Gunboat engine rebuild (again)

[Guest catweazle (Banned Member)]

Third picture down bottom leff corner, looks like a piece has been taken out in a large chip, no melting. Are you sure you've not had valve to piston contact? The chipped piece may then have migrated round and done the rest of the damage. The rest of the top of the piston doesn't look too badly overheated.

The only other way that large chip could have been removed is on the last few downward strokes of the piston as it overheated due to some other cause. Looking how clean the area is at the fracture point I would expect to still see this large chip on top of the piston once stripped down. You've not mentioned seeing it anywhere so my guess is the first scenario sticky valve!

Hi Norman,

you raise some interesting thoughts there.The lighter colour on the damaged area has been exagerated by the flash.its no where as obvious as that in real life.There are no obvious lumps anywhere,there are deposits

on the valves and seats.The vave guides were replaced recently,they were purpose made as none were available.i remember thinking at the time there sloppy,but the company had all the correct figures for them so should of been ok.There are no seels so i guess they get plenty of lube.

When i took the valves out to check the seats they slid out easy.

[Chrisg]

It might be the photo but the thrust faces look reasonably undamaged which might rule out overheating or a lube problem

 

It reminds me of the damage of the early ford crossflow engines that use to burn pistons out which i think was a mixture or timing problem

[Guest catweazle (Banned Member)]

It might be the photo but the thrust faces look reasonably undamaged which might rule out overheating or a lube problem

 

It reminds me of the damage of the early ford crossflow engines that use to burn pistons out which i think was a mixture or timing problem

Catterpiller have looked at the pics today,funny enough here on the forum,The engineer from the round britain race on Horatia is saying injector.i will reserve my opinion till i prove it,still not sure.:nono:

[Degsy]

Cat seem to be totally convinced it's an injector problem then. I assume you are having the injector tested.

[Guest catweazle (Banned Member)]

Cat seem to be totally convinced it's an injector problem then. I assume you are having the injector tested.

I will do mate but there not the easiest things to test,have to post a picture there just a small tip screwed to an extention tube held in the precombustion chamber by a large nut.no more than 1inch long the tip.

[Stormin]

I know you said it's a job and a half to test the injectors on the engine but can't you just take them to diesel specialist to be tested on a flow bench? They'll probably clean them at the same time.

Not quite the same as seeing how they perform on the end of your pump put at least you'll know if they give an even delivery of fuel.

[Degsy]

I know you said it's a job and a half to test the injectors on the engine but can't you just take them to diesel specialist to be tested on a flow bench? They'll probably clean them at the same time.

Not quite the same as seeing how they perform on the end of your pump put at least you'll know if they give an even delivery of fuel.

 

 

Exactly what I was thinking but I'd be inclined to have the pump checked at the same time in case its overfueling on one pot.

[Guest catweazle (Banned Member)]

I know you said it's a job and a half to test the injectors on the engine but can't you just take them to diesel specialist to be tested on a flow bench? They'll probably clean them at the same time.

Not quite the same as seeing how they perform on the end of your pump put at least you'll know if they give an even delivery of fuel.

I must put picture up of injector,its not your conventional,pull to bits clean,reset spray braking point and off you go.they cant be stripped and cleaned,cat say even if it tests ok on bench dont use it.they say maybe the pipe is detereating internally and thats where the dirts come from,there is a screen in the nozzle .i am still on the fence on this.

[Guest catweazle (Banned Member)]

Exactly what I was thinking but I'd be inclined to have the pump checked at the same time in case its overfueling on one pot.

