Modifying a 99 barrel to 650ss spec

Hi Ian,

Once I was young and knew no better. I bought a spigotted barrel (early) for my Navigator and machined the spigot off so that I could fit it onto my spigotless (later) Navigator engine.

Now the pistons seemed to be too high!! They protruded from the top of the new cylinders by the height of the removed spigot !!! And hit the head at the outer piston edges !!

Still being young and now only slightly wiser, I rounded the top edges of the pistons with a bastard file so they didn't hit the head. Bodged the head steady because my engine was now 2mm less high. Ignored the fact the compression ratio was greatly increased. Found enough adjustment for the (now) 2mm too long pushrods. And flogged it.

This from the same Plumstead factory you are dealing with. So please be careful the same spigoted/spigotless story is not repeated.

Peter

Why even consider relining? Bore/hone  your barrel to plus .060"   RGM list pistons at £195 plus vat.  Relining is done when you have a worn plus .060 barrel.
Your crank/conrods should be ok as you say they are unmarked (conrods clear of the barrels skirt)
So why the concern about why 'the barrels need to be heavily modified'   

The DSNs are correct re. the advice on converting a 99 or even later 77 barrel for use in a 650.
It is not just a case of chopping a few chunks out of the sides of the bores/liners.
The photo depicts a 22709 barrel casting which would have the narrow pushrod tunnels suitable only really for non-SS pushrods. Sometimes these tunnels do have enough room machined in them (by accident) to take the fatter SS pushrods but most of the time this does not happen. The  SS pushrods then catch on the tunnel lip and rubbing against each other.You really need the  22710 casting made for 650SS engines in late1961.  These had the front exterior of the pushrod tunnels extended forward by around1/8th inch and the tunnel bores more accurately machined.

A couple of points regarding boring out the barrel to +60". (or even 80" was available at one time.) This tends to make the spigots very thin and prone to breaking and not only at the top of the liner but also at the bottom. Again the photographs show the bottom of the bores are not central in the cylinders. A rebore exaggerates this problem.
If a rebore is chosen, then do have the spigots machined off. With standard pistons fitted, the tops will nearly be level with the top barrel flange and the spigot gap in the head will accept any protrusion.
As an extra safety point, just in case the pushrods run out of adjustment, it is possible to purchase solid copper head gaskets in several different thicknesses.

Do not machine the spigots off, or at least not until the machinist or whoever measures your barrel and assess it for spigot thickness. Looking at your photo in your previous posting the spigot will be ok even when bored to plus 60. Measure the spigot thickness with a set of verniers and report back.  What stroke is your crankshaft? if it is 82mm it is a 600 crank, 89mm for a 650  Find out what you have got before deciding on the course of action. Have your pushrods been binding in the pushrod tunnels? if not, no action needed there. The conrods haven't been touching the barrels skirts so no action/machining needed there either. 

Ok, confirm your barrel is at plus .040 (measure at the btm or top of the bore with your vernier should give you an idea of its current size, even if it is not as accurate as i would prefer) At plus 40 it most likely has been rebored twice, maybe three times before, depending on what oversize pistons were available back then. Now in the past when the cylinder has been set up on the boring machine and depending on how skillfull/diligent the machinist was in setting up and aligning the machine has caused the spigot error to manifest itself.   If i was boring this cylinder i would set the machine to take as little from the 'thin spigot wall side' as possible along with boring the cylinder to the correct size. A good engine shop should be able to do this, if not look elsewhere. If your cylinder will accept a .060 plus rebore be aware it is just .010" per side so even if the cylinder is set up central, your spigot thickness at the thinnest is down to .045 to .049, still plenty strong enough, now if your engine shop will correct the error (as much as it can) that has crept in over the years, It might keep the spigot thickness to .050  - .055 at its thinnest. It all depends on how worn the bore is and who you get to do the job.    

Photo IMG 2957 - Is that SS stamped on the top of the barrel face at the rear???
That would explain the oval shaped pushrod tunnels. Generally the aperture is a figure of 8 shape.
 

No, its BB seen in  IMG 2948

You know that when you remove the spigot there is an alloy insert available to fit into the spigot recess in the cylinder head to maintain the compression ratio?

I was going to suggest HT Howard in Slough for the job, but a quick Google failed to turn up any active website, and another search facility (Cylex) shows the following message:

"H.T Howard & Co.ltd; Unit 15, The Business Village, Wexham Road, WEXHAM, Slough, Berkshire England, SL2 5HF

*Business is reported as closed."

Does anybody have any further info on them, as I had my ES400 crank and barrels attended to by them 3 or 4 years ago, and I was very happy with them.

Edit:
Just found the following on Facebook (whatever that is)
" 2/10/2022  HT Howard - Engine machining specialists

Unfortunately due to economical situation worldwide we have sadly to announce that we have to close our doors after over 75 years trading. We like to thank all our customers over the years and decades for your custom. We wish you all the best!

Your HT Howard Team"

Oh dear.

Have you had the bore measured? .. Its possible that a hone and a new or used  set of pistons with new rings will work . Has done on our Atlas for the last 15 years.

Heyup Kit - from my experience I don't recommend a +060 thou rebore for a 650.  The 600 is more docile and will be OK.  So show us an image of the crankcase /crankshaft down from above. The 650 barrel has a habit of cracking around the bore,  level where the bottom of the head to barrel bolt holes end.   Those pistons are about 9.5:1 compression and standard compression will be about 8.9:1 using flat topped varieties.  Later 650 barrels without the spigot should be satisfactory with your cylinder head pre-downdraught or big fin, big valve type but only use the Hallite or Klingerite head gasket from a reputable supplier and ensure the head base is flat.   As Alistair said you can use an insert to fill the spigot recess if you plan to use all the power available. Good luck, howard