JP Head Gaskets contd!!

[frangar]

Hi

 

Right have now got the heads off and although I'm going to run a straight edge and blue over them tomorrow its not looking too bad.....the gaskets have a good indent on them from the liners...they are showing signs of blowing on the face between the gasket and the head rather than block and gasket.

 

I think the cause may have been that the nuts which fit to the rocker tubes were nowhere near as tight as the ones fitted to the studs...those needed a breaker bar to undo whereas the ones fitted to the rocker tubes i could undo with a normal socket ratchet..My question is should they all be to the same tightness eg 120-150 lb/ft or is there a good reason as why they weren't as tight???

 

But the strip down was fairly pain free...one advantage of blowing gaskets is that I now can get the engine stripped and head off in about 3 hours!!...spent the longest time looking for the joint in the handstart chain which flew into the bilge.....

 

Will post some pix tomorrow to see if anyone spots anything I may have missed!

 

Cheers

 

Gareth

 

PS also the gaskets were not marked with any makers name etc...which does make me wonder how good they were as well.....and as I thought no jointing compound was used...will definitely be using Wellseal on the rebuild

[Timleech]

Hi

 

Right have now got the heads off and although I'm going to run a straight edge and blue over them tomorrow its not looking too bad.....the gaskets have a good indent on them from the liners...they are showing signs of blowing on the face between the gasket and the head rather than block and gasket.

 

I think the cause may have been that the nuts which fit to the rocker tubes were nowhere near as tight as the ones fitted to the studs...those needed a breaker bar to undo whereas the ones fitted to the rocker tubes i could undo with a normal socket ratchet..My question is should they all be to the same tightness eg 120-150 lb/ft or is there a good reason as why they weren't as tight???

 

But the strip down was fairly pain free...one advantage of blowing gaskets is that I now can get the engine stripped and head off in about 3 hours!!...spent the longest time looking for the joint in the handstart chain which flew into the bilge.....

 

Will post some pix tomorrow to see if anyone spots anything I may have missed!

 

Cheers

 

Gareth

 

PS also the gaskets were not marked with any makers name etc...which does make me wonder how good they were as well.....and as I thought no jointing compound was used...will definitely be using Wellseal on the rebuild

 

Yes I'd say all should be done to about the same torque. They're all doing about the same job, in terms of head layout, and ISTR that the force applied by a bolt is more or less independent of the thread pitch, but determined by the torque on the nut/bolt spanner. I'm not a theoretical MechEng though, quite willing to be shown to be wrong.

I think the book calls for oil on the gasket faces, but I'd still go for Wellseal if there's a history of trouble.

It does sound as though you need to at least check the heads on a surface plate, if there isn't somewhere handy which could skim them.

 

Tim

[frangar]

So does anyone know of a good machine shop in the midlands that would be able to check the heads & skim if necessary? Would also prefer if they would be able to remove the valves & replace them afterwards as I don't have a spring compressor. I'm based in Leicester but happy to take them anywhere if they will do a proper job.

 

Cheers

 

Gareth

[BEngo]

So does anyone know of a good machine shop in the midlands that would be able to check the heads & skim if necessary? Would also prefer if they would be able to remove the valves & replace them afterwards as I don't have a spring compressor. I'm based in Leicester but happy to take them anywhere if they will do a proper job.

 

Cheers

 

Gareth

 

 

Try John Stevenson at L Stevenson Engineers Long Eaton, unless you drive a Reliant. www.stevenson-engineers.co.uk has his e-mail.

 

Failing that have a look at the Federation of Engine Remanufacturers website, www.fer.co.uk or PM Baldock of this ilk..

 

N

[Timleech]

Try John Stevenson at L Stevenson Engineers Long Eaton, unless you drive a Reliant. www.stevenson-engineers.co.uk has his e-mail.

 

Failing that have a look at the Federation of Engine Remanufacturers website, www.fer.co.uk or PM Baldock of this ilk..

 

N

 

Stevo? He'd probably do it on his POS Bridgeport!

(in joke, like the Reliant quip)

 

Any engine shop or someone with a big enough surface grinder ought to be able to do it easily, the JP head has a machined top face & so wouldn't need any fancy fixturing.

 

 

Tim

[frangar]

Thanks for that chaps....will send him an email later...I tried doing a very rough check using a steel rule but it was hopeless!!! Cant seem to shift the changeover valves either but have got the injectors out...Hopefully he can get the both the valves and the changeover valves out if they need skimming...

 

Will see how it goes from here

 

Cheers

 

Gareth

[Timleech]

Thanks for that chaps....will send him an email later...I tried doing a very rough check using a steel rule but it was hopeless!!! Cant seem to shift the changeover valves either but have got the injectors out...Hopefully he can get the both the valves and the changeover valves out if they need skimming...

 

Will see how it goes from here

 

Cheers

 

Gareth

 

Changeover valves are much easier to get out with the head bolted to the engine......

(big spanner & a hide or copper mallet)

They won't interfere with skimming the head, but the chamber would need a really thorough wash & blow out afterwards.

 

Tim

[frangar]

Well just to keep anyone who is reading this upto speed....(blimey you must be bored!!)

