Cylinder Head

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MorrisJohn
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Cylinder Head

Postby MorrisJohn » Sun Sep 19, 2021 1:09 pm

I’m in the process of replacing the cylinder head gasket. I’ve noticed when I set the head on the block, with or without a gasket, that if I press down on the exhaust manifold I’m able to rock the head slightly while it sits on the block. I’ve uploaded a short video clip to YouTube (link below).

I’ve checked and can’t see it catching on anything.

The head and block surfaces both look very good, smooth, flat and clean. I will get a metal ruler/torch to double check the head is flat. Copper gasket spray has also been suggested.

The car has no known history of overheating and the engine has done a few thousand miles since professional rebuild. Previous head gasket failed between numbers 3 & 4. Heater tap is always left in open position.

Should the head be able to move in this way, and should it be fine once it’s torqued down?

https://youtube.com/shorts/iO6jBy9LpSc?feature=share

les
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Re: Cylinder Head

Postby les » Sun Sep 19, 2021 2:53 pm

It seems to me John that is natural, pushing down one side like that is bound to lift the other side, not necessarily an indication that the head is warped. Doing what you’re doing if it wasn’t for the cylinder head studs you’d tip the head right over!
Unless I’m missing something?

MorrisJohn
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Re: Cylinder Head

Postby MorrisJohn » Sun Sep 19, 2021 3:07 pm

Thanks for the reassurance Les. It’s just I changed it once already and the new one didn’t seal, no compression. So doing it all over again with another new gasket.
les wrote:
Sun Sep 19, 2021 2:53 pm
It seems to me John that is natural, pushing down one side like that is bound to lift the other side, not necessarily an indication that the head is warped. Doing what you’re doing if it wasn’t for the cylinder head studs you’d tip the head right over!
Unless I’m missing something?

philthehill
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Re: Cylinder Head

Postby philthehill » Sun Sep 19, 2021 3:09 pm

Just tried rocking a 'A' Series cylinder head on a 'A' Series block and the rocking action is completely normal. So just fit and enjoy. :D


MorrisJohn
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Re: Cylinder Head

Postby MorrisJohn » Sun Sep 19, 2021 3:26 pm

:D Thank you!
philthehill wrote:
Sun Sep 19, 2021 3:09 pm
Just tried rocking a 'A' Series cylinder head on a 'A' Series block and the rocking action is completely normal. So just fit and enjoy. :D

oliver90owner
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Re: Cylinder Head

Postby oliver90owner » Sun Sep 19, 2021 7:19 pm

I will get a metal ruler/torch to double check the head is flat.

Does that mean you have not yet checked it properly?

Checking the head (and possibly the deck) for flatness, with a straight edge, should always be carried out whenever a cylinder head gasket failure occurs. Simply put, it avoids a recurrent gasket failure, if either is not within specification.

MorrisJohn
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Re: Cylinder Head

Postby MorrisJohn » Mon Sep 20, 2021 1:00 pm

Across the width of the head is consistently flat. No light from torch visible under ruler at all.

Across the length in the centre area a small chink of light does get through.

Having never done this before I don’t know if it’s within acceptable tolerances and if the head gasket should seal this up, or if head requires skimming? As I say, engine has never overheated as far as I know.

If I move the (new) ruler and use an end of it rather than the middle the chink of light gets even smaller.

The block surface seems 100% perfect.

I’ve attached some photos of the head below.
Attachments
DCF7CB04-4686-4F3E-891F-45B1B40F5867.jpeg
DCF7CB04-4686-4F3E-891F-45B1B40F5867.jpeg (2.07 MiB) Viewed 382 times
53F695FE-88BF-4C62-8B47-1849E46C7C91.jpeg
53F695FE-88BF-4C62-8B47-1849E46C7C91.jpeg (1.84 MiB) Viewed 382 times
08A55DE2-C3AC-4F8A-BC27-CDFE02E2E6F2.jpeg
08A55DE2-C3AC-4F8A-BC27-CDFE02E2E6F2.jpeg (2.52 MiB) Viewed 382 times

les
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Re: Cylinder Head

Postby les » Mon Sep 20, 2021 1:19 pm

I think that picture has exaggerated the gap; the light has reflected on the head surface, try a feeler gauge at that point to give a true reading.

