Pulled out my engine today

[RaceDiagnostics]

Some measurements today.

Micrometer set to 92mm.

Bore gauge set to zero in the micrometer.

These are the measured values at the top, middle and bottom of the bores in both the transverse and longitudinal directions. The measurements were taken at 13degC rather than the specifications which are probably taken at 20degC.

I have made an estimate of the for the likely values at 20degC but am not sure how accurate this is given the micrometre is also calibrated for 20degC.

Let me know if you think I should use a different value for cast iron.

The bore wear limit is 0.1mm just below the top ring, so it looks like I am well below this limit across all cylinders.

As for the pistons, the measurements are below. I was really surprised how much under the spec value they were, so I brought one into the house tonight to make a comparative measurement at 20degC and found the piston skirt on piston 1 was 0.025mm larger than at 13degC so used that value to adjust all the values. As the pistons are tapered, the bottom of the skirt measurements are the only ones that really make any sense.

So the bottom line of what I was wanting to check was the piston-bore clearance which has a spec limit of 0.08mm. From the table above you can see that piston 4 is the only one out of spec. However I am not really convinced that my measuring methodology is good enough.

It is also a PITA that the factory fitted the wrong pistons in positions 1 and 4, the marking on the block calls for piston code "2" and piston code "1" was actually fitted, that adds to the excess clearance.

Given standard size pistons in any group size are no longer available, fitting a larger group size piston is not an option.

Boring out the block to use the first repair stage pistons (92.5mm) would cost at least £1200 for the aftermarket pistons and machine work, for me I don't think it's worth it for one marginal cylinder.

What are your thoughts, please also offer any advice on my calculations.

 

[Nick DV]

Can't offer any advice, but I applaud your attention to detail and meticulous work Fantastic job

 

[Jay1st]

In the Us they use something called Plastigage or Flexigage, for adjusting the crankshaft journals and fining the correct thickeness to be used. It seems to work pretty well and it's hassle free.

 

[Gareth_16V]

I think your measurements are very thorough - I would probably not worry too much about 7 degrees C of thermal expansion coefficient as I would assume all of your engine components and all of your measuring equipment lives in the same area (the garage?) anyway, and therefore are all cold soaked to the same temperature. Therefore if the standards on the micrometers show that they're correct I would think you'd be good to go.

It depends on what you want to do with the engine - if it's a light refresh to fix a known issue and leave the rest then it would probably be fine to rebuild as-is and keep an eye out for increased oil usage or blowby over time. Are you replacing the piston rings? If so, you'll need to hone it anyway.
If it's a full-on concours or you wish to make everything brand new then it would be a bore to a known size and reset the piston to bore clearances to as new.

 

[Rannsachair]

In the Us they use something called Plastigage or Flexigage, for adjusting the crankshaft journals and fining the correct thickeness to be used. It seems to work pretty well and it's hassle free.

My Plastigauge is made in England:

I would live with the extra thousandth of an inch clearance on piston 4, especially for the cost to rectify. If it was not burning oil or generating piston slap why go to the expense.

 

[RaceDiagnostics]

Snap!

 

[Cobbler]

I would live with the extra thousandth of an inch clearance on piston 4, especially for the cost to rectify. If it was not burning oil or generating piston slap why go to the expense.

My feeling is that a thou is going to make no difference as long as it’s round. The rings will take that easily. Rings don’t like oval bores.

 

[daedalusminos]

Have you measured the ring gaps in their respective bores?

 

[ronan]

My feeling is that a thou is going to make no difference as long as it’s round. The rings will take that easily. Rings don’t like oval bores.

Or bores that taper, causes ring flutter i believe, the ring opens and closes making the gap either non-existant or huge.

 

[RaceDiagnostics]

I got three quotes for engine cleaning and a cross hatch hone.

WM Anderson Kirkcaldy - £75+vat --- just a parts washer clean
Agra - Dundee - £120+vat --- not clear if its a parts washer or chemical dip
JEM - Falkirk £280+vat --- hot caustic bath clean

 

[Rannsachair]

I got three quotes for engine cleaning and a cross hatch hone.