 

Had a look at the FER website and phoned these people who are in Coventry:

 

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

 

who were very helpful and skimmed the heads and replaced a leaking core plug (which I didnt even know about). The core plug was discovered when they did a pressure test, all in 24 hours and for what I think is a very reasonable price.....they also had lots of engine porn!! I never knew fire sprinkers where powered by large diesel engines!!

 

Anyway now have all removed parts painted and going to paint stripped block tomorrow...then think I'm going to put the heads back on using new studs etc (should I replace the push rod tubes as well?) torque it all down using Wellseal on the gaskets then leave it for a couple of weeks while I go away for work then recheck the torque when I come back...to allow the new studs to stretch and Wellseal to ooze etc...does anyone see a problem with this? Then I can put back the manifolds/exhaust etc. and hopefully all will be well....!!!

 

Cheers

 

Gareth

[ditchcrawler]

Well just to keep anyone who is reading this upto speed....(blimey you must be bored!!)

 

Had a look at the FER website and phoned these people who are in Coventry:

 

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

 

who were very helpful and skimmed the heads and replaced a leaking core plug (which I didnt even know about). The core plug was discovered when they did a pressure test, all in 24 hours and for what I think is a very reasonable price.....they also had lots of engine porn!! I never knew fire sprinkers where powered by large diesel engines!!

 

Anyway now have all removed parts painted and going to paint stripped block tomorrow...then think I'm going to put the heads back on using new studs etc (should I replace the push rod tubes as well?) torque it all down using Wellseal on the gaskets then leave it for a couple of weeks while I go away for work then recheck the torque when I come back...to allow the new studs to stretch and Wellseal to ooze etc...does anyone see a problem with this? Then I can put back the manifolds/exhaust etc. and hopefully all will be well....!!!

 

Cheers

 

Gareth

And re torque after you have run it for a few hours after it has been hot a few times.

[Timleech]

And re torque after you have run it for a few hours after it has been hot a few times.

 

As has already been said, that aint easy on a JP, especially a marine version.

 

Tim

[ditchcrawler]

As has already been said, that aint easy on a JP, especially a marine version.

 

Tim

In that case "rock and hard place" comes to mind. The new studs should help

[Timleech]

In that case "rock and hard place" comes to mind. The new studs should help

 

It's not normal procedure AFAIAA with these engines. No harm in trying a torque wrench on the exposed nuts, just to see if there's anything to take up. I'd be quite surprised if there were.

 

Tim

[GUMPY]

Don't forget that as you have had the heads done you will need to check the gap between the piston and the chamber using lead shot on top of the piston and possibly add shims along with the head gaskets........

Had to do this on the JP3.

Also you should put the manifolds on at the same time as the heads to minimise the chances of cracking them.

If you need a copy of the manual that describes this its on the internalfire website

Edited July 20, 2010 by idleness

[frangar]

Don't forget that as you have had the heads done you will need to check the gap between the piston and the chamber using lead shot on top of the piston and possibly add shims along with the head gaskets........

Had to do this on the JP3.

 

 

I might be wrong but if the heads are skimmed the clearances between the top of the piston and the face of the head will be the same....if you change a piston/liner/crank etc then they will need checking...I agree it is good practice to check them anyway...I do wonder tho if you risk damaging the head gasket by torquing down..checking the bump clearance then re-torquing...any thoughts anyone?

 

Im willing to be proved wrong!!

 

Take you point about the manifolds but they seem much easier to line up on a twin...I can see that they would be harder on a triple...I must admit I try not to separate the exhaust manifold and silencer as the joint between the two can be a right bugger to get gas/water tight...it does make for one heavy unit tho!!

 

Cheers

 

Gareth

[GUMPY]

I might be wrong but if the heads are skimmed the clearances between the top of the piston and the face of the head will be the same....if you change a piston/liner/crank etc then they will need checking...I agree it is good practice to check them anyway...I do wonder tho if you risk damaging the head gasket by torquing down..checking the bump clearance then re-torquing...any thoughts anyone?

 

From memory you don't torque it down to do the test after all the lead is very soft, just tight would be enough.

[Timleech]

I might be wrong but if the heads are skimmed the clearances between the top of the piston and the face of the head will be the same....if you change a piston/liner/crank etc then they will need checking...I agree it is good practice to check them anyway...I do wonder tho if you risk damaging the head gasket by torquing down..checking the bump clearance then re-torquing...any thoughts anyone?

 

Im willing to be proved wrong!!

 

Take you point about the manifolds but they seem much easier to line up on a twin...I can see that they would be harder on a triple...I must admit I try not to separate the exhaust manifold and silencer as the joint between the two can be a right bugger to get gas/water tight...it does make for one heavy unit tho!!

 

Cheers

 

Gareth

 

You're right that skimming the heads should not affect the clearances. Check the gasket thicknesses though, are old and new the same?

There's no way (other than putting on another identical new gasket!) round the issue that it's not a 'new' gasket by the time you've checked the bumping clearance, shouldn't be a problem if everything is good as well as scrupulously clean though.

You could pull the head down to a somewhat lower torque for the testing if it worries you, the difference in gasket compression should be quite small.

 

Tim