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Number six cylinder not working


Dean Weston
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Compression in number six cylinder very low not firing, So going to take head off and try to find out problem.

Thus I need a new head gasket.

My question is, how do I tell which head gasket I need recessed or not.

Also if it's the valves, is it good practice to change them all?

 

Thanks for your help

 

Dean

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Did you do a "wet" test? Couple of squirts of engine oil on the cylinder via plug hole, See if compression increases substantially compared to other cylinders.

 

If valve seats are damaged, you may be needing hardened inserts. But see what the issue is first!

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Dean, what car do you have?

 

Does the old gasket have a tab at the back, bulk head end? Tab, recessed. No tab, not recessed. But you'll find out when you get the head off. Recessed are, well, recessed.  :lol: You can feel/see it around the top of the bore.

 

Have you tried a wet test (Drat! Clive beat me to it!) A substantial increase in compression indicate ring problems :( 

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Thanks for all your replies, No wet test completed, changed all electrics and then compression test.

 

Held ht lead to top of spark plug, very large spark hitting the top of the plug.

 

Put petrol down the bore of number 6 still nothing.

 

So I started to take it apart again...

 

 

My new problem is can't get the cylinder head off , its jammed . Is this common?

 

Thanks for your help, I could not run this car without all your help, but through experience (unfortunately) I'm getting loads better!!!!!! Lol

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Dean,

VERY low compression usually means a valve problem, damage or seizure.  The oil test will increase compression by sealing the rings, however bad, but doing nothing for a damaged valve (or piston).

Did you inspect the valve movement on No.6?   

Either way, it's a head off repair, but you may need observations to help diagnosis.

 

Petrol down the bores??????   Never a good idea!

 

As Doug says, with the head off, the recess around each bore is obvious.

 

Getting the head off is a common problem.  The answer is to take out ALL the head studs, by double nutting, a stud extractor, or welding a nut to the top of the stud to convert it into a bolt.  ALL these mean new studs.

The head rarely sticks to the block, but to the studs.  Once they are out, then a soft haammer, or a BFH with wood block to break its force and stop it damaging the head will shift it.

 

John

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Ask doug about a stuck head ,he has a big tee shirt for that one all studs were a nightmare with a 3ft breaker bar and the head was still glued solid

And the studs were not the slightest corroded

 

Is this a mk1 or mk2 engine ??

 

did you double check there was tappet clearance ..?

 

always use new hard washers and heavy duty nuts , bet the old washers have deformed and this looses torqure

 

pete

 

 

 

pete

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Yes, it was a nightmare! Thankfully Pete & Jill came to my house, many miles, to assist. Wouldn't have got it off without them. 

 

Tried double nutting, had to get half height nuts as there was not a lot of thread exposed, but they wouldn't budge. 

 

Pete's "never been known to fail" impact driver, well, failed! But we used the gripping end of it with both of us on a 3ft bar and managed to shift them. 

 

As John says, new studs required and don't forget new washers and head nuts. 

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As John says, new studs required and don't forget new washers and head nuts. 

 

And they MUST be hardened washers too. If you fit normal ones they will deform with time, the nuts will go loose, and headgasket will fail. 

Proper ones from Triumph suppliers (canley classics)

 

But if the old ones come off and are in good condition, reuse them.

 

Wait until you have a list of required parts before ordering anything. Saves time/postage/hassle in the long run.

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Dean,

 

Just to add my experience of wrestling off a "stuck" cylinder head; I ended up investing in a mains powered impact wrench attached to a stud extractor to shift the studs as nothing else would touch them. I would also suggest that you order a couple of extra hardened washers because one of mine turned to plasticine and was squeezed out from under a nut when I was torquing up. Good luck

 

Wayne 

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