Engine prejudice (Follow-up to GM V8 thread)

[PCUK]

Knowing full well the bad reputation of the Samurai conversions, which also seems to include all GM V8 diesels, I was wondering where the bad reputation first appeared.

Were these engines known to be unreliable as marine units prior to Samurai converting them or has the Samurai tarnished the entire engine? Bearing in mind that millions of these engines and their successors have been built since 1982 can they be that bad.

If they are, why did Samurai base their business on them (apart from the fact that the base engines were cheaply available from US military disposals).

And now in the present day, why has Marine Diesel (Sweden) again based their business on the 6.5 litre model and its successor, the 6.6 litre. (This appears to be a fairly substantial company).
Forum members on any subject only represent a tiny minority of actual users and it is the problems that become exaggerated as these are the matters that are highlighted in forums.

Are there therefore thousands of satisfied GM V8 diesel owners out there that we never hear about? Come on, don't be shy, own up!

My personal 'Bete noir' of engines is the Perkins 4107; the second worst diesel engine ever built in the history of diesel engines. But there are thousands still knocking about and giving no trouble to their owners, but I would rather go sailing than have one in a boat!

So, are these prejudices mainly personal gripes or they factual?

In the previous thread, Farsco stated that he never had confidence in his twin installation, but did the engines give any reason for this or was it the bad press that started the worry in the first place?

All opinions gratefully received.
Cheers,
Peter

ps PIc attached of offending lump for Farsco!

 

[Latestarter1]

Peter,

Not much to choose between the Navistar V8 and the 6.2/6.5 GM V8's as both engines were technically poor. Short stroke and IDI are major 6.2/6.5 culprits. IDI engines have huge internal temperature and pressure gradients, add the short stroke and combustion work is a nausiea. Always a juggling act as there is potential for piston to out run the flame front as IDI combustion takes a while to get the fire going.

Born out of original GM Oldsmobile engine division V8 work the GM 6.2 V8 was a solution looking for a problem. 6.2 has mechanical Stanadyne fuel pump, the very similar 6.5 has Stanadyne mechanical pump with electronic governing. The solution is to use 6.2 pump on 6.5's. #1 problem is that 6.2 pump does not respond well to being juced up as timing can go all to heck, the #2 problem with jucing up IDI engines, particularly with crude IDI engines is that the pre-combustion chamber tends to limit the amount of fuel which can be burned. I have had a so called 6.5 250 on the dyno, would never pull advertised power, try to MAKE it deliver the goods and you end up with a torque curve like a sway back horse.

The result of all the above is that head gasket integrity is a major issue even with low rated engines. The Hummvee is loved by suppliers to US Army as it consumes rebuilt engines like crazy. GM got out of the 6.5 and Hummvee when relations with military became hot. Handed over the design of replacement engine to Isuzu who came up with a clean sheet, still short stroke, but now DI with common rail. Isuzu GM V8 is a far better widgit and fits into a Rolls Royce Corniche a treat!

Marinediesel.......ask anybody who did the RB 2008 which boat was the lemon......Garmin with Marinediesel 6.5's blew a motor before leaving the Solent, then blew a second in Irish sea, suspect James May or Nick Knowles would not vote for these engines.

Marinediesel have now switched their attention to the 6.6 Isuzu as has Gale Banks in the US http://www.banksmarine.com However the Banks version was launched two years ago and looks real neat however they are stuggling to get it certified to EPA Tier III and I am not aware of any production engines being sold, likewise no reports on the Marinediesel version of the 6.6 other that the fact that it looks a real ugly marinisation and weasel words as to emission compliance.

The outfit in Devon with a Japanese name took a technically poor motor and just lumped a marine motor together working in farm barn on a dirt floor!

Play with your GM V8 and enjoy it if it works for you, new heater plugs with have it on the button.

 

[Chris_d]

I'm probably guilty of spreading some bad Samuri propaganda mainly from looking at a few boats with them resting in the engine bay (installed is not the correct description), none were working and all being sold as projects.

The photo you have posted says it all really, sorry looks like something knocked up in a barn.

I'm sure the base GM engine must have some merit but the only one I have heard running made a swish sportscrusier sound like a tank.

 

[malcolm2]

As maybe one of the few people who ever owned a boat with MarineDiesels, I personally would say the biggest problem was not the engines themselves but the bad experience everybody had with the Samurai meccano kit conversions. OK the GM engine was far from bullet proof, but you could probably say the same about some engines from the Volvo range past or present.

My concern now would be more from the point of view of getting simple things like replacement belts, and particularly those items that are effective marine only, like riser gaskets etc.

One thing I would say is, I would never go through the hassle of re-engining a boat with engines that were never on the boat manf engine option list.

Keep meaning to write a book about all twists and turns of the project. eg having had both engines in their packing cases loaded on to a hire van with a fork lift truck. Then realising when we wanted to unload them, that there was no way they could be moved on to the van tail lift without the aid of said fork lift truck. Solution: tie rope on to packing case then around conventient telegraph pole, and drive van forward.

 

[PCUK]

Thanks all, So at present it looks as though these engines were duff from the start.
I'd still like to hear from any others who have had a good experience with them.
Surely there is someone, somewhere!

 

[malcolm2]

I would be interested to know how many "failures" were or are down to any inherent weaknesses in the basic GM engine. And how many down to bodged marinisation or cheap DIY installations. A further factor to consider is the questionable source of the basic blocks imported by Samurai from the states.

 

[PCUK]

Malc,
That made me think. I wonder how many actual catastrophic failures have occurred to these engines while underway.

I'm now convinced that it is not a good lump but at my level of boating, if the engine explodes there are plenty more down at the breakers ready for converting!

 

[malcolm2]

If discounting applications, such as racing. Or in other words just your typical average leisure motorboating use. I suspect none, or at least none that can be atributed to failings in the engine design itself. Ok maybe it was not a rip roaring sucess in the Humvee in the long term. But considering the extreme uses that a military Humvee gets used for, and allowing for "battlefield theatre" mistakes like forgeting to put oil in it, it was/or is probably pretty reliable.

The boat in question was sold a long time ago, so not totally up to speed with what MarineDiesel are up to now. But it always struck me as a pretty sound marine conversion. Unlike the Samurai.

 

[PCUK]

I have to say that the Samurai conversion on this one looks fairly competent. It uses a well known heat exchanger and oil cooler and the exhausts are competently made so maybe I'll give it a go and report back after some reasonable period. Nothing to lose, if it fails, I'll change it for something else.

Still waiting for reports from satisfied users!

 

[PCUK]

Took all the glow plugs out. A couple partly glowed, the rest simply warmed up a bit!
One broke the end off in position so that's a head-off job. B*gger it!!!

Still waiting to hear from anyone with these engines who is happy!