Cylinder hone

[Colin Wilks]

It's about 45 years since I last de-glazed a cylinder bore and I suspect the technology has moved on a bit in the interim. I have been recommended a "bobble hone", which has carbide blobs on the end of flexible arms, like an industrial strength bottle brush.

I have found these in the UK -  https://www.pacehigh.co.uk/bc-style-flex-hone

How do others achieve the ideal 45° cross hatch in their cylinders, and if you use a bobble hone, what grit do you use?

My engine was rebuilt professionally around ten years but less than 1000 miles ago, and I am fairly sure the PO allowed the bores to glaze by leaving it ticking over. Compressions are all fairly even at around 95psi, but it smokes and burns oil. I have it apart as I'm having to replace the camshaft bush bolt, so it's not much more effort to take the pistons out "whilst I'm in there".

Hope this finds everyone, safe, healthy and not climbing the walls.

Colin

[Stuart Giles]

The 45 degree cross hatching you've seen comes from using a Delapena style rigid hone after the cylinder has been bored; not really something either needed or easily reproduced in a home workshop. The ball hones work well though and are massively quicker than using one of the three legged spring loaded devices to do the job. 

I use 180 grit Flex-Hones (their trade name) on cylinder bores.  It might be worth checking out how much the one you'd need for an A7 block -the 2 1/4" size- would cost shipped from the USA; the prices from the UK supplier were utterly usurious last time I checked. 

Pretty well all of my Flex-Hones came from this ebay seller https://www.ebay.co.uk/itm/2-1-4-Engine-Cylinder-FlexHone-Flex-Hone-Hone-180-grit/352839388050?epid=1029632980&hash=item5226ddcb92:g:9loAAMXQBwlRW9P~  the postage works out cheaper if you are buying several sizes/units at the same time. Usual disclaimer, only a customer etc. applies

[Colin Wilks]

Thanks for that Stuart. I've asked Pacehigh for a quote on a 57mm 180 grit job, so it seems I guessed the grit correctly. The postage from the US Ebay sellers certainly put me off. I'll see what Pacehigh come back with. The bobble hone definitely seems the way to go though.

[Bob Culver]

The spring loaded ones are fine and frequently appear second hand very cheap as so little use now. Produce the cross hatch pattern. Their shortcoming is that ride on any ridge at top or bottom of cyl and any waves.  And care required not to damage the stones. For cast iron rings honing was not considered essential but oils have changed. Differences in oil consumption can be very elusive to explain.
Quite a few older workshop manuals describe simple use of very fine abrasive paper.
Go easy You can quickly replicate 20,000 miles of wear, 100,000 in the lower cylinder.

[Colin Wilks]

I remember using the three stone jobs. Speed of drill and the up and down movement seemed pretty important (obviously when you think about it), but I think the bobble hones are probably more idiot proof, which is always a consideration, with me at least.

[Zetomagneto]

For the the relatively small cost I would take it to you local engine reconditioner, only 
needs a quick glaze bust by the sound of it

[A G Wood]

For the the relatively small cost I would take it to you local engine reconditioner, only 
needs a quick glaze bust by the sound of it

This, if you can manage it.
The flex hone [bobble hone] is meant to be a glaze buster, and as such does a good job on pre-used bores. Also there's no damage to the hone or anything else if you overshoot.
Spring loaded rigid stones tend to miss bits as BC points out.

[Colin Wilks]

Pricing up the Flex-Hone gives nearly £60 from UK and not much less than that from USA (once import duty is added to eBay price and delivery). 
I have decided that in the first instance I shall lift the block off the pistons and have a go at the bores with some wet & dry paper. With a light behind I should be able to see the effect and costing my time @ say £10/hr I can afford to spend a pleasant hour on each cylinder and still come away with a profit! 
No 1 cylinder was oiling up in stop start traffic so the rings will come out to check gaps and orientation. My guru advises .005" gap is good (.0015" per inch of bore plus a bit for luck), so if they're less than .010" I shall probably leave well alone. 
I was tempted to put it all back together and thrash it for a couple of thousand miles, but checking things out feels better to me, so I shall probably end up taking the engine out so I can re-install the block onto the pistons without the potential agony of breaking the last ring in if I do it in situ.

[Zetomagneto]

Hi Coiln, I have  3 legged spring loaded Draper hone you are welcome to borrow, just pay the postage.
Pm me. Gene