Head Gasket

[carrierdave]

Hi there, I have just rebuilt my engine and got to the point where I started her up. Upon running I had large amounts of smoke from the exhaust that did not reduce. I therefore decided to remove the head and investigate the problem.
It would appear that oil had been forced into number one cylinder from the small oval shaped hole in the head, which feeds oil up to the camshafts.
I am now having the head skimmed as a precaution to ensure that I have a good mating surface.
As per the Miles Wilkins book I used Wellseal on the head gasket ? Has anyone experienced this problem before? Can anyone suggest an alternative compound or should I put it on dry?

Thanks

Dave

[type26owner]

I have some expertise in this area but don't have the time to write a lengthy reply right now, later on this evening I will. Are you using the standard copper/aluminum head gasket? New rings? Valve stem seals? Stock cams?
-Keith

[carrierdave]

Hi Keith,
Thanks for your interest. Yes I have used new rings and I have checked both the guides and valve stems for wear ? They are all within the limits of the workshop manual.
The head gasket was a standard one from Paul Matty ie copper/Aluminium and the cams are standard.

Someone did suggest the following to me - That Graphogen could act with the oil causing it to loose its viscosity making it easier to penetrate the gasket, or over pressure in the block causing high pressure in the head thus forcing oil down the guides!!

Thanks
David

[type26owner]

David,
Since you have the head off look inside the exhaust ports at the guide area and look for the trace of oil streaming from the guide into the exhaust system. Virtually all twincams heads I've examined have this telltale trail of oil if they are not fitted with valve stem seals.

Are the rings chromed and where the cylinders honed? What oil are you using? Valve stem seals? Stock cams?
-Keith

[carrierdave]

Hi Keith,
The head is away being skimmed at the moment so I am unable to check. When I took the head off there was about 2mm of oil laying on the top of number one piston with a small amount in the others.
Oil was also found around the front corner where the oval oil passage is. I also noticed oil fouling at the gasket joint between the manifold and head to number one cylinder (gasket blowing).
I have no oil stem seals ? I thought that these were never fitted ? If they should then where would you suggest that I get them?

The rings again were genuine Lotus parts, the top one chromed with the second one being copper coated and then the normal oil scraper.

Oil used was a semi synthetic 15/30 motor oil I was using to flush out the Graphogen. Cylinders were honed and the camshafts are standard ones.

Rgs

David

[type26owner]

The reason the oil was laying on top of #1 piston is because the oil in the head drained out because the block and head galleries match up right there as you noticed. That's normal when the head is pulled free. The reason that it's like this is the oil supplying the head does not come directly from the block's main gallery but is routed first through the first bearing journal of the jackshaft. IIRC, that jackshaft journal is fed oil from the block's main gallery and there are either two or four indentations which are about 70 degrees long in the jackshaft's journal which fill with pressurized oil and when the jackshaft rotates by about 270 degrees there is another oil passage which allows the oil to escape and that's the passage that leads up to the head. Diverting the oil this way does two important tasks. First, it meters the amount of oil going to the head by the rpm not just by the pressure. Two, it works as a one-way check valve so the oil gallery in the head does not drain out everytime the engine is shut off.

Not that the head gasket can't leak just as you assert but I've never seen that happening before. What is common though is to have a rather large oil leak right at the outside recessed corner where the head and block and timing chain rear plate meet where it soaks the dizzy area constantly. Also have seen oil weeping from the head gasket along the lenght of the dizzy side from the oil drain holes for the old pushrods not sealing. Had both the bi-metal and the composite high-tech gaskets leak from there. This is easily fixed but not with Wellseal. Have you read the techincal specs for that stuff? From the specs I'd say that's a very poor choice for that application.

I'll continue this later. Have to be tomorrow maybe since I got my arm twisted to reline the kitchen cabinets tonight. I obeyed.
-Keith

[david.g.chapman]

Last time I had the head off I used RTV - the orange high temperature stuff. Some head gaskets have beads of this sealant impregnated into them off the shelf.

This should work unless the head is badly warped.

Don't use too much- just a thin even layer both sides.

Dave Chapman

[carrierdave]

Thanks for your comments Dave.

I have just received the head back skimmed and minus 10 thou across all of the head, so its not warped!

I think I will try torquing the head down over several hours to see if a gradual application pulls the head squarer.

Every thing else seems fine so hopefully this will work - Unless you have any other ideas or suggestions Keith?

Thanks to all (so far).

David

[type26owner]

When you get your head back do the inspection for the exhaust guides leaking cause that very probably is your source of the blue smoke. If that turns out to be so I can tell you exactly how to remedy that situation. Hopefully you told the shop which is doing the skimming of the head surface to NOT blast it with glass beads. You do know why?

