New Crank Required? Streached Big End Cap?

[oldtuckunder]

Hi Folks

 

Late into the year to start the engine rebuild, but been a busy winter and starting greatly hindered by parking the ferguson tractor outside the vitesse garage in November and then removing the transmission for a simple repair! Believe me you can move a car on trolley jacks, but a tractor split in half is going nowhere.

 

Anyway three months later and finally pulled the engine and box from the Vitesse to find out the source of the rumble that started after Shelsley last year. Stripped the engine down this evening and looks like not good news, it was a big end that started knocking but I'm not 100% sure of cause and effect and would appreciate words of wisdom as I have to try and get everything sorted for Gurston in April.

 

All the mains and big ends look good apart from number 5 big end. I have attached a couple of pictures unfortunately the flash obscures some of the damage to the shell, but its through to the copper and looks jagged and ripped. The journal is dulled and imbedded with tiny bits of bearing material.

 

 

 

 

 

I think I can spot the cause if you look at the journal picture you can see a small half moon next to the oil hole where the journal surface has disappeared. The journals are ground +30 so my suspicion is that there wasn't enough hardening left next to the oil hole and a tiny piece fell out and chewed the shell.

 

Of course it could be that the shell broke down and the bits broke up the surface of the journal around the oil hole. These were King Tri-Metal shells. Crank was ground and rebalanced with new shells 2 years ago only about 1500 miles but a number of those at 6-7K RPM.

 

So I think the crank is toast - correct?

 

I have one further conudrum which I'm not sure is cause or effect. The shells in the worn number 5 are loose in the big end cap now, i.e. instead of being a sort of snap fit they are sloppy. The tags still stop them rotating so I don't thing they have been going round and round the journal inside the cap, so I was wondering if I could have streached a big end cap at high revs which allowed the shell to slop around which caused the damage to the crank, or if just the excessive wear to the shell face has made it sloppy in the cap. Anyone seen anything similar.

 

Just trying to work if I need a new crank and a new set of rods, or if I can get away with just a new crank.

 

Just answered my own question, just tried a shell from one of the other caps and it snaps in with click and is firm, so its not a cap problem.

 

So looks like a hunt for a good 2Ltr crank shaft

 

Alan

 

 

 

 

 

[john.r.davies]

I fear that in trying to take close-ups holding the part in one hand and camera in the other has made the focus poor,but I can see your 'half-moon'. That's lost metal from the crank surface, right? In which case the pieces went somewhere and you are probably right that they started the damage. If all the other big ends are good, then you have a full explanation.

Aren't oil way openings in the crank journal surface supposed to have slightly chamfered edges? Were yours drilled out to a large size, or cross drilled and this omitted?

 

If you have another crank, I'd ditch this one, but I'm lucky to have a local and expert machine shop owner, and I'd get his opinion first.

 

7K is a lot, even for a carefully prepared 2L engine!

 

JOhn

[RogerH]

Hi Alan,

depending on the cost of a new/replacement crank and any work required there is a company in Birmingham that can weld and grind the crank journal

back to size. This is apprx £200/journal.

Haven't got their name but they do attend the NEC show in November.

 

Roger

[oldtuckunder]

I fear that in trying to take close-ups holding the part in one hand and camera in the other has made the focus poor,but I can see your 'half-moon'. That's lost metal from the crank surface, right?

 

Correct lost metal, have managed to get a slightly better picture of crank and damaged shells, top layer of bearing just ripped off exposing copper layer.

 

 

 

Aren't oil way openings in the crank journal surface supposed to have slightly chamfered edges? Were yours drilled out to a large size, or cross drilled and this omitted?

 

Not drilled out or cross drilled, but no chamfered edges on the big end journals, but there are on the mains. Looking at all the big end drillings none of them look perfectly round (tried to take a picture but just too much reflection) I wouldn't think that the +30 grind that the crank had would have removed the chamfer but it might have, It will be interesting to see what the drillings are like on the new crank. Cross drilling recomended?

 

 

If you have another crank, I'd ditch this one, but I'm lucky to have a local and expert machine shop owner, and I'd get his opinion first.

