Head Gasket sealer?

[Mikerb]

My JCB 3CX Perkins 4.236 engine has blown another head gasket in the same place. Following on from my last two posts; Bursting pipes! and Smoke Rings.

The block is slightly damaged from getting the liners out on the rebuild I did

First time.

IMAG0798.jpg

Second time, looks like the exhaust pressure is eating the gaskets up.

IMAG0812.jpg

Damage on the block.

IMAG0815.jpg

Taking the block out for a reskim isn't really an option due to cost and effort, it's an old machine and I've spent too much on it already, so can I use something along with a new head gasket that will help seal against the less than perfect block? I'm thinking about using Permatex 80008 to stand up to the heat and pressure, or Holts gun gum as I have both of these products.

Obviously using it sparingly to avoid over-squeeze into the cylinder!

Someone mentioned copper grease but I think it will be blown out of the way.

[jcb4cx]

you could try JB weld and sand it down to a smooth level finish over the damaged bit

https://www.youtube.com/watch?v=PsUYUZ3eqTM

[Jeremy Rowland]

You could also try some 'liquid metal' its a bit like a body filler type compound but supposed to be for repairs like this; I am sure I have seen it used in the past in cases like this, you'd acquire it from any good tool retailer/engineers merchants.

Jeremy

[Stormin]

As long as you have removed the projecting weld splatter or any other projections preventing the head sitting down properly there shouldn't be an issue here. A slight pitting shouldn't affect the seal. Is the liner projection within specification? Most of the sealing to the fire ring should be as a result of the liner projection squeezing the fire ring on the gasket. From the photo's in previous post projection of liner on number three looks lower than four. You can get shims to correct this. You can also check the deck of the block locally using a good ruler as a straight edge and shining a light behind or using a thin feeler gauge to check for gaps.
I have seen a copper spray used to help seal head gaskets and also the old Fergie tractors and others used to use a product called wellseal. Good luck removing the head again after using that stuff though.

[modelman093]

http://www.belzona.co.uk/en/products/pu ... epair.aspx

[Mikerb]

Stormin - are you're saying that No.4 liner is sitting too proud and not letting the head seat down enough to make a seal? That would make sense.
The first lip of the liners do not sit flush with the block, should they do so?

I'm not sure what you mean by fire ring, as the gasket doesn't make contact with the liners at all as you can just about see here:

the gasket sits around the liner, the hole in the gasket is about the same as the liner hole in the block, if that makes sense.

Now... the engine is a bit of a mish mash - when I bought it, it had a 4.212 block installed, but the rest, head, sump, pistons etc are 4.236. The rings were blown, so I rebuilt it. Speaking to Simon Vicary he suggested to install new 212 liners with new 236 pistons as it was. But I shouldn't think this would cause compatibility problems as I'm led to believe that the two engines are based on the same block? As discussed in length here if you're bored: JCB 3CX engine?

[Mrsmackpaul]

Did you use copper spray I seem to re call mentioning that in a previous thread ( sorry if I forgot to mention that ) I maybe wrong there, torque it down this time and leave the rocker cover off when running till its warm and keep on retorquing it around and around and around a whole heap of times till the motor is warm stick a sheet of card board in front of the radiator will warm up much quicker have plenty of rags at hand as some oil will no doubt spill with it running with out the rocker cover on

hope this helps all good advice

Paul

Also something to think about the head gasket doesnt seal on the block as such for the compression it seals on top of the sleeve so if its stick proud and all the sleeves are stick proud around about the the same like withing a few thou head gasket should seal up fine as stormin said a steel rule can help in checking this by using feelers gauges between the sleeves and measure the height but I doubt this is a problem but it should be checked just make sure

make sure you torque the head in the right sequence start from the middle and work out

If the torque is meant to be say 70 pounds always start off a lot lower say around 40 run around the head then 50 around the head again and 60 and so on slowly increasing till it torqued down properly and always in the same order start from the middle and work out

check your tension wrench is working right I cant stress this enough check it with someone elses once you start off low on the torquing grab a mates tension wrench and just go over the same studs again with a different tension and check its clicking at the same time

I never really do any of this to this extreme only when I have problems and twice I have found the tension wrench to be faulty as in once broke head studs the other time to loose then went and bought a real high quality tension and really look after it and have never had another problem

[Mikerb]

The rocker needs to come off to gain access to some of the head bolts so can't do it while the engine is going.

This is the sequence I used

and I did gradually over about 5 or 6 cycles torque it down.

I have struggled finding the correct Torque settings, it ranges from 80Nm to 135Nm.

Like I said, the gasket doesn't contact the sleeves, you can see clearer on cylinders 3 and 4 in the picture above, the hole is larger than the sleeves and the lip is thinner than the gasket, so it must be the gasket that seals the gas compression.

[Jeremy Rowland]

The rocker needs to come off to gain access to some of the head bolts so can't do it while the engine is going.

The other thing I struggle with is finding the correct Torque settings, it ranges from 80Nm to 135Nm.

Mike are you sure that does not mean its a two stage torque setting? First stage torque to 80Nm the re-torque to 135Nm? Changing the subject slightly; the liner protrusion is quite critical but it would obviously protrude further by where the cylinder block is damaged between the two cylinders, so if its in the correct tolerance around the liner except by the damage you know its okay and all you have to do is repair the damaged block face.

Jeremy

[Mikerb]

Hi Jeremy, those two figures are from different things I have read, another one said 120Nm and its different depending on what bolts are used, a bit confusing. For example: https://www.powerlinecomponents.com/lit ... e_spec.htm

I can't see the protrusion having a roll to play in the gasket failure because the gasket doesn't seal on the liner because the diameter is greater than the liners diameter. I'll take some more detailed pictures tomorrow to illustrate this.

(I've edited the post you have just quoted on, I think while you were replying, just so you don't miss any information)