The problem with head gaskets is the surface finish must be within a very narrow limit of finish or the chances of it sealing long term are poor. Too smooth or too rough a finish will doom the outcome almost with absolute certainty. Guessing you're using the Payen AF_880 head gasket. No where have I seen the specs for the required finish to have that gasket work well. J. Payen Ltd does not have a website and the techincal engineers at Federal Mogul don't have the phone number either. I won't use those gaskets again because I've had them move the metal sheets by as much as a 1/4" due to expansion coefficients forces and the surface finishs being wrong. Got some revealing pictures if you're interested.

The gasket I've used recently is the Felpro 8360 PT-1 Permatorque. The surface finish required is Ra 30 to 60 microinches. My recommendation is to apply a Ra of 30 to 45 and a Rmax of 60 to be safe. The reason is anyone familiar with surface finish knows it's impossible to describe a surface with a single callout. This link will explain finishes if you're puzzled and why just calling out a Ra is not okay; the pictures tell it all.
<a href='http://www.predev.com/smg/parameters.htm#Ra%20-%20Average%20Roughness' target='_blank'>http://www.predev.com/smg/parameters.htm#R...age%20Roughness</a>

The 8360 PT-1 requires some modifications to work on the twincam. I'll finish this later but here's some more links to head gasket sealing which are relevant.
<a href='http://www.aa1car.com/library/ar996.htm' target='_blank'>http://www.aa1car.com/library/ar996.htm</a>
<a href='http://www.enjoythedrive.com/content/?id=25826' target='_blank'>http://www.enjoythedrive.com/content/?id=25826</a>

-Keith

[carrierdave]

Hi Keith,
Very interesting, there's a lot more to head gaskets and mating surfaces than I imagined.
I have checked around the bottom of the guide and there are no signs of excessive oil contamination.
Another item I would have expected to see from a leaking oil seal would be large amounts of soot on the back of the valve.
When I have taken engines apart before, because of excessive oil consumption, I have generally found a large build up of soot on the back of the valve where it burns; There was very little and even less carbon.

I would say that the gasket is not the greatest match in the world and there are a number of area?s where the gasket does not match to the head or block completely; leaving several holes partly blocked. In some cases the holes are less than half the actual size in the head!!

I will be assembling the head over the weekend and hope to be at a point where I can run her late Sunday.

I intend to put the gasket on dry and hope that this will cure the problem. If you have any more thoughts please let me know.
kind regards

David :huh:

[type26owner]

David,
If you've got new new chrome top rings then don't use any synthetic oil. Ideally you should be using break-in oil for the first 500 miles. Don't baby the engine either: give it some throttle but stay well below the redline. Don't do what I did the first time when I screwed up and glazed my cylinders and it took 25K miles for them to bed in properly.

I was able to track down the UK email address of the Payen application engineer and am waiting for the reply on the proper surface finish for those copper/aluminum and their composite headgaskets.
<a href='http://www.federal-mogul.com/aftermarket/uk/contacts.html' target='_blank'>http://www.federal-mogul.com/aftermarket/u...k/contacts.html</a>
Put the cursor on the Payen brand icon and the contact info will popup.

I would still apply some hi-temp silicone RTV adhesive on both sides of the gasket where the oil gallery in the head takes a dog-leg right off the slotted opening with it's crush ring perimeter through the headgasket. That's why those gaskets leak to the outside there so often. Personally I would also apply a tiny bit around each water passage on the block and the head. What normally happens there is water will infiltrate under the gasket and rust the block. That rust area has more volume then the cast iron so the area will blossom up slightly pushing up the gasket and head and stretching the headbolts enough so areas just adjacient to the blossom are not clamped with enough stored energy to resist the forces exterted from the temperature expansion differences and the combustion pressure hammering the gasket. Just so happens there are passages on both sides of the thin gasket webs between the cylinders. The adhesive will extrude under this level of clamping pressures but will fill the micro voids in the surface finish of the metal so the water can't. Those areas have to be super clean to have the silicone adhere and best to use one rated for high-torque, high-temp and rated to stick to oily surfaces. I use the Permatex Ultra Copper. ALL the manufacturers warn you to not use their product on the headgasket. Reading between the lines it's clear they mean don't try to seal the metal crush rings in the gasket against the combustion cylinder pressures. I concur with Dave Chapman in that it works great everywhere else though.

Here's a heads up. Follow the Lotus Manuals' advice on using dowel pins to aligne the gasket while doing the head reassembly. Only use the two holes in the block as illustrated because the gasket has tight clearance holes for those headbolts only. The other holes are oversized by a bunch and you'll have the gasket skew which will could cause the crush seals around each cylinder in the headgasket to not work properly.