 

Found and ordered a NOS crank today for £100, described as needing a 10/10 grind, but I won't order bearings until we see how it comes out! if it does!

 

 

7K is a lot, even for a carefully prepared 2L engine!

 

Yes! But it just spins up there so quickly :-) I'd like to think I managed to keep around 6.5 limit most of the time, but Rev Limiter sat in box waiting to be fitted, hopefully it will work better than my brain when competing! Am also hoping that the new 4.11 diff will help a bit allowing me to get up into third a bit earlier rather than holding on in second screaming because there isn't time to change up and then down again before the next corner. We shall see!

 

Anyway time to start raiding the Piggy Bank again for a full rebuild, balance again :-(

 

Have a couple of other issues that I need to look at with the engine stripped, so no doubt will have a few more questions for the collective brain to ponder to see just how far I have to go :-)

 

Alan

[LGFromage]

The Mk1 and Mk2 Vitesse engines have a different crank with the Mk2 being more robust. Hopefully the replacement crank you have found will suit your engine. Please do not ask how I know.

 

Good luck,

 

Tim

[oldtuckunder]

The Mk1 and Mk2 Vitesse engines have a different crank with the Mk2 being more robust. Hopefully the replacement crank you have found will suit your engine. Please do not ask how I know.

 

Good luck,

 

Tim

 

As is normal with the world there is also a half truth, or as with E-Types a series 1.5 :-)

 

Early MK1 2ltrs up to HC4500 had the same small journal crank as the "late" 1600's and MK1 GT6 but from HC4501 the MK1 Vitesse had the same large journal crank as all the later MK2 2ltrs.

 

And tis rumoured that actually in the 2ltr 6 the small journal crank is actually better, smoother and revs better, and that Triumph only went to that crank in the two litre to standardise across all the 6 cyl varients. I unfortunately have the later large journal crank as far as performance goes, but fortunately as there are a lot more about!

[oldtuckunder]

 

Aren't oil way openings in the crank journal surface supposed to have slightly chamfered edges? Were yours drilled out to a large size, or cross drilled and this omitted?

 

 

Not drilled out or cross drilled, but no chamfered edges on the big end journals, but there are on the mains. Looking at all the big end drillings none of them look perfectly round (tried to take a picture but just too much reflection) I wouldn't think that the +30 grind that the crank had would have removed the chamfer but it might have, It will be interesting to see what the drillings are like on the new crank. Cross drilling recomended?

 

NOS crank arrived late this afternoon still waxed and wrapped in its original paper. At first inspection I thought it might not even need a grind just a polish, but then found a bit of surface rust on back of no 2 & 5 journals, so a grind it is.

 

Thought I'd have a close inspection of the oils holes for chamfer, and yes they do all have one, well thats an exageration they all do have part of one! to my eye it looks like in the factory who ever did this either didn't give a **** or the machine was set up badly. All have a bit of a chamfer but none with a complete one around the whole hole, some are towards leading edge, some trailing, some off to the right and some off to the left, infact any direction you can think of apart from central.

 

So the question is does it matter, did they all come out the factory like this? or as its a NOS item is it from end of production run when all the tooling was going sloppy? Should I try and get it corrected when the crank is being ground?

 

Interestingly as my original crank must have been one of the earliest large journal 2L ones, the chamfers on the Mains on that are also not central so it looks like they may have always been made like that. On closer inspection of the old crank I can see that there are traces of off centre chamfers left, but not having anything to compare with I just thought they were just not perfectly round.

[oldtuckunder]

 

I have one further conudrum which I'm not sure is cause or effect. The shells in the worn number 5 are loose in the big end cap now, i.e. instead of being a sort of snap fit they are sloppy. The tags still stop them rotating so I don't thing they have been going round and round the journal inside the cap, so I was wondering if I could have streached a big end cap at high revs which allowed the shell to slop around which caused the damage to the crank, or if just the excessive wear to the shell face has made it sloppy in the cap. Anyone seen anything similar.

