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JP Headgaskets


flatplane8

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Indian!

 

Not sure just how suitable they are, though I know someone who basically rebuilt their JP with Indian parts and it worked - but for how long! ;)

 

Mike

Edited by mykaskin
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Indian!

 

Not sure just how suitable they are, though I know someone who basically rebuilt their JP with Indian parts and it worked - but for how long! ;)

 

Mike

 

Some are unused old stock too, so genuine stuff.

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Indian!

 

Not sure just how suitable they are, though I know someone who basically rebuilt their JP with Indian parts and it worked - but for how long! ;)

 

Mike

 

 

So where else are JP gaskets made now? Almost certainly not in the UK, & there can't be much 'old stock' left around. :rolleyes:

 

Tim

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Another minor update, the heads all pressure tested ok, so it's just two exhaust valves and a skim required. They are going to take 2-3 thou off just to clean up the mating faces. Is this enough to make it a good idea to check the piston to head clearance as per the manual?

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Another minor update, the heads all pressure tested ok, so it's just two exhaust valves and a skim required. They are going to take 2-3 thou off just to clean up the mating faces. Is this enough to make it a good idea to check the piston to head clearance as per the manual?

 

Skimming the head won't affect the piston clearance. If it was right before, it should be right again, subject to the gasket being the correct thickness.

 

 

Tim

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Skimming the head won't affect the piston clearance. If it was right before, it should be right again, subject to the gasket being the correct thickness.

 

 

Tim

 

Does it matter that the valves are now closer to the piston?

 

Mike

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Does it matter that the valves are now closer to the piston?

 

Mike

 

That's a different question, though it is affected by skimming the head, the book covers it.

<Exh valve head must be not less than .012" under face of head, and inlet not less than .004".

Neither must be more than .100">

 

 

Tim

Edited by Timleech
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That's a different question, though it is affected by skimming the head, the book covers it.

<Exh valve head must be not less than .012" under face of head, and inlet not less than .004".

Neither must be more than .100">

 

 

Tim

 

Thanks Tim for that reminder, a skim will affect this value so I'll tell the engine shop. Of course, with a flat combustion chamber like this the head to piston clearence won't be affected by a skim - thanks for clarifying.

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I can confirm that SEP have a lot of Old New Stock....inc the headgaskets....yes they are more expensive than the indian ones but they are worth it....they are stamped Made in England and from memory think the ones I got were made by Coopers....he has quite a lot of other JP bits as well and is a nice bloke to deal with to boot!

 

HTH

 

Gareth

 

PS had my heads skimmed and all is still good at the moment!

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Update - I'm picking up the heads tomorrow, cleaned, skimmed and two new exhaust valves installed (which I supplied). I was staggered at the price, when I first spoke to them it was £30 per head to clean and check, however with a skim (£30 per head) and some other work its come to over £600!! Perhaps I'm missing something, but I'm not seeing where the extra money has gone, its not like they've been gas flowed. Will be discussing tomorrow ;)

Edited by flatplane8
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I had three double heads done as you know, pressure tested and skimmed picked up yesterday £150 + Vat, they made the blanking plates etc and gave them to me. Do you want three plugs sending, I had forgotten about them. £600 sounds they they are taking the p**s. Southern prices??

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I was charged £60 per head for skimming & pressure testing...it also included fitting a new core plug....all turned round in 48hrs.

 

It was done by these people in Coventry

 

http://www.enginepower.org.uk/

 

Sorry that doesnt help you!

 

£600 does sound a bit steep.....what else does that include being done?......think thats worth asking about esp as they have given you prices already...would have at least expected a phone call if the price was going to leap up!

 

Cheers

 

Gareth

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Got the heads back and they've done a good job, but it must be southern prices (e.g. pressure test three heads = £117). I restated that I wasn't happy with the way the cost had mounted.

 

Anyway, I'm currently painting them and cleaning up the bloack face. In terms of refitting the heads, I gather the idea is to put a little bit of oil on the nuts and then tourque them down in stages, using a diagonal pattern. This table here seems to suggest 100ft-lbs for the normal nuts and 150 ft-lbs for the nuts on the tubular studs over the pushrods. Does that sounds like the best approach?

