top end engine rebuild questions

[aljohnso]

Hi,

my landy developed a severe smoking problem from the oil filler pipe and with the new regulations it was no longer allowed in the pub.

I have now removed the cylinder head on the way to replacing the rings etc.

I have a couple of questions if anyone has the answers I would be very happy

The head looks good, there is a moderate build up on it which is more white coloured in the outside cylinders than the centre ones (centre ones are quite black)

The cylinder bores are nice and smooth - no scratches but the middle 2 pistons seem to be slightly loose in the bores (pushing the top side to side with my finger)

My guess is that the rings are siezed/worn/broken on the middle 2 pistons.

I will clean up the head and remove the pistons next.

• How do I measure the cylinder bores accurately in order to decide the size of the rings I should get?
  
• I read something mentioning 'cord' rings, do they exist, are they better, where do I get them?
  
• Are the rings ok to fit to the existing pistons or should I get new pistons with oversize rings already fitted?
  

[Gareth Dickens]

Correct answer.

Use a cylinder bore gauge. Measure at least at 3 depths in cylinder. Take at least 2 measurements at each depth at 90 deg to each other. Work out taper of the bore and ovality.

Measure pistons - same method.

Work out piston taper and ovality.

Work out clearance between piston and bore.

Quick check.

Can you feel a groove or ridge - top of ring travel.

No - hone sleeves and put new rings

Yes - rebore -new pistons and rings

Don't know about cord rings

If your pistons are not worn ( do visual inspection and measure)- Just replace the rings. Do not use oversize rings. As far as I know oversize rings go with oversize pistons. Match your rings to your pistons.

[aljohnso]

yes I can feel a groove, can I not use the hone to break that groove and then fit slightly larger rings? The groove is quite small but I can feel one.

Rebore means taking the engine out and I don't have the kit to do that unfortunately

Al.

[Tonk]

oversize rings are fitted to oversize pistons which requires a rebore

[Gareth Dickens]

yes I can feel a groove, can I not use the hone to break that groove and then fit slightly larger rings? The groove is quite small but I can feel one.

Rebore means taking the engine out and I don't have the kit to do that unfortunately

Al.

Strip the engine as far as posible inside the vehicle. Remove sump. Loosen conrod bolts. Take pistons out. Take off inlet and exhaust manifold. Now youre left with only the block attached to the bellhousing. Loosen the bellhousing bolts. Loosen the engine mounts and you and a mate pull the block out. Offer him beers.(this greatly improves willingness to help)

To make this job easier you could remove fenders (you guys call em wings) and/or the radiator and grill.

Building it back in situ will be a battle of note, so I suggest you beg, borrow, or steal the engine hoist equipment you need from a buddy.

If you feel a ridge it is worn (cylinder). You can hone it and measure it. Check if it is worn. If not put same size rings back - check stamped number on piston. If it is worn -rebore new piston and rings. To hone you are doing half of the big work allready. Your pistons need to come out. Once youve stripped it down you may as well change your main and big end bearings.

[Hybrid_From_Hell]

aljohnso

Fill in your profile and location - it might help you via kind and helpfull members here

Nige

[jwriyadh]

When you get the pistons out remove the top rings. If you feel carefully they will most likely have a lip where they have worn against the piston. Note that.

Beg, borrow or steal some standard rings, with a ring inserted in the piston ringslot measure the ring clearance, compare to the workshop manual. The pistons will be worn, do not re-ring them, rebore and new pistons are most likely required.

jw

[aljohnso]

Hi all,

thanks for the excellent information.

I finally got round to dropping the sump and removing the pistons.

Looks like I may have got lucky, the rings in 4th cylinder are broken, the top is broken in about 5 places and the lower in 1. My feeling is this probably explains the blow past. In an extra stroke of luck, the cylinder bore is unscathed

The cylinders do have a SLIGHT ridge at the top but as it's slight I think I'll try and hone the cylinders a bit then put standard rings on again (and replace the big end bearings which were a bit worn)

Happilly all is standard size (I presume that's what STD means printed on there)

At the end of the day now I've done it once I can get the head and pistons out in a couple of hours so if it doesn't work it's not much lost.

Thanks for the info on removing the block above, I'll have to do that if this doesn't work

I'll let you know if it fixes it

Al.

[aljohnso]

Just to let you know,

I honed the cylinders, put on new standard sized rings, put new big end bearings on and refitted the tarted up cylinder head and the engine no longer smokes out of the oil filler tube, goes a lot better and seems to use less fuel. I fitted an overdrive at the same time (wish I had bought one years ago). That was a busy Saturday ;-)

Took it out for a drive on Sunday and all was well - well almost

I have noticed however that the oil pressure light comes on sometimes at idle when the engine is hot. I think I have caused this by using a mix of 15/40 and 10/40 oil instead of my normal 20/50. I'll drain it and bung some 20/50 in instead and hope the problem goes away. Now I know it's working ok I'll buy it some oil

thanks for all the helpful advice

al.