Piston arrow direction

[Brit01]

Thanks for the sound advice guys.

I'm a bit concerned about getting the speed and forward/backwards motion correct to produce good results.

I have a drill with variable speed, I can set it down to almost 1 rpm, but getting a cross hatch of around 45 degrees is my concern. If it's too steep or the opposite I could end up with worse results with the new rings than with the old.

[4v6]

Just find yourself an old block with similar bore size or even a section of correctly sized smooth bore pipe and practice on that to get used to it.

Use engine oil though, don't do it dry at all.
You'll find that you'll need to stroke the tool fairly briskly (at least I did) and it's very easy to produce a perfect finish.
These Flexhone's remove minute amount's of material, they're utterly foolproof.
If I can use one, anyone can!

[Brit01]

Good to know they are foolproof.
Thanks

Yes I was thinking of practicing on some tube first.

Maybe even a fruit tin if I can't find a bore the right size?

Order done from USA.
3 1/2 inch S/C 240 grit.

What size bores can I use this on for practicing, thinking if I can't get a 3 1/2 inch tube?

How much do the nylon strings stretch under the centrifugal force?

[4v6]

Size will be on the packet, all will become clear when you use it.

[Brit01]

shipped already from NY on its way to TX!!! Now that was fast service. blimey!

[WhizzMan]

You can try for half an hour to get the correct pattern and angle without risking honing too much. As long as you keep enough oil on, you won't wear down the bores in that time.

[Brit01]

great good to know as trying to find a spare bore or pipe here will be difficult.

I have a spare 5w/40 synthetic 1 litre bottle hanging around I never used.
This oil should be ok??

Regards

[Guy Croft]

I know Homme (Whizzman) has OK'd 240 grade but I did tell you 180 for chromed top ring.

See also GC Q&A.

G

[Brit01]

Yes my mistake sorry.

Ordered the wrong grade! I have no time now to change it before my colleague comes down. Stuck with the 240 grade.

Multitasking at work! Too much on my plate.

May buy the 180 grit now and sell the 240 here.

[Guy Croft]

You should use the same oil for honing that the engine will be bedded/run-in on, which - if Flexhoned right - only takes about 20minutes.

That oil needs to be a mineral grade 10w40 not a synthetic, though one can bed-in on semi-syn OK. I use Castrol Magantec. If you bed-in a unit with cast-iron bores on a fully syn oil like Mobil 1 it will never bed-in/dry up. You save those for the post bedding-in phase.

With your steel chrome plated/faced rings (I assume they are steel) you might be alright with your 240 grade item.

I reserve 240 for moly coated/faced cast-iron and and race grade PVD chrome ductile-iron top rings.

You will rarely hear me remark on methods that appear to be at variance with my own adopted practice. For my part once I have the top-level info from the experts I talk to about things like this I rarely experiment or deviate because it's too risky with client proprty so I really cannot remark qualitatively on what will happen.

G

[Brit01]

Thanks GC.

Well I ordered the 180 grit also just 30 mins ago.

I'll be breaking in the new cams with a semi 20w/50 and replacing with Motul 6100 semi 15w/50 that I have bought.

Also pasted up the lobes and faces of the tappets with molykote.

Do you recommend draining the oil after the 20 minute break in or after a longer period of driving?

You need to first dress the wear ridge off the tops of the bores or it will hit the new unworn rings, do this by hand with 180 grade abrasive paper & NO other method.

Also you talked about sanding down the edge/ridge of the bores with 180 paper (to enable to slide the rings in without catching on the edge).

What angle and how much needs taking off? Do you happen to have a close up photo as an example?

Regards

[Guy Croft]

Not quite on the right lines there.

1. The tops of the bores should always have a light chamfer typ 0.3mm x 30 to allow the rings to go into the bores. They may already have this from the factory. On a sharp-edged bore it can be achieved using your finger with 120 grade abrasive. An Olympian standard of accuracy is not needed but don't undercut the gasket fire ring.

2. Rings and bores wear together. But because the ring pack is located some distance from the top of the bore there will be an unworn section right at the top of the bore, and there with your fingernail you might feel a small step. This is common on older well-used engines. You need to chamfer that step by hand with 80 & 120 grade prior to honing or it will knock out the new top ring. See dwg below.

The Flexhone will improve the job you have done on both of these but don't rely on it to get rid of either edge in the first instance. Watch out by the way for the balls of the hone scoring the block face - bolt an old gasket down as a protector.
An old hone which has worn to give more intimate contact betw ball and bore works better and quicker than a brand new one. Don't rush the honing even if it says 30 sec on the packet, give each bore a good 'thrashing' - say a minute or more. The dimensional change will be unmeasurable.

RD 'ridge dodger' rings are rarely seen/aval these days; they had a relief in the side to clear a step on a worn bore.

G

[Brit01]

Thanks for the extra info and diagram. That illustrates it perfectly.

My 'XX' piston rings may have the 'RD' on the first ring I believe.
I will check when I get home to confirm.
I think the 'XXX' rings have a special patented coating also.
Not allowed to mention the make of the rings, am I?

[Brit01]

These are the edges of the rings:
Top ring has a flat top and chafered inner edge.

[WhizzMan]

I know Homme (Whizzman) has OK'd 240 grade but I did tell you 180 for chromed top ring.

See also GC Q&A.

G

Oops.. I should have kept my big mouth shut. Will the chrome cut harder in the surface than regular steel? Will this mean a worse end result, or just longer time to bed in?