 

Just trying to work if I need a new crank and a new set of rods, or if I can get away with just a new crank.

 

Just answered my own question, just tried a shell from one of the other caps and it snaps in with click and is firm, so its not a cap problem.

 

 

 

 

Just a quick follow up on this - I was wrong.

 

Dropped the new crank off at the engineers this afternoon and got them to check the No 5 Rod, it was .008" oval, so my rods are scrap also.

 

Good job I already had a back up plan in case of this eventuality.

 

Don't know if the rod caused the bearing failure, or the bearing failure caused the cap to stretch. If its the former then I may have been unfair questioning the quality of the King Bearings.

 

Anyway my comment that popping another set of shells in and that they fitted properly, can now been seen for the rubbish statement it was.

 

Any major big end problem get the Rods checked properly.

 

I hope I would have caught the problem at rebuild with the Plastiguage, but it would have been horribly late in the day, and worse still might not have done.

 

Alan

[john.r.davies]

Found this article this morning: http://www.iabg.de/fileadmin/media/Geschaeftsfelder/Automotive/PDF/mtzw-010-0436-8_W_Kurbelwelle_IABG_1_.pdf

 

Although you have decided to scrap the crank, you might be interested, OTU! The paper is an academic discussion of a new method of testing crankshafts, but the first paragraph states as an engineering 'given' that "zones that are susceptible to fatigue fractures can be both at the transition points (fillets) of the crankwebs to the crankshaft journals and pins and at the oil duct inlets and outlets of those crankpins." (My underline)

So the loss of metal from around an oilway entry/exit has to be evidence of stress damage, whose extent must be wider. Knowing that could have saved you a lot of soul searching and investigation. If I ever see it in future, I will scrap that crank without hesitation.

 

John

[oldtuckunder]

Found this article this morning: http://www.iabg.de/fileadmin/media/Geschaeftsfelder/Automotive/PDF/mtzw-010-0436-8_W_Kurbelwelle_IABG_1_.pdf

 

Although you have decided to scrap the crank, you might be interested, OTU! The paper is an academic discussion of a new method of testing crankshafts, but the first paragraph states as an engineering 'given' that "zones that are susceptible to fatigue fractures can be both at the transition points (fillets) of the crankwebs to the crankshaft journals and pins and at the oil duct inlets and outlets of those crankpins." (My underline)

So the loss of metal from around an oilway entry/exit has to be evidence of stress damage, whose extent must be wider. Knowing that could have saved you a lot of soul searching and investigation. If I ever see it in future, I will scrap that crank without hesitation.

 

John

Very interesting document, and by extrapolation explains why #5 might be the first to fail at that point, but very nice find, now have a copy filed for future reference, thanks!

[RogerH]

Hi John,

that article is nearly very good. It is well known that corners and holes are serious stress raisers. But where is 'the' most serious stress problem!!.

 

On a TR4 crank the #4 big end journal to crank web is the killer - I have my own ideas what is going on - others have ideas but are wrong .

 

It would have been nice for these chaps to have tested the crank to destruction and have had some means of seeing what was happening.

I thought from the front page colour pic that that is what they were doing. However calculating the problem is pretty good.

 

They don;t mention mechanical damage - machining scores etc - which are often greater stress raisers than radii or holes - you don't want sharp edges.

 

Roger

 

PS - the beauty of testing to destruction is that the crack faces give a mountain of information. #4 failure above has no torsional failure mode in it.

Edited March 16, 2015 by RogerH

[Peter Cobbold]

Had the b/e bolts strectched? They are solely responsible for resisitng maybe 1 ton of force as the piston goes over TDC on the exhaust/intake stroke at high rpm. Could that have be the initial failure?

[john.r.davies]

Roger,

Good to have a proper engineers opinion of that paper!

 

The authors were going by calculation, as you say, so the stress raisers they could deal with were the design ones. Production/machining ones would be beyond the ken of that method.

 

You refer to the TR4 big end journal to web being a known failure point.

Isn't that to do with crank torsion vibration, my other interest? Always greatest, nearest the flywheel.

