Thread: cylinder hone and new rings 3.9

I've been told by a few landy mechanics that the RV8 bores normally show very little wear even at high miles and same with the rings. It's more so the cam/lifters and chain that should be replaced around the 160k which is poor. I wonder why?

as an aircraft engineer and fixer of engines here and there,
if you take the pistons out of the cylinders, chuck the rings.

but if you also hone the bores, chuck the rings.

the rings are a vital part of the engine,
in a worn engine, if you think it necessary to hone the bores, then the rings are also worn.

if the honing restores the bore to new condition, which it should, if done properly,
[but motor car repairers have different standards to aircraft engine rebuilders]
you need to measure the finished bore size and then decide which oversize rings are required.

Honing a bore is quite technical to get it right. Firstly you need to achieve a cross hatch finish which is to say the hone marks are to progress from top to bottom in a diagonal pattern not round and round the hone should spin 1.5 to 2 times each time it goes from top to bottom and the remaining patern should leave a cross hatch ie lines crossing the one going down at 45 degrees to 60 degrees coming up again 1.5 to 2 turns coming back up. So if you have a drill spinning at 100 revolutions per minute you have to move the drill up and down 50 times in that minute to achieve the desired effect.
Now during the honing process you need to lubricate the stone sufficiently enough to remove the metal and stone particals as you go to prevent the stones from becoming clogged. Using kerosene is about the best for this process it flushes the particals as you go so you need a spray bottle with it in and either you or assistant constantly spray the bore whilst you move the drill up and down. With me so far now i forgot to mention if you are to do this in an engine with the cranksaft still installed or still in the car you need to cover the crank to prevent the debris from collecting around the main bearing journals or worse entering the oil gallery for the connecting rod. So once you have achieved all of this and the bore is nicelly finished you may find a lip area at the top of the bore this needs to be removed as you can break the rings during installation over this ridge. A tool called a ridge remover is required and must only be rotated in a right hand direction to prevent damaging the cutting edge of the tool. Start very slowly with only the lightest of pressure on the tool against the bore too much and it will jump amd bite causing corrasgations around the upper lip. Remove only enough to clean up the top edge above the upper ring land as i said before if this edge is left and the old pistons were worn the rings would not be going right to the highest point any more this is what causes the uneven wear. This ridge will break the piston ring when new piston and rings first go up and hit the ridge if you see what i meen.
Now having removed the ridge and honed the bore you need to flush out all remaining stone and metal from the bores by washing them then drying with clean rags until no more grey metallic particles are left on the rag. Do all cylinders the same remembering to only remove enough to remove the glaze off the cylinder wall and have a clean cross hatch finish. Put new pistons on rings not old ones they are worn out and should not be reused. The pistons can be providing there is no wear in the ring grooves, after reassembly and running the engine for a good 15 minutes checking for oil leaks and pressure etc you can go and run in the motor first don't over rev the engine let it start slowly and keep an eye on temp/ oil pressure then get into top gear run up to 80 and hold for 5 minutes back down to 50 for 5 min etc till you have done a half dozen times and if pressures and temp are good and there are no leaks all should be good Take it easy for the first 500kms. Hope this helps and i was not too long winded but after 40 years i find if people take the time to do it right the first time they don't have to come back and do it again. Never use silicone in an engine repair as it can extrude into the sump pan area and end up in the oil pickup system or worse block filter or galleries ending in disaster. Loctite or Hylomar are good products also Aviation gasket cement only use the soft finish one. Hope this helped. Frank

I was quoted around $200 to get the block honed at an engine repairer shop that had a special machine to get the job done perfect. Might be worth it?

Yes it would as long as the finish is correct and then ensure you clean the bores thoroughly much easier and more professional job doing it that way.

Originally Posted by Gippslander

Yes it would as long as the finish is correct and then ensure you clean the bores thoroughly much easier and more professional job doing it that way.

Most important of all is to fit the NEW rings into their prospective bores and check the ring gap, if the gap exceeds specs. (usually 19/20 thou. max.) get oversize rings, if you can't get oversize rings that will give you the correct ring gap, then it's time for an overbore to the next size up piston and ring setup. So before you do any honing check that the amount of bore removed will not exceed the size of the rings you are going to fit.
If there is a lip at the top of the bore it should be removed before honing as it will bugger the hone stones, might be ok with a ball type hone but they are ridiculously expensive. I would suggest that if you have a lip at the top of the bore that you can catch your fingernail on, it would be wise to purchase next oversize pistons and rings and have engine bored to suit, Regards Frank.
PS When running in engine use mineral oil, not synthetic for the first 1500klms or more and again after 1500klm oil change, never let the engine idle for long periods the engine needs to be driven with the revs up to help the combustion gasses force the rings to conform to the new bore, low speed and idling doesn't apply enough pressure to seat the rings properly. Next oil change you can use Synthetic, if you wish, as they say, drive it like you stole it.

Frank, why not synthetic for the first oil fill?

I would never hone an engine in situ with crank etc still in place. Not that I have done that sort of work, but from what I know, clean, clean, clean is 100% important. Small bits of bore and hone stone would not be good in the engine.....

Originally Posted by uninformed

Frank, why not synthetic for the first oil fill?

I would never hone an engine in situ with crank etc still in place. Not that I have done that sort of work, but from what I know, clean, clean, clean is 100% important. Small bits of bore and hone stone would not be good in the engine.....

Uni- my thoughts on this came about when I purchased a 2003 BA Falcon GT, which comes from the FPV factory with Castrol Formula R (now called Edge, I beleive) 0W-40 Synthetic. I run the engine in according to FPV, even though it was contrary to what I thought was the right way. Anyway I was using 1lt. of oil/1000klms. so Ford setup an oil watch regime up to 15,000klms and it was still using 600ml/1000klms.
So Ford removed and replaced the old engine and crushed it and fitted a brand new (same #) engine, which they had tested on an engine dyno and using Mineral oil. So the theory is that the 0W-40 Synthetic was not compatible with running the engine in by the usual method, so they give it a good thrash on the dyno first. They then told me to give it a good workout which I did at the Free FPV driver training course at Oran Park. At 5K on the new motor, the mineral oil was changed back to the Synthetic and oil usage was normal.
To me it seemed the Synthetic oil was too good at it's job and wouldn't allow the rings to bed in and that the mineral would.
But I may be totally wrong, someone like Rick130 (a recognised Guru on all matters OIL) would have a better more accurate explanation. I have always believed that an engine needs to produce high combustion pressures to properly seat/shape the rings to the bore for good power/compression/oil control and that doesn't happen at idle or low cruising speeds, IMHO, Regards Frank.