MorrisJohn
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Re: Cylinder Head

Postby MorrisJohn » Mon Sep 20, 2021 1:49 pm

0.0015” feeler gauge will only just fit between ruler and head with resistance, if ruler is just sat on. If any downward pressure is placed on ruler to simulate head sitting on block then the gauge will not pass under.
les wrote:
Mon Sep 20, 2021 1:19 pm
I think that picture has exaggerated the gap; the light has reflected on the head surface, try a feeler gauge at that point to give a true reading.

les
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Re: Cylinder Head

Postby les » Mon Sep 20, 2021 2:45 pm

Check to be sure, holding the rule down but 15 thou tight or not, is not good.

MorrisJohn
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Re: Cylinder Head

Postby MorrisJohn » Mon Sep 20, 2021 3:09 pm

The gauge I used was 0.0015”, the thinnest I have. It passes in some places with resistance. I think 15 thou would be 0.015”?

My 4 thou gauge (0.004”) will not pass through, so 15 thou definitely wouldn’t.
les wrote:
Mon Sep 20, 2021 2:45 pm
Check to be sure, holding the rule down but 15 thou tight or not, is not good.

philthehill
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Re: Cylinder Head

Postby philthehill » Mon Sep 20, 2021 3:15 pm

I would suggest that 0.003" is the maximum feeler gauge that you should be able to get between the head and rule. A steel rule is not the best straight edge to use as any distortion of the rule exaggerates the gap.


MorrisJohn
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Re: Cylinder Head

Postby MorrisJohn » Mon Sep 20, 2021 3:32 pm

Thanks Phil. I tried 0.002” and it will not pass between ruler and head, with ruler just placed on.

I think the last one was torqued down to 40lbs/ft. What torque setting would you recommend?
philthehill wrote:
Mon Sep 20, 2021 3:15 pm
I would suggest that 0.003" is the maximum feeler gauge that you should be able to get between the head and rule. A steel rule is not the best straight edge to use as any distortion of the rule exaggerates the gap.

les
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Re: Cylinder Head

Postby les » Mon Sep 20, 2021 3:52 pm

Sorry John, I misread your measurement ———can’t count !! :o

philthehill
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Re: Cylinder Head

Postby philthehill » Mon Sep 20, 2021 7:01 pm

If using standard Minor head studs the head should be torqued to 45lbf ft.
Personally I have always replaced the Minor studs with 'A' Plus studs and flanged nuts. These can then be torqued to 50lbf ft.
The 'A' Plus studs and flanged nuts are well worth purchasing.
http://www.minispares.com/product/Class ... o%20search


MorrisJohn
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Re: Cylinder Head

Postby MorrisJohn » Mon Sep 20, 2021 7:26 pm

Thank you. What a pity they’re currently out of stock (as is complete kit). I’ve signed up for an email alert when it’s back in stock. Sounds like a sensible upgrade.
philthehill wrote:
Mon Sep 20, 2021 7:01 pm
If using standard Minor head studs the head should be torqued to 45lbf ft.
Personally I have always replaced the Minor studs with 'A' Plus studs and flanged nuts. These can then be torqued to 50lbf ft.
The 'A' Plus studs and flanged nuts are well worth purchasing.
http://www.minispares.com/product/Class ... o%20search

paul 300358
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Re: Cylinder Head

Postby paul 300358 » Mon Sep 20, 2021 7:41 pm

Try Minimine, Stoke-on-Trent. Phone: 01782 595999

MorrisJohn
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Re: Cylinder Head

Postby MorrisJohn » Tue Sep 21, 2021 8:45 am

Thanks Paul.

Declan_Burns
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Re: Cylinder Head

Postby Declan_Burns » Tue Sep 21, 2021 10:54 am

You can fit longer ones wher the heater pipe is mounted. This enables the pipe to be removed without disturbing the cylinder head nuts which makes it easier when changing or replacing a thermostat.
Regards
Declan


Regards
Declan

MorrisJohn
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Re: Cylinder Head

Postby MorrisJohn » Tue Sep 21, 2021 11:56 am

Thanks Declan.

On the cylinder head I called an engineering firm just to check the price of a skim. Out of curiosity. I told them a two thou gauge wouldn’t fit though the gap. They said, as others have said, that was fine like that…but then tried to talk me into a skim anyway?


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