Many engineers recommend the enlargement of this port, so the purpose of this article is to examine why this should improve the running characteristics of the engine.

Where exactly are we talking about?

We are talking about the hole on the cylinder head which faces the top of the piston (the entrance to the pre-combustion chamber from the cylinder). It is the entrance that is ground out to be enlarged (rather than the chamber itself). Bear in mind where the head gasket goes (ie. don’t grind out any further than where the gasket sits).

Why does this help?

Enlarging this entrance allows the air out of the cylinder (been compressed by the piston) to enter the precombustion chamber more quickly, which improves the cranking speed (as it isn’t trying to push the air through such a small hole). This also allows the pressure in the pre-combustion chamber to build faster and higher than it normally would do. Obviously the diesel engine works by compression ignition, so this increase in pressure makes ignition more likely and hence should improve starting performance.  When the ignition occurs there is then a more free passage of the expanding gasses down into the cylinder (as we have now enlarged the entrance/exit to the pre-combustion chaber).

The ongoing development of diesel engines and preference towards direct injection tells us that anything which limits the flow of expanding gasses onto the piston reduces efficiency.

The differences in efficiency will only be small for each cycle, but remember that a 4 stroke engine turning at 2000rpm competes 1000 cycles per minute, so any small ineficiencies are magnified 1000 times and therefore become significant.

Hi Steve,
I’ve finally fitted the 23cs to my boat and both engines fired up first
time!!

Fantastic I’m really chuffed.

My background is in carpentry, although I now teach English in the local prison, and so your dvd is the only tuition I’ve had on
mechanics/engineering.

When working on the engines I had the dvd on the laptop and so repeatedly replayed each stage of the rebuild etc. There is no way I could have done the engines before and so a great thank you for the dvd and excellent advice.

Cheers Paul.

and some photos of the engines…

I’ve spent the past 30 months restoring her 3-4 days a week and should be launched early May. Betsie Jane is on the National Historic Ships Register.

I’ve also attached some photos of how I worked out TDC and 16 deg before. Basically sealed a clear pipe into the injector hole and stuck the end into a jam jar of engine oil. As I turned the engine over I watched the oil rise and fall, checked with the valve openings what stroke it was on and as the oil started to fall knew it was on the compression stroke. I marked the oil level on the clear pipe and repeated several times just to be sure. I then punched a small mark on the shaft which was 180 deg from the machined slot.

The white card was marked with a horizontal line which I lined up with a horizontal break on the engine and marked on the card 18 btdc. I then spill timed the pump on the bench and fitted it to the engine. This took several attempts, but perseverance payed off.

I’ve attached photos.
Cheers again.

And if you want to see the completed restoration.  Here is Betsie Jane.

The oil level on this Massey Ferguson 575 suddenly rose up the dipstick.

The oil hadn’t gone the milky/creamy colour consistent with water getting into the oil, but had become ‘thinner’ and had a slight smell of diesel.  Clearly diesel was entering the oil, but where was it coming from?

In this case the fuel lift pump was at fault and a replacement unit and an oil and filter change, the tractor was back to work.

Winter work for this 575 is handling the round bale silage feeder to roll out feed to the suckler herd.  This tractor once did all the ploughing and cultivating on this farm.  In 1960 a Ferguson TEF 20 was the main tractor, then came a MF35, MF165, MF168, then the MF575.  The 575 was a shift in driver comfort with a sprung seat, ‘Q’ cab, full cab glazing and a dedicated cab heater.  The cab could get very hot on summer days when performing tasks such as baling, where it was ideal to have all the windows closed to keep out the dust on long 10 hour days – starting as early as 10.30 am and sometimes baling right through to 8.45 when the dew started to come down.  Many of these days were spent with the side window open on the single door cab, or (if the wind was in the correct direction) with the door open to let in some cool fresh air.

Round bale silage feeder

Contented cows eating silage, after Vintage Tractor Engineer had repaired the 575

I have now seen the dvd over and over again.  My problem is determining how to set the timing between crank and cam.  Regarding cam the man in the DVD says something about turning the cam until both valves on cyl 4 does something, but I simply cannot hear/understand the English very well.  This cam position should then refer to crank TDC cyl 1, but how can this be determined if the engine is still mounted to gearbox.
As I understand the hole in the flywheel refers to 17 deg injection timing = “G” in the pump inspection plate.

I really hope you can kill my confusion.

NB!  My 23C tractor is rebuilt and running, but smokes light blue (unburned diesel) so I really suspect the timing. I have not touched the chain or pump gear during the rebuild.

Henrik Thomsen, Denmark

Hi Henrik,

When the pin is in the hole in the flywheel it is 16 degrees before TDC on
number 1 cylinder.

To set the timing chain, follow this procedure…

To set the camshaft, first of all, set the tappet clearance on number 8 valve (the valve at the back of the engine closest to the steering wheel) to 0.023in (when the cam and rocker is in its lowest position).  Then set number 7 valve to 0.025in.

Turn the engine away from TDC.  (The keyway in the front of the crankshaft [that holds on the front pulley] is at the bottom when cylinders 1 and 4 are at TDC.)  Therefore position the keyway on the right looking at the front of the engine (ie. 3 O’clock position – always turn it clockwise).  You do this so that the pistons do not hit the valves.

Now remove the timing chain, camshaft sprocket and the chain tensioner.

Next turn the camshaft clockwise until vavles 7 and 8 are “on the rock” (ie. exhaust just closing, inlet just opening).  Now the camshaft is in the correct position for the timing procedure.

It is now safe to move the crankshaft clockwise for number 1 cylinder to be on TDC.  You can determine TDC without using the flywheel marks (ie. with engine connected to transmission) by using the flywheel pin hole as a reference point.  Slide in the pin to the locating hole in the flywheel and then fix a protractor to the crankshaft, and place a pointer on the engine which will give accurate readings on the protractor.  Then remove the flywheel pin and turn the engine clockwise 16 degrees (as measured on the protractor), and therefore you are now on TDC for number 1 cylinder and are in the correct position to fit the timing chain, sprocket and tensioner.

Now don’t forget to re-set valves 7 and 8 to their normal running valve clearances as in the DVD (0.012in on inlet, 0.018in on outlet).

Now set the injection pump timing as per the DVD instructions.

It’s quite an involved prodecure, but this will mean you can time the engine without removing it from the transmsission.

Hope that helps, let us know how you get on.

Steve Ridsdale (VTE)

Unfortunately we can’t make any suggestions as to where to source this part, but it is probably just a seal which needs replacement and so would suggest stripping down the pump.   It should be an easy repair, and that way the originality of the tractor will remain intact.