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GT6 Engine .... What to check-out before refitting.


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I started working on the engine and gearbox that was fitted to my GT6 when I bought it over 4 years ago. All I know is that it starts and runs on all 6 cylinders. 

I gather that it is not the correct engine for this year of GT6. In fact, It might not be a GT6 engine at all. It may be from a Triumph 2000 saloon car. Because of that, I have decided that this engine may not be the one that I should re-build top to bottom or invest a lot of time or money into. However, It will probably provide adequate use to allow me to experience the GT6 on the road for a year or so and to decide where to go from there. 

I know nothing about the condition of the gearbox but have no reason to believe that the engine or box were the reason that the car was taken off the road over 10 years ago.

If I go ahead with this engine and box as a short/medium term arrangement, then the question I am asking myself I suppose is what inspection/ assessment/ of the engine and box can I make while it is out of the car ?

The pressure plate and disc looked unworn (in fact it looked as if they had just been fitted !!).

I cannot detect any crankshaft end float. Maybe I need to try harder because I expected to find at least some.

What else should I do at this stage while I have access to the engine and gearbox.

Lift the head ?

Remove valves and examine valves and seats ?

Valve stem oil seals ?

Drop the sump and check bearings etc ?

Replace crankshaft oil seal ?

ENGINE NUMBER IS ... ME87022HE by the way.

Any other pointers or suggestions will be most welcome.

Here are a few pics :

 

 

 

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Interesting........ there are some oddities here......

That is a Mk1 engine (2000 or GT6) by the cylinder head.  Pushrod tubes and stepped head with all ports in line....

but

ME is a mk2 engine number.  Also, the block, has the re-enforcement rib just above the sump flange on the manifold side which I would normally consider a late Mk2 feature.  So, something is odd.  It is possible to fit a Mk1 head on a mk2 block but it's not a straight swap as the Mk1 has 3/8" studs and the Mk2 7/16" so that has to be got around.  What size studs does it have?

The Mk1 head is a bit of pain for you as it means if you want to be "correct" not only do you need another head but also the manifolds etc.

Gearbox looks like a 3 rail with D type OD - which would be as expected.  Not quite expected are the two switches on the front of the remote.  One is the OD inhibitor switch.  The other is presumably a reversing light switch, but mounted there is a very early (even 3 synchro) feature.  Normally for the age of your car the reverse light switch should be on the gearbox top at the back under the remote.  If that is there, then possibly the second switch at the front is a mod to allow OD in second.

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Nick, Thanks for such a thorough reply. I understand what you mean by the "pushrod tubes" ... I will look up the rest of the items that you referred to to gain a better understanding.

It certainly sounds like someone went to some bother to end up with such a mixture of parts ... especially if they went to the bother of drilling out the head to accept bigger head studs. I will check the head studs tomorrow.

To further confuse matters, the boxes of spare parts for the car included another complete head 308351/517527 and also an inlet manifold (with carbs) , an exhaust manifold, a camshaft, pushrods. 

I am completely unaware whether the previous owner intended to fit that head to the engine in the car, whether the previous owner had already changed the head that is presently on the engine and if so did he drill out the head studs.

I have a lot to discover about the lump that is in the car and also to try and understand what kind of "journey" the previous owner was embarking on when he acquired a second head, manifolds and cam shaft along the way.

Thanks again for your help.

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Not quite expected are the two switches on the front of the remote.  One is the OD inhibitor switch.  The other is presumably a reversing light switch, but mounted there is a very early (even 3 synchro) feature.  Normally for the age of your car the reverse light switch should be on the gearbox top at the back under the remote.  If that is there, then possibly the second switch at the front is a mod to allow OD in second.

Nick,

I see the two switches on the remote and I presumed one was an OD inhibitor and the other was a reversing light switch. I will check tomorrow to see if there is another switch in the position you mentioned.

The one thing that struck me about the gearbox was how small and how light it is. I'm no expert on gearboxes but I really tought it looked undersize for the job. 

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49 minutes ago, UNFIT said:

To further confuse matters, the boxes of spare parts for the car included another complete head 308351/517527 and also an inlet manifold (with carbs) , an exhaust manifold, a camshaft, pushrods. 

