh (GPS) who knows?

In the end it is probably best to just drive it and enjoy the same consumption as an V8.

Getting closer for a S1 weekend in the bush. See ya

True, still not close to run in.
Using oil but not smoking .
Hot comp test reads 95 psi across the board .( I did forget to remove all plugs and open carb butterfly ) ill do them wet n dry when this weather buggers off , should be 125 psi from the factory , my old engine was between 105 and 125 psi with amazinly buggered crankshaft journal bearings and coke'd up valves .

Actually running well ,slight pop on turning the engine off( to advanced?) tops out at around 84 Kph (205r16.tires) .
That oil pipe at the back of the head seams critical ( metering plug or correct hole size) mines stoped fumeing ,leaking from the rockers and smoking as Much as I do. ..just gotta fix the speedo lol .. bit of an oxymoron that!!
My god mike don't say stuff like that... It's tempting the gods to smyte down my big end!!!...... I'm still using less oil than your's did before that little drive n clean up you did lol

Originally Posted by mfc

True, still not close to run in.
Using oil but not smoking . -------- Actually running well ,slight pop on turning the engine off( to advanced?) tops out at around 84 Kph (205r16.tires) .

That engine sounds like it needs the inlet valve seals done and a nice little drive in the country ( about the distance from Melbourne to Darwin and back ), if the engine has been burning oil, the run on, or pop noise is most likely caused by the build up of 'coke' deposited inside the head , this retains heat in localised spots which keep igniting the incoming mixture after the engine ( spark plug circuit ) has been turned off .

If you take the inlet rocker cover off, you will see that oil pools around the valve stems so when on the overrun, or idling there is high vacuum sucking oil down past the valve stems. In a old engine like that one of yours, those stem seals would be as hard as diamonds and way past doing their job, so the first thing to do is to fit new ones.

Any concerns with the rings will either come right as the engine does a few long runs with a few good oil changes or they are truly worn out and will get worse as time goes on.
Look for evidence that says the engine has been damaged from dust ingestion, see if inside the inlet manifold has a coating of dark grime around inside the ports, deposited from years of poorly serviced air cleaners and if that is clear with only red/brown fuel stain there is a good chance the rings are only stuck, gummed up in their piston grooves.

If the oil pressure light barely flickers when the engine is hot and running at a slow idle, I wouldn't worry about the bearings either. However if that oil light is slow going out up to a working rev and there is a distinct knock when the engine is working, it's time for a bottom end rebuild.
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Engine has had the valves lapped and new inlet valve seals put in. Only had one hard drive ( 100 Kms ) so far , hope it picks up a bit with driving ... Has had new con rod bearings and timing chain as well.. Not smoking badly either just a puff on clutch in at higher revs
Perhaps I need to drive further towards Perth lol... Otherwise it's rings ( witch were apparently replaced b4 I brought it) or glazing
I'll repost when I've done 500 Kms ..

Originally Posted by mfc

Engine has had the valves lapped and new inlet valve seals put in. Only had one hard drive ( 100 Kms ) so far , hope it picks up a bit with driving ... Has had new con rod bearings and timing chain as well.. Not smoking badly either just a puff on clutch in at higher revs
Perhaps I need to drive further towards Perth lol... Otherwise it's rings ( witch were apparently replaced b4 I brought it) or glazing
I'll repost when I've done 500 Kms ..

New rings are needing some running in and a looonngg trip to do just that.


With that pop or running on, try and sneak the vernier adjustment on the side of the distributor back a notch.

I have read back over your thread and your engine should not have chromed cylinders'. This is good, as the earlier engines with chromed cylinders', a distinct step/lip can occur at the bottom of the chrome, worn into the cast. That will stop new rings seating in.
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From the workshop manual;

Compression pressure (at starter motor cranking speed, i.e., 300 r.p.m. with engine hot and carburetter butterfly fully open ) ... ... ... 125 lb/sq.in. ( 8,8 kg/cm² ).

From Parts Catalogue;
Cylinder Head Assembly Part number 233430
This is the only part number listed for all the Series one petrol engines.
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Yea didn't open the accelerator and only removed one plug at a time, cylinders showed no steeping ( unlike the older 1955 engine) this engine is out of a late s one.... I'm running it in in the hills behind home so it's getting work at different revs . I'm trying the retard a dvance this arvo... Another 100 odd Kms