GT6 mk2: starting my engine rebuild

[DanMi]

P

48 minutes ago, Pete Lewis said:

WSM says  remove circlips in the pistons and put , push out with fingers  in a bucket of hot water  if the gudeon pin is tight    good enough for triumph 

Pete

That is to put the gudgeon pins into the piston/small end not the small end bush into the con-rod heating the piston for that would not help as not involved.

[chrishawley]

Might one add valve spring compressor?

Not sure it counts as 'special tool' but possibly weighing scales with a fine resolution (<1g) if you're particular about weighing the pistons and con rods and pairing them up by weight.

Are the valve guides being removed/replaced? If so, worth considering what might be required in that respect (opinions vary, so I'll duck the specifics on that one).

Materials, if not already to hand: Gasket maker (e.g Wynn's, V.Reinz) 200ml should do it: Copperslip for where it is appropriate (and not where it isn't!).

 

 

 

[DanielH]

Hi there, while I am waiting for royalmail to resume export service, I am working on the engine.

Apart from the engine stand and the black varnish, no progress was made.

 

The head was cleaned, no varnish yet, 

No cracks are visible. The valve seats have pits:

 

In terms of parts, currently I've got this:

•  big end
  • pistons 

    1

    149976020COUNTY

    PISTON SET +20 FLAT TOP

  • main bearing shells
  • Small End Bush Kit - 6 - 119813K6
  • Timing Chain (single roller) - 105131 + tensioner

  • Big End Bearing Set - Oversize +0.010 - RTC1751010 - OEM - Glyco Main Bearing Set - Oversize +0.010 - Glacier - RTC1752010

  • NO new oilpump
• head:
  • nothing

 

I guess I want to assemble the big end first, and get the head prepared in parallel.

Apart from cleaning the block, what should I do next?

1. big end?
   1. install the main shells + crankshaft, measure the play/clearances
   2. order a new oil pump??
   3. check the connecting rods, bring to the same weight?
   4. ??
2. head?
   1. get new valve seats? inlet and outlet? 
   2. order valve guides, valves etc?

As you see, I've got no plan yet...any recommendations are wellcome 🙂

 

 

[Wagger]

As you have had the cylinders re-bored, obviously, you are fitting oversize pistons. The ones pictured do not look new. Maybe they have been laying around a while.

Have you checked the ring gaps when placed in the bores, parallel to the top face? In new bores, flush with the top is ok. If these gaps are too small, then you risk the rings scraping the bores when hot, and fracturing.

You have fitted new shells, presumably you have checked each one on its journal for tight spots and play.

Your valve seats need re-cutting, looking at your pictures. As that will remove any absorbed lead, probably best to have the seats changed. Also check the valve guides for wear. Fit new guides before machining the valve seats. They must be concentric.

I have not read the whole thread thoroughly and do not know if you have done anything like this before, so, please forgive me if I am telling you to 'Suck eggs'. All of your efforts can be wrecked if you miss something.

[DanielH]

Hi Mr Wagger 🙂 yeah right, the pistons on the foto are the old ones, the new ones are still in their boxes.

>Your valve seats need re-cutting, looking at your pictures. As that will remove any absorbed lead, probably best to have the seats changed. Also check the valve guides for wear. Fit new guides before machining the valve seats. They must be concentric.

ok, first the guides then the seats. I should get them from Chris Witor, right?

thanks 🙂

[Wagger]

4 hours ago, DanielH said:

Hi Mr Wagger 🙂 yeah right, the pistons on the foto are the old ones, the new ones are still in their boxes.

>Your valve seats need re-cutting, looking at your pictures. As that will remove any absorbed lead, probably best to have the seats changed. Also check the valve guides for wear. Fit new guides before machining the valve seats. They must be concentric.

ok, first the guides then the seats. I should get them from Chris Witor, right?

thanks 🙂

May be better to have that done by a head specialist.  I had access to factory machinery for that sort of work on motorcycle alloy heads until 1990. It is a while since I tackled that sort of work. Some had alloy heads with inserts requiring warming the head and putting the seats in Liquid Nitrogen to cool them. Others on this forum may have more recent experience with iron heads.

[johny]

You can check the tolerances on the existing oil pump quite easily then if outside the limits change just some of the components or the complete thing. However there has been a problem where the clearances of some of the new replacements are still not good enough so I believe specialists like Witor offer, at a premium, to supply correct pumps.... 

[DanielH]

Evening all,

while I am still waiting for the Royal Mail to sort out their export service interruption, I had a look at my rocker shaft, that shows wear marks like this:

I guess my rocker shaft is toast, as well, isn't it?

Do you have recommendations for good replacements?

thank you 🙂

Daniel

 

 

[DanielH]

Hi there,

had a look at the oil pump today.

The endplate looks ok, very few marks:

Took the 3 measurements per the handbook (in mm):

1) clearance inner rotor <-> outer rotor: 0.25-0.30 (should be < 0.254)

2) clearance other rotor <-> body: < 0.20 (should be < 0,254)

3) clearance inner rotor <-> end plate: 0.20 (should be < 0.102) 

 

 

Soooo, it appears that this oil pump is worn out.

