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Cylinder Head Gasket Oil Leaks


Nigel Clark
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Triumph sixes - and probably the four pots too - are prone to leaking oil along the pushrod side of the head gasket. The reason seems obvious, as the head studs are clustered around the bores, providing insufficient clamping around the pushrod tunnels.The result is a messy oil leak down the distributor side of the block.

I've always understood the answer is to use Wellseal along the edge of the head gasket and around the rocker oil feed hole to seal this leak, and this has worked well on two six cylinder motors I've built in the last few years, both remaining oil-tight. When I discussed this problem with a well know trade engine builder, he advised using Wellseal over the entire head gasket.

My TR6 is the worst example I've found for this problem and it's always leaked oil from this this of the head gasket. Last time I removed the head, it was perfectly flat, as is the top face of the block. I refitted the head with a Payen recessed bore gasket (correct for this engine) and Wellseal on both sides of the gasket around the offending area. The engine has ARP head studs, washers and nuts, which I torqued down according to ARP's advice, using light oil to lubricate. I believe I've done everything correctly but it still leaks. The TR6 does breathe quite heavily, as there's always a bit of oil in the air plenum from the breather but even so, I can't accept it's impossible to make the head gasket oil tight.

With time on my hands in lockdown, I've removed the head again for another attempt. Before I put it back together, I'm looking for some more opinions from the wise ones here...

- How do you ensure the head gasket is oil tight along the pushrod side?

- Uncle Pete's favourite Loctite 574 is recommended for sealing flanges where this isn't a gasket. Would it work better than Wellseal on the problem side of the head gasket?

Any other advice before I reassemble with lots of Wellseal and crossed fingers?

Thanks in advance.

Nigel

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Nigel,

I don't agree that T6s are notorious in this way!   I've never had that problem, and never met anyone else who has, either.      Most oil leaking at the top of the engine comes from the rocker cover, but I would not suggest that to you.   Rather, I'd ask you to look at it in a different way.    As your engine persistently leaks and the block and head faces are flat, is there some other cause?     In particular,  is the head face at precisely a right angle to the clamping force from the head studs?     If not, then they may not compress the gasket evenly right across  the head, and less on that side.

As you have tried everything else, before slathering it in more (unnecessary, IMHO) sealant, can you measure that precisely, or get it to a shop that can?   And are all the head studs precisely at a right angle in the block, for the same reason?      

I feel that there must be something different about your engine, an unusual defect,  to cause this persistant fault.

JOhn

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45 minutes ago, JohnD said:

Nigel,

I don't agree that T6s are notorious in this way!   I've never had that problem, and never met anyone else who has, either.      Most oil leaking at the top of the engine comes from the rocker cover, but I would not suggest that to you.   Rather, I'd ask you to look at it in a different way.    As your engine persistently leaks and the block and head faces are flat, is there some other cause?     In particular,  is the head face at precisely a right angle to the clamping force from the head studs?     If not, then they may not compress the gasket evenly right across  the head, and less on that side.

As you have tried everything else, before slathering it in more (unnecessary, IMHO) sealant, can you measure that precisely, or get it to a shop that can?   And are all the head studs precisely at a right angle in the block, for the same reason?      

I feel that there must be something different about your engine, an unusual defect,  to cause this persistant fault.

JOhn

Thank you John, that's something I will consider. I'll fit he head studs and check with a set square to see if they are perpendicular to the block.

However, I have heard of a number of Triumph sixes that leak oil from this joint. I do agree that applying sealants really shouldn't be necessary.

Nigel

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I've just fitted the head studs and measured their angles in the block face, side to side and front to back. None deviate from right angles but more than 2 thou in the length of the stud's shank. I hope that has little impact on how the cylinder head is clamped but stand to be corrected.

Nigel

20200502_115737.jpg

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One other thought about what could cause poor clamping and oil leaking from the pushrod side.

It's a recessed bore block. If the block face has been skimmed in the past and the recesses weren't machined to match, the fire rings may not be able to compress enough and hold the cylinder head away from the block.

I've measured the depths of the recesses around the bores at 29 thou. The compressed fire rings on the old gasket are 30 thou thick. That seems fine to me, the old gasket has simply relaxed by 1 thou after removal.

Can anyone here advise how deep the recesses should be?

