Head Gasket

[type26owner]

Getting the surface finish wrong could cause a failure similiar to this one that I had.
-Keith
p.s. Rohan, to get a picture to appear in this forum it must be linked using the IMG button in the editing section. You must have a website to plunk it out in cyberspace so it can be linked to here.

[carrierdave]

Good morning all,
Well the heads not on yet, I decided to recheck the valve stems again. To be one hundred % sure I have ordered new exhaust values which I hope to have on Wednesday ? These should minimise the possibility of oil running down the guides.
Once I have done this I will need to seat/lap in the valves and then check the shim sizes/valve clearance.
Hopefully by this coming weekend I shall have it all back together and ready to run ? Its amazing ? every time you take her apart, there?s always something that you can spend money on - that?s probably why I?m broke!!

Regards

David

[cdraper]

Can somebody give valve stem seal details - where do they come from?

[type26owner]

Got this reply on my query of the exact surface finish needed for the cu/al (AF880) Payen gasket all the Lotus parts vendors sell. The PowerPoint document Geoff sent me is a must read item for anyone doing headgaskets! Look in folder Payen AF880 headgasket for the file Gasket5Failures.
<a href='http://briefcase.yahoo.com/[email protected]' target='_blank'>http://briefcase.yahoo.com/[email protected]</a>

Hello Keith,
The same RA finish value applies to the AF880 type gasket. Have attached file that may help explain some failures.

Best Regards
Geoff Waterhouse.

David, you're in denial just like I was for awhile. Betcha you'll still be puffing some blue smoke.

cbdraper, I'll start another topic with the info on the valve stem seals.

-Keith

[carrierdave]

Hi Keith,
Yes I am in denial. You are right.
I am denying myself the pleasure of purchasing a Lotus Europa.

Yes I will get a puff of blue smoke from the exhaust ? All Elan?s do on start up; that?s because there are ?generally? no stem seals.
The Elan relies totally upon the clearance between the valve and the guides too keep as much oil out as possible whilst still maintaining lubrication.
This engine was built to rev higher and longer than the standard Xflow unit therefore it needs the oil to lubricate as well as cool the guides.
What tends to happen is whilst the engine is off; oil will leak down the stem seal and sit on the top of the valves. When you start the car you get a puff of blue some from the exhaust as it burns.
The problem I had was when I removed the plug from number one cylinder the plug was covered in oil ? there was no way that it would have come from the valve guide.
Anyway it is all back together ? started up and no smoke!!!!! Apart from a little on start up!

Thanks for you?re input ? Its been very interesting.

David

[type26owner]

The problem I had was when I removed the plug from number one cylinder the plug was covered in oil ? there was no way that it would have come from the valve guide.

Certainly not the exhaust guide but highly likely the intake valve guide could be the source of an excessive amount of oil getting sucked in and fouling the spark plug. Please explain to me why virtually ALL modern day engines would have some sort of stem seals on all the valves if they are not useful to control oil consumption.

Here's something kind of odd that happened to me recently. I have to replace the umbrella type stem seals on my Dodge 318 every 25k miles. Last time I used the rope trick to keep the valves closed I got a knot in it while pulling it out of the spark plug hole and had one hell of a time getting it back out of the cylinder. :huh: :angry:
-Keith

[rgh0]

Keith

Modern manufacturers use seals because they work well and last long enough and are cheaper than top quality guides and valve stems and achieving the correct clearances in a production environment.

I use cu-si-ni guides and stainless valves and set them up at the bottom of the clearance tolerance range for a road car. This has given 50,000 miles in my plus 2 car without problems so far from smoke or oil burning. No puff of smoke even on startup. I use slighly higher clearances for my race heads but still towards the bottom of the tolerance range. I have never had to replace the guides in my race heads, but after 10,000 plus race miles at 8000 rpm I find no measurable wear in the guides of my most used race head . I have 2 I have rotated through my Elan over the last 20 years.

Rohan

[type26owner]

Hi Rohan,
It's been my impression that having a blue smoker or not is simply the luck of the draw but then again possibly not. Our BRM III racing twincam has the guide clearances set at .0015" intake and .0025" exhaust has no stem seals and it does not produce blue smoke either. Those same clearances on my stock S2 twincam and it billows out blue smoke. So much so before I added the stem seals I had to shut the Elan's engine off at traffic lights otherwise having idled for a minute it would put out so much smoke the traffic behind would disappear in a blue cloud when I took off. The only possible explanation for this that I can think of is the scavanging difference between the two radically different exhaust systems. Notice the S2 type exhaust system was not replicated later on and I've pondered as to why? It is about as simple as it can be and therefore probably cheap to produce but yet it was changed. :huh:

As far as the technology differences relating to engineering practices and metalurgy choices used in valve trains between then and now goes there isn't much change except for stem seals, smog laws and availability of synthetic oils. The same laws of physics still apply with which the design engineer can use to pin the bean counters ears back. :angry:
-Keith