The Engine Thread ...

[dasadrew]

This idea has been bumping along at the bottom for a while now - a thread where real hardcore engine technical bits and pieces can reside and be added to continuously. Oh well, it might work, it might not!

I'm just putting my engine together and am in the position of being able to take specific photos, ask specific questions and post my goofs so that others may not make them .

My engine is a Mk2 Euro and came to me after a history of head gasket failure and being left a couple of years with water in the block.

A few of the bores looked like this

DSC00053 (Custom).JPG







































and, after a lot of measuring and advice from this Forum http://www.stag.org.uk/forum/showthr...ed-some-advice the step was taken to sleeve all of the cylinders and use the original domed standard size pistons.

Both cylinder heads needed a skim, which removed 0.3mm (12 thou) and had the valve seats recut and new guides fitted. Having just now finished rebuilding the heads, the few points I noted were that, due to the recut valve seats being deeper into the head, the tappet shims needed were a lot thinner than he 'normal' sizes of 0.090" plus or minus a bit. To get these shims you need to shop about a bit and be prepared for some sizes not being available. I found the Lotus specialist "QED" to be very well stocked and they provided a hyper-fast service too. James Paddocks also have a good range. Be prepared that the shims which arrive exhibit differences. I had shims without chamfer, with one side chamfered, and with both sides chamfered! All were OK diameter wise.

Second top tip was to not always believe the machine shop. Valve seats cut sir! No sir, you don't need to do anything else to them. Popycock. When I was measuring the combustion chamber volumes with red wine, all was watertight (or winetight!). A little later, I checked them again prior to grinding out some volume with a Dremel and used white spirit. This poured out through a couple of valves and could only be put right by lapping them in with some fine valve grinding paste. Despite the advice from the machine shop, this step should really not be missed!

DSC00534 (Custom).JPG







































Whilst messing about with measuring head volume and adjusting tappets, I had turned the head upside down a few times with a broomstick in place instead of the camshaft to stop everything falling out. Luckily, when I was finished, I decided to double check the shims and pulled out the buckets. At least two of the eight shims had indeed left their place in the upper valve seat! Shock Horror! Won't be doing that again!

[dasadrew]

Talking about camshafts, I had decided to renew the sprockets and, back in those halcyon heady days of my youth, I always associaed a hexagonal disc with a nut. Not so on the Stag! After managing to put gouges into the little button which fits into the camshaft end by gripping said boss in a vice and trying to undo the "nut" with an air wrench, I then discovered that these nuts have no threads, but are fixed with superstrength thread sealer! At least I could salvage the boss (no longer available!) and reassemble - also with Loctite - to the new sprockets.

DSC00557 (Custom).JPG

[dasadrew]

Having an engine with recut valve seats, skimmed heads, skimmed engine deck and protruding pistons, one of my major concerns was the clearance between top and bottom bits of the engine. Having gone through all of the advice in this thread http://www.stag.org.uk/forum/showthr...hickness/page2 I assembled the engine with plastic shims to simulate a 1mm (40 thou) standard head gasket and popped some Plasticene onto the pistons befor turning over the engine very slowly!

This pic shows where the Plasticene needs to be and shows the amount of clearance in the squish zone at the piston's edge and also the indentations where the valves get near to the piston. Although all of the theory about skimmed heads and clearances would have clearly dictated use of thick gaskets, the actual situation is a lot better. Despite skimmed heads and protruding pistons there is enough clearance to run standard gaskets. This Plasticene check is therefore really worth doing especially now that Thick Payens are very rare gaskets.


DSC00561 (Custom).JPG








































DSC00563 (Custom).JPG

[dasadrew]

When fitting the timing chain tensioner for the Right Hand bank, I came across a little bush which came with a NOS set of tensioners from Martin (justriumph) (who also has a website now and who is always good for a few NOS surprises!). This bush wasn't in my original tensioners and features sporadically in the various publications. It appears that it fits into the engine block and protrudes slightly, thus reducing the diameter of the oil passage from the block into the tensioner body via the spacer block. It is similar to the bush installed into the tensioner body itself. If anyone has any info on this, I'd feel a lot happier!

DSC00572 (Custom).JPG

[dasadrew]

Whilst I was doing all of this trial fitting of heads and chains I stumbled across a problem which seemed to be of my own doing. The books mention fitting two dummy studs to aid in fitting the head. I dutifully fitted two studs in the holes where, er, well, the studs would normally go. However, the head won't pull off then past the chain and sprocket without dismantling the sprocket support bracket, due to the angle of the studs. In the Unipart book, it refers to fitting these dummy studs where the two short bolts go! (Maybe it does in the other books and I overlooked it). In any case, when I next go to remove and refit the heads (maybe now for the final time) I'll try out these little fellows which are from cut down old studs. I'm sure Russ (Kryten) would be able to shed light on this if it was an official BL way of fitting heads!

