Mk2 Engine Rebuild going into a Mk1 GT6 by a novice!

[AidanT]

7 minutes ago, Pete Lewis said:

are the other two allen key socket cap bolts ??

 thats the harmonic damper ring bonding

Hi Pete

No they are just loose nuts, left them on so I have a historic pic of what bolts nuts and screws go in which hole! Determined to put in back together the same way it came apart

 

[Colin Lindsay]

15 minutes ago, AidanT said:

Bolt out but to next problem. I assume the timing cover should be all bolts but.. please refer to the pic. Any ideas how to move these? The slots aren't great and they are about 15mm across, my biggest screw driver won't touch them

Be careful with them. They're hard to replace. If you need replacements some suppliers will try to fob you off with Philips-head versions stating that is all that is available but search for 5/16 x 3/8 pan head slotted machine screws and you'll find them.

[AidanT]

14 minutes ago, clive said:

You need  bigger screwdriver! And ideally a hammer-through type

Clive I've got an impact driver, never thought of that- just need an appropriate driver head - off to eBay!

[Anglefire]

46 minutes ago, AidanT said:

Clive I've got an impact driver, never thought of that- just need an appropriate driver head - off to eBay!

I used an impact driver - mine (some 30years old) came with several bits including slotted and cross head.  

[AidanT]

Well sometimes I forget what I have in the tool chest!  Manual impact driver and a load of heads including wide flat heads TADAAA! 

Ok so opinions please on the following pictures.  I thought the tensioner from all the comments above was going to be scary!! Not a bit of curved spring metal on the inside of the cover!!!  Got me there guys!!!

Btw  chain moves some 18mm on total left to right it feels nice and smooth when you run your finger down the side

 

[Pete Lewis]

its been apart before the centre dot timing marks are from a previous  world 

the chain looks fine . but you need to read up about cam timing as the 4 holes in the sprocket allow 1/4 tooth incremental adjustment and getting pistons and cam lobes at top dead centre is not a dark art but is very close .

you may need to ask about a piston stop and a dial indicator  to get it all spot on  on rebuild  or use the large rocker  equal gap and feelers method as in the WSM.

Pete

 

 

[Colin Lindsay]

4 minutes ago, Pete Lewis said:

its been apart before the centre dot timing marks are from a previous  world 

Same as my GT6 engine, a punched dot along a straight line.

[NonMember]

As Pete says, the chain and gears look fine. The tensioner is showing some wear but if it's original (or of same quality) it will probably outlast a lot of the available new ones. It would benefit from a clean and there's a spot of surface rust on the cover that wants scrubbing off.

[AidanT]

Thanks all

In terms of timing a gauge with a magnetic base doesn't seem too expensive 

When removing the cam sprocket, how many ways does that re-fit? So are there just two places to bolt to, so you can only get it right or 180 out?, or can it only go back one way???

Thanks

[Anglefire]

You can flip the single chain sprockets over too - which gives you several permutations to get down to the fine angles possible.  

[thescrapman]

Teeth on cam sprocket look a little pointy to me.

but they do look even each side

[Iain T]

You can find tdc using a piston stop. I'm sure there are some instructions on the forum or guggle it. Doesn't require a dial gauge and possibly more accurate. 

Iain 

[Pete Lewis]

you need a dial indicator if you want to connect the chain and you dont now if the lobe is at tdc 

theres a lot of rotation either side of the cam lobe with no change in lift 

so you use a DTI and  big protractor disc on the cam 

rotate cam to give a known lift mark protractor  turn cam other way to get the same lift marl the disc

tdc is halfway between the two marks 

doing the same on a crank is easy if you bolt a home made stop on the block face which will 

block the piston rising fully   again use big disc and mark the stopped position in both directions 

halfway is TDC

the 4 holes in the sprocket each pair gives 1/4 tooth 

turn the sprocket over and the same applies you get another pair of 1/4 tooth 

so the 4 positions give a full 1 tooth adjustment 

you can do all the above tests and find the dot marks are spot on or as normal as pevious work may not have any of the correct settings and they are actually hopelessly  miles out 

as you are going to a lot of  trouble and asking lots its an area you need to get your head round    its pretty easier than it reads 

there can be a TDC mark on the flywheel but like the front that needs the rear plate and F wheel fitted same as TDC pointer  is only on the timing cover and thats not fitted either 

 

 

Pete

[AidanT]

10 hours ago, Pete Lewis said:

so you use a DTI and  big protractor disc

Is this DIY or can you buy one? Think I'd be pretty crap at something like that though maybe a print off the web backed by a bit of card??