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Got the heads back and they've done a good job, but it must be southern prices (e.g. pressure test three heads = £117). I restated that I wasn't happy with the way the cost had mounted.

 

Anyway, I'm currently painting them and cleaning up the bloack face. In terms of refitting the heads, I gather the idea is to put a little bit of oil on the nuts and then tourque them down in stages, using a diagonal pattern. This table here seems to suggest 100ft-lbs for the normal nuts and 150 ft-lbs for the nuts on the tubular studs over the pushrods. Does that sounds like the best approach?

 

Generally speaking threads should be clean but not oiled before torquing down, oiling them can have a big effect on the result of a given torque.

 

Tim

Edited by Timleech
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Generally speaking threads should be clean but not oiled before torquing down, oiling them can have a big effect on the result of a given torque.

 

Tim

 

Thanks Tim, been a while since I've done this, hence the questions. Do those two different torque figures sound correct, or should it be the same value on all six head studs?

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Personally I did 120 ft/lbs on all the studs....mine you that was using new studs (not pushrod tubes tho) It seems that the studs can corrode and thus weaken....perhaps have a good look at them.....I coated the studs (but not the threads) in copper grease to try and stop it happening again...apart from the oil your theory sounds good!...oh make sure your torque wrench is accurate!

 

Good Luck!

 

Cheers

 

Gareth

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Personally I did 120 ft/lbs on all the studs....mine you that was using new studs (not pushrod tubes tho) It seems that the studs can corrode and thus weaken....perhaps have a good look at them.....I coated the studs (but not the threads) in copper grease to try and stop it happening again...apart from the oil your theory sounds good!...oh make sure your torque wrench is accurate!

 

Good Luck!

 

Cheers

 

Gareth

 

100 lbft feels pretty much like a safe limit to me on the solid studs. The tubular ones are harder to judge, very little elasticity in them. If it needed an accurate torque wrench, I reckon Listers would have put a figure in the book ;)

 

Tim

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100 lbft feels pretty much like a safe limit to me on the solid studs. The tubular ones are harder to judge, very little elasticity in them. If it needed an accurate torque wrench, I reckon Listers would have put a figure in the book ;)

 

Tim

 

 

Fair enough Tim!

 

I do always breathe a sign of relief when I do the last stud up and nothing has broken!......I do wonder how good some of the cheaper torque wrenchs are tho....sometimes I think if they under read then you may be going tighter than Mr Lister thought!

 

Cheers

 

Gareth

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100 lbft feels pretty much like a safe limit to me on the solid studs. The tubular ones are harder to judge, very little elasticity in them. If it needed an accurate torque wrench, I reckon Listers would have put a figure in the book ;)

 

Tim

 

The table I linked to above suggests 150 ft-lbs for the tubular ones. I'm not sure why they would be signifigantly more than the solid ones, as it would seem to give uneven clamping in theory....

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The table I linked to above suggests 150 ft-lbs for the tubular ones. I'm not sure why they would be signifigantly more than the solid ones, as it would seem to give uneven clamping in theory....

 

That's my feeling too, as clamping force is, I'm told, not much dependent on bolt pitch and the tubular studs are spaced around the cylinder in pretty much the same pattern as the rest of the studs but I might pull them a little tighter simply because they don't have the same feel as the solid studs.

 

I'd be interested in input from our South coast friends on this one.

 

Tim

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Morning Tim,

 

You must always remember that JPs date from the two men and a whippet era when torque settings were a grunt or a grunt and a half! I have dismantled many JPs that have probably never been down since build. I'm often surprised how slack the nuts are and am convinced that,on assembly,a high torque setting is not really needed so long as the mating surfaces are flat and square to each other. That said I've come across a few that need dogging down to seal. My personal worry is the corrosion around the block studs to block threads. They often pull out and need tapping oversize to take an insert.

 

I suspect that 100 ft lb is plenty tight enough for the head studs and would agree that the 150 ft lb quoted for the tubular studs is ok. Be careful with these though, especially the cross drilled JK type, as they are liable to shear across the hole.

 

If they haven't sealed the head at these torques there is a problem. The block tops can distort ever so slightly, especially if the engine has been frosted at some time. We end up block repairing 50% of the JPs we see so it's common enough.

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