Lubricants and sealants for engine reassembly...

[JimEB]

Hi all,

I'll be bolting my PI's partially stripped engine back together next week (head is off, the pistons are out, cam/cam followers/crank still in situ) and am open to advice on which lubricants and sealants to use.

I've got some Graphogen to protect the new main/big end shells and oil pump (simply stripped, cleaned and inspected).

A recent article by TRGB in Practical Classics recommended using Wellseal for the head gasket, but I think I've heard in the past that grease could also be used, as advised in the Works Manual.

As for the sump and water pump housing gaskets, I'm thinking some form of instant gasket.

What do you do when reassembling an engine?

Cheers  ;)

[piman]

Hello Jim,

I have always greased the (copper) head gaskets, and Hylomar on gaskets, more to hold them in place rather than as a sealant.

Alec

P.S., I also run a tap into all threaded holes, to ease assembly.

[Richard B]

Never bothered with sealent on a 6 pot head gasket; now a Stag head gasket thats a different matter.  :'(

How straight is the aluminium bridge piece at the front? If you removed it, that can be a sod to seal.

[69vitesse]

Permatex, hylomar and silicone RTV.

= Leak free life

[nang]

Like many others, I'm sure, have had the misfortune of getting the head off and cleaning off the resulting mess of a sealant stuck on gasket.
Must agree with Ted on this one. LOL
Tony.

[Davemate]

Blood,sweat and tears !

[Peterrc]

Just done this job and was advised by the machinist that the head gasket was pre-treated and did not require sealant.  Perhaps you could ask your gasket supplier if sealant is needed.  I know that no instructions came with mine.
Clean the studs and stud holes and lightly grease the studs.  Make sure that you have the correct torque for the head nuts.  For the Vitesse it is Early Heads 45+ Ft lbs Mk 2 heads 65+ Ft lbs, quite a difference, don't know about the PI.

[Richard B]

All 2.5's use the 7/16"UNF nuts at 65lb/ft

[Peterrc]

Richard_B wrote:

All 2.5's use the 7/16"UNF nuts at 65lb/ft

Being a PI I thought that might be the case.

[Tim Bancroft]

I always use Payen head gaskets and never use sealant.

Hylomar as a sealant for all other gaskets.

TSSC sell steel bridging pieces, if alloy one is ok, use the correct length set screws.

For the camshaft I have always drenched the thing in STP, seems to work for me.

Are you changing the timing chain?

Dale Barker of Moordale told me years ago to use Valvoline VR1, have done since then, very pleased as the oil seems to hold oil pressure. I know many don't agree, but I run oil coolers with an in line oil thermostat, I am convinced they increase the life of engines.

[TedTaylor]

The lightest smear of grease on a copper gasket - the principle being that as the head is torqued down and the gasket compressed there is slight (planned for) movement between parts of the copper face of the gasket and the mating surfaces of the head and block.  This very thin layer of grease assists this movement.
On composite gaskets I understand they have a layer of varnish on the mating surfaces to act as a sealant/lubricant already and should be fitted dry.

With the other gaskets I tend to use either Hylomar or grease as the whim or experience takes me - bit of a case of look at the job and decide though if in doubt I use Hylomar.
In my early days (goes back to the early 1960s) we used grease for card and paper based gaskets though where mating surfaces were slightly damaged would use a sealant (red Hermatite on aluminium or brown on cast iron) but once introduced to the magic of Hylomar in the late 1960s the old Hermatite was dumped, though I think they make a product now similar to Hylomar.

Could not agree more with Alec over cleaning up all threads before reassembly - either careful wire brushing and inspection that threads are clean but more usually use of a tap/die (don't forget to blow out any blind holes to clear the crud).  If threads are dirty then part of the torque figure (if used) is taken up with working against the muck.  Any old cheap and nasty tap/die will do as you are simply cleaning not cutting.

There is discussion about whether to reassemble threads dry or lubricated.  Personally I always put the me mearest smear of very light oil on the threads of nuts and bolts (not studs which should always be dry or use 'studlock' as appropriate) so that they look 'damp' but not 'wet'.  One very cautionary note is that if putting a bolt into a blind hole with with too much oil on it a hydraulic seal can be generated such that as the bolt is tightened it causes so much pressure in the hole that the sides 'blow out'! :-/

Hope this rambling answer helps.

