Copper Head Gasket

Heh Paul, thanks for the drawing it certainly helps in communication  ;) I've gone off to make a new Cylinder head to your blue prints !!

Hope you dont have the patent, because I've amended to take account of 81 dia. Liners and head recess which doesn't accept this dia very well without mods.

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I think the problem with this engine is down to poor valve sealing, not the gasket. 
 
GregT said:
Marvellous the trivia you learn on this forum....but shit, fisting bears....now I've seen it all.

Seriously though, that sort of leakage on a head gasket, copper or whatever, can be caused by the piston to head clearance being too tight. Under high revs things do stretch and yes, when they touch the head does do a little jump. The resulting staining of the gasket can very often look just like that.
Without going right back on this thread to check, didn't that gasket come from a blown motor ? Broken rod ?
Absolutely sure the pistons hadn't touched ?

Please no more Bear porn....
Click to expand...

Thanks Greg, Got you now. Yes the motor was blown with composite gasket in, motor blew later in 2009 after Breganze. In honesty yes the L/H piston had at some point touched the head, it had a crank rebuild, rebushed conrods and the left con rod small end bush was fitted pissed, no specialist names mentioned.. ! One cylinder was affected and I didn't notice until I saw the witness marks on half of the piston. replacement rods removed that issue.

The broken rod was the RH one .

Good to know, I will emphasise one piston was affected at some point....
 
Regarding insufficient squish causing combustion blowby past the gasket. From my understanding (and I am glad to be proven wrong) it is on TDC exhaust when there is no downforce at all on the piston that there can be contact, at which point there isn?t any pressure to blow out. At TDC compression there is huge force downwards on the piston and were there contact at this point there would be serious contact at the free stroke and likely horrendous noise at first startup after assembly. For piston contact to be sufficient to lift the head there would surely be easily visible damage to the piston. These Laverda engines require 1mm static squish clearance which gives close to zero in operation (race) which is the goal. Often it is piston to valve contact rather than to the head that causes problems.
I agree that the large surface of the copper gasket must require very even flat surfaces. Does anyone here have enough experience with copper gaskets to say that Robs used one was not sealing correctly?
 
I wonder if the differential expansion of aluminium-block and iron-liner has the effect of very slightly reducing the load across the gasket, in the area in conatct with the liner? Over such a small distance the difference would be microscopic though.    P.
lav%20liner%20head.jpg
 
bob said:
Matthew Corbett [son of Harry] lives just a few miles from me in a picturesque canalside cottage [I think Sooty earned a few bob over the years]. The cottage is a bit of a landmark , especially for narrow boat users, and is always referrred to locally as 'Sooty's House'. How's that for a bit of thread hijacking trivia....
Click to expand...

Bob,
I hope that this is not a lead in to cottaging. :o

Scrumpy
 
Hi,

We used to use copper head gaskets a lot on our race engines and still do occasionally for one off builds etc.

They do have their advantages,
1.Reusable being the main one,
2.Ease of manufacture,
3.Longevity, They rarely burn out even under extreme pressure and adverse conditions,
4.Can be simply made in various thicknesses to adjust squish / CR etc.
5.On supercharged alcohol engines they are often indispensable when bores are too close together to use "Wills rings" or you need the thickness of a gasket.

They also have there disadvantages!
1.They leak!  almost always when removed you find very slight signs of gas leakage around the bores,
On water cooled engines, under initial start-up you can find bubbles in the water for the first minute or so when you have an engine with waterways very close to bores! This stops when warm.
On others when running you can often see tiny bubbles around the edges of the gasket area.
These leaks are tiny! so small not to cause any problems anywhere! (other than on vary odd cases where you have a badly designed engine in a race car (pre-war GP etc) and you have waterways within millimeters of bores, when you must drain down the water when standing for any length of time)
1a. All these disadvantages can be alleviated with the use of 1mm steel wires round the bores, "if you really need to"

My opinion.
Julian
 
CLEMTOG said:
The next batch of gaskets will not be touching the liner Paul, only the block.
CLEM
Click to expand...

 At the risk of affecting your delicate sensibilitys Clem, that is the major problem with the current copper gasket. A gas tight seal must be made at the edge of the combustion chamber. Moving the seal to outside the liner will result in gas blowing into the stud holes. On a standard 80mm barrel the land between the edge of the stud hole and the edge of the liner is only 0.3mm, there is no way an area of relitively soft aluminium will support a seal over such a small surface area. Leaving the top of the liner unsupported ie. not clamped by a flame ring is also courting disaster. I have removed and replaced countless liners using a domestic oven, they become free to move in the barrel sleve at relatively low temperatures, certainly less than a motor gets when working hard. By leaving the top of the liner unsupported there is a very real risk that the liner will start to move around when the engine gets hot.


  Keith.
 
a very good point Keith, well made.No distress caused.
being keen is OK, but I value comments such as these, Red mills the gaskets to suit his 82mm bore.Of course the liner does have to be "contained".There seems no easy way to make the copper gasket 100% suitable for the spigotted 1000 (75mm bore) other than removing the liners for decking and then refitting them, which probably redistorts the top face of the block.
CLEM
 
Hi Guys

I split this topic, leaving the copper head gasket technical stuff here in technical, and moving the Teddy Bear sex porn thread to General under a clearly descriptive topic heading..... any anguished cries of censorship, nothing has been deleted, only moved and clearly described....put any more teddy bear postings in General, please.