Nigel

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Has the head been skimmed off square in the past although it maybe flat on the face is it square from side to side, seen a 1500 head like that in the past, had to have it reskimmed to square up, they took 1 thou off one side and 6 off the other to square the head up and guess what, no more oil leaks

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Thank you Hugh.

I haven't come across that before! I had the head skimmed by a machine shop that I trust about 10 years ago. It is still flat when checked on the lower face.

I will try to measure the thickness of the head in different positions tomorrow, which may give a clue if it's been skimmed at an angle rather than square.

Nigel

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7 hours ago, Nigel Clark said:

It's a recessed bore block. If the block face has been skimmed in the past and the recesses weren't machined to match, the fire rings may not be able to compress enough and hold the cylinder head away from the block.

In my experience they are a bit prone to weepage on that side.  I do usually put a bit of extra sealant along that edge.  Typically good quality automotive silicone.

What you mention above certainly has potential.  I've noted some variability in the fire-ring depths when measuring engines, though whether this is factory variation or later work I really don't know.  Hugh's suggestion is something to think about also and should be fairly easy to measure with the head off.

Nick

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1 hour ago, Nick Jones said:

The victor reinz stuff is possibly the best stuff I have used. The OEM sealants (vauxhall, nissan etc etc etc) are also excellent, and I believe made by threebond. Again brilliant stuff. Knocks the spots off most RTV  instant gaskets.

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12 hours ago, Nigel Clark said:

Thank you Hugh.

I haven't come across that before! I had the head skimmed by a machine shop that I trust about 10 years ago. It is still flat when checked on the lower face.

I will try to measure the thickness of the head in different positions tomorrow, which may give a clue if it's been skimmed at an angle rather than square.

Nigel

Which would be the same as non vertical studs!

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Thank you to everyone for your thoughts and comments.

I've measured the cylinder head this morning to see if it's been skimmed off-square as Hugh suggested. Taking six measurements with a digital caliper at three positions along each side (front, centre and rear), I get figures all in the range 3.377 - 3.379", so within 2 thou. The repeatability of each measurement is about 1 thou, so I would say within my measurement capability, the cylinder head is square. It's been skimmed by just over 20 thou from its nominal height of 3.400". With a 20 thou over-bore, this must equate to a compression ratio of 10.0:1 or maybe a fraction higher. This could explain why it runs so well and prefers 99 octane fuel!

Thank you Nick and Clive for the suggestion of Victor Reinz silicone, I've ordered a tube. I'm familiar with Reinz quality, they are OEM suppliers to much of the German car industry and I've used their gaskets on a couple of BMWs.

I've had another look at the top surface of the block. Though it appeared flat when I first checked, there are in fact very slightly raised areas around each of the stud holes on the pushrod side. I've run a nearly new, perfectly flat fine oil stone over this area and round patches soon polish up around each stud hole. The manifold side of the block is perfectly flat. Could this be a Eureka moment? This slight distortion of the block face around these particular studs would certainly be expected to reduce clamping on the pushrod side.

The question now is what to do... The correct answer would be to pull out the engine and strip it down to get the block refaced. That's not happening, it's a strong engine and it's a long way from needing a rebuild. I'm considering lightly relieving the raised areas around the studs with the oil stone. It will need care, and probably best to err on the side of removing too little metal.

Please can you offer opinions?

Nigel

PS: I wanted to post a photo of the raised areas around the studs but it's not possible to see them in a phone photo. I will try again with a DSLR and ring flash.

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sounds like you have found the culprit, something we all need to be observant of on any head off jobby,

sealer on head faces is always a tricky one the heads pant about a lot in operation and needs to grip the gasket , I wonder if upping the CR added stress to the block tappings 

and this has led to some local deformation around the studs ??? but its been done on many before so  who knows 

we have seen block threads torn by over gorilla tightening ,   not  youres nigel 

Pete

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Ive very rearly seen one that dont leak,

just look at the pics of folk,s engines, coverd wid oil.

there, im my mind a few prob causes, esp wid the bigger engines.

