It the sixpot an interference engine?

[Roger]

My 2000 Mk I engine has a sever loss of power, and I'm trying to establish if the root cause could be that the camshaft is not properly aligned with the crankshaft so that the valves open and closes too early or too late. After all, the PO had installed the dizzy 180 degrees out, so he might as well made mistakes when he asembled the camshaft and chain.

So far I have only done a quick and dirty check according to the “point of balance” method described in WSM. If I understand the instructions correctly then piston #1 should be at TDC when valves 1 & 2 are at the point of balance (one going up, one down). It is not at TDC, far from it. Either I’m doing something completely wrong, or my camshaft is indeed at least 3, 4 or more (!) teeth (tooth?) out. I wish I had checked this when I had the cylinder head off, it would have been so much easier and more accurate. Now my question. Before I remove the timing chain and start to correct this I would like to know if our six pot is a so called interference engine or not. Does anyone here know? I assume it is a non-interference engine, but it would be nice to know for sure before I start fiddling with the cam chain. I have invested in new valves and I would like to keep them stright and shiny. Thanks in advance /Roger.

[Colin Lindsay]

Just as a thought - It's been mentioned on the forum many times before about the timing marks on the pulley moving off their original spot, so whilst your engine may be correct the marks are now well off-kilter. John D / Pete and the other 6-pot owners will advise on options.

[Pete Lewis]

it doesnt carry on to say at the tdc point the gaps under each of 1 and 2 should be equal 

they dont finish the test of ...bit of Triumph daftizum 

if you end up with unqual gaps then the cam sprocket needs some adjustment

to test TDC  make a piston stop from and old spark plug witha bolt added  turn by hand each way and witha card disc mark the stop positions  tdc is half way between the two 

with that checks the damper ring has tdc aligned with the cover pointer 

on my 1600 the ring was able to rotate as the bond had failed  and john has a engine test rig to prove dampers 

Pete

 

[Roger]

53 minutes ago, Colin Lindsay said:

timing marks on the pulley moving off their original spot

I should have mentioned this in my first post: I checked this with one of those fancy USB endoscope cameras you can put through the spark plug hole. The mark has not moved, it is at TDC.

[Roger]

46 minutes ago, Pete Lewis said:

it doesnt carry on to say at the tdc point the gaps under each of 1 and 2 should be equal 

they dont finish the test of ...bit of Triumph daftizum

Someone should write a new edition of the WSM and clarify things and fill in all the missing information... Thanks Pete.

[Steve P]

When I built a 2.5 engine for my Vitesse I downloaded a free Cam timing disc from the net, stuck it on some cardboard and used that to time the cam. First time I had done this and It worked spot on. 

Even tried to fire when I was spinning it over to get the oil going as I forgot to disconnect the coil.

S

Edited December 30, 2023 by Steve P

[johny]

1 hour ago, Roger said:

My 2000 Mk I engine has a sever loss of power, and I'm trying to establish if the root cause could be that the camshaft is not properly aligned with the crankshaft so that the valves open and closes too early or too late. After all, the PO had installed the dizzy 180 degrees out, so he might as well made mistakes when he asembled the camshaft and chain.

So far I have only done a quick and dirty check according to the “point of balance” method described in WSM. If I understand the instructions correctly then piston #1 should be at TDC when valves 1 & 2 are at the point of balance (one going up, one down). It is not at TDC, far from it. Either I’m doing something completely wrong, or my camshaft is indeed at least 3, 4 or more (!) teeth (tooth?) out. I wish I had checked this when I had the cylinder head off, it would have been so much easier and more accurate. Now my question. Before I remove the timing chain and start to correct this I would like to know if our six pot is a so called interference engine or not. Does anyone here know? I assume it is a non-interference engine,

Not interference unless head skimmed and/or high lift cam fitted?

[Roger]

2 minutes ago, johny said:

unless head skimmed and/or high lift cam fitted?