Now back to the exhaust guides leaking oil and causing blue smoke. It was billowing in my case before I retrofit the valve stem seals and that got rid of 100% of it. Here in California you're not allowed to have any smoke coming from the tailpipe.

By the venturi effect of the escaping exhaust gases any excessively supplied oil will be sucked out of the exhaust guide and away from the exhaust valve entirely so don't look on the valve head or stem for any evidence of an oil leak. Where it will show quite clearly is a straight line away from the guide along the surface of the port in the head and out the manifold. Because the head in an overhead cam arrangement and the valves stick down that means the track of oil is going to be on the top of the port. If the engine is in the car and you're looking in the exhaust ports then the only way you're going to be able to see this is with a small pocket mirror and a flashlight. It's almost impossible for there not to be an oil leak to some degree if valve stem seals are not installed. The camlobe followers act like hydraulic pistons ramming the oil down towards the guides and on the exhaust side there are no oil drain holes in the cam area galleries other then the chain well at the front of the engine for the oil to escape. With the pitched up orientation of the front of the engine I'd say it was designed to burn oil.

Okay, there's probably more to know but I'm to burned out now to remember it. Oh, those al/cu gaskets have many of the water passages just the right smallish size hole to plug up in nothing flat. Best to remove the all sediment built up in the bottom of the block.
-Keith

[Frank Howard]

As a side note, I made up a couple of "installation studs" per the manual to help align the head, gasket and block during assembly. The problem I had was the chain guide would not allow the head to go straight down over the temporary studs without a twist first. The only way this could be accomplished was to remove one of the temporary studs. So I never used them, at least one of them. Any ideas as to what I was doing wrong?

Frank Howard
'71 S4 SE
Minnesota

[carrierdave]

Hi Frank,
Now you mention it you are correct, the chain slap plate fitted to the right hand side of the timing chain cover does stick out and obstructs the head/ timing chain cover when you lower it onto the block.

From what I can see it is only the centre part of the slap plate that is actually used so it maybe possible to cut it back by 10 to 15mm, so that the head goes straight on?

I had a similar problem ? What I did was to suspend the head on my engine hoist over the block, lower it to a point where it had cleared the slap plate and was central to the block. Then I inserted the gasket from the side whilst pushing the temporary studs down through the head and gasket and into the block.
Doing it :blink: this way also eliminated the possibility of the temp. studs digging into the head as I tried to line it up - Otherwise its a job for two people if the engine is in the car.

Because there was no pressure on the gasket I was able to centralise the gasket before any weight was put on it.

A fiddle I know, but what on a Lotus isn?t a fiddle!!!

Dave

[type26owner]

Frank,
Takes two persons to do it without much of a struggle. It can be done by a single person but it requires the front dowel be retracted while clearing the proud chain guide and while the head is resting on the gasket at the rear it's tilted up at the front with gap of about 1/4" so you can insert the dowel down through the gasket and engage the counterbored hole at the top headbolt threads in the block. What makes this tough is I do not use the cork gasket between the head and the timing chain cover anymore cause the synthetic oil wicks right through it making a mess. Just use a bead of RTV silicone adhesive there now.

David,
Happens my head is off at the moment too. The sleeve in #3 cylinder that I'm guessing the PO had installed slipped down below the top of the block by about 10 thou. My engine consumed most of the water while driving home from Thunderhill racetrack. I made it home just barely. So cheer up it can get worse.

Hey, here's a heads up for everyone using synthetic oil. The elastomer tube which seals the crankcase breather vent to the head had swelled and was cracked on the outside but was not leaking any oil. However the vent hole through it was reduced because of the swelling so that it was nearly choked off as far as I can tell. Not a good thingie to have happen! Going to cut it in two and reinsert the pieces in the block and head and measure the apertures.
-Keith

[type26owner]

Hello Keith,
The surface finish for your cast block should be 60micro inches RA.
Head finish aluminium should be 30 to 60micro inches RA.
These figures assume use of fibre type gasket, if multi layered steel gasket is to be used then head finish should be a Max of 30micro inches.
I have no value for rocker box gasket JM460.
Hope this helps.

Best Regards
Geoff Waterhouse
Technical Services Administrator.

The message above is the reply I recieved from the Payen applications engineer. Not sure the answer applies for the al/cu gasket though. I'll try to get that cleared up. Below is the message I sent Geoff.
-Keith


Hello,
I'm seeking the recommended surface finish required to
use on a Payen AF_880 headgasket on a '66 Lotus
twincam. Would you also supply the value for the Payen
JM460 type headgasket. The block is cast iron and the
head is aluminum.
Thanks,
-Keith Franck