Monday, 18 March 2019

Long block rebuild

It’s taken a couple of months to decide on a course of action and source the parts to rebuild the engine block.

9-Apart Porsche dismantlers had a good crankshaft of the right type (5 chain rather than the later 3 chain design). Without this there would have been no choice but to go with a second hand engine.   With two of the cylinders scored the option of iron cylinder liners was considered, but in the end we managed to obtain a used crankcase which we preferred.  

With these key parts sorted we were able to send the cylinder heads away to be skimmed, valve seats re-ground and valves stem seals replaced.   

Two of the pistons in cylinders 5 & 6 were scored so we had to replace these with used ones.  The no. 6 conrod was also beyond repair. 

Whilst doing this we balanced all of the pistons and the conrods.  This is fairly simple as they are designed with specific areas where minimal material for balancing can be removed. 

Then with the help and expert guidance of Archer Motorsport Services the engine was re-assembled with a standard engine rebuild kit of parts.  This included;
  • Bearing shells
  • Piston rings
  • Conrod bolts
  • Timing chains 
  • Chain tensioners and guides
  • Head gaskets
  • Cylinder head bolts 
  • Gaskets and oil seals 
  • IMS bearing 
  • Sealant and assembly paste 

Under hard cornering g-forces the oil can have a tendency to either stay in the cylinder head and not return to the sump or pool in the side of sump away from the oil pickup tube.  

To help prevent oil starvation we have fitted the Porsche x51 motorsport sump.  This isn’t a deeper sump but does have larger and improved baffles to ensure that oil returns and stays in the centre of the engine. 

The long block assembled with our lower temp thermostat and metal impeller water pump re-fitted.  

Inside the engine bay we have de-greased and cleaned everywhere, plus repainted the chassis cross member which was starting to rust. 

Before reinstalling into the car the engine block needs the intake manifolds, fuel rails and ancillaries refitting.  

The final area which will also needs attention is the clutch and flywheel. Both need replacing (as you would expect after 80,000+ miles) along with several parts of the clutch mechanism which wear out.    

So still plenty of work to be done before the engine can be run in!

Sunday, 6 January 2019

Engine Strip Down

Having got the engine out of the car the remaining ancillaries and intake manifolds etc were removed from the top of the engine, leaving us with what is known as a long block.  It was pretty dirty with oil residue from various leaks over time and a nice coating of Castle Coomb grass! for good measure.

We borrowed an engine crane and loaded the engine into the car, taking it over to Archer Motorsport Services in Hertfordshire.  With some much appreciated help we were able to  dismantle the engine in just under three hours.   The aim was to identify the root cause of the failure, determine if the engine is even rebuild-able or just scrap and form a plan on what to do next.  

Working on cylinders 1-3 first the cam covers and camshaft assembly came out pretty easily.  Next the cylinder head bolts are removed and binned.  These are single use so have to be replaced regardless. 

Inlet and Exhaust camshafts above connected by timing chain.

Pistons exposed - some carbon build up as expected

Cylinders 1-3 pretty clean and unmarked

The valves and pistons on this side of the engine looked pretty good.   Also there is no sign of bore scoring in the cylinders and only light carbon build up on the pistons. 

Moving to the sump we found evidence of a destroyed bearing shell. A lot of fine particles in the oil residue and some larger pieces of metal on the magnetic oil pickup - which isn’t good.  

On the cylinder 4-6 side, again the valves and camshafts were the same as 1-3, but removing the cylinder head we could immediately see the piston no.6 was loose with no big end bearing left.  This was the cause of the knocking when the engine ran.  

Crankcase split exposing the crankshaft box and pistons 4-6

The lack of a bearing shell has caused the conrod to damage the crankshaft surface. This is beyond the amount that can be ground so its scrap.  

Crankshaft removed - spot the damage!

No.6 con-rod damaged the crankshaft surface after the bearing shell disintegrated

It has also caused some scoring of the piston in the cylinder bore as there was too much play going up and down in the cylinder.  

Cylinders 4 (least) to 6 (most) marked/scored

Cylinder 6 is renowned for oil starvation issues in these engines.  It is the furthest from the oil pump.  This cylinder was showing low compression when we tested the engine a year ago.

It’s a marginal call as to whether to rebuild the engine or replace it with a used engine.  With a used engine likely to have at least 70-80,000 miles there are two considerations.

  • The engine will be starting ti suffer from wear such as our engine
  • There is a higher risk of a catastrophic problem since the engine history is likely to be unknown

We think therefore it is worthwhile trying to rebuild our engine.  To do this we need to source a good crankshaft first.   Then we can get cylinders 6 (and possibly 5) re-lined using either steel or Porsche Nikasil liners.  The head will need to be skimmed and the valves lapped, then it can be re-assembled with new consumables, bolts, gaskets and bearings.  Re-assembly should take a day.  

