How did ST assemble engines when they were new

[shuggie159]

I know of all the time and effort we should go to decking the liners before assembly. But how was it done in the factory? And what tolerances did they routinely achieve?

 

I'm wondering.... if and when I eventually put my engine together..... if say I have one liner that is say 2 thou high. Could I reduce the height of that liner but 'milling' that liner, by rubbing it on a sheet of wet and dry on top of a flat bed. Time is not an issue, but is it realistically possible.

[RogerH]

Hi Hugh,

I think the biggest problem in assembling the engine is actually getting accurate measurements.

The bottom of the block where the liner sits may have muck and corrosion going on.

The top of the block may not be as flat as ideal.

And your measuring method may be iffy.

Firstly you could measure the length of each liner to see if they are all the same (from top to the Fo8 sealing flange)

The Fo8 should be uniformly thick

You could use a DTI or depth mic' to measure the protrusion. I prefer a 0.5" diameter silver steel rod that is a good inch longer than the liner diameter.

You can then use feelers under the steel rod. Being a round bar the gap under it is always uniform - unlike a steel rule that can bend/flex.

 

You could get the liners as good as possible and then clamp the head down on it to make sure everything is down as far as possible.

 

If you still have a proud liner then yes you can reduce the height. I have used a lathe and removed the odd thou' from the Fo8 seat.

You could use wet&dry and a flat plate and rub away

Whatever you do you must ensure that the liner faces are square, otherwise you will have odd protrusion readings around its circumference.

 

You do have a 0.002" tolerance to get the height right so is easily do'able.

 

So your question - did ST work to these tolerances - of course they did (but then the price of bacon is going up).

I'm not totally convinced that you have to be spot on to a thou' or two. The head gasket has a serious amount of give in it.

 

But if you can get it as near to the workshop manual numbers then you will be OK.

 

Roger

[ctc77965o]

Not specific to liners or triumphs, but this film has lots of jag engine assembly from back then:

https://youtu.be/lKJPFRNO344

[Motorsport Mickey]

Agree with all Roger has said, however to answer your original question regarding ST original builds they would all have been done exactly as the workshop manual dictates...but they had it easy.

They didn't have 50 plus years of cast blocks being stress relieved with hundreds of thousands of miles use and the constant hot cold cycles of an engine in use causing the block to move and the liner seats to splay out, and the crankshaft mainbearings to be twisted and hammered by the intermittent explosion of the power stoke. The blocks hadn't had their molecular structure distorted by the cylinder head studs lifting the top deck surface which was originally found such a problem in use that the original complete sets of short studs were supplemented by 4 of the interior studs being exchanged for much longer length items which impose their loads much deeper in the block avoiding the problem. The exterior studs didn't have enough block strength to allow the same treatment and retained the short studs.

So do all you can to achieve the measurements quoted on liner heights. Don't think that they are some fictional process without any actual end product, it matters that the liners are all as close to equal to each other (even more important than the liner heights). If different to one another (especially if the interior liners are lower ) they reduce the clamping load upon the gasket around that liner. I always regard that as a possible gasket failure point.

Although the composite gaskets have an amount of give in it which allows variations in liner height to be accommodated, a series of liner heights showing 5.5.3.5. won't allow the cylinder head to clamp the 3 thou liner with the same clamping force, the 5 thou liners to either side of it preventing the cylinder head deforming onto the gasket.

Yes, I know the cylinder head is a 3" thick casting but the head will deform under the clamping load of 105 lb ft being applied through the studs. If the liner height is 2 thou less on the end liners you stand a chance that the gasket seal will be ok because the head will deform (ie bend) because there is no other support beyond the end liner up to the end studs. It's quite common for a head gasket failure to be at the rear behind number 4 cylinder, this cylinder runs hottest (furthest from the water pump) and so it's more likely to become mallable allowing the cylinder deck surface to lift, and as said if a compromise is to be made on liner height you can get away with it for longer on the end liners.

 

If you want to be picky (and I am) you first confirm the crank journals are in line in the block, if not they should be line bored to bring back to parallel. Then the block deck surface is confirmed as being absolutely parallel and square to the crank centre line, if not the block should be skimmed correct. Then the liner shoulder surfaces in the block are confirmed as being the same distance down from the block deck surface and square in both axis, if not they are jig bored square and the same depth. It's also possible the liner spigot diameters below the liner shoulder surfaces will have moved from being vertical but I sacrifice those in favour of a good Figure of 8 seal on the liner shoulders.

After all that you should then be in the same position as the factory was 50+ years ago when all this stuff was new and freshly machined without any stresses screwing up all the running clearances...see I told you they had it easy.

 

Mick Richards

[shuggie159]

I accept all you say about, how to achieve ideal tolerances; and I also can understand how over the course of repeated stress cycles the original components have deformed.