 

John

[RogerH]

Hi John,

I have had apprx 6 broken cranks (# 4 BE journal) analysed by my metalurgist at British Airways and ALL failed in a tensile mode.

There was NO torsional problems at all.

if both webs at #4 BE journal could be held still and a large force put on the journal then you would have a shearing force but it is not help stationary.

 

The crack begins in the radii of the journal and progresses under tension (bending) until it pops.

 

The area that fails is quite big in cross section for a torsional failure considering the journal at the oil way is much smaller.

 

My theory of how it breaks is this - (are you sitting comfy)

 

When the pistons go up and down the crank will flex. Flexing as such is not a major problem under normal conditions.

#1 BE journal rotates/flex through the front main bearing (MB). It reacts against the mechanical fan - but the fan is small/light so can be diverted from its plane of rotation.

#2 BE flexes about the centre MB as does #3 BE . These two bob up and down with differing loads due to ignition (bang) but rock about the MB.

#4 has a unique problem - the flywheel is massive and will not be moved from its plane of rotation. So, the BE journal wants to flex and does. But, all the flexing is in the journal = nothing is shared/reduced. Indeed the web/MB journal also would like to flex but is significantly bigger than the BE journal. The BE journal is the weak point.

 

Any machine scoring in the BE journal radii will concentrate all the stresses in a very stressed area.

 

There is a bit more to it than that but that is it in a nutshell.

Clearly there must be torsional forces in the crank and would be acting on the MB/web interface - and obviously the rear MB has all the torsional load - buit has it ever failed - not to my knowledge.

 

Roger (time for tea)

[oldtuckunder]

Had the b/e bolts strectched? They are solely responsible for resisitng maybe 1 ton of force as the piston goes over TDC on the exhaust/intake stroke at high rpm. Could that have be the initial failure?

Its just possible but not conclusive, and I don't know what is cause and effect given the damage to the shells etc. But.. I have just measured all the bolts and all the others are 1.911, 1.912, 1.913 the ones on 5 are 1.914 and 1.915, so possible. I checked all the bolt torques before dismantling as I wondered if one has loosened, but they were still all spot on.

 

But I can add it to the list of possibles which are now, crank failure around the oil hole, bearing failure, cap stretching, bolt stretching.

 

Unfortunately which came first is hard to determin.

 

If it happens again after the rebuild then it must be me! as it will be a new crank, different make of rods, different make of bolts and different make of shells.

[Peter Cobbold]

Roger,

Try google videos for: FEA+crankshaft + vibration

Maybe there'll be a pattern that matches your failure point.

eg https://www.youtube.com/watch?v=Mcp_Y0h_oXQ

 

 

Peter

Edited March 16, 2015 by Peter Cobbold

[oldtuckunder]

In final stages of rebuild and have found one more possible culprit of #5 Big End failure, I may have had a sudden or spasmodic loss of oil pressure, but have found something that I will now check at every oil change.

 

As oil supply problems were a possible cause of failure as part of this rebuild I have been replacing virtually everything connected, so today I was putting in the new oil pressure relief valve plunger and spring. By chance I thought I'd just compare the dimensions of the new plunger with the old one and also the spring pressures, so dug the old one from the tray and on pulling the spring from the plunger I found some awfull indendations on the shaft of the plunger as though the spring had been trapped on it. If this happened when the plunger was is "relief" mode then when rev's dropped I could have lost almost all oil pressure for a while.

 

I have no idea who I purchased the last plunger and spring from, but probably one of the large Triumph parts retailers. It was interesting that the new one came from Chris Witor who stresses that his are to the correct hardness, certainly comparing his new one to the old one they are chalk and cheese in terms of finish, the old one looking like soft steel compared to the new one.

 

Anyway given how easy to check, and how cheap, I think at every future oil change I'm just going to pop the pressure relief nut and check what the plunger and spring look like.

 

Stupid isn't it, its made to be easily accessed, but who ever does?

 

Alan

[oldtuckunder]

Help!

 

Looking for some serious expert input here as I'm not sure what to do/think.

