Technical Head gasket?

[tobywood13]

Parts and tools are in the post. In the meantime, I’ve been studying the Haynes guide to head gasket replacement. It seems that the engine described in this guide is not the FIRE lump that my car has, as the pictures look a little different and some descriptions sound like they’re talking about the older MK1 pushrod engine. Is this the book everyone uses as a guide, or is there a later edition specific to the FIRE engine?

 

[Mike1alike]

Aside from finding somewhere near me who can skim the head, is there anything else I should order to replace at the same time?

You should definitely replace the valve seals and probably the camshaft seal, too.

 

[Pugglt Auld Jock]

Parts and tools are in the post. In the meantime, I’ve been studying the Haynes guide to head gasket replacement. It seems that the engine described in this guide is not the FIRE lump that my car has, as the pictures look a little different and some descriptions sound like they’re talking about the older MK1 pushrod engine. Is this the book everyone uses as a guide, or is there a later edition specific to the FIRE engine?

Yup that's the manual I used way back when we had Felicity - the purple Panda in my avatar picture. It's Haynes manual No 0793 (look on the bottom of the spine of the book). The Fire engine specs are listed in the Supplement section chapter 13. This is what I referred to when I did a head gasket on mine. The engine shown in the chapter 1 section is the old pushrod engine.

 

[Pugglt Auld Jock]

Yup that's the manual I used way back when we had Felicity - the purple Panda in my avatar picture. It's Haynes manual No 0793 (look on the bottom of the spine of the book). The Fire engine specs are listed in the Supplement section chapter 13. This is what I referred to when I did a head gasket on mine. The engine shown in the chapter 1 section is the old pushrod engine.

I was just rereading the torque settings for the head. It recommends tightening to 20 Newton metres first then going round them all again at 30 Nm. Look on page 13.16 Fig 13.8 for the tightening sequence. These are pretty low levels of tightness and intended to take up any "slack" and seat the head into the gasket - eliminating air gaps etc. It also sets everything up for the "main event" which is done by tightening all bolts, in the same sequence, by 90 degrees (quarter turn) and then again by another 90 degrees (so in total a half turn all together). Going up in steps like this makes sure it tightens down nice and "square" with all bolts exerting the same clamping effect. You'll find this is much tighter than you'd usually tighten a bolt and I always worry a little that something is going to strip or snap. But the bolts are made from very "special" steel and are threaded deep into the block. Years ago, on older designs of engine, I have had head bolts and studs snap but I've not had that problem on anything for many years. Maybe because, on these older engines the head studs etc were often reused. Now a days though, these parts are often "stretch to yield" so must not be reused - you can only fully tighten them once. In fact if you then slacken them, even if the engine has never been run, you still have to chuck them away and get new ones! I strongly recommend buying only good quality bolts.

Angle tightening? Oh yes, I'm a big fan of this. Just think about it. Especially where head gaskets are concerned, what's of most concern and importance is achieving the desired amount of clamping effect - or "squeeze" on the gasket if you like. But tightening with a torque wrench is really only applying a turning effort to the bolt/nut and the wrench clicks off when a certain amount of resistance to turning takes place. The condition of the threads, whether a lubricant is on the threads or they are dry. Also the face of the head of the bolt/nut where it bears on the head will resist turning depending on cleanliness and lubrication etc. So the torque wrench will click off when a certain resistance to turning is met. This only loosely bears any relationship to how tightly the head is "nipping down" on the gasket. So it's only too easy to fail to get a sufficient clamping effect and "crush" on the gasket.

Angle tightening goes at this from a completely different point of view. If you think about the thread on the bolt, then you can absolutely guarantee that if you turn it one turn into it's threaded hole it will advance by the pitch - the distance from the top of one thread tooth to the top of the next - Unless either the thread on the bolt, or in the hole, strips then it has to screw into it's hole by this amount. So, you can say with confidence, that turning the bolt through however many degrees will mean it advances into it's hole by "X" amount. Now you can guarantee that, unless the bolt bottoms out in it's hole, turning it through a certain number of degrees guarantees a certain amount of clamping effort will be applied.

