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About head gasket

 
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chris79  



Joined: 29 Jan 2014
Posts: 551
Location: milan

PostPosted: Fri Mar 31, 2017 4:18 pm    Post subject: About head gasket Reply with quote

I have a question about head gasket, if a thinner head gasket can increase compression why milling the head there are no compression increase? I don't understand, is the same than cut the block.
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CÚdric  



Joined: 27 Aug 2004
Posts: 1869
Location: Sweden

PostPosted: Fri Mar 31, 2017 4:42 pm    Post subject: Reply with quote

Since there is no combustion chamber in the head there will be no compression ratio change by milling the head. But you should do it anyway to make the head perfectly flat if you have it all appart, so you dont get any more leaks.

To raise compression you have to either mill the block or use thinner gasket. Dont forget that your engine probably need 98octane after the CR increase.
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chris79  



Joined: 29 Jan 2014
Posts: 551
Location: milan

PostPosted: Fri Mar 31, 2017 6:26 pm    Post subject: Reply with quote

Just thinner gasket is equal to cut minimal part from the head.
If I remove mm on block or on the head the result is the same, block and head are nearest.
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CÚdric  



Joined: 27 Aug 2004
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PostPosted: Fri Mar 31, 2017 9:05 pm    Post subject: Reply with quote

chris79 wrote:
Just thinner gasket is equal to cut minimal part from the head.
If I remove mm on block or on the head the result is the same, block and head are nearest.



No, the results are not the same, the head on the non turbo engines do not have any combustion chamber, thus no change in compression if you take of any material.


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chris79  



Joined: 29 Jan 2014
Posts: 551
Location: milan

PostPosted: Fri Mar 31, 2017 9:50 pm    Post subject: Reply with quote

Then even thinner head gasket don't increase cr.
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morghen  



Joined: 21 Jan 2005
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Location: Romania

PostPosted: Fri Mar 31, 2017 10:44 pm    Post subject: Reply with quote

Yes it does.
Head gasket is like an extension of the block...part of the combustion happens inside the head gasket enclosed volume.
If you use a thinner headgasket you increase CR...but not by a whole lot.
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chris79  



Joined: 29 Jan 2014
Posts: 551
Location: milan

PostPosted: Sat Apr 01, 2017 4:26 am    Post subject: Reply with quote

This part is correct for my car?

0,063"
Guardalo su eBay http://www.ebay.co.uk/itm/201604502412

Or better this 0,050" ?
Guardalo su eBay http://www.ebay.co.uk/itm/351759796733
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 794
Location: Maysville, Colorado

PostPosted: Sat Apr 01, 2017 6:04 am    Post subject: Reply with quote

I just paid about $95 + shipping for a .040 head gasket from Cometic. The standard Reinz head gasket is much less and seems to be about .066" thick. My machinist charges about $100 to mill the block, which will probably need to be surfaced anyway and it doesn't cost any more to take 1mm than .25mm. Surfacing by 1mm will remove about 5.8cc from the combustion chamber which should raise compression by approximately(I didn't do the math) 7/10 of a point which would be significant in a 9.3 euro motor.

If you did that the cam would get retarded a bit which is bad(again no math but I think about 3 degrees:. Summit Racing has an offset cam key kit which I believe is for an early 1980's 2.2 Dodge ??? which would allow for making that up and advancing it a bit. As I recall the cam key kit is about $65 but that includes 3 or 4 different keys for various offsets. Ideola has a better adjustable cam setup but it is more expensive also.

Look at Ideolas website for the compression ratio calculator and try using different deck heights (mill the block) and head gasket thicknesses.
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chris79  



Joined: 29 Jan 2014
Posts: 551
Location: milan

PostPosted: Sat Apr 01, 2017 6:39 am    Post subject: Reply with quote

But I think​ no remove block, compression was good, I would like only replace head gasket and fix valve intake myself.
It's necessary mill the block?
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MikeJinCO  



Joined: 08 Jun 2010
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PostPosted: Sat Apr 01, 2017 9:36 am    Post subject: Reply with quote

Probably not. When I first had my '77 apart with a blown head gasket I just got the head surfaced probably .1 to .2mm and lapped the valves and it sealed up well or reassembly.
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morghen  



Joined: 21 Jan 2005
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Location: Romania

PostPosted: Sat Apr 01, 2017 4:31 pm    Post subject: Reply with quote

chris79 wrote:
It's necessary mill the block?

Only if you really want to increase the CR
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Paul  



Joined: 02 Nov 2002
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PostPosted: Mon Apr 03, 2017 3:51 am    Post subject: Reply with quote

Measure the block height and compare to the spec to determine if anything can be milled.
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924RACR  



Joined: 29 Jul 2001
Posts: 8169
Location: Royal Oak, MI, USA

PostPosted: Mon Apr 03, 2017 10:40 pm    Post subject: Reply with quote

+1 that the Dodge/Mopar offset cam keys work, and work well, for the cheap cam timing answer (again, not as good as the Ideola cam gear).

When just doing a headgasket on a street car, use a long metal straight ruler to check for warping. Place it lengthwise and also on the diagonals, and see if you can fit any feeler gauge more than maybe 0.002" through any gap. Same thing to the top of the block. If you can't fit a feeler gauge through there, then it's flat and can be reused without machining - which is in fact often the case, with these motors, in my experience.

It's a bit harder with the valves in the way, but...

In short - odds are you don't need to have the block or head cut...
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