 

Just stripped the bottom end and I have exactly the same problem again with #5 Big End (only worse maybe).

 

As they say, once is unfortunate, twice may be a coincidence but three times.........................

 

Brief recap.

 

Stripped engine in 2013 after long layup just for refresh and found that #5 BE was a bit scored and a tiny bit of marking on #6.

 

Crank reground, King Tri Metal competition shells, and complete bottom end rebalance. Did a couple of hill climbs in late 2013, and then half a dozen in 2014 and then developed a rumble. The thread above is what I found early last year when rebuilding the engine again.

 

So the bottom end rebuilt with brand new crank, brand new rods, new blue printed oil pump, VP Mains, and the new AEM "VP Replacement" BE shells. Again all rebalanced, and the block had hours and hours of cleaning with every single plug out just to make sure it was spotless.

 

Engine did a handfull of events last year before developing a rumble again at Shelsley, and got put away until I could find time to investigate. Finally pulled engine this week!

 

The pictures below (if I can load them) show what I found.

 

 

Wow all of a sudden I can load pictures to the forum again without deleting old ones!

 

Anyway as you can see from the photo's #5 BE cap is now a nice heat hardend blue, compare to #6 also shown, 1-4 are also perfect. The second shot shows the blueing also extending up the rod.

 

The third shot shows what happend to the shells. If you can make it out the shells have spun in the cap and its the back of the shells that had actually turned into the bearing surface and worn away (generating all that heat as no lubrication) and they have been squeezed out and a lip formed over the edge of the cap/rod. The proper bearing surface although through to the copper in a couple of patches is not that badly marked, slight radial surface scratching and showing more wear in line with the oil hole in the crank. One of the tangs from a shell is snapped off and still wedged in its indentation in the cap.

 

So my theory of the destruction process is as follows (other suggestions gratefully received)

 

At some point for some reason (probably at high revs) the shells grabbed/stuck to the journal, at which point the force snapped the locating tangs and the shells then spun in the cap. From that point on it was probably a lottery if the shells were spinning in the cap or the journal was spinning in the shells, or most likely a bit of both either alternatively or at the same time. Suffice to say there was a lot of heat generated.

 

OK where do I go from here in tracking down the cause?

 

I have two theories:

 

1) Its me ragging the engine, The failure in 2014 could have been as I was really enjoying have the car out on the track again. But the original scoring on first rebuild I'm sure wasn't, and last year I was running a rev limiter set soft at 6200 and hard at 6500 which isn't over the top for a well built lightend, balanced 2lt 6 pot. And why just #5?

 

2) There is something wrong.

 

OK if it isn't 2) then do I just rebuild again, set the rev limiter hard at 6k and see if it survives this season?

 

Or do I think its 2) and try and find out why?

 

I want to think its 2) but that gives me a problem as the what is a bit of problem.

 

My guess when the engine went bad in 2014 (as per above thread) was that when #5 went, it was a result of either the King Bearings, a crank failure (the chip), a crank oil blockage, a failing BE cap (it had gone oval), or a bad oil feed to #3 Main and thus #5 BE, loss of oil pressure.

 

So the rebuit engine had a NOS crank, new Rods, different bearings, new oil pump, new pressure relief valve. The only thing that is the same is the block itself!

 

OK so if there is an inherent problem with the block what could it be? Well the only thing I can think off that would cause the problem is lack of lubrication. But here's the problem, the oil feed to #5 is via #3 Main which also feeds #4 BE, I have taken the cap of #3 Main and #4 BE and they are as sweet and clean as a whistle and look like they have only done the 500 miles they have.

 

OK so is the feed from #3 Main to #5 BE through the crank the problem? Well one crank maybe but two different cranks, seems too much of a coincidence.

 

Could it be the Rods, Well again we have the problem of two different types/makes both deciding that that they will pick on #5.

 

Could it be the bearings, Again two different reputable makes deciding that they will pick on #5, and again streaches coincidence a bit.

 

 

OK guys I'm looking for sensible suggestions or even wild ideas, as I'm not sure where to go to start tackling this problem!

