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

[Pete Lewis]

if the  bores are std  then std size rings 

there are other snags like has the piston ring groove worn so the rings are a slack fit 

if not reboring i would still fit a ' Stepped ' top ring ,as any small wear ridge will soon break a normal ring when it comes into contact at the top of its stroke 

yes must get in the bore and dull it down as its worn nice and shiney your new rings will not run in and bed down   making the whole exercise a waste ,  with smoke and oil burning for ever 

called glaze busting  can be done by hand or using an expanding hone pads  in a drill as shown earlier 

very easy DIY but time consuming  needs a sort of figure  of eight action  not upsy downsy 

why do you feel the crank needs a  polish ???  the shells so far look fine 

as example .........some would put them back in 

Pete

 

[NonMember]

I agree with Pete - that looks like a hone (don't need to be too determined, it's only to bust the glaze, not to remove any metal) and new rings should give good life.

[AidanT]

1 hour ago, Pete Lewis said:

there are other snags like has the piston ring groove worn so the rings are a slack fit 

Once I have pulled all the pistons, would you be able to tell from a video with me moving about?

 

1 hour ago, Pete Lewis said:

why do you feel the crank needs a  polish ??

Only reason for this is what looks like a ring of rust under one of the shells - one of the early pics 

1 hour ago, Pete Lewis said:

if the  bores are std  then std size rings 

Chicken and egg situation,  how would I know if the bores are std? 

Stepped top rings sound like a good idea!! 😁

The top of the pistons are stamped with a number / letters. Is this of any use or interest?  Btw, one has a different letter code!

 

Aidan

 

[Iain T]

Aidan, I know the avid diy'ers will shoot me down but if you can get the block to an engine company the price of getting bores honed is really cheap, a few tens of pounds. They can also measure the bores, prior to honing and advise of size and condition. Unless you are going to make engine building a hobby the cost of buying a hone and bore gauge plus knowing how to use them and interpret results isn't in my opinion worth it. They can also advise on ring groove wear. 

Iain 

[AidanT]

I will at least have a chat with the machine shop.  I will need the flywheel skimmed in any case as it has a coat of rust on it, so a visit is inevitable 

Btw, what's that coating you have to clean off things like replacement brake discs?

Aidan

 

[Pete Lewis]

18 minutes ago, Iain T said:

Aidan, I know the avid diy'ers will shoot me down

thats sound advice from Iain if you are delving into the  unsure  world 

as for pistons the crown will be stamped with + something  if its oversized due to being bored no marking would seem std.

the is normally a sort of triangle arrow head to mark front/forwards  

any letter is the factory mark for grading   ie the best fit of piston  to bore on orig assemble 

so as original there were graded   piston diameters   

cant get at it right now but grade size and letter codes are in the workshop data  im sure 

 

the presevative on bare machine surfaces can be a variety of products  generally brake cleaner removes most of these    

 

on production we had a product that didnt need clean off it disappeared  on first use , cant remember what it was called almost a dry wax type of stuff and it stopped clutch discs sticking to flywheels with trucks in storeage   

Pete

 

[NonMember]

1 hour ago, AidanT said:

Only reason for this is what looks like a ring of rust under one of the shells - one of the early pics 

The ring of rust was in the gap where the oil way in the shell means nothing was in contact. If there's anything flaky there you will probably have to get it reground, but if it's just surface discolouration then I'd leave well alone. The working surface looks good.

As to Iain's invitation to shoot him down... While it may only be "a few tens of pounds" to get a machine shop to hone your bores, this three-prong honing tool is only 16.

 

[Iain T]

2 hours ago, NonMember said:

While it may only be "a few tens of pounds" to get a machine shop to hone your bores, this three-prong honing tool is only 16.

However as with all manual operations and even cnc machines it's much easier if you have been shown how to do it by an experienced person. The 'black art' comes hugely into play with all manual ops and can make the difference between a good job and cocking it up. It's really down to each individuals choice but I can't help feeling Aidan has a greater chance of getting a nice cross hatch by the machine shop. 

Iain 

[AidanT]

Other questions for the weekend. In continuing to strip, do I need to remove the crank to check the main bearings and shells? 

Will I need to re- time from scratch when I replace the timing chain?