That sounds like the rest of your mk2/3 engine. The 308351 casting is definitely for the later “mk2” head style. Chris Witors list doesn’t show 517527 but 517528 is listed for early Mk2 2000, Vitesse mk2 and GT6 mk 2. Should be a shallow chamber one for flat top pistons. Probably still earlier than your car and the block but good base.

Dunno why someone has (apparently) gone to the trouble of sticking a Mk1 head on a Mk2 block. Reputed to give a sweeter engine than the Mk2, but the Mk2 is generally reckoned to be more powerful (GT6 Mk1 95 bhp vs 104 for Mk2) and have more tuning potential.

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You are spot on Nick. ...517528 .....  Senior moment here.

What would you suggest in this case ? Remove the head that is on her and check over /prepare the 517528 head for fitting on instead ?  

 

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What do you intend the engine to be when you have finished with it? If it only going to be a road/fast road engine, then IMO either head would be fine, the only sticking point is if you want a performance exhaust manifold, these are not as easy to come by for the early head (different port spacing, and most performance manifolds are designed for the later heads).

As Nick says, if you plan to tune it to an inch of its life then a layer head is probably better.

With the engine, unless in a rush I would strip it down and check it. If it is planned as a stop gap then re-using bearings etc is fine, if building for longer term I would consider replacing bearings, checking bores etc.

Phil

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First thing is to check the head stud diameter.  I'm only guessing!

Mk1 have 3/8" UNF from the factory, but do sometimes get opened out to 7/16" UNF as 3/8" doesn't really allow quite enough torque/clamp and HGF is not unusual.

All Mk2 have 7/16" UNF and HGF is rare.  Obviously the block is drilled and tapped to the larger size.  My assumption based on the ME prefix and visual appearance of the block is that it is a mk2 one and will have the 7/16" tappings with the holes in the head opened out to suit.  If the block is tapped 3/8" that might change the thinking a bit!

My personal preference would be for the Mk2 parts
- Correct for the car
- Less prone to HGF (all studs go through the full head thickness)
- Head can be torqued without removing the manifolds (not so on Mk1)
- Less prone to manifold gasket failure
- Less prone to exhaust manifold cracking
- Slightly more powerful from the factory (to be fair this is at least partly cam dependent)
- Arguably more tuning potential & manifolds common with 2.5
- Greater choice of inlet and exhaust manifolds

Clearly the engine has had work at some point.  If you are lucky this is relatively recent in mileage terms and done to a good standard.  Minimal end float is a good sign.  I'd be taking the head off and dropping the sump to check bores, bearings and oil pump.  Note the 2000 sump is different from the GT6/Vit one (angled base vs. flat) and the front plate will have had legs for the mounts.  Hopefully these items have been exchanged for the correct GT6 ones when the engine was built..... 

 

 

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Thanks for that information lads.

Nick, you were spot on.... the head studs are 7/16" so it appears that the Mk1 head was drilled out to suit the larger head studs.

I removed the head from the engine today.  The raised casting mark on the Mk1 head is V2921. There is another raised number that I cannot read. It looks like 300488 or 508486 .

Anyway, I now have 2 heads (pics below)

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I also spent an hour looking through the parts that came in the boxes marked "engine parts". This has given me some indication of what the PO might have been planning to do with the engine. The parts include camshaft, cam followers, pushrods, timing chain and sprockets, distributor, petrol pump, 2 exhaust manifolds, inlet manifold with carbs. head studs etc. 

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I would like to use the Mk2 head for all the reasons that Nick states. It appears that i have most of what I need to fit it to the engine. The Mk2 head would appear to have shallower combustion chambers. Will that be a problem when fitted to the block that I have which has domed top pistons ? Should I use the camshaft, followers and pushrods that were in the engine that I stripped or should I consider using the camshaft, followers and pushrods that came in the boxes of parts with the mk2 head. ? 

 

I will drop the sump tomorrow and check out the items that you suggested.

Thanks for help and suggestions to date.

 

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37 minutes ago, UNFIT said:

Will that be a problem when fitted to the block that I have which has domed top pistons ?