 

Alan

 

 

 

 

 

 

Edited February 4, 2016 by oldtuckunder

[Nick Jones]

ISTR that I've seen others talk about problems with #5.

 

Myself, I've not had problems with sixes (though I did a break a number of 4s in the 80's and 90's). My now retired Vitesse lump was still as assembled by Triumph in the late 60s, has done somewhere between 150 and 200k and has been ragged regularly since falling into to my hands in 1989. For a couple of years I was regularly bouncing it of the rev limiter set at...... 7,200 rpm...... Not intentionally I might add, I had cocked up and happily got away with it. Still was running sweet with good oil pressure, but the oil burning......!

 

The new one has the rev limiter set to 6.5k and gets there very quickly. Only about 5k on it so far, but no problems to date. My point..... they can certainly survive spirited use over many miles.

 

So, what is killing yours?

 

Points to ponder, oil supply

- as you say #5 is fed from rear-most centre main. The feed from this is taken from the main gallery at the distributor bush. The bush must be removed to clean this properly and it's always worth checking that the oilways are fully drilled right to the point where the horizontal hole from the gallery intersects the angled hole from the bearing saddle and that they meet dead on. Have you done this? Some like to drill these out but I've never bothered.

- The feed for the main is taken from the main gallery after it's worst bottleneck but if this was an issue you'd expect to see issues further forward too. 1, 2 & 3 are supposedly the worst afflicted by high rpm oil starvation. This can be sorted by adding an eternal feed to to turn the main gallery into a ring main.

- Aeration. As you are hillclimbing (and sprinting?) you'll be throwing the car around, sometimes in sharp sloping corners. I don't know if you have baffled your sump, but possibly oil surge is leading to the pump getting the occasional gulp of air. I have no explanation why this should always kill #5!

 

You may well have seen this already but it's got alot of interesting stuff in it.

http://sideways-technologies.co.uk/forums/index.php/topic/5712-competition-oiling-draft/page-2

 

Steve Smith in particular knows alot about oiling problems and bearing failures as his engine is required to rev to 8000 and hold it on the long straights of the western US tracks. His problems mostly went when he installed a dry sump..... but then he's pushing the envelope further than most.

 

Other factors

You've been concentrating on the bottom end, but how about detonation. More famous for killing pistons, but it stresses the whole engine. If you have an issue with #5 such as lean running due to uneven fuel distribution, higher CR on that pot, less exhaust valve lift or something along those lines then it may be that #5 is failing because it sees more thump. Suggest having a careful look at the spark plug piston crown and ring lands to see if there are any signs of det. Note that if uneven fuel distribution is in the frame, 2 & 5 are regarded at the problem cylinders so compare with 2.

 

Nick

[Guest ntc]

Was the 4 pot line bored with caps like the 6?

[oldtuckunder]

ISTR that I've seen others talk about problems with #5.

 

Myself, I've not had problems with sixes (though I did a break a number of 4s in the 80's and 90's). My now retired Vitesse lump was still as assembled by Triumph in the late 60s, has done somewhere between 150 and 200k and has been ragged regularly since falling into to my hands in 1989. For a couple of years I was regularly bouncing it of the rev limiter set at...... 7,200 rpm...... Not intentionally I might add, I had cocked up and happily got away with it. Still was running sweet with good oil pressure, but the oil burning......!

 

The new one has the rev limiter set to 6.5k and gets there very quickly. Only about 5k on it so far, but no problems to date. My point..... they can certainly survive spirited use over many miles.

 

 

So, what is killing yours?

 

Points to ponder, oil supply

- as you say #5 is fed from rear-most centre main. The feed from this is taken from the main gallery at the distributor bush. The bush must be removed to clean this properly and it's always worth checking that the oilways are fully drilled right to the point where the horizontal hole from the gallery intersects the angled hole from the bearing saddle and that they meet dead on. Have you done this? Some like to drill these out but I've never bothered.

