om617 performance - how bad should it be?

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superapan
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Location: Sweden

Hi fellow GW:ers!

I'm a fairly new owner of a 1985 GW. Once upon a time, it was a 280GE 4-speed manual, but had its engine swapped in the 90s to a 1978 om617.912 4-speed automatic. It also had an STT turbo kit fitted to it, which should mean roughly 100 bhp.

I've had my fair share of old cars, but this is by far the slowest vehicle I have ever driven. This weekend, I towed an empty covered trailer (so it caught some wind). Whenever it was the slightest uphill, I couldn't make it past 40 mph. It even started running a bit hot from flooring it so much.

I haven't done any diesel purge, valve adjustment, fuel filter replacement or anything (yet). But what can I expect? From different web sources, I gather a stock 300GD auto (NA) did 0-60 mph in like 25-30 seconds. I haven't attempted 60 mph during the months I've owned it. One note is I'm running on 285/70r17. Could that be enough of a rotational inertia to totally gimp the truck?

So, how bad should it be? I'm starting to wonder who in their right mind swapped from a 280GE with 156 bhp to this dinosaur?

Any input is greatly appreciated :-)

Arnie
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Re: om617 performance - how bad should it be?

Hello,

if the engine is in good shape, with good injectors and properly tuned, the vehicle should be quite driveable. With a standard, 460, soft-top, 300GD , normally aspirated,  auto,  I towed a 2.5 tonne trailer across France, through Switzerland and up and down  the hairpin-bends of the St Gotthard pass into Italy. It would cruise at an indicated 80 mph / 130km/h (albeit taking a while to wind-up to that speed - probably actually a little less than 75 mph) on the motorways and maybe 15 - 30 mph up the steep pass, but it was fine.

Possibly, your turbo set up or fueling are not completely as they should be?

Also, the original 280GE gearing may not be quite right for a diesel, which probably would have had lower gearing in the final drive. You'd need to check this. Tyres are also way too big, which definitely won't help. The 285 width is probably best left for AMGs and the like, and the rolling diameter on 17" rims will also be greater than stock, not helping the gearing.

 

 

mgrays
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Re: om617 performance - how bad should it be?

It will be no ball of fire. I have a similar 617 engined with turbo car. It can do 70-75 (GPS measured).. and I have been in one doing 100 indicated downhill.. but really it is happiest at 60-65mph as it goes from 18 mpg back to 22 mpg.

Towing is steady... again it is happy at 60-65 mph but temp rise on hills.. this engine likes rpm to cool it so do not be tempted to lug up hills below 2,300 rpm.

Tyres and gearing is what is doing for you.It should be 70mph at about 3,000 rpm or so in top gear on GPS. I have 31" tyres which are oversized but the speedo is now correct instead of over reading.Your rims are 199mm sidewall + 431mm rims = 829mm without sag for weight. Mine are 787mm so 5% smaller .. so you are 10% bigger than standard as a guess..

 

 

Arnie
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Re: om617 performance - how bad should it be?

mgrays wrote:

Towing is steady... again it is happy at 60-65 mph but temp rise on hills.. this engine likes rpm to cool it so do not be tempted to lug up hills below 2,300 rpm.

Yes, definitely: Low gears and high revs to climb and to keep things cool.

power increases all the way to max RPM

 

 

 

scouse g
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Re: om617 performance - how bad should it be?

You do have to wring it's neck to get anything out of it, your in Sweden, could you track down a 617a out of a hagglund bv206 ?

prwales
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Re: om617 performance - how bad should it be?

An ordinary non turbo 617 should be able to run at a steady 60-80 mph without too much trouble, even if heavily laden

superapan
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Re: om617 performance - how bad should it be?

Thanks for input everyone.

I will do the above mentioned, that is a diesel purge, replace oil, replace filters and do a valve adjustment (I've bought a compression test kit too). Next winter I'll go for new tires. I reckon a set of 265 wide, as opposed to the 285 I have on now, should help some. If this doesn't help me well enough, I'll have a talk with Dieselmeken Göran. Last resort is a switch to an om606...

 

 

superapan
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Re: om617 performance - how bad should it be?

scouse g wrote:

You do have to wring it's neck to get anything out of it, your in Sweden, could you track down a 617a out of a hagglund bv206 ?

Forgot to reply to this: When I did my army service, the BV206s we used had like a Ford petrol V6 mated to a MB automatic. Lots of BV206 went on export, maybe one of those models had the 617A. That should make it quite rare in Sweden, unfortunately.