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Location:
Lost in the K hole
Registered:
May 2002
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I supported Toymods
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I renounced punctuation
Registered:
May 2002
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Re: how a 7m block and head *should* look (big files)
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Wed, 24 September 2003 12:54
 
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FFS Ed...I have sent you PS7! Stop dropping these ridiculous hints! 
PS...I'll send you the resized versions of the above.
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Location:
Sydney
Registered:
March 2003
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Re: how a 7m block and head *should* look (big files)
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Wed, 24 September 2003 13:44
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F*ck, learn to scale your pictures son!. 
Nice machining, where's the o-rings? 
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Location:
Melbourne
Registered:
May 2002
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Re: how a 7m block and head *should* look (big files)
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Wed, 24 September 2003 13:53
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I hope your still going to lap that surface Ed those remaining mechine marks go nicely from bore to water jacket  and your runing a metal gasket?
your going studs and the dowel pins are a tight fit on the gasket so no need for "bite" in the surface (make shure your dowel holes in the head are still deep enough seeing that you have taken lots off)
Allan
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Location:
Sydney
Registered:
March 2003
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Re: how a 7m block and head *should* look (big files)
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Wed, 24 September 2003 14:03
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| Allan wrote on Wed, 24 September 2003 23:53 |
I hope your still going to lap that surface Ed those remaining mechine marks go nicely from bore to water jacket and your runing a metal gasket?
your going studs and the dowel pins are a tight fit on the gasket so no need for "bite" in the surface (make shure your dowel holes in the head are still deep enough seeing that you have taken lots off)
Allan
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Lapping the head/block is a wank, it's an American thing due to them obviously having trouble finding a machinist who can perform the right machine finish.
I know of 2 people who run MHG's on their 7m's and neither block or head was 'lapped'.
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: how a 7m block and head *should* look (big files)
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Wed, 24 September 2003 14:10
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That's pretty fine machining Al....it's just that Ed won't lower himself to using MSPaint to reduce the image size so that the bores don't look to be 200 mm in diameter.
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Location:
Melbourne
Registered:
May 2002
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Re: how a 7m block and head *should* look (big files)
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Wed, 24 September 2003 14:38
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i look at it this way why risk it for a couple of hours work!
Im shure ed has spent more time on his cam covers!
Allan
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Location:
Lost in the K hole
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Wed, 24 September 2003 14:42
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funny thing is allan, you havent even SEEN my cam covers
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Location:
Melbourne
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Wed, 24 September 2003 14:53
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Yes but i have my spys....
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Wed, 24 September 2003 14:55
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From my experience when I was grinding telescope mirrors, it is quite hard to lap a perfectly flat surface on a glass sheet. It's OK for thermostat housings and the like, but I don't think I'd risk it with a head. The presumption is that the glass sheet remains perfectly flat whilst 30+ kg of head is being vigorously rubbed back and forth over it. I can't see that happening!
If the head gasket were to blow, you would have NO comeback. The machinist would have no trouble seeing the lapping and wipe his hands of the matter.
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Location:
Central Coast, NSW
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Wed, 24 September 2003 23:31
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those are lovely ed... makes me wish I had my block machined when i did the metal head gasket installation *cringes*
I feel like my car is a time bomb
Dan
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Location:
Melbourne
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 00:17
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| gianttomato wrote on Thu, 25 September 2003 00:55 |
From my experience when I was grinding telescope mirrors, it is quite hard to lap a perfectly flat surface on a glass sheet. It's OK for thermostat housings and the like, but I don't think I'd risk it with a head. The presumption is that the glass sheet remains perfectly flat whilst 30+ kg of head is being vigorously rubbed back and forth over it. I can't see that happening!
If the head gasket were to blow, you would have NO comeback. The machinist would have no trouble seeing the lapping and wipe his hands of the matter.
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Thats why its done with a thick bit of glass ON TOP of the head,
And like you have any comeback anyway, will just say it was put together wrong if it was or was not how can you prove anything.
Allan
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 02:13
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i've seen his cam covers.. and they look pretty damn plain to me!
They are also taking up valuable 18R real estate
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Location:
c'town, NSW
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 02:25
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im not sure the focus should be on Eds cam covers but rather Ed's timing cover........... ohh dear.... 
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Location:
Lost in the K hole
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 02:28
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eds timing cover is just fine!
1 bloody sticker, and the world burns you alive...
karl - think you should see the 'other' cam covers i have at home 
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Location:
Melbourne
Registered:
May 2002
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 03:47
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Allan, IIRC from my telescope making days, the glass thickness needs to be at least one sixth the diameter in order to prevent significant distortion (remember we are talking thousandths of an inch and less here). Glass is also not particularly thermally stable so Pyrex is preferred. So, by my reckoning, we are looking at a Pyrex blank that is around 700 x 400 x 120 mm in order to adequately lap this 7M head such that you can be confident that the lapping tool is not introducing imperfections in the surface (I'll ignore the whole technique thing which is probably more important). I can assure you that you can blow a head gasket a month for the next year for the price of that sucker.
I'm not sure what trip Reg Reimer was on when he wrote that.
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Location:
melb
Registered:
May 2002
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 10:03
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Chris, whether you need to lap the head at all on a 7M is open to debate. Certainly we have all taken heads from other motors to the machinist had them skimmed and just bolted them on with no other grief. Heck, in my student days I'll confess to just cleaning the surfaces and bolting the head on without any machining (with no probs, although I wouldn't recommend this).
This issue arises with the finicky 7M and its propensity to blow head gaskets. People have looked at a range of things including head bolt tension, head bolt construction, surface irregularities and the head gasket itself. A certain finish is required when using a MHG, ideally quite smooth. Often the machine shops leave quite a 'rough' finish to provide some 'bite' with the fibrous head gaskets, but this is thought to cause problems with a MHG. Therefore it has been recommended that the head be lapped. Of course, you could take your head to a good machinist that understands these things and they will machine the head so that it looks like a mirror (very fine cuts like Ed's).
A glass sheet is traditionally used for lapping. It is poured as a liquid and therefore should form a perfectly flat surface (of course we all know it is extruded nowadays so it is subject to its own imperfections). The premise is that by using one perfectly flat surface, you should be able to make another using some abrasive. That is correct and wrong, as with differing techniques one can make a flat surface OR a spherical surface (definitely not the desired result!).
I can recommend Crankshaft Rebuilders in Nunawading - they did a beautiful job on my head.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 10:39
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so, lapping like this is bad??
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Location:
Lost in the K hole
Registered:
May 2002
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 13:36
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No, but would you lap your head? 
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Location:
Lost in the K hole
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 13:46
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| gianttomato wrote on Thu, 25 September 2003 23:36 |
No, but would you lap your head?
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no, but would you lap my head?
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 13:53
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| ed_ma61 wrote on Thu, 25 September 2003 23:46 |
no, but would you lap my head?
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Mum, the strange man is offering me lollies.....
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Location:
Melbourne
Registered:
May 2002
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Re: how a 7m block and head *should* look
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Thu, 25 September 2003 14:04
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Crazy non turbo people....
Allan
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how a 7m block and head *should* look
