Detroit 6/71 - Work required

Got the last price for the puzzle ... Piston Crown, pin and pin retainer seals @ £144 ... so bust my budget again!!

£610 (incl VAT) for all parts ... 1x crown, piston rings for all six holes, all cylinder head and water jacket seals exhaust, water manifold and oil-pan seals... so just over £100 per cylinder... plus a wee bit of labour !! Parts on order and a bit of dismantling left before I start putting the lump together again...
 
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Divemaster1 said:
Got the last price for the puzzle ... Piston Crown, pin and pin retainer seals @ £144 ... so bust my budget again!!

£610 (incl VAT) for all parts ... 1x crown, piston rings for all six holes, all cylinder head and water jacket seals exhaust, water manifold and oil-pan seals... so just over £100 per cylinder... plus a wee bit of labour !! Parts on order and a bit of dismantling left before I start putting the lump together again...
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Very interesting, Sounds an awful lot cheaper than a rebuild of a yanmar..!
 
Firefly625 said:
Very interesting, Sounds an awful lot cheaper than a rebuild of a yanmar..!
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Remember;

1) I provide the labour which is the majority of ££
2) I have no need to re-build turbo (yet), but can run slow without ... and engine would really not complain....
3) If I had to do a full factory re-build of all cylinders (incl liners and pistons etc.), I would probably end up with a parts bill of around £1,600 - 2,000
4) Also remember that most DD's share parts, which makes spares cheaper... ( a two cylinder 71 series, share the major serviceable components with the V16)

However, I also have access to some nice resources that will assess wear parts (liners, clamshell bearings etc.), and make an informed recommendation on expected life of the parts from experience in industrial application and what I get is an indication that the parts removed so far should be good for thousands of hours and that someone have done a "less than perfect", probably un-necessary job (the broken parts).... whilst charging the previous owner for a full re-build.... (I have copies of the bills), but all the seals appear to be re-used with traces of additional sealant .... which should not be part of a proper job...

So, respect for those that do a proper job.... that is not easy nor is it fast, hence the cost !
 
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Picked up the parts today... 6 sets of rings, piston crown (threw in a piston for good measure... no cost...)... and a whole lot of seals.... (no animals was hurt in the making of this post)...

Aberdeenshire-20140423-00058_zps330ba6ce.jpg


The parts were on the shelf last week, but was otherwise engaged..... plan is to take one piston out, replace rings etc., and re-assemble one-by-one...
 
No ... and a personal view NOOOOOOOOO!

Probably the last thing I want to be reminded of is how much fuel goes through the iron lumps as I push throttles forwards and they start singing :)

Also, for the size, these small lumps push through an awful lot of fuel (more than a four stroke) that is being returned to the tank as the fuel also perform part of the cooling process, so not sure how you'd have to size the instruments to cope with that..

Irrespective, believe that you'd pay a lot for it and would take many years to get payback from it...
 
So more stuff removed this week-end, but most importantly stuff going back in again....

Piston & Liner 2, 3 and 4 are out and 2 & 4 re-built and inserted in liner .... Piston & Liner 2 inserted in block again, clamshell bearings & cap all torqued up to crankshaft.... so one in !! :)

Piston & liner 4 ready and waiting to go in, and piston & liner 1 is loosened and moved up ... just need to drop clamshell bearing & cap ... hopefully half an hour work and she'll be out...

Piston 3 was the damaged one and have taken that one home as more work is needed here ...

Basically piston crown cracked .....which can clearly be seen here.

Highland-20140427-00060_zps7a60a889.jpg


When removing the liner, I noticed a "nick" at the top of the stroke which could have been causing the piston damage.... or be caused by it....

Highland-20140427-00061_zps2cee9cfa.jpg


Needless to say, I will not be inserting this liner again, but will use a spare liner from other engine....(same series of course).

Started to remove the piston retainer pin cap by drilling a hole and flipping it off...

Highland-20140427-00062_zps0654dcfb.jpg


But as I need to remove the conn-rod etc in the re-build, I've taken it home, with the liners and piston rings to do the re-build during the week....

Highland-20140427-00063_zpsb72d6544.jpg


Getting there ...... :)
 
Divemaster1 said:
When removing the liner, I noticed a "nick" at the top of the stroke which could have been causing the piston damage.... or be caused by it....

Highland-20140427-00061_zps2cee9cfa.jpg
Click to expand...

not an engine expert (by any means...) but this liner looks well and truly shot!
Are the others fine?
Your two stroke pistons are way too long from my experience of fully forged semi-racing petrol engine ones. Wonder how this nick was done.
Could it be the actual crown bits that flew off that managed it (?)

looks like you'll be ready for the calendar summer start.

well done

V.
 
Yup Vas ... that liner is an ex-liner!!!

Suspect I know why as well.... top compression ring (out of three ... also called "fire ring").... was an "old style" ring for engines below 60 Hp per cylinder.... and we're above (just...) this. DD changed Turbocharged straight six's to different rings when the 485 HP engine was introduced and I'm fitting those rings... (and different liner for this cylinder of course).
 