Yes.......517528 should be 3.3" thick.  Domed piston (or 2.5) heads are 3.4" thick or more.  So are you saying that your engine with the Mk1 head on it has domed pistons?  All the Mk1 engines had flat pistons - CR will have been monstrous...... do you think it's actually run like that?  Or do the chambers look like they've been opened out?

https://www.chriswitor.com/cw_technical/head_applications_chart.pdf

Can you see a part number etched on the cam - usually crudely done on a flat section towards the front. 308778 (factory Mk2 GT6/Vit) would be a nice find if in good condition.

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Hi Nick. Yes it has domed pistons alright. The chambers dont looked to have been opened out. They look original.

I dont know how long she had been running with that head/piston/block setup but the valve heads and the chambers have the signs of having been run.

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I started the engine in 2014 and let it run for a few minutes before removing the engine from the chassis.

 

As you point out, the CR would have been greatly increased by the dome top pistons . I wonder what the PO (or maybe the owner before him) had in mind.... because drilling out the head to take the 7/16 studs would seem to be an extreme enough move without factoring in that it appears that the head was mismatched to the block/pistons in more ways than one. 

One thing about tinkering around with these old cars is that they never cease throwing up puzzles for us to ponder.

Ok then, so it would seem that I wont be able to use my MK2 head with the block/piston set up that I have.

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Probably not much different from the Mk1 head..... Though possibly valve / piston contact. Brad (Red Rooster) had some of that due to a stretched timing chain - that with the correct head depth for domed pistons, so clearly not much space to spare!

Surprised it wasn’t an issue with the Mk1 head tbh. I guess the greater squish deck means the chamber is deeper and the valves that bit further away.....

Would happily swap your shallow head for a deep one, but weight and geography are troublesome. The good news for you is that the deep ones are much more common.

Given the engine building talent on display thus far.... I reckon you need to take a careful look inside this one!

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11 hours ago, Nick Jones said:

Probably not much different from the Mk1 head..... Though possibly valve / piston contact. Brad (Red Rooster) had some of that due to a stretched timing chain - that with the correct head depth for domed pistons, so clearly not much space to spare!

Surprised it wasn’t an issue with the Mk1 head tbh. I guess the greater squish deck means the chamber is deeper and the valves that bit further away.....

Would happily swap your shallow head for a deep one, but weight and geography are troublesome. The good news for you is that the deep ones are much more common.

Given the engine building talent on display thus far.... I reckon you need to take a careful look inside this one!

I do think that had more to do with the gudgeon pin embedding itself in the bore rather than the chain.

RR

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Before you invest too much effort/hope in the Mk2 head, you need to check that there are no cracks between the valve seats. As Nick says, there must have been a reason for the PO going the route that he has.

Ian

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28 minutes ago, Nick Jones said:

Sure that didn’t help....... but I thought you had valve marks in more than one piston?

I did but think that was due to the chain stretching as the gudgeon pin dug itself deeper into the block.

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1 hour ago, Gt64fun said:

Before you invest too much effort/hope in the Mk2 head, you need to check that there are no cracks between the valve seats. As Nick says, there must have been a reason for the PO going the route that he has.

Good advice, but this head isn't going to be any use with domed pistons..... so unless you are going to swap to flat top pistons (maybe bores are not great anyway?), it isn't question no.1...... although if deciding to swap pistons you clearly need to know whether the head is ok to use....... Arrrrrgh!

Found RR's previous thread - most of the juicy stuff is on page 1......

 

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Hi Nick.

I found and read RR's thread last night. A man wouldnt sleep well after reading it lol. Hello RR and welcome to this quandry that I have on my hands. 

I went back at this again this morning. 

I cleaned up one chamber on each of the heads just to get a visual idea of the differences. The chamber on the later 517528 head is a completely different shape and appears to be much greater in volume. The chamber on the mk1 head is really quite small in comparison. I tried to get readings of the comparitive depth of each chamber and they appear the same (or very close). I mesured from the face of the head to (a) the head of the valve and (b) the top of the chamber. I cant be 100% but the depths are very close. Also, my 517528 head measures 3.300 in height so that would suggest that it hs not been skimmed.

I'm scratching my head here with wondering how that engine ever ran with the mk1 head on the domed pistons. As you say, the cr must have been very high not to mention how valve/piston contact didnt occur. Things must have been very close. 