Finally is there a real issue regarding tensioners? If so, are there sources for good ones?

Thanks Aidan 

[Nigel Clark]

You will need to undo the main bearing caps to look at the state of the shells, and lift out the crankshaft to see the opposing shells that are fitted in the block.

Removing the timing chain will require re-timing from scratch unless you put the chain back without anything moving - but you need to remove the cam to check it for wear and the crankshaft as above.

Timing tensioner and chain replacement... Unless it's badly worn with groves from the chain, keep the original tensioner. When replacing the tensioner and/or the timing chain, go to a reputable supplier. Pay for a top quality replacement e.g. chain from Germany, not further east! I've seen chains from India where the sides of the links were so rough it would quickly cut into the tensioner blade.

If you don't mind me saying, I feel you need to really get your head around how far you're going with this engine rebuild. Half measures when rebuilding a tired engine usually end in disappointment. Doing the job thoroughly, everything needs to be stripped, cleaned, inspected and measured before deciding what machining is needed. Then you're ready to rebuild, with clinical cleanliness and precision. The result will be an engine that's strong and trouble free for years.

Please keep asking any questions, we're all here to help and to learn.

Nigel

[Pete Lewis]

removing the split pin that holds the tension blade pin in place is an interesting escapade 

you need to read up cam timing and sprocket timing carefully 

you can set the cam lobe tdc with the rockers or make a piston stop and use a dial indicator 

more on this later 

Pete

pete

[Peter Truman]

In recent times I’ve left the pin and split pin in place and pulled the old tensioner spring out intact by rotating it around and opening the two blades of the spring a little similarly I put the new spring in by opening the two leaves a little to enable the sleeve part of the spring to push past the locating pin.

I haven’t had any subsequent issues as before fitting the timing chain cover the two leaves of the tensioner spring are slightly sprung apart, I assume the pressure exerted by the spring closes the two leaves of the spring up!

Time will tell but it’s relatively easy to remove the timing cover and fix!

I have a new set of duplex cam and crank sprockets plus timing chain (origin unknown) do I need a special timing chain spring tensioner? Is it wider 

[thescrapman]

That trick with the tensions only works for simplex tensioner, duplex tensioner are too wide for the gap.

THAT is when it gets interesting doing the split pin.

[Anglefire]

When I fitted my duplex chain (Canley Classics from memory) I don't recall any particular issues with the tensioner. I do know the timing is every so slightly out-  as it happens to the good as it effectively brought the torque down which is no bad thing on a 1500.

[AidanT]

 

I've seen a full kit on Paddocks for a duplex system with German Chains, but its around the £100 mark - Is it worth the investment?

The car however will not be a daily whilst I own it so it will never do a massive mileage

I will buy the chain etc, once I have added pictures on here and got your opinions on both it and the sprockets; I will check the chain as per the manual before I remove it

10 hours ago, Nigel Clark said:

If you don't mind me saying, I feel you need to really get your head around how far you're going with this engine rebuild. Half measures when rebuilding a tired engine usually end in disappointment. Doing the job thoroughly, everything needs to be stripped, cleaned, inspected and measured before deciding what machining is needed

Nigel

I want to do this properly, but don't own any of the kit to measure anything apart from a micrometer and feeler gauges. The head is being done professionally, so I may end up taking it to a machine shop in any case, but if that's the case I want to have the knowledge  to be specific on what I want them to do, That's where your opinions are important here.

Once all is sorted, I will obviously need help putting it all back together again !!!

 

Aidan

[NonMember]

13 minutes ago, AidanT said:

I've seen a full kit on Paddocks for a duplex system with German Chains, but its around the £100 mark - Is it worth the investment?

I would say not unless you're intending to seriously tune it up. The duplex gives no real benefit other than being stronger. You don't need it any stronger unless you rev to silly revs (8000+).

The reason the 2500 engines had a duplex chain was purely that the first incarnation of that engine was the PI, with all the extra load of the metering unit hanging off the cam.

Incidentally, a "fast road" cam with long period actually puts less load on the timing chain than a short period cam. It's down to the slope of the valve lift, which has to be quick if the period is short but can be more gentle if you've got plenty of period and overlap. Long period with a fast lift causes loss of torque at low revs, so it's more of a race cam than a fast road.