Paul LeClair
 
i find clem's gaskets work just fine on 1000's when properly prepared
and i like doing away with the O rings on the studs. but i do retorque
much sooner than generally specified.
first time after the first heat cycle of the running engine

the beauty of the copper gasket on a race engine is the ability to reuse the gasket
in spec classes heads come off after every race weekend to touch up valve sealing
maintaining a competitive engine is not a low maintenance endeavour

run a hot rod engine for street and track? expect higher maintainance than in std tune
and higher component failure

seems to me the folks having issues are generally running 80mm+ bore sizes with tuned engines.
i recall head gaskets have been an issue with non spigoted liner triple race engines for years.
whether anyone went as far as grooving the liner to accept a wire ring is unknown to me ...

a blown head gasket is usually a symptom, not a cause. consider;
the uneven clamping load of different stud lengths at the same torque,
a cylinder head that is not positively located to the the cylinder assy,
the case deck may not be dead true parallel to the crank,
hard or soft spots in the various castings,
dare i say, even the 180 firing order may be an issue

it could be a little of all of the above and more stacked the wrong way
the closer an engine is to its edge the sooner the weaknesses are found

all engines have idiosyncrasies eg;
big V8's need torque plates for the block for boring and honing
the 8v alfa 2.0 needs a torque plate on the head to cut valve seats
broken timing belts causing valve to piston contact can flat spot rod bearing inserts

rob, red and others are pushing the development envelope in different applications
applying newer technology to old designs moves the limits
whenever someone gets around to fitting some wire mind the nominal extra thickness
may cause a different sealing problem

cheers,
scott



 
well seeing as the bears have pissed off from this thread I may as well post a report here on our experience with the copper head gaskets

basically, they suck on a 82 mm bore high compression Laverda engine, both engines experienced oil leaking problems
Silver engine turned itself into a smoke machine in 3 laps, when stripped we could see the track marks from the oil passage ways into the combustion chamber
Black engine had a slight smoking problem when changing down gears but was okay under power, but we had oil leaks to the outside of the engine that we could not stop

in desperation, Saturday night we stripped the black engine and installed 2 base gaskets to lower the compression, hoping to keep the head seated better
seemed to work to a point, we made it through the Sunday program but still with oil leaks to the outside of the engine, not good seeing Blair come back in after each race covered in oil

we are limited in clamping force by the alloy engine cases and the ability of the thread to stay in place, we went to 26 ft/lb but still we had no effective seal
as the larger pistons foul the flame ring on a standard gasket I have to either reduce piston size to revert back to a standard gasket or have MLS gaskets made, which I intend to do
having to reduce bore size sucks big time, we need capacity and compression to try and be as competitive as possible
I actually wish to increase bore size even further in the future so I have a few issues to overcome
head sealing issue will be solved by having modern MLS Head gaskets made that will allow me to seal on at least an 82.0mm bore
then I can work on the through stud design that will allow me to increase the clamping force to 30 ft/lbs as a minimum to help contain the compression ratios that we need to run

in the end we got pretty damn good at dropping and installing engines on the Spaceframe and for those that think it should be an easy fit, it isn't
Big thanks to Jotaman, Bruce K and Cosi for all your help on the weekend, I very much appereciated all your help
next time we will bring work gloves so we can drop a hot engine quicker
Red


 
Red,
http://www.specialisedgaskets.com/
You probably already know about this mob. The neat thing about them is that they're linked into a global network of suppliers of gaskets. Which means that if you give them a gasket or they make it, it goes on their data base. This allows anyone in any other country to access that particular gasket. They made up some aluminium base gaskets for a mate of mine's Morini and were particularly interested in obtaining all his gaskets so they could copy them.

If you haven't talked to them they might be useful.


Cheers
Chris
 
Red, Sounds like a pretty gruesome weekend to me, very frustrating when you put a load of work in and things go pear shaped. We've all been there...
Regarding the removal of spaceframe engines from the frame I assume you've trimmed the head finning? It makes the job a lot easier. It's still not the sort of job I'd want to do in the paddock though!
 
Bob there must be a Rubex Cube type move to get it in,been around for maybe 6 installs and maybe half go really easy,the first was just me and Crispin and it took 20 minutes got me thinking this is easy but the other half were asolute barstards,there has to be a knack.
 
Looking at the 1200 i have here I assume that the problems with big bore 1000's don't occur with the 1200 head and barrell ?

Is there room to dowel and O ring the oil passages through the gasket face ?
Can the pressure oil passages be made external ? This is a known fix for big bore Suzukis...
 
Vince said:
Bob there must be a Rubex Cube type move to get it in,been around for maybe 6 installs and maybe half go really easy,the first was just me and Crispin and it took 20 minutes got me thinking this is easy but the other half were asolute barstards,there has to be a knack.
Click to expand...

:D If the head fins are shaved in certain areas you need to do is get a jack under it, loosen all the mounts , drop the front a wee bit and then release the back mounts , pull the chassis back and then drop the motor and drag it out sideways. When I built my bike I could tell that it was going to be traumatic to  get the motor in and out unless those fins were relieved and so I did a bit of judicious grinding and sanding until I was happy the motor would drop in and out. Fortunately I never had to do it in anger, as I said ,  1000cc four stroke engine removal isn't the sort of thing you want to be doing in a race paddock if you can avoid it.

I think the world's leading authority on spaceframe engine removal is the porn king, Rufus Bear. Ray's dropped the motor on that bike more times than he can shake his King Dick 1" Whitworth at it.  :D :D
 
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