At this stage, would it prove any purpose to fit the later head onto the engine, torque it down and turn it by hand to see if I have valve clearance. ?  The later head would definitely reduce cr if the size of the cumbustion chamber is anything to go by.  Or am I better off just forgetting that and start looking out for a set of flat top pistons ? Or alternatively a later head with greater depth chambers designed for domed top pistons.

The mad part of all this is that I was just going to fit the engine as it was when I got it without lifting the head ... 

By the way, the camshaft in the parts box is marked 308778. 

The domed top pistons appear to have H73 stamped on the crown. Nothing other than that only "front". That would suggest that the block hasnt been bored.

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Thanks for that Phil. It would appear that the head, cam, manifolds , carbs etc. that were in the "engine parts box" came from a mk2 GT6.  Maybe the PO acquired them to fit on the engine which it seems is a combination of Mk1 head and Mk2 block. Maybe the PO thought that By fitting those other parts that he would return the engine back to full Mk2 spec. 

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2 hours ago, UNFIT said:

Maybe the PO thought that By fitting those other parts that he would return the engine back to full Mk2 spec. 

Apart from the domed pistons (which I suspect caught him out) he would be right.  Exactly what I used to build the engine in my GT6.  But that was based on a Mk2 Vitesse bottom end with flat pistons.

2 hours ago, UNFIT said:

The mad part of all this is that I was just going to fit the engine as it was when I got it without lifting the head ... 

Probably as well you didn't!  To b

 

2 hours ago, UNFIT said:

The chamber on the later 517528 head is a completely different shape and appears to be much greater in volume.

To be fair, it would quite likely work ok just pottering about on light throttle.  But if you gave it any stick, I reckon the pistons would end up like RRs pretty quick (the melty bits not the valve marks)

 

2 hours ago, UNFIT said:

The chamber on the later 517528 head is a completely different shape and appears to be much greater in volume.

Yes completely different shape. The volume must be quite similar though as the CRs are 9.5:1 (MK1) and 9.25:1 (Mk2).  Suspect the Mk1 is a bit deeper which is perhaps how it could run without the valves and pistons meeting.  You could try clapping the Mk2 head on and seeing if all misses but it's a bit pointless as the CR will be too high to run like that anyway.

Your options going forward are:

Find a deep chamber head and run the bottom end as it is.  Which might be the path of least cost/resistance if the bottom end is good.

Get some flat pistons (to match existing bore size if good, for next oversize if re-bore needed) and rebuild with those.  The Mk2 head would best be checked for valve seat cracks (between the valves on 1 and 6 is the most common area) before making any solid decisions.  The flat pistons, Mk2 head and 308778 cam would give you a Mk2 GT6/Vit engine, which is the best of the 2Ls in std trim.

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I put out the word among the Triumph owners over here about a mk 2 head with deeper combustion chambers and/or flat top pistons. Things are very quiet over here at the moment with Covid lockdown and all that (5 km travel limit) so I dont see any possibility of getting along to see any heads or blocks that might surface if indeed any does.

I hadnt much on this morning so I fitted the mk2 head and torqued it down and fitted the pushrods and rocker shaft etc. There was no interference when I turned the engine by hand. 

Hopefully something will turn up over here but in the meantime I have plenty of work on the interior fit out to keep me going.

 

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35 minutes ago, UNFIT said:

I hadnt much on this morning so I fitted the mk2 head and torqued it down and fitted the pushrods and rocker shaft etc. There was no interference when I turned the engine by hand. 

Interesting.  I'm slightly surprised and it adds to the mystery of why the Mk1 head was fitted.  If you get really bored you could repeat the exercise with a bit of plasticine or similar on the dome to see how much of a miss you have.

 

However, some quick and dirty estimates on the CR:
Looking back through some notes from the head work I've done, sthe standard Mk2 2L head has a chamber volume of approximately 32.5cc.  This gives about 9.25:1.  Figures found on the internet (posted by our own JohnD a while back) suggest that the volume of the dome on the pistons is 8.7cc, meaning that the chamber volume is effectively reduced to 23.8cc.  That equates to a CR of 12.25:1...... which is waaaay to much!

I've not ever had a close look at the bottom of a domed piston, anyone know if the dome is solid?  This is, if you machined the dome off, would it become the same as a flat-top piston, or is material taken out beneath to maintain a more even thickness, meaning you'll end up with a hole if you try this stunt?

 

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