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Rob, Hunt is still on-going!! .... and don't worry, nothing is left in sump .... removed two large hatches (approx. 40 x 25 CM) in sump, so have full access to wipe out sump completely... and oil pump input strainer :)
 
So the story still continues for those interested... Not many pictures, but slow and steady progress.... 5 pistons with new rings, 1 piston & liner changed and one cylinder to go... all inserted are torqued to 75 lb ft, as manual prescribes.

So far we have had;

Cylinder 1, no failure (knew that through visual inspection before removal and had new type top compression ring)... these pistons have 3x compression rings
Cylinder 2, Second compression ring failure, old type top compression ring
Cylinder 3, First & second compression ring failure, old type top compression ring
Cylinder 4, Piston Crown crack, Liner damage and top two compression ring failures, old type compression ring
Cylinder 6, no failure (knew that through visual inspection before removal)

Cylinder 5 is still outstanding as I needed to remove oil pickup screen before I an get clear access to the nuts holding the Conn-rod clamshell cap. Screen removed, battered & bruised, but feel I am on the homerun... This piston have a second compression ring failure and is old type rings.

Picture showing oil pickup screen ... to the right, with nuts clamshell is piston 4 conn-rod clamshell... no 5 is behind the screen...

Highland-20140504-00066_zps785e25c0.jpg


So all-in-all, a fair bit of ring failures, and no wonder he was slow starting ... :) .... all I now have to do is to sort out number 5 and re-assemble correctly ... sounds easy after all this stuff....
 
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Robg71 said:
Glad its all coming apart reasonably nicely...
Hows the knuckles.... Still have any skin left....
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Nicely !!!! Liners where old rings are a pain to loosen ... best way I've found is to;

Lubricate liberally from top and through scavenging ports and leave soak in ... repeat, repeat, repeat ....

Insert steel rod with rubber ends through scavenging ports (cut to right length of course), protect the piston crown with cloth and rotate engine slowly putting tension on ... lube again and again ... rotate a bit ... a balance between how much load you want to put on that piston crown and scavenging port ... leave with tension if it does not move .. repeat the above ... eventually it will start moving ... they have been down there for a while, so is understandable that they are firmly in ... Piston liners go back in to the same hole they came out from after clean-up...

Knuckles ... Thanks to proper gloves, I'm not too bad ... still bruised though...
 
Keep going Alf, the improving weather should be good inspiration :)

Didn't the other engine rebuild require just one new piston and ring sets as well?

Btw, I'll be back in Inverness later this month, will PM you and hopefully catch up at the marina or wherever?
 
AndieMac said:
Keep going Alf, the improving weather should be good inspiration :)

Didn't the other engine rebuild require just one new piston and ring sets as well?

Btw, I'll be back in Inverness later this month, will PM you and hopefully catch up at the marina or wherever?
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The other engine was a single cylinder (piston crown and to compression ring) failure ... all others were OK ... In this case I have One Crown failure, and in addition four cylinders (incl crown) with failed compression ring(s) .. so on this one I'm replacing rings on all six...

If we're up there, you're always welcome onboard !!
 
good going Alf,

you still think that the top up with semisynth (or whatever multigrade) oil on the delivery trip is the reason (or one of the main reasons) for these failures?

cheers

V.
 
vas said:
good going Alf,

you still think that the top up with semisynth (or whatever multigrade) oil on the delivery trip is the reason (or one of the main reasons) for these failures?

cheers

V.
Click to expand...

Vas, TBH I do not know.... and as that now is getting on to nearly ten years ago, it is difficult to say... However as she has been getting gradually worse, over the later period of time... and I have pushed the decision to re-build to the side for quite some time. What is certain is that the major failures are in the cylinders that have piston rings designed for engines that delivers less than 60 Hp per cylinder. The engines were factory built at a low 325 Hp which is well within this bracket. Engines was then upgraded by local DD at install to between 385 and 410, which is above the bracket... and the fact that port engine have the right (upgraded rings) and Starboard have some upgraded, others not... implies that whomever the upgrade did not have all the parts available, or what I suspect more is that this engine never had the rings changed at the outset of the upgrade and have since been partially re-built with the upgraded rings. Reason for saying this is that there is evidence of sealant being used on top (underneath) of the cylinder water jacket seals... Once the old rings started to fail, the "good" cylinders take on additional strain which will have caused further damage beyond their design limits.

Of course the design of these lumps, and their configuration means that any ring failure means that the broke pieces are simply spat out through the non-pressurised side of the scavenging ports, so little or no damage is done to the liners when the rings fail...

Still rather surprised that they ran so smooth (once started) with four cylinders failures that probably would have caused some more issues in equivalent four strokes, or more modern units... or to put it a different way ... I am surprised of the extent of the failures, as she would only have two cylinders that really would fire from cold...
 
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