Ok, but why do the initial low value torquing? Well, all the above is only true if, before you start doing the angle tightening, the gasket has no airgaps etc and the head is nice and square on to the block. It goes without saying that everything is spotlessly clean and you've assembled the parts carefully. Then you fit the head bolts and spin them in by hand until they just seat. Now, by going round the tightening pattern at a very low torque value, the head is pulled down square, and miniscule irregularities are flattened. Because the torque value is so low, the friction of the threads in the holes and under the bolt head is also very low so has little effect on the tightening - as long as threads etc are all nice and clean. This first tightening "squares" everything up nicely but you'll find that, as you go round the tightening pattern, because there's relatively large movement of the head relative to the block, as the gasket takes up it's initial "settled" position, you end up with the first bolts you tightened now being somewhat slacker than the last ones. This is why you now go round them all again at a slightly higher torque - but still very low compared to how tight they will finally be - so that, after this second tightening, you end up with all bolts at roughly the same tightness - at these low levels of tightness the friction doesn't really become an issue so you end up with the head nicely "snuggled down" against the new gasket and cylinder block. Now when you do the angle tightening - where friction would be a big factor affecting clamping effect - you will get a nice even application of clamping effect.

If you think about it enough you'll be able to pick holes in the theory but, compared to fully torque tightening head bolts, doing it by angle tightening is a much better procedure.

Edit. Have a good read of the procedure in the manual before you start just in case I've misquoted something here won't you?

 

[Pugglt Auld Jock]

If you want to be "super careful" you might like to check the bolt holes in the block for "thread pull" I learned a lot about this rebuilding Hillman Imp engines which have an alloy block - so the metal is softer. The problem is that when the bolt was previously tightened - quite possibly when it was assembled in the factory - these bolts are done up so tight that sometimes they will slightly pull the area directly around the hole slightly proud of the flat face of the block. Think about it, if the block face isn't truly flat then the head won't be able to properly clamp up the gasket no matter how tight you do the bolts! This was such a problem on the Imp engine that I automatically used to, not just Helicoil all the holes in the block, but also deliberately cut out the top of the hole with a slightly larger drill so that the thread started slightly lower than the deck face of the block. If you want to check a block for thread pull on these holes then, after you've cleaned it all up ready to fit the new gasket, take a fine file with no handle on it and place it flat on the block face covering the hole. Now rub it back and forwards several times applying light pressure - take care, you don't want to damage the block face - Now look carefully at the hole. Does it have a bright ring round it? If it does then this was produced by the fine file removing some of the raised metal around the hole and you know you've got a pulled thread which will have to be rectified before continuing. If you ignore this, and the thread is pulled to any appreciable extent, the gasket is going to be liable to blow again at some time in the future before it normally would.

I always check for this when doing a head. But, thankfully, can say it's much less likely to be a problem with cast iron blocks. Felicity blew her head gasket well and truly - cylinders one and two - but there was no sign of thread pull on any of the head bolt holes.

 

[Pugglt Auld Jock]

Parts and tools are in the post.

Tools? I'm intrigued. What are you getting? I'm just wondering if you're ordering up locking tools? These early engines were timed using marks on the pulleys and engine castings. I'm just being nosy and anyway, I love tools so want to know what you're getting!

 

[ZaphodB]

Let's hope they pack the head gasket separate to the tools....

 

[tobywood13]

Tools? I'm intrigued. What are you getting? I'm just wondering if you're ordering up locking tools? These early engines were timed using marks on the pulleys and engine castings. I'm just being nosy and anyway, I love tools so want to know what you're getting!

Needed a new torque wrench, as my one starts at 60Nm, and an angle gauge for the final 90 degrees. Nothing particularly complicated. I’ve contacted two different engineering workshops near me who’ve offered to skim my head, so I should be all set.

 

[Pugglt Auld Jock]

Needed a new torque wrench, as my one starts at 60Nm, and an angle gauge for the final 90 degrees. Nothing particularly complicated. I’ve contacted two different engineering workshops near me who’ve offered to skim my head, so I should be all set.

Always worth taking into account that torque wrenches are not particularly accurate at either extremes of their range. I think digital versions are not as bad as the older manual types though.

 

[tobywood13]

Parts are all here, finally. I was wondering if anyone could give me a step by step walkthrough of how to get the head off? What parts do you need to remove first, what parts can stay on etc. Don’t want to take off unnecessary bits, or risk rounding/snapping bolts for no reason.

 

[bugsymike]

Parts are all here, finally. I was wondering if anyone could give me a step by step walkthrough of how to get the head off? What parts do you need to remove first, what parts can stay on etc. Don’t want to take off unnecessary bits, or risk rounding/snapping bolts for no reason.

As @Pugglt Auld Jock mentioned @#23 "
Yup that's the manual I used way back when we had Felicity - the purple Panda in my avatar picture. It's Haynes manual No 0793 (look on the bottom of the spine of the book). The Fire engine specs are listed in the Supplement section chapter 13. This is what I referred to when I did a head gasket on mine. The engine shown in the chapter 1 section is the old pushrod engine."

