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Tanky

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what makes you think its the head thats the common factor in the failures ???

are you  using a head gasket with a tab at the back edge for recessed blocks ???? 

there has been some poor gasket stories recently 

what are your compression figures   , ???

pete

 

 

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Hi Pete.

Yes the gasket has a tab. I got it from Rimmers. I was getting compression figures of about 80 across the board.

I changed the head gasket and she fired up but with a lot of blue smoke after about 15 minutes of running. Then the oil was milky when I checked it. So head off again this time with stem seals, new gasket again, torqued down and she wouldn't start. Fettled with the timing and got all that right with help from Alan Gourley and a proper mechanic friend of mine. Like I said we spent hours trying to get her started, then she started for about 15 minutes running at 1600 revs. Then she stalled as we were setting up the timing gun and she just would not start again. She then started for a few seconds then died. After that there was a note change and she turned over really quickly...figured out it was loss of compression, did a compression check and absolutely no compression across the board. I can only think that the gaskets from Rimmers are poor quality (both?) and they keep blowing but when they come back off there is no sign of damage on them. Or my head is warped or the valve guides are shot... I've lapped in the valves, I've changed all the head studs and nuts I've taken off the electronic ignition and gone back to the original dizzy and coil. It's getting fuel and a decent spark from a fully charged battery...

Thoughts?

Cheers

Charlie

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Burning oil in big quantities is often bores/rings not head. Unless its the head gasket has failed between the rocker feed perhaps (Or anywhere else to be honest) and the cylinder.

Payen Gaskets are the best and tend to fail less ( I did have one go recently, very shortly after fitting.) 

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Charlie,

Apologies for 'Granny and sucking egg' moment but if there is no sign of damage to the gasket(s), poor/no compression across the board and milky oil did the head get tightened down in the correct sequence to the correct torque an then repeated to make sure no errors?  Washers and nuts all sound?

Dick

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I will also apologise in advance for any suggestions on sucking eggs...

There's plenty of good advice in previous posts above.

A gasket from Rimmers would not be expected to fall in a matter of minutes, so clearly something else is wrong. As said already, Payen gaskets are among the best.

Have you checked that the face of the head is flat? Rather than an expensive replacement head, lightly skimming the present head may be all that's needed.

Another thought: is it possible there was a serious airlock? If the engine ran for 15 minutes without proper coolant circulation through the head, the gasket will almost certainly be toast and the head may have warped, needing a skim as above. These engines will easily get airlocks when refilling with coolant, raising the front of the car helps.

Good luck,

Nigel

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Hi Dick,

Yes all done in sequence with new studs and nuts. Started at 20 then 40 then to 52 as the first 9ne failed at the stated 46 in the book. Why even if it wasn't torqued down correctly would it fail to start?

Do I need to get a thicker gasket? I don't know if the head has been previously skimmed. Should I get it skimmed and have the engineering firm supply a gasket?

Thanks

Charlie 

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the two designs have very different sealing(fire ) rings

recessed block  has a groove machined around the bore in the  block  top face 

a  gasket for a recessed block ( with a tab at the back) has the rings raised from the flat gasket so they fit in the recess and this contains/supports the rings 

a flat bock is just that just a flat face with the bores as expected the gasket is pretty flat , and does not have the recess to help the  support (no tab at back)

fit the wrong one to the wrong type engine and very early life failure is definite ,  

if you have lost coolant . burning /smoking/repeated failures/  no miles etc  then  i think   this is the place to start looking 

Pete

 

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'78 Spit block should have fire-rings....... IF it's the original block......

The manner of failure sounds more like the opposite way round - non-fire-ring gasket being used on a fire-ring block.  When you put a fire-ring gasket on a flat block you either get water pouring out the side as you are filling the system or it does it pretty much as soon as the engine warms up and the system pressurises, but the engine keeps running and compression is fine.

I have heard (from Chris Witor) of similar issues with recent Payen fire-ring gaskets (AK280) for the 6 cylinder engines because the fire-rings are not correctly formed.  He thinks there is a tooling problem.  Not previously heard of this extending to 4 cylinder though?

Nick

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recessed block looks like this

823028872_1500firering.jpg.4e176ec88d202a83e487a8b40d2f132f.jpg

Flat ones don't have the machined recesses around the cylinders.

One other thing to check..... do the threads on the studs extend below the top surface of the head.  That is, can you be sure that when you tighten the nuts, they are clamping the head and not bottoming on the stud?  The nuts should have hardened washers under them (ordinary bolt shop ones won't do - they crush) or use flanged nuts from Minispares, which are excellent and hold the torque reliably.

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As said above, with that parts combination, compression is fine, just fluid loss/mixing as the fire-rings don’t compress enough to allow the rest of the gasket to seal.

Really sounds like recessed-block-with-flat-gasket-failure mode to me. Though as the correct, tabbed gaskets are being used the gasket quality has to be questioned. Also the amount of clamp being applied, whether through nuts bottoming, duff torque wrench or whatever. Any head damage or block damage sufficient to to cause compression loss on all cylinders after a few minutes unloaded running should be visible to the naked eye.....

Nick

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Charlie,

Clearly you're going to have to remove the head again. When you do, please could you post photos here, showing the gasket, the top of the block and the gasket face of the head? Before you remove the head, photos of the nuts at the tops of the studs would also be useful, plus photos of the studs in situ after you've removed the head and gasket.

There's lots of experience here and we all want to help. Photos will take some of the guesswork out of our long range attempts at diagnosis.

Nigel

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1 hour ago, Pete Lewis said:

yes   exactly so ....flat

good to have the two photo's  shows exactly what the difference is 

Pete

Worth a million words.

21 hours ago, Nick Jones said:

 use flanged nuts from Minispares, which are excellent and hold the torque reliably.

Nick - I'm too lazy this evening to check my manuals; what size for the Herald studs? I might give them a go. Cam4545?

Or are they same as Paddocks?

http://www.jamespaddock.co.uk/head-stud-nut-improved-3

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