 

Theres two elements to this saga that still 'niggle'.

 

1 Given all we know about the slap-dash assembly process in the body works, why would we think the engine shop was any different?

 

I can't imagine mechanics putting together components out of parts bins, torquing the head up, undoing it, measuring the protrusions, sourcing perhaps slightly under/over size liners, re-assembling, torquing up, repeat, repeat. Sending the bits off to the machine shop and trying to reunite all the bits later. Nonsense, I'm sure these engines were thrown together, but they worked, and as we know and love, they worked well.

 

The point is the final product was no doubt able to accept quite wide margins of latitude in the parts tolerances.

 

Not with standing the fact that we are not starting with the same uniformity of parts they did, surely careful measurement and love can reproduce a similar out come to the initial product.

 

I'm not talking about producing a works racer here, (where I'm sure, ST would have pulled out the stops and actually got their feeler gauges and micrometers out of dusty draws). Just a lowly kerb crawler.

 

So on to point 2

 

I don't want to have all the faff of pulling my engine out. (I've done it before, its no great hassle, I know) Problem is that my current garage isn't big enough to allow use of an engine crane, and the slope outside would make the operation interesting to say the least.

 

My proposal was, as said above, to swap the liners over to get the best possible deck height variance and then slowly tinker with the protrusions with abrasive and a true surface. OK depends how good I am with feelers and how deformed the block is. Surely this doesn't need to be rocket science.

 

Worst case scenario, I need a new set of liners and a new head gasket.

 

Best case scenario, I can feel well chuffed that its working (but with a nagging doubt it could have been done better)

 

Thank you Roger, Mike, and Dave.

 

Anybody out there any experience of the DIY options?

[Motorsport Mickey]

I think I've somehow mislead you.

 

These engines are almost ultimately rebuildable without having to resort to taking the engine out and stripping. Your initial question was how was it done at the factory and I can tell you that the engines would have been built using common engineering practices. Those would encompass batch manufacture and measuring and sizing of components. The blocks would have been machined and measured and then the liner sets selected to give the best liner heights within the ranges given.

Their advantage would be as have been outlined above, freshly manufactured components without wear makes it easier than where we are today, however there is no reason why individual liners cannot be "tailored" to suit the engine if requirements regarding dimensions and it's orientation of liner plane needs amending. Indeed I've done it myself where I've damaged individual liners and so there should be no problem proceeding as you've outlined above.

 

Mick Richards

Edited March 28, 2016 by Motorsport Mickey

[ctc77965o]

You see the same in that jag video, they weighed the conrods and created matched sets, they dynamically balanced the crank..you can see the guy taking rough chunks off to get it ballpark right..in general, they knew they had ranges of machining tolerances and they often matched sets of "large end of spec" parts or mid-spec or low-spec rather than randomly assembling based upon the full range of the casting/machining spec.

On Jag V12s there are A and B stamped pistons and liners...engines were built "all A" or "all B", both are nominally same bore size, but the A are the large half of the spec range and the B are the small half of the spec. In doing so they've minimised the risk of a large end-of-spec piston in a small end-of-spec bore and vice versa...instead of setting ultra-tight machining specs which could slow production and lower yields.

Edited March 26, 2016 by ctc77965o

[AlanT]

Do NOT try to remove 2 thou from a liner by rubbing on abrasive.

 

If you were used to doing this, and had a granite surface plate, you might do it.

But it will take ages. Half a thou is as much as I'd try to remove doing this.

 

It takes quite a while to polish half a thou of a shaft rotating at 1000 rpm.

[shuggie159]

The Jag video is very informative. I don't think I was giving the old engineers enough credit.

 

If I can get any of the old liners out without completely destroying them, I'll try and select the best one to experiment with.

 

I have an old surface plate to which I can stick down wet and dry (120, 400 ???). I rather suspect that the material will abrade away easier than one might expect. Constantly turning the cylinder you are working across the width, which allows the minute parts to escape without being trapped in the abrasive matrix. I have previously dressed the base of CI planes etc and the material seems to dress quite easily. Perhaps the cylinder material is much tougher, we'll see. My gut feeling is we're talking hours not days. But (hopefully) time I have a plenty.

 

I start work very slowly. Lots of planning and worrying. Then a period of frenetic activity that usually works out much better than imagined. But I like to think it is the extent of the worrying the causes most of the outcomes to be successful.

 

Cheers Guys. Its great to have such a wealth of knowledge to bounce ideas off of.

[RogerH]

Hi Hugh,

if you need any machining you know where I am.

 

Roger

[AlanT]

Find someone with a surface grinder.