Through careful sourcing of the parts we need this should be only marginally more expensive than a used engine - but giving up the piece of mind and greater assurance over the condition of the engine at the end of the process.

Wednesday, 7 November 2018

Engine Out Day

The engine runs, but is knocking badly.  Regardless of whether we rebuild it, replace with new or used it has to come out.  Then we’ll take it apart and inspect the internals before deciding on which route to take. 

We have done everything on the car ourselves bar welding the rollcage and more recently pressing new rear wheel bearings.  At lot of the prep work is jobs we have previously done. Because of this we really want to do this ourselves and are absolutely positive we can. 

I compliled two checklists of what to remove, disconnect, separate etc and then cross checked them so nothing is missed.  Neither are comprehensive and it now totals over 50 steps.  The two sources I used were the Jet 1 YouTube video series and Pelican Parts engine removal guide.  The latter is more of a guide of guides as most of the details is in smaller jobs they have covered separately. 

The principle of labelling everything, taking notes and photos cannot be under estimated. It is likely to be months between removal and refitting so there is no way of remembering what went where or connected to what when we come to refit it. 

We don’t have a lift or an engine crane so the general approach is to have the front of the car raised on std car ramps ramps and the back jacked up at an angle using jack stands. The gearbox will come off first and then the engine lowered on a jack onto a trolley and pulled out under the rear of the car.  Simple?  

With the car on the ground we started disconnecting everything at the top of the engine which connects to the body, this included the air intake, ecu wiring loom, oil filler and air pump pipes.  For road cars a major headache is the air conditioning lines and compressor so we avoided that luckily. 

Getting the car up on ramps and jack stands allowed more space underneath. Rear bumper and exhaust were previously removed so we cracked on with chassis braces, anti roll bar, cats and drive shafts - all of which we have removed before so no stuck bolts to contend with. 

Under the middle of the car we drained the engine oil, coolant and power steering fluid removing all the coolant flexible pipes at the same time.  Tiny metallic particles were in the oil which isn’t a good sign.  

As we don’t have and engine lift or cradle to drop the engine onto we decided to remove the gearbox first to reduce the weight and sheer size of the engine.  Several of the bolts were seized so it took hours to remove and some of the engine block threads will need to be repaired as a result. 

After stopping that evening we came back to the car the next morning and removed further weight in the flywheel.  The only tool we didn’t have was a large torx socket for the flywheel bolts - so a quick trip to Halfords was in order. Now with the engine supported on the large jack the final front engine mount was removed and it lowered slowly to the floor.  The car ideally would have been higher still to pull the engine out, but we manged by rotating it on the jack by 90 degrees and pulling it out front under the back of car sideways.  

Job done in ~13 hours. 

Thursday, 25 October 2018

Trouble at Donington

After around 30 race weekends, plus track days and testing in between the internal bearings called time on the constant high rpm and back acceleration that is involved for a competitive race engine.

A hour earlier we were mulling over a good but slightly perplexing qualifying. I had gone 2 seconds a lap faster than ever before around the Donington Park national circuit, but somehow ended up 10th on the grid.  With the benefit of testing (2 days for some) everyone else just went 2.5 seconds faster!

The temperature was rising as the afternoon kicked in so we needed to reduce tyre pressures and the rear end was a little unstable under braking in qualifying so a tweak of the suspension was needed. Nothing else to report other than looking forwards to a great race, which was setup with 5 cars capable of winning and another similar group behind.

I leave the engine running in the holding area to ensure it’s fully up to temperature and we head out on the green flag lap. It’s a little slower than usual and I’m weary I have new tyres which will come up to temp quickly.  

I reacted quickly as the red lights went out, but the car in front didn’t.  Jinking to the right I realised there was only half a car width of race track and didn’t fancy getting on the damp grass under full acceleration so backed off. 

The car behind jinked left  making several places and went on finished o the podium.   Two cars tangled and went off first lap and the top 10 was pretty close through the first 3 laps with me watching at the back of the pack.  It started to stretch out over the next few laps but I was nicely in touch with the two cars in front coming right onto them every time they made any mistke or held each other up.  Coming down the fast final straight I felt a slight rumble fro the engine under braking and then there an almighty vibration, shaking the car as I tried to accelerate out of  the last corner. I'd never had an engine go on me before, but it was obvious our race was over.   I switched it off immediately wanting to avoid as much internal damage as possible and pulling off to a safe place at the side.  

As the race went on no less than four additional cars broke down or pulled off with mechanical issues.  

In seven race seasons, this is only the second time that we have had to pack up early, with no hope of running in the later races. But as frustrating as it feels, our engine has never let us down and been far more reliable and performant than many others since we started.