- The feed for the main is taken from the main gallery after it's worst bottleneck but if this was an issue you'd expect to see issues further forward too. 1, 2 & 3 are supposedly the worst afflicted by high rpm oil starvation. This can be sorted by adding an eternal feed to to turn the main gallery into a ring main.

- Aeration. As you are hillclimbing (and sprinting?) you'll be throwing the car around, sometimes in sharp sloping corners. I don't know if you have baffled your sump, but possibly oil surge is leading to the pump getting the occasional gulp of air. I have no explanation why this should always kill #5!

 

You may well have seen this already but it's got alot of interesting stuff in it.

http://sideways-technologies.co.uk/forums/index.php/topic/5712-competition-oiling-draft/page-2

 

Steve Smith in particular knows alot about oiling problems and bearing failures as his engine is required to rev to 8000 and hold it on the long straights of the western US tracks. His problems mostly went when he installed a dry sump..... but then he's pushing the envelope further than most.

 

Other factors

You've been concentrating on the bottom end, but how about detonation. More famous for killing pistons, but it stresses the whole engine. If you have an issue with #5 such as lean running due to uneven fuel distribution, higher CR on that pot, less exhaust valve lift or something along those lines then it may be that #5 is failing because it sees more thump. Suggest having a careful look at the spark plug piston crown and ring lands to see if there are any signs of det. Note that if uneven fuel distribution is in the frame, 2 & 5 are regarded at the problem cylinders so compare with 2.

 

Nick

Hi Nick

 

Thanks for the input.

 

"The new one has the rev limiter set to 6.5k and gets there very quickly. Only about 5k on it so far, but no problems to date. My point..... they can certainly survive spirited use over many miles."

Mine also gets to 6+ in a blink of the eye!, but yes lots of tales of the 2Ltr happily spinning 6-7K.

"Points to ponder, oil supply

- as you say #5 is fed from rear-most centre main. The feed from this is taken from the main gallery at the distributor bush. The bush must be removed to clean this properly and it's always worth checking that the oilways are fully drilled right to the point where the horizontal hole from the gallery intersects the angled hole from the bearing saddle and that they meet dead on. Have you done this? Some like to drill these out but I've never bothered."

Haven't drilled out or checked that they intersect cleanly, but had put it on the list for this time, but have to ask the question why not #4 also hit?

"- The feed for the main is taken from the main gallery after it's worst bottleneck but if this was an issue you'd expect to see issues further forward too. 1, 2 & 3 are supposedly the worst afflicted by high rpm oil starvation. This can be sorted by adding an eternal feed to to turn the main gallery into a ring main."

Yes aware of possible front gallery starvation, and have built a spider & accumulator to fit, as I expected this time to find the problem further foward and not a repeat of #5.

"- Aeration. As you are hillclimbing (and sprinting?) you'll be throwing the car around, sometimes in sharp sloping corners. I don't know if you have baffled your sump, but possibly oil surge is leading to the pump getting the occasional gulp of air. I have no explanation why this should always kill #5!"

Sump is baffled, I have a big red warning light from a sender at the front of the gallery (that should see the biggest drop?) But I have never seen it come on. Was thinking of doing more baffle work, and hopefully the accumulator would help, its just that I have a feeling that I'm just rearranging deck chairs with these.

"Other factors

You've been concentrating on the bottom end, but how about detonation. More famous for killing pistons, but it stresses the whole engine. If you have an issue with #5 such as lean running due to uneven fuel distribution, higher CR on that pot, less exhaust valve lift or something along those lines then it may be that #5 is failing because it sees more thump. Suggest having a careful look at the spark plug piston crown and ring lands to see if there are any signs of det. Note that if uneven fuel distribution is in the frame, 2 & 5 are regarded at the problem cylinders so compare with 2."

Its a good train of thought, but I think I have most of it covered. The chambers + gasket + crown were all meticulously volume matched, and I deliberately didn't go for a high compression its currently 9.3:1 actually lower than the std 9.5:1 of the Vitesse. I have run compression tests and they all come out almost spot on. No signs of detonation, the inlet manifold has had a lot or work to ensure that 2 & 5 aren't restrictive, and as I run a dual Innovate LM-2 data logging the mixtures on 1-3 and 4-6 independantly I have done a lot of work getting good mixture control and know I don't go lean, if anything its always a tad rich, even on WOT.