MUT

[JimEB]

Thanks all for your input  :)

Richard: I've not yet taken the bridge out to get to main cap #1, but will do so very carefully, once I've got the block supported so I can remove the engine crossmember to improve access. As for the head stud torque, my late works manual says 60-75 lbft   ;)

Tim: I've not fully stripped the engine - the block's still in the car and I've not touched the timing gear/camshaft/crankshaft. This is a partial, get-the-car-back-on-the-road rebuild rather than an engine out full rebuild. Simply a matter of spare funds... The engine will be treated to a proper rebuild (balancing, lightening, fast road cam...) at some later date when I've got the proper funds. As for oil, I've been using VR1 for a while now and have fitted a spin-on filter thingy.

Ted: it's a Payen composite head gasket, so I'll fit it dry. I'll follow your and others' advice re tapping/cleaning (again) the threads and studs. I'll oil the head studs to ensure even torquing-down; I'll eventually use copper slip on the inlet/exhaust manifold studs.

Can't wait to get all this done  ;D

[tiggrr1]

All good stuff but may I suggest a little silicone sealant around the oil feed to the rockers at the rear of the head gasket, only the thinnest of smears (too much may block the feed).

It stopped the dribble of oil down the back of my engine block.

Of course the new head gasket may have helped too  ;)

[Velocita Rosso]

tiggrr1 wrote:

It stopped the dribble down the back of my engine block.

That`s what happens when you become an old Triumph driver...... ;D

[tiggrr1]

:P :P :P

[JohnD]

May have mentioned this before, but as people have said, oil the threads of head studs.....

I've just ruined a block.    Two causes:
1/ The WSM says to torque in the head studs
2/ My torque wrench was wrong, by about 20%

The result was that I cracked the block at the forward right hand stud hole, and the block is ruined.    "Stitching" is very expensive, and it was into the water jacket anyway, so probably would not have worked, so the block now really is a boat anchor.  

Enquiry since has told me that most people do NOT torque in head studs, just finger tight plus a tweak.  Yes, as unprecise as that!

One other point, which I followed in this case, is to ensure that there is a vent cut in any stud threads that go into  blind hole.    Air at the bottom of the hole will just compress, but water, oil or grease will not and that could blow the casting too.    If the studs are not cut, it's easy to do with a 'Junior' hacksaw  and a steady hand.  Make the cut into the side of the stud, through the threads, parallel to the length of the stud.   Ensure that the cut will show above the base when the stud fully home, so that it is fully vented.
John

[oil_on_the_carpet]

As per the street racers…


Clean out thread in block with plug tap

Clean out hole with fully evaporating solvent like IPA and bit of rag on zob stick

Run die nut down your stud threads

Clean stud with fully evaporating solvent like IPA

Drop 5/16" ball bearing into hole

VERY lightly using barely damp with oil brush lubricate stud threads with 3:1 oil or ARP lube

Thread in studs by hand until they bottom out on ball bearing

Make sure when fitting nuts and washers they are lubricated too, especially the interface between the washers, head and nut.

Get your self a King Dick or Norbar torque wrench - you get what you pay for, these are guaranteed +/- a few %


Life without preloaded stress.

[That Man]

ARP Catalogue wrote:

A stud should be installed in
a “relaxed” mode – never crank it in tightly using a jammed
nut.
If everything is right, the stud should be installed finger tight.
Then, when applying torque to the nut, the stud will stretch
only on the vertical axis. Remember, an undercut shorter stud
will have a rate similar to a longer, standard shank stud. This
provides a more even clamping force on the head. Because the
head gasket will compress upon initial torquing, make sure studs
and bolts are re-torqued after the engine has been run.

I've always thought these people know what there talking about

Gordon

[69vitesse]

If  you torque the stud down into the the hole, bottom end is now fixed. This means instead of the thread 'setting up' and spreading the load evenly along all the threads in the hole, the stretch occurs progessively towards the top, and this is what can cause the hole to break out.

[Tim Bancroft]

Got to agree about Norbar torque wrenches. Mine was bought by my father in 1969 and is still accurate. Excellent bit of kit.