That should give the basics, any books I have are for skilled engineers and only deal with the correct torque settings etc. for reassemble.
Obviously the first thing you will need to do is drain the coolant, then disconect the battery,remove inlet and exhaust manifolds, cam belt covers, remove spark plugs, set engine on timing marks, remove cam belt, make sure you do not turn engine over again until reassembled with cam belt correctly timed or you will damage the engine, remove cam shaft cover which should expose the cylinder head bolts, make sure you have the correct socket to fit those bolts and with a cold engine undo all of them, I suspect they are all the same length if not keep them in correct order to aid reassemble, the same with all items you undo, it may help if you take photos including of any wires you have to disconnect. When you are sure all cylinder head bolts out and that nothing else is in the way, it should be possible to give the head a shake and it will release from the engine cylinder block, be careful to lay it down on a soft surface to prevent damage, then inspect old head gasket and other engine parts for indications as to your engines problems. Then in simple terms reassemble with new or repaired parts as required, torque cylinder head bolts correctly etc. Confirm cam belt timing correctly done on new belt etc. Turn engine by hand at least two full revolutions to ensure no physical damage, add coolant and engine oil plus new oil filter, reconnect battery, then fingers crossed start the engine. Simple if you have a lifetime of experience.
I have probably missed a few things, so perhaps others will contribute.

 

[tobywood13]

As @Pugglt Auld Jock mentioned @#23 "
Yup that's the manual I used way back when we had Felicity - the purple Panda in my avatar picture. It's Haynes manual No 0793 (look on the bottom of the spine of the book). The Fire engine specs are listed in the Supplement section chapter 13. This is what I referred to when I did a head gasket on mine. The engine shown in the chapter 1 section is the old pushrod engine."

That should give the basics, any books I have are for skilled engineers and only deal with the correct torque settings etc. for reassemble.
Obviously the first thing you will need to do is drain the coolant, then disconect the battery,remove inlet and exhaust manifolds, cam belt covers, remove spark plugs, set engine on timing marks, remove cam belt, make sure you do not turn engine over again until reassembled with cam belt correctly timed or you will damage the engine, remove cam shaft cover which should expose the cylinder head bolts, make sure you have the correct socket to fit those bolts and with a cold engine undo all of them, I suspect they are all the same length if not keep them in correct order to aid reassemble, the same with all items you undo, it may help if you take photos including of any wires you have to disconnect. When you are sure all cylinder head bolts out and that nothing else is in the way, it should be possible to give the head a shake and it will release from the engine cylinder block, be careful to lay it down on a soft surface to prevent damage, then inspect old head gasket and other engine parts for indications as to your engines problems. Then in simple terms reassemble with new or repaired parts as required, torque cylinder head bolts correctly etc. Confirm cam belt timing correctly done on new belt etc. Turn engine by hand at least two full revolutions to ensure no physical damage, add coolant and engine oil plus new oil filter, reconnect battery, then fingers crossed start the engine. Simple if you have a lifetime of experience.
I have probably missed a few things, so perhaps others will contribute.

Thanks for that, that’s exactly what I needed. The specifics of which wire goes where etc I’ll have to work out as I’m going through, as the Haynes guide is for a quite different engine setup!

 

[bugsymike]

Thanks for that, that’s exactly what I needed. The specifics of which wire goes where etc I’ll have to work out as I’m going through, as the Haynes guide is for a quite different engine setup!

Even the "The Fire engine specs are listed in the Supplement section chapter 13"?
Take lots of notes and photos and most important take your time without distractions.

 

[tobywood13]

Got the head off! Wasn’t too hard, took about 2.5 hours. Hardest bit was getting the intake manifold to come off. Head is quite significantly warped, so I’ll drop it off at the machinists now, hopefully it can be brought back in tolerance.

Obvious signs of gasket failed in cylinder 1, pictured. That cylinder’s spark plug was also covered in gunk. Hopefully, with a skim and a new gasket it should be right as rain.

 

[bugsymike]

Got the head off! Wasn’t too hard, took about 2.5 hours. Hardest bit was getting the intake manifold to come off. Head is quite significantly warped, so I’ll drop it off at the machinists now, hopefully it can be brought back in tolerance.

Obvious signs of gasket failed in cylinder 1, pictured. That cylinder’s spark plug was also covered in gunk. Hopefully, with a skim and a new gasket it should be right as rain.