The problem is no one but cat has the test rig for this pump,it underwent a £2000,rebuild 100 hours ago,so i dont want to find a problem there,because of the rairety of the pump,the insurance for the carrage is enough to pay for a conventional pump test.The only way it can overfuel is by supplying fuel at the wrong time ie full throttle at half throttle.For it to change the quadrant screw would have to of come loose allowing fuel timing to change.Untill we get down to testing it ourselves we can only guess.Ordered and paid for the parts today,didnt ask the price.:shake::shake::shake:

[Degsy]

The problem is no one but cat has the test rig for this pump,it underwent a £2000,rebuild 100 hours ago,so i dont want to find a problem there,because of the rairety of the pump,the insurance for the carrage is enough to pay for a conventional pump test.The only way it can overfuel is by supplying fuel at the wrong time ie full throttle at half throttle.For it to change the quadrant screw would have to of come loose allowing fuel timing to change.Untill we get down to testing it ourselves we can only guess.Ordered and paid for the parts today,didnt ask the price.:shake::shake::shake:

 

 

I think thats what's known as 'OH TISH'

[N.O.S.]

That's the one, Degsy -

 

Ohtish Redding, singing

 

"Sitting on the dock by the bay,

watching the engine get stripped right down"

[Tony B]

The description of 'Sitting in an ice bath under an ice cold shower whilst being hit hard from underneath and tearing up £10 notes' ,comes to mind.

If anyone can crack it Catweazle, I'm sure you can.

[Degsy]

That's the one, Degsy -

 

Ohtish Redding, singing

 

"Sitting on the dock by the bay,

watching the engine get stripped right down"

 

Not quite what I had in mind but....

:rofl::rofl::rofl::rofl::rofl::rofl:

[Tony B]

Catweazle will now have the refrain running through his head every time he goes near the boat. :shake:

[Guest catweazle (Banned Member)]

That's the one, Degsy -

 

Ohtish Redding, singing

 

"Sitting on the dock by the bay,

watching the engine get stripped right down"

T--t :rofl::rofl::rofl:

[N.O.S.]

T--t :rofl::rofl::rofl:

 

That's a relief - I was worried you would send Patweazle up to sort me out :sweat:

[Guest catweazle (Banned Member)]

That's a relief - I was worried you would send Patweazle up to sort me out :sweat:

Thats ok,we do seem to be lost for something to do over xmas:beer:

[Guest catweazle (Banned Member)]

Parts arrived today,because it was cash securicor had to take back the payment,ruddy hell dick turpin lives.

I have measured everything,so when it happens again you wont have to ask me the same questions.

for the people who dont know,this is how you check the ring gap in the bore.you push the ring down with the piston to make sure its square.

all the ring gaps were within the limits of between 17/28 thou.

[Guest catweazle (Banned Member)]

Checking ring clearance in piston,within limits 2/4 thou.

[Guest catweazle (Banned Member)]

Injector ,just for Richard.huge isnt it.

i was happy to re use this piston from the previous repair,but they wouldnt let me.

Would you of used it ?

[Richard Farrant]

Injector ,just for Richard.huge isnt it.

 

 

 

 

As is the price no doubt :shake:

 

Are you going to get the pump checked out for the delivery to that cylinder, or will you just change the injector and see how it goes?

[Stormin]

Sowhat is that insert in the top of the pistons?

Looks like a poppet valve but I assume it's got some other relevance.

Are you still on schedule to get to the fuel station before the price hike?

[Guest catweazle (Banned Member)]

As is the price no doubt :shake:

 

Are you going to get the pump checked out for the delivery to that cylinder, or will you just change the injector and see how it goes?

We will do a crude comparrison test on the engine,with old and new injector and hope it shows up ,to start with.

[Guest catweazle (Banned Member)]

Sowhat is that insert in the top of the pistons?

Looks like a poppet valve but I assume it's got some other relevance.

Are you still on schedule to get to the fuel station before the price hike?

Its a steel insert to help protect the piston in the most vunerable spot.

We wont make the fuel pontoon,but the marina has offered to fill it up before the date,i dont like the idea of them towing it round,but have no choice.it will probably take 300 galls at 80pence a litre so there quids in any way.:shocked:

[Stormin]

80 pence a litre :shocked:

 

I thought you were trying to get diesel at off shore prices, UK tax (rip off) free at around 20p a litre or something.

Then after November you were then forced to use UK red diesel, at agricultural tax rates, at approx 50p litre.

Seems like I've missed something.