So you kind of see my conudrum, do I try the couple of extras like checking the oil way drillings, redo sump baffling, add the spider and acumulator and just rebuild and try again, but if the same thing happens I'm not sure what I will do. And the dumb thing is there are people with 2.5 6's that have been ragging the same unrebuilt engine to 6K+ on hillclimbs for many years without problems, and its the 2.5 thats supposed to have the weak crank!

Or do I just junk this engine and start a fresh one?

Alan

[Nick Jones]

Neil,

 

I'm sure the small 4s also have the crank saddles and caps line bored.

 

Alan,

 

I agree that it is difficult to explain why 5 and not 4. Especially since once 5 starts to give way it'll be haemorrhaging oil and robbing it from 4.....

 

Some strange torsional resonance? How's your crank damper (yes, yes, I know, clutching at straws!)

 

Just because your tell-tale isn't coming on doesn't necessarily mean there's no air in the oil system - just that it's pressurised too. Can't explain why it all seems to end up going through #5 though....

 

In your place I'd probably start by checking the relevant oilways very closely including the one in the crank. If nothing found...... the temptation to start again with another engine would be there I think - but you have alot invested in this one (in cleaning alone!).

 

I take it you have had the distributor bush out?

 

What rods are those?

 

Nick

[Guest ntc]

Thanks Nick

I did not know, how do you know after all these years that they match?

[oldtuckunder]

 

I agree that it is difficult to explain why 5 and not 4. Especially since once 5 starts to give way it'll be haemorrhaging oil and robbing it from 4.....

 

Some strange torsional resonance? How's your crank damper (yes, yes, I know, clutching at straws!)

 

Just because your tell-tale isn't coming on doesn't necessarily mean there's no air in the oil system - just that it's pressurised too. Can't explain why it all seems to end up going through #5 though....

 

In your place I'd probably start by checking the relevant oilways very closely including the one in the crank. If nothing found...... the temptation to start again with another engine would be there I think - but you have alot invested in this one (in cleaning alone!).

 

Even with the shells rotating and as sloppy as hell I still had 75 psi cold and 40 psi warm on tickover, so even with one very worn bearing oil pressure seems to be an indicator of bugger all.

 

The crank damper appears to be good, possible resonance problem from very light flywheel? but that sort of diagnosis is getting way beyond my pay grade

 

I think I have to start by a good inspection of the oilways, and if nothing obvious maybe change the block (which would be a shame as its the one it came out of the factory with) but I think I know where there is a MK1 block available and its the only thing left unchanged. I guess if I change the block and the problem reappears, its time to say bugger getting a sweet high performance 2Ltr and go for a grunt 2.5 would be such a shame though as thats like admiting defeat.

 

Alan

[Motorsport Mickey]

Thanks Nick

I did not know, how do you know after all these years that they match?

Not answering for Nick, but in my case because when I build an engine if there is any more than 1/3rd of 1 lb ft torque required to turn it in its new bearings (that's about how much force you can impose by spinning with your FINGERS alone) I know there's a problem either with crank and it's bearing surfaces or the block main bearing housings.

It gets taken back down and both items are checked as for being parallel (if you have a miller or machine capable of traversing between the housing surfaces, and checking with a DTI (clock) or between the journals of a crank on V blocks) and if not returned to a reliable engineering firm who will charge you £40 (about an hours labour) for doing the same.

I've had 4 cranks which have bowed when being Tuftrided (Nitriding would likely bring about the same results) with the worst one being nearly .010 thou !. Returned them to the firm who'd reground and heat treated the crank and collected them back within about 48 hours straightened, ( hit with big hammers on the webs until it submits apparently ! a specialist skill), used them in race engines with excellent results and good reliability.

So far never had a block which has gone out of line on the main bearings housings, maybe I'm just lucky.

 

Mick Richards

Edited February 5, 2016 by Motorsport Mickey