No hight lift cam, but the head was slightly warped which has been corrected. I do not know how much material that had to be removed in order to get a flat surface. Should I be worried?

[johny]

Id be surprised but maybe one of the tuning boys (or girls) can answer that...

[Roger]

I have read the text in the WSM above many many times by now, and things that confuse me is that there are a lot of instructions to turn things, but no information in which direction. I just assume they mean to always turn both crankshaft and camshaft clock-wise looking at the engine from the front of the car (as the crankshaft rotates when the engine is running). Also, it would help if they would relate this point of balance to the engine strokes in writing, not only with Fig. 58. The point of balance is at TDC at the end of the exhaust stroke and when the induction stroke just begins. If I get it right...

Edited December 30, 2023 by Roger

[johny]

Yes always CW but unfortunately diagram 58 is only generic and doesnt really help. The only time valves 1 and 2 are closed at TDC is the firing position. In the diagram its the other two radial lines even though they look to be miles away from TDC!

[Roger]

Short status report from The Åland Island after much engine turning 😊 I have adjusted rocker clearance to 1 mm for valve 1 & 2 when pushrods 11 & 12 are at their highest points by the book. After that I do have 1 mm clearance for both valve 1 & 2 when cylinder 1 is at TDC between the compression and power stroke. However, when #1 is at TDC between exhaust and inlet stroke I do NOT have 1 mm clearance for valve 1 & 2. In fact, inlet valve is partly open at this point. I’m confused, should it not be the other way around?!

The inlet valve should open 18 degrees before TDC between exhaust and induction stroke, and exhaust valve should close 18 degres after TDC. I assume the extra clearance 1 mm is there to be able to detect that there are same number of degrees (18) before / after TDC but in mm instead. My gut feeling is that inlet valve opens way too early during exhaust stroke (hence carbs spitting petrol fumes) and severe loss of power. Brain trust, help me out here…

Edited December 30, 2023 by Roger

[johny]

3 minutes ago, Roger said:

Short status report from The Åland Island after much engine turning 😊I have adjusted rocker clearance to 1 mm for valve 1 & 2 when pushrods 11 & 12 are at their highest points by the book. After that I do have 1 mm clearance for both valve 1 & 2 when cylinder 1 is at TDC between the compression and power stroke.

Seems your valve timing is set correctly....

[JohnD]

The original engine is not "interference".    But as johnny said, a high-lift cam and big skim can make it so.

Thank you Colin for the namecheck on loss of true TDC.   Roger, as suggested above, it may be that the damper on your crank pulley has shifted.    Triumph added a crank damper to the sixes, when nine of their fours had one, because the longer crank shaft would bring the frequencies at which torsional vibration  will occur down into the rev range, when in the fours they are above.     The damper is a heavy steel ring, the "inertia ring", bonded by a rubber ring to the hub of the pulley.      After more than  fifty years in the heat and oil of the engine compartment, there is no wonder that the rubber has perished, many dampers are no longer effective, some have lost adhesion so that the inertia ring has turned, taking the TDC markings away from their proper place, and a few have become completely detached!     I have published a detailed account of Torsional Vibration, in TRaction and the Courier.    See “Crankshaft Torsional Vibration”, Traction March/April 2020, pp41-43

I am, I think, the only person in the World who can test crank dampers on my engine rig!    I would gladly do that for you, Roger, postage from Sweden might not be cheap, but I have provided this service for people in Germany and France.   But a quick test will show you if the inertia ring has shifted: determine TDC by another method, a piston stop is best.   When you know true TDC, is that the same as your crank pulley indicates?    If not, the ring has shifted and the damper is useless.

John 

 

 

[johny]

He he, the pulley issue is so well publicised now John I think its the first thing everyone checks. See above😁

[JohnD]

No one knew before I started to whinge on about it!