[AidanT]

Should have said - any recommendations on chain manufacturer? i see there are quite a few Rolon's in the market place  - no idea if these are German or even if its like Lucas - a name and not a real manufacturer

(Shopping list growing ! 😁)

 

thanks

 

Aidan

 

[rogerguzzi]

Hello Aiden

                     Rolon is Indian and rough Irwis is the good one there may be others?

I have a Rolon you can have for free!

Roger

[Nigel Clark]

47 minutes ago, AidanT said:

 

I've seen a full kit on Paddocks for a duplex system with German Chains, but its around the £100 mark - Is it worth the investment?

The car however will not be a daily whilst I own it so it will never do a massive mileage

I will buy the chain etc, once I have added pictures on here and got your opinions on both it and the sprockets; I will check the chain as per the manual before I remove it

Nigel

I want to do this properly, but don't own any of the kit to measure anything apart from a micrometer and feeler gauges. The head is being done professionally, so I may end up taking it to a machine shop in any case, but if that's the case I want to have the knowledge  to be specific on what I want them to do, That's where your opinions are important here.

Once all is sorted, I will obviously need help putting it all back together again !!!

 

Aidan

Hi Aidan,

A good machine shop will measure bores, pistons, crankshaft etc and advise on what needs doing, e.g. reuse old pistons with new rings and bores honed or rebore and new pistons, refit crankshaft with new standard bearing shells or regrind and fit with undersize shells. Don't worry about having to do all the measurements yourself.

As for a source for the timing chain, my advice is to go to a reputable supplier (not necessarily the cheapest) for all your parts, including the chain. We're talking of the kind of supplier that would only sells parts he's happy to fit to his own Triumphs, for example Chris Witor or Canley Classics. As a further check of the new timing chain, run your finger round the edges of the links. If there's any feeling of roughness, reject it and find another.

One more suggestion... Practical Classics magazine is running a seven part series on the complete strip down and rebuild of a Spitfire engine at TRGB. It covers pretty much every step of overhauling a small Triumph engine with colour photos (unlike a Haynes manual), and words explaining each step. Part 5 is out now in the January issue, no doubt the earlier parts can still be purchased as back numbers. I have to admit a connection, as I photographed and wrote this series for Practical Classics!

Nigel

[johny]

Does it really need new timing chain and sprockets if youre not going to do huge mileage? Remember you could be replacing original items with poorer or at least unknown quality ones.... 

[AidanT]

16 minutes ago, rogerguzzi said:

Hello Aiden

                     Rolon is Indian and rough Irwis is the good one there may be others?

I have a Rolon you can have for free!

Roger

Hmm  just got mailed back from Canleys and they swear by them - I get most of my kit from them. Maybe you got a fake ???? 

We have only ever sold the Rolon branded 105131 timing chains (thirty plus years), never had an issue with quality. Tensioners come from the same supplier, and the same sort of timescale.

Canleys

 

Regards   

5 minutes ago, johny said:

Does it really need new timing chain and sprockets if youre not going to do huge mileage? Remember you could be replacing original items with poorer or at least unknown quality ones.... 

This is provisional Johny! I've not even taken the cover off yet  - As said I will be adding more pics over the weekend to get everybody's  view

Aidan

 

[rogerguzzi]

Hello Aiden

                   Fair enough but the edges are rough and wear tensioner butthen it depends on mileage to be done!

Plus just remembered the one I have is a Duplex one

Roger

[Sparky_Spit]

Hi Aiden - one tip before removing the timing chain and sprockets.....  Set the engine at top dead centre with piston no1 on the firing stroke.  The timing marks that are scribed on the engine's front plate and sprockets should all line up. There may also be some centre punch marks.  Mark all these with a tiny blob of paint.  Then take some pictures for reference when you put it all back together again..  See below for what I mean.

 

[AidanT]

Thanks

Great advice  will do this Sunday 

Cheers

 

Btw, is County a good chain manufacturer???

 

[ludwig113]

whatever you do, take LOTS  of pictures before and during the dis-assembly , building an engine isn't difficult but you have to be methodical, make notes and take pictures.

unfortunately you will probably have to buy some semi specialist tools especially if you're doing timing/top dead centre etc.

 

paul