 

[Colin Lindsay]

There are a lot of them online, just search 'timing gear protractor' or the like, but most of them seem to be purchase items and I'm not sure how accurate they'd be if translated to a print version. It's bound to be do-able if you find the proper template; someone must have uploaded one.

[AidanT]

Hi 

Thanks Colin but I think I have my head around this at least for the crank- it could actually be blank as all that's needed is along with the gauge is to mark the disk at the two points the gauge shows the max height and split the markings in the middle- that's tdc 

How do you get the gauge to reach the cam lobe? And which one for tdc?

[NonMember]

16 minutes ago, AidanT said:

How do you get the gauge to reach the cam lobe? And which one for tdc?

With the crank at TDC No. 1 firing, the valves on No. 6 should be "on the rock". What this means is that the exhaust valve is still closing when the inlet starts opening, so the TDC position is when they're equally open.

To measure this, the book method is to fit the valve gear and set an artificial tappet clearance, to plainly identify the fully closed position. Then rotate until you can measure both valves equally lifted (or the clearance equally reduced, if that's easier). You could do the equivalent with two dial gauges and just the cam followers fitted. I'm sure somebody here will have a cunning trick using a few pieces of string...

[Anglefire]

I created a protractor in acad - I've attached the pdf version. Just print it out on stiff paper or card.

Cam Timing.pdf

[AidanT]

Thanks for the pdf 

Just thinking about the cam, surely one of the other lobes on the cam must be at the top when the crank is at TDC???

 

[Pete Lewis]

just fit the cam followers and you can measure lift from the top of the block 

might need anything stable dropped in the follower as an extension 

pete 

if you dont have a dial indicator  wait till the heads on and use the WSM method of a wide but equal tappet gap  ..its quite easy to do 

just read the book a couple of times to get the gist of what you are doing 

all you need is the crank accuratley ( have alook at the back plate and f wheel for tdc marks ) at TDC and a set of feelers 

 

[DanMi]

I used a second cam follower upside down and 2 dial gauges, you need to find the point when both cam lobes of no4 (4 cyl) have equal lift one opening one closing and the value doesn't matter. At that point the crank needs to be no1 tdc. I wouldn't use the marks on the wheel as there is about 5 degrees of movement on the bolt holes. I would if doing it again do the cam timing with only no1 piston in as that will make turning the crank easier. This is assuming a standard camshaft.

[Pete Lewis]

 Hi Dan     hence many make a piston stop 

it all depends on what state of build you have,    in bits,     part build ,,,,ready to run  

with no timing cover fitted there are few options apart from put the cover on off on off 

Pete

 

[DanMi]

Agreed Pete but I meant not use the stamped marks on the cam wheel, from previous alignment, without measuring the timing as the wheel on the cam has quite a lot of rotational movement from the bolt holes. I just made up a pointer for the crank, but using the flywheel would be easier

[Iain T]

On 06/04/2020 at 10:14, JohnD said:

"So, seeking for further amusement" I reviewed my files and found this:

 

This piston stop is easily made from a piece of square/rectangular tube, or some angle iron.

It will allow you to find more accurately the TDC than is possible with a dial guage.

If you want to do the job without removing the head studs, then two lengths of tube with washers on top, will secure the stop in place over the studs.

Jphn

PS "Seeking for further amusement"    Stanley Holloway, may amuse you.  His version of "Albert and the Lion" is famous, and he did many others, for instance "Sam Small"

 

Post from JohnD showing a home made piston stop. 

Iain 

[Roger K]

Interested to know how that is more accurate than using a dial gauge?