[Motorsport Mickey]

Not specific to liners or triumphs, but this film has lots of jag engine assembly from back then:

https://youtu.be/lKJPFRNO344

 

Yep, can't go wrong when you have an engine built by men in brown coats, although I was amused at 10:51 in the film when the commentator says " the conrods are selected to be within 2 drams of one another" presumably those would be engines to be used in the Scottish market ? lol.

 

Mick Richards

[Alec Pringle]

 

possibly confusing for USA viewers, as I don't think they use the dram - 1/16 ounce or 1.77 grams - but only their own version of the fluid dram, 1/8 fluid ounce ?

 

Enlightening that the conrods are to be within 3.5gms of each other by factory spec . . . . . .

 

Cheers

 

Alec

[Guest ntc]

Think you will find the liners was pressed in and then checked.

[mike3md]

So, if on checking they weren't within tolerance, they pulled them out and tried again?

 

I wonder......

 

Mike

[Motorsport Mickey]

This isn't a bad paint finish on a panel or an out of view component that doesn't matter, on a crucial dimension which can cause critical failure in use such as liner height protrusion I wouldn't be surprised if they were Batch checked and adjusted, only way to establish that cylinder head gasket clamping forces are correct and equal.

I'd expect the liners on a set number of engines per shift were checked on a Go-No go DTI set up, takes about 5 secs a bore, and replacement of new liners in a newly machined block could be done in less than 2 minutes, 4 hydraulic pullers in unision only take seconds to attach and operate, and there's no 50 years of **** and corrosion in place here to prevent their easy removal.

Also because it was all new engine blocks and liners produced in batch engineering I wouldn't expect there to be many failures of sorted and graded sets of liners to match the blocks so I wouldn't expect there to be unreasonable numbers of units having to be reworked.

 

Where's Dave Gleed when you need him ?

 

Mick Richards

Edited March 27, 2016 by Motorsport Mickey

[Guest ntc]

Hi Mick

You are right, as told to me by a Triumph Quality inspector on the line tr2/3 ,sadly no longer with us lived in the end, the South of France next door to my brother in law.

[oldtuckunder]

 

1 Given all we know about the slap-dash assembly process in the body works, why would we think the engine shop was any different?

 

 

Whilst we sometimes tink these old engines were thrown together just lokk at the attached pic of the flywheel from my Vitesse, note the number forged in the head of the bolt and the number stamped in the flywheel, this demostrates that even in production the flywheel, clutch cover and even the bolt postions were quite carefully balanced. The later cover plate stampings to match the flywheel are from my balancers ensuring that the cover plate goes on in correct orientation.

 

But suffice to say that they did take care assembling these engines originally.

 

Alan

 

[Ian Vincent]

Just a thought following on from all the discussion about liner protrusion, what should the measurements be when you lift head to say fix a blown head gasket?

 

Assuming you aren't going to disturb the liners, the figure of eight gaskets will have been crushed into place by the head bolts (copper or aluminium, they will both have deformed permanently beyond their elastic limit), so how much should the liners protrude?

 

Rgds Ian

[RogerH]

Hi Ian,

I may be wrong here but this is my take on things.

many head gaskets are changed throughout the fleet of TR's and the liners and Fo8's are never removed and reset.

Upon original fitment the torquing of the head, heat of the engine and time allow the liners to sit into the Fo8 as far as they cam possibly go.

 

If/when you remove the head the liner may spring up the odd gnats but will not become unsealed.

 

If you measure this protrusion it will not be the same as when fitted.

 

When the head is refitted the gasket (assuming a composite gasket) will deform uniformly and apply pressure to where it is needed.

 

So the original 3- 5 thou is there for the unsealed Fo8's etc. After the head gasket does its job.

 

Roger

[Motorsport Mickey]

As per the workshop manual, between 3 and 5 thou.

 

In my experience (sometimes rebuilding the same race engines yearly) the FO8 gaskets compress less than 3/5ths of bugger all. If the liner height is less than the 3-5 stipulation clamping force on the gasket is likely insufficient and head gasket problems will likely follow.

All the figure of 8 gaskets do is provide an initial seal, when fitted with Wellseal and after a year or two of running the bottom end is normally sealed watertight, (that's why it's important to fit liner retaining washers torqued to about 40 lb ft ,not critical, to avoid the FO8 liner seal being disturbed).

The problem with stripping a running engine that only shows say a 2 thou liner height is we all think that because it's running ok we'd rather not touch it because of the following work required to reseat the liners with correct liner heights. As said before a set of 5.5.3.5 liner heights can be problematical for sealing, although within the workshop stipulation range, the 3 thou liner height not receiving the same clamping force as those either side of it.

I pay great attention to making all the liner heights the same whether set at 3. 4. or 5 thou height and ensure the liners are correctly pulled down, retained and measured again before the cylinder head is fitted. Obviously only the final fitment has Wellseal added to the FO8 gaskets.

 

Mick Richards