DSC00570 (Custom).JPG

[dasadrew]

At one stage I was getting a bit frustrated as to where all of the guides and bolts go and, being confronted with only some very dark black & white photos, I decided to take some pics whilst mine is bright and shiny duríng the trial fits! Might be of help to someone out there.

DSC00555 (Custom).JPG








































DSC00567 (Custom).JPG







































Incidentally, the manuals say that the front sprocket on the crank should be checked to make sure that it is in the same "plane" as the auxiliary shaft sprocket, and to 'pad' it out as necessary with shims. On my engine, the sprocket was already too far forward even without shims. I even went to the length of swapping thin and thick thrust washers on the crankshaft to move the cankshaft ever so slightly backwards but this did not solve the situation. Finally, I ended up skimming off a bit from the rear face of the crankshaft sprocket. It was only 5 thou or so but restored my confidence that the chain would run true! Maybe the replacement auxiliary shaft or lower sprocket is dimensionally slightly different to the original?

[dasadrew]

With both heads temporarily fixed in position with plastic shims ensuring a 1mm (40 thou) spacing to the block as with standard gaskets, it was time to lower the inlet manifold into position to check its fit.

The inlet manifold also sits in standard form on 1mm thick gaskets, so I placed plastic shims in place and lightly tightened up the manifold to both heads. By then trying to slide another piece of plastic between head and manifold it could quickly be determined if the faces were parallel to one another. In my case, it became obvious straight away that the blue area was standing proud. It was posible to file this off slightly along the edge, and then use a flat surface with wet-or-dry in various grades to get the surface back to being flat, but at the slightly different required angle. A check again with the plastic shims shows that all is parallel and the bolts just drop into their threaded holes in the head without any forcing or bending or elongating of holes. Phew!!

DSC00573 (Custom).JPG








































DSC00574 (Custom).JPG








































DSC00576 (Custom).JPG

[singapore stag]

Very good Drew. I am sure it will be very useful to those rebuilding or comtemplating rebuilding their engine.
Quick question....don't you grease or oil the parts as you fit them along?. Never done anything like this myself just wondering..

Sukh.

[mike@thenook]

Brilliant work Drew and extremely useful!

Cheers

[DJT]

Good stuff Drew. Reference the dummy studs. I have a pair identical to yours that I made when fitting Stag heads for the first time back in '92. I must have got the info from somewhere and it has worked every time since.

[dasadrew]

....Quick question....don't you grease or oil the parts as you fit them along?. Never done anything like this myself just wondering..

Sukh.

Absolutely! I use an Engine Assembly Grease LiquiMoly LM48. I know other people here use Graphogen. They are greases designed to provide initial running protection and then dissolve in the engine oil. The shiny bits seen here are, in the literal sense, "dry runs" to check assembly sequence and fit (and make some nice photos!). When I do the final assembly, I'll use the grease again or oil itself (for example in the cylinders and in very fine microbores like in the tensioner bodies where the grease could act as a plug and prevent oil getting through.

Drew

[dasadrew]

There are discussions every so often on cleaning the cam covers and what to do with the hidden wire gauze under the filler cap. I'd bathed my covers in engine cleaner sometime back and also managed to get a jetwash nozzle to blast through that gauze area, so I was planning on leaving that alone. At the very last minute I decided to drill out the spot welds and clean out the gauze after all. Shock Horror! This is what the gauze and the retainer plate looked like. It certainly wasn't fulfilling any breathing function anymore and, at some time, that crud may have found its way back into the engine. It's probably a paste made up of carbon deposits, old oil, .... and iron filings!

DSC00581 (Custom).JPG

[Goldstar]

Drew thanks for taking the time to put this thread together; it will be extremely useful to many of us. The addition of high quality photographs makes it more so. Keep it coming as they say.

Regards

Paul

[dasadrew]

This next little detail shows what Peter at LD Parts is referring to on his Website http://www.ldparts.co.uk/shop/shop.p...41baf042605483 as he writes: (I'm sure he won't mind me quoting and advertising at the same time!)

"Notice also the slit along the rear gasket. If the gasket ever starts to fail, then the water is drawn into these slots and then is pushed out via two grooves milled into the head, leading into the Vee. If these slits are not present, as is the case in some aftermarket gaskets, then when they fail the coolant disappears out of the exhaust leading people to think the head gasket has gone as water level goes down but there is no telltale leak to the Vee."

In this pic you can see both the grooves in the head together with the old gasket which was fitted to my car and also a standard aftermarket gasket in the background without the slot. In my case, the Payen gaskets would be too thick, so I'm cutting new ones (with the slot) from a sheet of 1.0mm Elring Abil N gasket material bought at the local motor factors.

DSC00594 (Custom).JPG








































DSC00595 (Custom).JPG

[dasadrew]

After an overnight bath in engine cleaner, then unravelling and an hour in the ultrasonic bath, this is what those gauze scrubbers look like now!


DSC00596 (Custom).JPG








































DSC00597 (Custom).JPG