Petter PAZ1

 ALL REFERNCES TO PHOTOS ARE UNDERNEATH THE PHOTO
    The Petter PAZ1 is a small single cylinder diesel engine designed for low speed industrial and marine applications, it was designed and built by the Petter engine company in the UK. It only produces 1.6hp but is a very heavy and long lasting engine, even this 40+ year old model shows little signs of wear. The engine being a diesel has high compression and therefore requires the use of a decompressor lever to aid starting. The engine is started by handle on a half speed shaft giving the effect of the engine turning at twice the speed the starting shaft is rotating at, this half speed shaft can also be used to drive inplements requiring a lower driving speed. The PAZ1 is designed to use many components and is actually built in the same engine block as its petrol conterpart, the Petter A1, instead of a magneto this engine has a rather complex governor system.

   2010 - present
   This small engine was found in a cement mixer left in a hedge just up the road, we aksed the owner about it and agreed we could take it away, the cement mixer was scrap but still gave a fight getting the engine out! The engine is in good mechanical condition internally as it was left full of oil, however all external parts including the fuel system components and fuel tank were completely seized or rusted, these were sent to a specialist to be reconditioned. Unfortunately we were away for a week and left the new parts in a cardboard box on the bench, over the week we had a lot of rain and the garage leaked over the bench, the box filled up and the "new" fuel pump and injector sat in water for over a week, the current condition is unknown but they may require another re-condition.
   The first job we had was to remove the flywheel, being a single cylinder diesel engine the flywheel is a huge casting and constitutes a huge amount of the final engine weight. We tried a number of methods but the only one that seemed to work in the end was fashioning a puller out of some box section steel and M12 threaded bar

   Home-made flywheel puller:
   This allowed us access to the internals of the engine, the photo below shows the main crankshaft and the half speed camshaft/starting shaft. These are both timed and have timing marks on the gears to ensure they go back together the correct way.

Internals: 
   As mentioned above, the engine has a governer to ensure the engine does not race or stall, this confused me briefly as the governer had timing marks but didnt mathc up with any displayed on the main crank gear, however i found out that this is because the Petter A1 petrol engine has a magneto that must be specifically timed to the crankshaft uses the same gear, therefore the gear has a timing mark but is it not necesarry to time the governor on this engine. The governor uses a centrufugal system to vary the engine speed, a lever is moved back and forth dictated by the speed of the engine, this then acts directly on the fuel pump via a spring, this governer suffers from a lack of damping, encouraging the engine to hunt, especially when cold/

Governor (external):
  The exhaust was removed to clean out and we soon found that the exhaust port was almost completely blocked by carbon deposits (shown below), this is typical of a diesel engine running at low revolutions and would have significantly hindered the performance of the engine and probably also the starting ability, this could explain the engine initially being abandoned, we later found that the carbon had built up in the valve seats preventing the exhaust valve from closing fully, this has the effect of decompressing the engine and would also dampen performance further.

Exhaust elbow:
   Once the above was removed, we were able to take the cylinder haed off, the cylinder is quite big giving the engine bags of low end torque, ideal for low speed industrial applications, all the mechanical work we intend to do consists of the newly reconditioned fuel system components, new big end bearings and piston rings, we will also hone the bore to remove glazing (another symptom of slow running diesels) in the hope of inmproving performance. The photo below shows the valves being compressed prior to removal, this means i could clean out the valve seats and regrind the valves into their seats to ensure that the engine retains maximum compression, the springs that return the valves to the closed position are very strong so care must be taken using the valve compressor to prevent injury.

Removing valves:
   7/21/2012 - 11.00pm
   Today we attempted to shot blast the engine, this makes removing the paint and surface rust on the engine much easier, the engine has been stripped right down into all its main component parts for shot blasting, we will partly re-assemble the engine before spraying the engine as this means we dont damage the paint job doing this job later on.

Grit Blasted parts: 
   7/23/2012 - 08.30pm
   Today we took the fuel tank down to Redhill Engineering as it had a few small holes in it, thought they reckon it might be easier to fabricate a new one from scratch so we have left that with them, i also ground/lapped the valves using abrasive paste to ensure a good seal before re-assembled the head (valves and rockers). I will show this as photos with captions as it took some time and a valve compressor.

1. Valve components and head on the bench, the inlet valve also has a skirt on the inside to smooth out air flows in the inlet port: 

2. Cleaning ports on head, big lumps of carbon came out:  

3. Grinding in valves using CHEMICO abrasive paste, this can be purchased on ebay :- http://www.ebay.co.uk/itm/251098123965?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 :

4. Checking valve seting after grinding is finished, note the inlet valve is a lot bigger than the exhaust valve, the inlet valve also has a skirt on the inside to smooth out air flows in the inlet port: 

5. Exhaust valve all finished and in place with spring and keepers: 

6. Photo of the inlet valve being compressed prior to keepers being inserted, note the valve compressor tool compressing the high tension springs, interestingly this engine has two lave springs per valve, one inside the other: 

7. Bothe valves finished, and keepers inserted, seating test completed (WD40 in head to make sure valves dont let it past) with complete success. All thats left to do is bolt the rockers back on and the head only needs a bit of paint, note the split pin through the top of the inlet valve ensuring the skirt on the bottom of the valve stays in the same place.:  

8. Finally, rockers are back in a nd the head is ready to go back on the engine, after a bit of paint of course! i would have sanded and painted the head before doing this job but we need to get the engine finished for late August and there is still a lot of work to do, i have applied loads light machine oil to ensure the engine has adequate lubrication when first started:
   We inted to paint the engine in "Mid Brunswick Green" the engine was originally painted in an industrial yellow colour, however we think that as the engine is no longer being used for an industrial application then the green is more appropriate, however we will keep good records of the engines history as this is important too.
   7/28/12 - 10.33pm
   Ran into a problem today, just as we were finishing off the shot blastig i began cleaning errant pieces of grit out of the sump and off the gears read for the forst stages of re-assembly. However i noticed (luckily) that the oil pump was jammed, a small piece of grit had obviously found its way into the pump preventing the plunger (driven by the camshaft) from pumping. So the camshaft, cam followers, oil pump pushrod, oil filter and poil pump plunger have all had to come out, i am currently waiting for exploded diagrams hoping they wil help putting the pump back together, but all the grit blasting is finished and hopefully we will be able to start re-assembly and painting soon. 
  9/16/12 - 9.38pm
  Sorry havent been keeping up with the posting, engine had its first rally today, NVTEC North Somerset Weekend, Engine has been painted (few problems here) and runs well, will put up some pictures and maybe a video when i have time, been a bit busy as hydraulics and steering need attention on the Massey besides a well overdue oil change! 
  10/28/12 - 1.40pm
  Will finally put some photos up of the PAZ 1 finished!

 

Engine is still very hard to start but runs well once started so i put this down to genearal wear that would be uneconimical to fix, the engine runs well at shows and starts well from hot. This project is now finished. 


Note Stuart Turner water pump, restored at same time as engine, unfortunately we did not have the correct pipe connections at the time so it had to be bodged! but both ran well during the day.