[johny]

Whinging always works👍

[Roger]

16 minutes ago, JohnD said:

But a quick test will show you if the inertia ring has shifted: determine TDC by another method, a piston stop is best.   When you know true TDC, is that the same as your crank pulley indicates?

Thank you John for your detailed explanation. I did check that TDC match the mark on the pulley by looking into the cylinder with an endoscope camera. I know the accuracy is very poor with this method, but the camera has quite high magnification and very small movements of the piston can be detected. It is not a perfect method, but at least is should give me an indication if the mark is completey wrong.

[PeteH]

9 minutes ago, JohnD said:

No one knew before I started to whinge on about it!

I seem to remember the articles being published in the Courier? It interested me, as I was involved with frequency dampers on a 3 Cylinder double acting opposed piston marine engine. That invoved massive springs in a housing weighing several tonnes, rotating at 120+rpm. Once "fettled" it did work.

Pete

[Pete Lewis]

its far best to use a piston stop, there is a lot or rotation without piston movement when at TDC

doesnt need the head off   use something like a extended spark plug 

Pete

[Roger]

15 hours ago, johny said:

Seems your valve timing is set correctly

I beg to differ Johny! No one really answered my question whether the 1 mm clearance should be measured at no 1 cylinder on TDC on the compression stroke or at TDC on end of the exhaust stroke. When the piston reach TDC on the compression stroke then both valves are closed both when the piston is going up, and also when the piston starts to descend on the power stroke. Hence,  at this TDC I can rotate the crankshaft & camshaft +/- 10 degrees and I still have 1 mm rocker clearance on valve 1 & 2. At this TDC position the clearance do not show the position of the camshaft since I obviously can turn the camshaft many degrees in both directions without any change in clearance.

However, when #1 cylinder is at TDC on the exhaust stroke then the camshaft reach the “point of balance” hence the clearance in mm can be converted to degrees on the camshaft and the position can be established.

I’m daft at these things, first time I do it. I had to put a camshaft from another engine on top of the rockers, turn the engine and look at the lobes at both TDC to get the picture.

So, please correct me if I’m wrong: The 1 mm rocker clearance should be measured when no 1 cylinder is at TDC at the end of the exhaust stroke (?)

[johny]

Sorry its got to TDC explosion as you can see from diagram 58 this is the only time when both 1 and 2 valves are closed. Are you measuring the 1mm gap accurately as this should change as you rotate the cam? The balance point is only when you have exactly the same clearance on both valves...

[Roger]

15 minutes ago, johny said:

this is the only time when both 1 and 2 valves are closed

Yes, but my thinking was that increasing the clearance to 1 mm will prevent (delay) them from opening / closing at TDC on the exhaust stroke hence a clearance can be measured also at this point. They should open close 18 degrees before / after TDC on this stroke, but the increased clearance delays this from happening? Uncle Pete? John? Anyone else who can elaborate on this subject?

[Pete Lewis]

think for the new year  dont think so deeply  ha 

ive only used feelers and the gap when the heads on when its off a dial indicator on the cam followers

at least visuals  are easy on the H /V etc range  getting your view of the cam gears on the 2000 is a bit of an  acrobat  Ha !

worst job i was given was a spitty with a hell of a rattle at idle  thinking tensioner problems but no 

some PO had centre popped the cam sprocket on its mounting face , tight but able to clatter 

quick zip with a dremmel disc and all silent  .  tensioner was like new 

but one small dot made one heck of a racket 

Pete

 

[johny]

1 hour ago, Roger said:

Yes, but my thinking was that increasing the clearance to 1 mm will prevent (delay) them from opening / closing at TDC on the exhaust stroke hence a clearance can be measured also at this point.

The 1mm clearance is to ensure the tappet is well clear of the cam otherwise the gap could be small and more difficult to measure. Look at drawing 57 which shows lobe 1 exhaust just about to open and lobe 2 inlet just closed.

There is a recent good (but long) thread on here on exactly the same subject....