WM Anderson Kirkcaldy - £75+vat --- just a parts washer clean
Agra - Dundee - £120+vat --- not clear if its a parts washer or chemical dip
JEM - Falkirk £280+vat --- hot caustic bath clean

I have used both Wm Anderson and Agra in the past and was happy both knew what they were doing.

I suppose the question of whether to go for just a parts washer or a hot caustic bath comes down to the parts: the caustic bath will remove all the oil residue contamination, so if you think it looks bad enough could be worth doing. From the photo's I have seen much worse.

 

[slim_boy_fat]

Agra also have a place in Banff - I've heard good things about them over the years.

 

[RichardM]

Hot Caustic - I wouldn't have any aluminium parts done in it.

 

[RaceDiagnostics]

It's a cast iron block.

 

[mylesdw]

I think you would normally remove the core plugs and gallery plugs for hot tanking or you will never really get the residue out.

 

[RaceDiagnostics]

Catch up for the last couple of days.

I gently cleaned up the decks.

Checking the decks for flatness with a straight edge.

The thinnest feeler gauge I have is 0.04mm and that would not fit under anywhere.

The same for the main bearings with the old shells.....

.... and without the shells.

Moving on to measure the crank pins and main bearings.

Then finally heading off the the machine shop.

 

[RaceDiagnostics]

Next I went on to measuring the rod bolts and basic bore with and without the old bearings.

The rod bolts all measure within spec which is 8.0mm minimum (original size is 8.4mm), they were all ~>8.3mm.

The rod measurements were taken with and without the bearing shells. Using the basic bore sizes and thickness of new bearing shells I can also predict the likely sized when new shells are fitted.

These are the crankshaft measurements for the main bearings and crankpin bearings. Again, using the basic bore sizes and thickness of new bearing shells I can also predict the likely sized when new shells are fitted.

Now using the measurements of the crankshaft main bearings and crankpin bearings I can calculate the clearance with the old bearings and what it will likely be with the new bearings.

As the crankpins measured up ok I went ahead and ordered new standard size big end bearings today, I already bought a set of main bearings some time ago.

Next I will start working on the heads.

 

[RaceDiagnostics]

I started off today removing the old piston rings and checking the wrist pin clearances.

Good news, all the wrist pins were in spec.

As were the rod bush and piston bushes.

Next I started cleaning the cam shaft bearings and the pistons in a degreaser, they cleaned up fairly easily, despite being cleaned in a cold solution at about 6 decC, the weather turned colder today.

Next I measured all the cam towers....

...and the cam shaft journals.

Now the bad news.

The cam bearing clearance are out of spec, the left (from the front of car) bank just over, the right bank worse. New bearing sets are NLA from MB and ~600 a side at places that still have stock.

Well that is a pita, I will remeasure tomorrow but don't really expect them to be any different. I will search the web tonight to see what I can find.

To take my mind off this I moved on to stripping the heads, but this valve spring compressor wouldn't fit into the valve springs so will pick up a conventional one tomorrow.

 

[Bullet2012]

Loving this, hope you are enjoying the process as much as I am reading all about your journey.

 

[Rannsachair]

I started off today removing the old piston rings and checking the wrist pin clearances.

Good news, all the wrist pins were in spec.

As were the rod bush and piston bushes.

Next I started cleaning the cam shaft bearings and the pistons in a degreaser, they cleaned up fairly easily, despite being cleaned in a cold solution at about 6 decC, the weather turned colder today.

Next I measured all the cam towers....

...and the cam shaft journals.

Now the bad news.

The cam bearing clearance are out of spec, the left (from the front of car) bank just over, the right bank worse. New bearing sets are NLA from MB and ~600 a side at places that still have stock.

Well that is a pita, I will remeasure tomorrow but don't really expect them to be any different. I will search the web tonight to see what I can find.

To take my mind off this I moved on to stripping the heads, but this valve spring compressor wouldn't fit into the valve springs so will pick up a conventional one tomorrow.

Good news the journals are ok, pity new bushes are not available though.

Do you have an American workshop manual? I had forgotten they called gudgeon pins wrist pins