 

1, the breather aint big enough, its same size for a 1300 as it is for a 2500

so go figure hoo much pressure inside engine, there is Alottt, like alott of gasses coming oot,

an if ye tek the breather of whenst under load at revs, { RR sessionee } then its a veritable gale blowing

{ this aint just on T engines either }

And, t,show its true, most wont leak oil potter,n aboot, but will spew it oot at high speeds an  WOT

this is why it comes oot every where, like front,rear oil seals, dizzy area, dizzy shaft,into dizzy,  rocker box, time,n cover

dipstick hole,sump bolts,sump gasket,

high speed an  small  pedal movements dont cause it as much, as there no as much by pass rings pressure.

 

Bigger breathers  help alott, esp if the gasses are sucked oot

 

2, type of gasket an how its used.

some are coverd in a fine glue, others a fine silvery stuff, , which comes of  on yer fingers whenst ye rub it.

 an which is supposed t,melt whenst hot, an mek a seal.

thats why some area of heed, the gaskets stuck fast, others its not

 

Wots under the gasket thats no sealed, oil.

some times water, thats why its a good idea t,run engine wid nee water init for 5 mins or so t, try an get the gasket

varnish glue t,melt.

 

3, hoo the heed / block has been finnished can and does cause problemo,s

circular scratches going oot wards, esp if deep  is a recipe for disaster t,me.

 

What will help,  for a while, or alang time, dependant on hoo good yer prep is, 

is t,ruff up the heed an block wid some wuff wuff sand paper,

and sand ..along or aroond  the block , heed,  this is so all the scrape lines are running aroond the block / heed, not out of it.

and get some good silicon mastick, the stuff that teks for ever t,set,

the longer it teks t,set, the better it sticks, think its Low modulous type, but no sure at moment.

Thats why some silicons in  peel off easy,  like in a strip whenst pulled. an others stick like sheite,

wont even budge wid a sharp chisel or blade.

 

and put a thin smooth film owa both sides of gasket on plug side,

DONT, start engine for a dayor 2, as mastick will no ev set, been there fun it oot.

 

And, Petes, an my choice of sealant, the Orange Loctite, , just dont work very good on this area,

possibly cos its try,n  t,stick  t,the gaskets glue bits, no the gasket, so when glue does melt, it comes adrift, as it sets solid

no like the mastick that stops pliable

Hoo doo i no, cos I tried it, so got the Badge which says it no works.

 

Gudluk

M

 

 

 

 

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Nigel,

AH HA!   Raised areas in the block face around the head studs!    Well spotted!

You said that the face had been skimmed a little.  When this is done, the first turn of the thread in the block should be drilled out.    Studs should not be inserted to bottom in their holes, but to butt the end of their threads in the top of the hole.    This can apply a lot of lateral pressure on the surrounding metal, which will yield and bulge!     If the first turn of thread is down inside the hole, then no bulge will occur.

Studs should be inserted no more than fingertight but some manuals list a torque setting for them! 60-80lbs-ft!!    That's guaranteed to bulge the face, unless the threads have been counterdrilled.

 

If that is the reason for your oil leak, then my statement that these engines only leak oil from there (everywhere else, but not there!) if something is not right, stands!    

John

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blown block ....also the reason OE stud have a slot/groove linear down the threads so if there is any oil coolant down the hole it doesnt hydraulic the block when you screw the studs in 

the groove gives an escape route  

and i agree studs  hand tight/ nipped  no gorilla antics      , just torque the nuts 

Pete

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Marcus,

Thank you for your detailed response, good to hear from you. Looking closely at the face of the block I can see a pattern broad arcs, apparently from a cutting head when it was resurfaced long ago. Of course they run across the block, so could provide pathways for oil to come out of the side. Sandpapering the top of the block sounds a bit extreme, what grade do you use? I will use the Victor Reinz silicone recommended by Nick along the pushrod side of the gasket and leave it a few days to cure - I can't really take the car far in lockdown anyway!

 

John, Pete,

Thank you for your comments again. I normally fit the studs finger tight, after cleaning the holes and blowing out with compressed air, so hopefully no risk if hydraulic pressure developing. I've owned this car for about 15 years and it's always leaked oil here, so who knows what a PO may have done?! I never spotted the bulging around the stud holes when I've had the head off before, and only spotted it by chance this time. I had noticed a small nick in the face of the block near the gasket fire ring recess next to cylinder No.5. I couldn't tell with my finger if this was raised and could possibly disturb the gasket, so I ran the oil stone lightly across it. The mark next to 5 wasn't raised but the stone revealed the raised areas around the studs. Pure fluke that I found this!

