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| Mike's Project Thread http://www.gt4dc.co.uk/forum/viewtopic.php?f=1&t=4873 |
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| Author: | Sirius [ Mon Mar 12, 2012 10:33 pm ] |
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So over the weekend I had a little spare time to investigate the cylinder head a bit further. As you might remember from posts further up the inlet cam had been installed with the caps in the incorrect locations. So I removed the caps and camshaft here are some pictures of whats there: INTAKE 
EXHAUST 
Any one care to comment on the surfaces? I am not very good with this sort of thing. Is it scrap? |
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| Author: | Nibbles [ Mon Mar 12, 2012 11:52 pm ] |
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Don't look too terrible to me. First step is to plastigauge them (installed correctly) and see if the incorrect installation has caused excessive wear. http://uk.rs-online.com/web/p/special-a ... s/2224444/ Ignore the misprint in the BGB, clearance should be 0.025mm - 0.062mm (1thou - 2.4thou) |
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| Author: | MrDB [ Tue Mar 13, 2012 11:41 am ] |
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remeber the cam bearings dont see massive loads compared to crank. If still within spec overall they will be fine.. |
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| Author: | two_OH_five [ Tue Mar 13, 2012 12:18 pm ] |
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Look as scrap to me. Maybe you can ode or to hammer out the twist in your chassis 
Seriously, needs measuring to decide If it's borderline then maybe look into coatings - The folks who make cermakrome also make a spray on dlc type for bearing surfaces Remember, unless you buy brand new there's always a chance a replacement is just as bad so spending a few quid might make sense |
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| Author: | Nibbles [ Tue Mar 13, 2012 12:30 pm ] |
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If you find a problem, a few ideas here: http://www.gt4dc.co.uk/forum/viewtopic. ... light=head |
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| Author: | Sirius [ Tue Mar 13, 2012 8:14 pm ] |
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I've ordered some plastigauge as Chris suggested, it should be here tomorrow. Clearly I will read the instructions but are there any hints or tips on using it? |
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| Author: | Sirius [ Wed Mar 14, 2012 9:44 pm ] |
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The plastigauge arrived and being impatient I did a google search and followed the instructions carefully. I measured the clearance on the cap and the head bearing surface. Making sure I torqued the caps to the correct degree. Below are the results: 
It would appear that journal 5 on both cams is just outside the tolerance although this could possibly be due to that journal having the oil way and being more difficult to get an accurate reading. Would be glad for comments. My assessment at the moment is that given I am unlikely to find another decent head I will go with this one as the clearances look mostly fine. |
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| Author: | Kris [ Wed Mar 14, 2012 10:07 pm ] |
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I'd reuse the head... imho, the clearances are less important on the camshaft than when compared to the crank and big ends |
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| Author: | Dorris [ Thu Mar 15, 2012 3:26 pm ] |
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Was this done with valves in or out? Dorris |
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| Author: | Diceman [ Thu Mar 15, 2012 5:59 pm ] |
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Good point dorris. I don;t know correct procedure but I would assume that total clearance will remain the same but may result in a shift between cap and head clearances. As a side note Mike - did you measure the camshaft journals for wear? I suspect that camshaft journals are much harder than the head so less likely to wear but if you are putting those big cams in your clearances may alter slightly. it would be worth a quick check with a micrometer anyhow. |
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| Author: | Sirius [ Thu Mar 15, 2012 7:52 pm ] |
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Done with valves in - is it supposed to be done with valves out? I haven't measured the journals yet, I don't have a micrometer available at the moment. All I really wanted to establish was is it likely to be alright or not. As the initial findings are good I will now send it away to be refurbed - they can do all the proper measuring to find out if its any good. |
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| Author: | Diceman [ Thu Mar 15, 2012 8:04 pm ] |
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Ah ok - so job's a goodun then 
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| Author: | Muddy Water [ Thu Mar 15, 2012 8:32 pm ] |
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Quote: I don't have a micrometer available at the moment
I have one you can borrow 
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| Author: | Nibbles [ Thu Mar 15, 2012 11:00 pm ] |
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Just checking - You quote cap and head, did you measure both together (i.e. plastigauge on head, cam in, plastigauge on cam, cap on) if so, redo it measuring just 1 side at a time. When 'oil clearance' is quoted, it means total, i.e. size of outside - size of inside, not clearance each side. Otherwise, I agree with Kris. Clearance on cam is not so critical as the bottom end. |
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| Author: | TrackToyFour [ Fri Mar 16, 2012 1:14 am ] |
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Diceman wrote: ..... if you are putting those big cams in your clearances may alter slightly......
 is there something we should be told?
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