Lotus Elan

Cylinder Head Carbon

PostPost by: Chancer » Thu Mar 23, 2017 7:31 pm

But you probably love Taboul? and cous-cous :roll:
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PostPost by: vincereynard » Thu Mar 23, 2017 7:51 pm

Chancer wrote:But you probably love Taboul? and cous-cous :roll:


Aren't they characters in Madame Butterfly?
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PostPost by: 2cams70 » Thu Mar 23, 2017 11:44 pm

Perfect emissions from a VW/Audi??? Is that on a chassis dyno or on road !!
1970 Ford Escort Twin Cam
1972 Ford Escort GT1600 Twin Cam
1980 Ford Escort 2.0 Ghia
Peugeot 505 GTI Wagons (5spdx1) (Autox1)
2015 Honda City 5spd.
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PostPost by: Quart Meg Miles » Fri Mar 24, 2017 10:24 pm

I've just removed most stuff from the combustion area with White Spirit on a cloth; engine has done 11,000 miles in last three years and only a bit, around my oily rear cylinder, needs to be chipped off. A bit of wood dowl should do it.
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PostPost by: john.p.clegg » Sat Mar 25, 2017 6:03 am

..as Rohan said
" the hard brown deposits on the exhaust valve that continues to build overtime."
are the best tell-tale signs and are harder to remove., I slip them in the lathe and carefully ,free-hand remove the crud.

John :wink:
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PostPost by: vincereynard » Sun Mar 26, 2017 10:56 am

The head cleaned up easily with carb. cleaner and a copper brush.
All the valves have a fair bit of relatively soft black deposits. There is not much evidence of the hard mid brown stuff except on the valve heads.

p1050067.jpg and

p1050071.jpg and


To me it looks like it was given a decoke at some time in the reasonably recent past, but there is little evidence of it having had new valve seats, which I would have though a first step for a "lead free" converted head. I was also hoping for new valves !

p1050070.jpg and


Your opinions please?

Vince
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PostPost by: rgh0 » Sun Mar 26, 2017 11:21 am

Hard to tell without measuring it up but valves and seats dont look like just 500 miles old.

I would check the valve stem diameter along its length - they wear in barrel shape and the guides they wear in hour glass shape. I would similarly check the followers and their sleeves.

I would also check the depth the valves are seated at by measuring valve length and valve stem top to cam centre line.

Most of these heads have been played with a lot over the years so you need to do a lot of measuring and not assume anything is standard or that standard parts will fit.

cheers
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PostPost by: JJDraper » Sun Mar 26, 2017 11:24 am

I have an idea that lead-free valve seat conversion for the twincam engine is not really required. This is due to the cooler running of the valve seats in alloy, thus, unless you are running something radical in compression and cams, there is little discernable valve seat recession. Closing up valve clearances would soon show it up if it was happening.

More of a problem in iron head classics.

Opinions?

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PostPost by: rgh0 » Sun Mar 26, 2017 11:40 am

The original Twin Cam seats are fine with unleaded fuels

cheers
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PostPost by: vincereynard » Sun Mar 26, 2017 11:53 am

An aluminium head should be OK mechanically as it has hardened valve seats as standard. (hopefully!)

The issue here is that the P.O. paid a fat wedge for a a lead free converted head and it appears that the only work done was, maybe, a quick decoke!

screenshot-from-2017-03-26-12-46-01.png and


Presumably the same muppets who made a mess of the water pump installation.
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PostPost by: Craven » Sun Mar 26, 2017 12:20 pm

Not to be too pessimistic! But those exhaust seats look a mess, what are the shim sizes? have the valve stems been shortened ( top of collet grove to top of stem ) standard valve = approx. 0.140 inch.
Maybe of some help.
Ron.
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PostPost by: vincereynard » Sun Mar 26, 2017 10:01 pm

Thanks for the posts chaps. Looks like I'm in for a lot of checking and measuring.

The seats might look a mess, but I filled the chambers with paraffin and they showed no sign of leaking which is a plus.
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