 

I'm learning all the time.

 

Nigel

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Oil leaks mainly come from the, also Mk1 pushrod tubes, the oil feed between the block and the head. As far as the oil feed leaks are concerned then a very small amount of sealer on the gasket either of the feed hole normally resolves the problem. From my experience this also applies to the small four cylinder engines. Having owned two new Triumphs this problem wasn't present and would only appear after an engine rebuild. Did the factory use a sealer around the feed hole, probably, some I have talked too who were involved say yes.

Dave 

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7 hours ago, dave.vitesse said:

Oil leaks mainly come from the, also Mk1 pushrod tubes, the oil feed between the block and the head. As far as the oil feed leaks are concerned then a very small amount of sealer on the gasket either of the feed hole normally resolves the problem. From my experience this also applies to the small four cylinder engines. Having owned two new Triumphs this problem wasn't present and would only appear after an engine rebuild. Did the factory use a sealer around the feed hole, probably, some I have talked too who were involved say yes.

Dave 

If I recall correctly , John Kipping used to recommend putting a small smear of sealant around the oil feed hole from block to head, when replacing the head gasket.

Gav

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The pressure in the rocker oil supply must be minimal, but Nigel had leaking all along that side, presumably from the push rod galleries, where there ISN'T any oil pressure,  only crankcase gas pressure!     So a 'smear of sealant' isn't going to cure it!       He's been most observant to catch this fault!

I run a CR of 10.5, use no extra sealant of any sort, and have no oil leaks!  (Oh, ye gods of Triumph, please forgive my uppity bravado!)

 

Triumphs have been unfairly mocked, for their unpatented Chassis Corrosion Prevention System and for 'marking their territory'!     The classic leaks include sump flange (over tightening, belling the flange holes), the timing cover (over tightening, stripping the thread in the bridge piece), the front crank oil seal (misfitting), the rear crank oil seal (wear on the crank), the gearbox (blocked vent, and omitted copper washer to bell housing), diff (blocked vent and worn pinion oil seal).  All either user errors, wear or in the case of the alloy bridge piece, use of UNF thread where Triumph should have stipulated UNC.    No doubt for 'good production reasons'.  

Any more?    A leaking head gasket should not be on the list!

John

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Why wouldn’t a smear of sealant help with a low pressure joint face? It does.......

Presuming you have bigger breathers John? Marcus is right on the money about that. These engines sweat when worked hard unless they are very fresh or they have big breathers.

Nick

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Thank you again gents, really insightful input here. I will be using the Victor Reinz silicone when it goes back together, regardless of any theory that may say it's unnecessary. I don't wish to repeat the cylinder head removal exercise for a good long time!

As mentioned in an earlier post, this TR6 engine breathes more heavily than other Triumph sixes I've known, including a 100k mile 2 litre and the freshly rebuilt 2.5 litre in my GT6. I base this comment mainly on the fact that the TR engine regularly puts oil in its air plenum, whereas as the other two have never visibly oiled their air boxes. A bigger breather should help, as Marcus says.

Nigel

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Nigel, i use a 60 grit,  and change to a new bit often,

as its quite amazing wot comes off a clean heed, !!!

 

after rub,n right way,  then is imperitive t,give it all a wesh wid thinners , { its aboot 6 squid for 5 litres,  }

and plenty of clean rags /cloots  too

as for fisrt 3-4 wipes, yer  nice new cloots  will be acky black,

clean untill they dont go black

 

Another bit of seal,n I doo, is all the way alang the front, an a little roond the ends,

this is on the oot side, the bit where the heed is shorter than,t block an there a wee ridge there.

this makes it a good sealing lip / step .

agen, clean wid sand paper, wesh off, and then run a small bead of the black silicon alang the whole front

as this will let it be a 2 nd line of defence, it works wee,l too if done right,!!

 

it helps t,get a straight line of sealant if ye use mask,n tape

put this on both bits no  need,n sealed

and apply goo, then go alang it wid yer finger, and sqesh it oot , try no to put too much on

as it dont tek much, and pull off when finnishedm it  can be then gon owa wid finger,

IF its left a dodgy edge,   wid there being too much goo at edges.

 

Be very miserly when putt,n some sealant aroond the rocker feed gole,

as it,ll squesh oot, an can block the wee wol there.

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