Cutting a recess around an engine bore - is this a difficult project?

tapkaJohnD · Dec 9, 2021

Late production Triumph six cylinder engines had a recess machined into the block face around each bore, that took a raised ridge on the cylinder head gasket. This improved the seal of the gasket.

Triumph owners seeking raised performenace and higher compression may wish to "deck" the block, which would remove the recess. The recess is about 40thou deep. It is often said that recutting the recess is impossible, or very difficult. Is this in fact true?

I'm no machinist, but I imagine that any shop that can rebore cylinders could set that machne to cut the recess. I'll be grateful for opinions or explanations for experienced machinists!

Thanks,
John

Cyclotronguy · Dec 9, 2021

It was pretty common "in the day" to add a groove at the top of a bore to take annealed copper wire. A pretty simple job with a boring tool in a horiz jig bore (vee layout engines) An inline block would be pretty easy on a verticle mill if the mill is robust enough

You'd want t fixture off the main bearing boss's, but you'd do that anyway when you deck the block. That said I don't think a B'port sized knee mill is going to be up to the task.

Milland · Dec 9, 2021

Sealing groove cutting can also be done by hand with the appropriate tool. Basically, it's a close-fitting plug of hard plastic or lubed metal that acts as a pilot, a handle of some length attached to the plug to act as a turning lever, and a small cutter, much like a grooving lathe bit that either mounts to the turning lever outboard of the plug, or in its own separate carrier.

The grooving tool is set such that the radius from center of the plug is appropriate to the groove size, and projects downwards so when the plug and handle sit flush to the top of the block, the groove is at the correct depth.

The operator has to use some care, as only a slight bit of pressure is used for each rotation to cut a small chip. It might take 10 minutes to do one groove depending on depth and width of the channel. But otherwise it's a straight forward process.

Engineshop · Dec 9, 2021

Any decent automotive machine shop should be able to easily do it for you on their boring machine. I just finished cutting 6 sleeve counterbores on a 6 cylinder tractor engine that is an almost identical process.

Is is it a TR6 ?

CarbideBob · Dec 9, 2021

Normal block boring machines do not do this well.
It is not a hard to do the cut with a trepanning tool if circular as in the above "oring" head cut if the right machine but one needs the tooling.
Not sure that decking this a great idea to higher compression ratio. In fact to me it seems like a very bad idea with a very, very small if anything gain.
Yes you reduce the squish area but that is not always good and rods/cranks stretch with RPM.
I do not know this motor and design so a lot of talking out of my ass here ... internet...
Bob

jim rozen · Dec 9, 2021

Would annealed copper seal between cast iron barrels and aluminum heads?

David_M · Dec 9, 2021

Cyclotronguy said:
It was pretty common "in the day" to add a groove at the top of a bore to take annealed copper wire.

Another way is to use coated (or uncoated) gas-filled metal O-rings. Wills Ring - Wikipedia

Offys still had the best method for a good seal.

JohnEvans · Dec 9, 2021

David_M said:
Offys still had the best method for a good seal.

Yeah but valve jobs were a bit of a pain !

David_M · Dec 9, 2021

JohnEvans said:
Yeah but valve jobs were a bit of a pain !

That's true.

GregSY · Dec 9, 2021

O-ringing blocks used to be common practice with racing engines, using copper wire as the o-ring. This has fallen out of vogue as gasket technology has improved. I'm guessing most shops did this operation using a hand-held tool....I doubt many bothered setting up a machine to do it. Someplace I have a pic or two of the o-ringing tool....looks a lot like a 2-sided drill press quill handle...one ball/handle for each hand and a cutter.

Ah, yes, I remember now...the ISKY GROOV-Matic.

David_M · Dec 9, 2021

GregSY said:
...the ISKY GROOV-Matic.View attachment 336563

Ed is alive and 100 years old. Who remembers his 8-cycle camshafts?

Milland · Dec 9, 2021

GregSY said:
O-ringing blocks used to be common practice with racing engines, using copper wire as the o-ring. This has fallen out of vogue as gasket technology has improved. I'm guessing most shops did this operation using a hand-held tool....I doubt many bothered setting up a machine to do it. Someplace I have a pic or two of the o-ringing tool....looks a lot like a 2-sided drill press quill handle...one ball/handle for each hand and a cutter.

Ah, yes, I remember now...the ISKY GROOV-Matic.View attachment 336563

I mentioned that option in #3

cg285 · Dec 10, 2021

my grandfather showed me, in the early 70's, cutters he made to do that. they were piloted (bore specific) with several cutters held in with set screws. the cutters were turned by hand until they bottomed out on the deck

Hobby Shop · Dec 10, 2021

If that block is less than 18” high, you could have all 6 cylinders finished in 45min-1hr on K&T 2D.

slowmotion · Dec 10, 2021

I do a lot of them, and it's .025" deep.

Triumph TR6, milling head gasket counterbores in RMC V40 - YouTube

standardparts · Dec 10, 2021

GregSY said:
O-ringing blocks used to be common practice with racing engines, using copper wire as the o-ring. This has fallen out of vogue as gasket technology has improved. I'm guessing most shops did this operation using a hand-held tool....I doubt many bothered setting up a machine to do it. Someplace I have a pic or two of the o-ringing tool....looks a lot like a 2-sided drill press quill handle...one ball/handle for each hand and a cutter.

Ah, yes, I remember now...the ISKY GROOV-Matic.View attachment 336563

The Isky tool is still sold and o ringing block drag race blocks, especially aluminum is still done. Old school used to be copper wire cut to length but now there are one piece rings.

Lots of vids on youtube demonstrating the ISKY tool.

deltap · Dec 10, 2021

I did this once on an inline 4 diesel that I could not get a head gasket for. I made a gasket from sheet copper and sealed it with ss wire. I cut the grooves on a BP mill with hand ground treapaning tool. Wish I had known about the the kit.

Engineshop · Dec 10, 2021

CarbideBob said:
Normal block boring machines do not do this well.

Not sure why you would say that Bob ? My boring machine will do it quite easily and it is a very common operation on a lot of diesel and industrial engines.

1yesca · Dec 10, 2021

Engineshop said:
Not sure why you would say that Bob ? My boring machine will do it quite easily and it is a very common operation on a lot of diesel and industrial engines.

yup like lots of 6.0 fords

slowmotion · Dec 10, 2021

More to the OP's point, the more common method of increasing the CR on a TR6 is to deck the head. I've taken as much as .125".

Cutting a recess around an engine bore - is this a difficult project?

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