Question: is the quality of the oil pumps from the "usual suspects" good enough? 

thanks 🙂

Daniel

 

[DanielH]

Somebody here mentioned a premium product:

https://www.chriswitor.com/proddetail.php?prod=217488RP

Is this your recommendation?

thanks 🙂

[Iain T]

I would phone Chris Witor to make sure you get the correct parts and providing he sells both get the shaft and oil pump from him. 

Iain 

[johny]

yes the pump is a bit more expensive but guaranteed to be within tolerance. This may now no longer be a problem with these pumps so you could speak to other cheaper suppliers to see if they can do the same guarantee?

The new pump will have an alloy body and will probably be longer than yours so giving a greater output plus the strainer is incorporated into the suction tube and you may have to ditch/modify the grill that your sump has across it....

[DanielH]

ok, just ordered the bush+pump from Chris. There goes the money.. 🤑

[Iain T]

You will notice the difference in pressure. My blueprinted oil pump is 80-90psi when cold and 65-70 when hot at around 3000rpm and never less than about 30 at tick over. For the price an excellent purchase! 

Iain 

[NonMember]

23 minutes ago, Iain T said:

My blueprinted oil pump is 80-90psi when cold and 65-70 when hot at around 3000rpm and never less than about 30 at tick over.

That sounds like what I get from my GT6, using a pump that I "toleranced" (certainly can't claim blueprinted) myself some 30 years (and several RBRRs) ago. Of course, the NOS crankshaft I fitted at the time also helps.

[Pete Lewis]

dont forget the PRV controls the pump output   more than the pump itself 

Pete

[johny]

but at low revs when hot the PRV does nothing as it should be fully closed and system pressure is just down to the tolerances of pump and bearings. Its why in the worst cases the oil pressure light can flicker on at tick over☹️

[DanielH]

Evening, 

I was checking my crankshaft before fitting it again.

Which of these grooves are from the front oil seal? Can I tolerate that or should I sand them out?

 

 

Then I noticed these wear marks on the timing chain gear:

Is that ok? Or should I replace that?

Thanks 🙂

Daniel

 

[JohnD]

18 minutes ago, DanielH said:

Evening, 

I was checking my crankshaft before fitting it again.

Which of these grooves are from the front oil seal? Can I tolerate that or should I sand them out?

 

 

Then I noticed these wear marks on the timing chain gear:

Is that ok? Or should I replace that?

Thanks 🙂

Daniel

 

"Sand them out?"  Aaaaaaaaaaaaaaaaaaaaaaaaargh!   Don't! That groove is far too deep! Remove enough metal to remove the groove and it will NEVER seal! Two solutions, a SpeediSleeve from SKF: SKF Speedi-Sleeve | SKF or another, better collar for the crankshaft. I think this is a six cylinder?  Canley's will sell you one for £12, or else I have a few, none of which are as  worn as that!

The wear marks on the timing chain drive sprocket look near catastrophic!  That's not wear, that's fractures!  The old chain , or else the tensioner, must have been very loose, flogging the teeth as it lashed!  Again Canley's can sell you one. or if I have one it will be in better condition than that!

PM me if you would like me to search my store!

John

[johny]

I reckon both those grooves are from the oil seal because the sleeve was first used with the shamfer at the front and then because it was so worn a PO installed it the other way round. It looks as if it could continue to be used as its shown in the photo and thats actually the same way the manual indicates. However they are available new and any wear does mean theres more chance of the front seal leaking...

As John says the sprocket looks pretty worn and it would be best to replace both of the sprockets and chain together. I would guess this engine has done some miles🤔

[Pete Lewis]

Crankshaft, Flywheel, Connecting Rod, Piston : Canley Classics

canley  available   to order 133235    £12.16  

Pete

 

[Ch.All.ch]

Hallo Daniel.

Have you tried contacting Christoph Maus in 31675 Bückenburg.De. www.spitfirescheune.de

Christoph is very helpful and GT6 experience.Tel:0049 5722 288 7980.

Cheers Chris

 

[DanielH]

Evening,

checked the main bearing clearance and end float today.

Cleaned the surfaces, inserted the new main bearings, and 2 STD-size thrust washers, new main bearings and tightened the main bolts to spec.

End float was: 0,2mm (spec: 0,157-0,203mm)

Replaced them with a STD (0,09")  and +5 (=0,095") thou thrust washer, which yielded this end float: 0,08mm

Reduced the thickness slightly and achived an endplay of 0,160mm

Resumed to check the bearing clearance.

Removed the bearing caps and inserted plastigauge and tightened the bearing caps down to spec.

Resulting widths were ranging between 2.0 and 2.5thou, which is in spec.

If you guys won't come up with objections I'll get some proper assembly lube (was using WD40 for this task) and do the final assembly of the crankshaft.

Greetings

 

[Pete Lewis]

yes wd40 is cats pee    youre right to get some assembly or engine oil in there  for the last assembly

Pete

 

[johny]

Yes and you can always power up the oil pump with an electric drill when everything is assembled to ensure oil gets everywhere before starting up for the first time...