That's good, remove any sendor units etc. from head as often get damaged at machine shops. Also when collecting from machine shop just run your hand across the surface as I have seen them machined flat then dropped onto bench causing damage to surface.
Clean surfaces then check engine bloke for flatness, using a good steel straight edge and a 2 thou of an inch feeler gauge, you shouldn't be able to pull through without dragging the straight edge.
Clean threads where bolts go into engine block throughly, if new head bolts required I run an old bolt against a grind stone to give three flutes so it can act as a tap to clean threads. If new bolts come with special grease put a very light smear on threads and follow cylinder head tightening instructions.
I assume new cam belt fitting kit with bearing guides etc.?

 

[Pugglt Auld Jock]

Got the head off! Wasn’t too hard, took about 2.5 hours. Hardest bit was getting the intake manifold to come off. Head is quite significantly warped, so I’ll drop it off at the machinists now, hopefully it can be brought back in tolerance.

Obvious signs of gasket failed in cylinder 1, pictured. That cylinder’s spark plug was also covered in gunk. Hopefully, with a skim and a new gasket it should be right as rain.

It was No1 which failed on Felicity and I believe it's often No1 cylinder where the problem is encountered.

I may be a little late making the following recommendation, but I found REINZ gaskets were definitely of above average quality when I was so involved with Hillman Imps (which are known for head/gasket problems.) They are still very much in the business and, for myself, I'd be looking to buy one of their products.

 

[tobywood13]

Head has been machined, now I can start reassembling it whilst I wait for new exhaust and intake gaskets to arrive. Does anyone know the torque specs for the camshaft bolts?

 

[bugsymike]

Head has been machined, now I can start reassembling it whilst I wait for new exhaust and intake gaskets to arrive. Does anyone know the torque specs for the camshaft bolts?

Try reading the photos I put on #18 in this post.

 

[bugsymike]

Try reading the photos I put on #18 in this post.

Also make sure the valves are out of the way of the pistons when you bolt head on!!!
Not now, but later if you remind me of EngineSeries etc. I will post details of cambelt timing.
Most of all don't forget the bit about how tight bolts have to be "Strip the threads and back half a turn " is a joke!!!

 

[Pugglt Auld Jock]

Head has been machined, now I can start reassembling it whilst I wait for new exhaust and intake gaskets to arrive. Does anyone know the torque specs for the camshaft bolts?

I thought you have the Haynes manual? If so then torque figures are given at the bottom of page 13.6. Where it states:
Camshaft bearing cap bolts
M8 - 19Nm (14 lbf ft)
M6 - 10Nm (7 lbf ft)
We are talking about the early engine here - that's the one with the square rubber oil filler cap and the oil pipe which plugs into the centre cam bearing support pillar - which is to say it's not the later engine where the oil supply went through the cam cover itself. If you don't have the Haynes manual you really should get one as it describes all you need to know and does so in "simple" language that even idiots like me can understand.

Mike makes a good point about making sure you don't bend any valves when installing the head - some of the valves will be open due to the design of the cam - it's unavoidable. The older engines, like this one, were timed up using marks on the cam and crankshaft pulleys. Unfortunately, lining up the crankshaft pulley marks brings No1 and No4 pistons to around TDC - I can't remember if it's precisely at TDC or just near. So it's possible to bend a valve if you're not careful. So, before starting to install the head line up the crankshaft pulley mark with the mark on the oil pump casing, just as you would to time it but then turn the crank anticlockwise until all the pistons are half way up/down the bores - so a quarter turn. Now, when you put the head on there's no danger to the valves. When you come to fit the new belt line up the cam timing marks first then turn the crankshaft clockwise until the crank timing marks line up. That way there's no chance of the valves and pistons getting "friendly". Remember also that when you're finished fitting the belt and before you reinstall the belt covers and auxilliary belt Turn the crankshaft SLOWLY through two revolutions - which of course rotates the camshaft once. This is to check for valves and pistons coming into contact - which, of it happens, will feel like a resistance or stop further rotation being achieved. Do this with spark plugs removed as this lets you "feel" for problems with greater sensitivity - the compression makes it more difficult if the plugs are in and if you do it quickly the flywheel rotating will make damage more likely if a valve and piston do come into contact, so It's "softly softly catches the problem" - or something like that?

Finally. Many say that the early 1.2 engines, and all the 1.1 versions are non interference - so, as yours is an early engine maybe valves touching pistons isn't a problem. I prefer to play safe myself, and I'm a natural born worrier! so do it as described above. I'd be very pleased to hear of other procedures people follow?