the best engine conversion for a mk3?

[4x4-581]

So.....do you just pay the extra fuel for the 281 donk or would you be better off with a diesel conversion?
I'd love a detroit 453t with a road ranger but is it practical?
My range of average trip is 2000km round.

[Diana Alan]

Personally I'd be going with a more modern turbo diesel.  I'm a fan of the Isuzu like the 6BD1-T but whatever you get, I'd also go with with a matching 6 speed overdrive box or 7 speed double overdrive box to compensate for the ratio across the transfer.

The sump of the 6B** donks have to be modified to allow clearance on the front diff.

The big problem is the G/box length to make sure there is enough for the jack shaft.

[Acco 4x4]

Go Cummins!!!!! Available everywhere and cheap! A 6bt or newer variant would be nice, bolt it to a roadranger, 6610 or 6613, you can never have too many gears! At the end of the day it doesn't really matter what you pick, Personally i do believe the Isuzu option is certainly worth real consideration. I also believe the "KISS" method.
What is your truck used for?
Hobby? Work? Road speed? and lets not forget your budget. This will of course be the final decider.
Have you thought of putting the old diamond on LPG? This would be easiest.
 If you work on known engine specs and performance of your truck, basically any change will be a good one. Believe it or not, even the old commodore VN V6 would give you more HP and NM than the old donk and this would still be better on fuel. How about a LS1 from a commodore etc, you can go full automatic or get a bell housing from Dellows to fit SAE3 to bolt it to roadranger.
Diana Alan had a valid point with "modern"………
 
At the end of the day, it all comes down to your choice and preference.

Remember…….. You can never have an engine too small, just not have enough gears!!!!

[4x4-581]

The main reason behind a conversion would be for better cruising speed, but i do wonder how the transfer case and diffs would handle the increased speed.

[Acco 4x4]

Providing your drive train is healthy (serviced) i see no reason why an increased speed will cause you any problems. As far as gears and bearings go, as long as they are lubricated correctly, no worries. Your uni joints will also be fine provided they are in serviceable condition and you haven't changed the angle on them (as in lifting the truck etc….) The drive drain will obviously have its limitations to the torque it can handle so id think a 60 series detroit might be a bit big, but also saying that, it does come down to how you drive it. For example, a young hoon doing burnouts everywhere will destroy the same car as a sensible driver could drive for ever with no problems. So having said that, being sensible about it, there is a wide variety of choices to pic. As i said before, a rough budget would be good to start with then go from there.
So either way, you will need to chose if you want a diesel, turbo diesel or petrol engine. Then gearbox….. use the original, or change to a newer manual or even go auto….. Having a remote transfer case really gives you ease of fitting anything.

[Sambo]

I put in an isuzu 6BD1-T with the isuzu gearbox. Totally transformed the truck, although it is still geared way too low for highway speeds. I have a set of 5.29 diff gears to correct this. Overdrive gearbox would probably be the better (cheaper) option.

[Diana Alan]

I put in an isuzu 6BD1-T with the isuzu gearbox. Totally transformed the truck, although it is still geared way too low for highway speeds. I have a set of 5.29 diff gears to correct this. Overdrive gearbox would probably be the better (cheaper) option.

Which Isuzu box did you use?

AFAIK a lot of the 6B** boxes are direct in 5th, so I would like to know which ones to avoid.  (The box number is on the RHS low down.)

Did you use the mechanical (shaft) change mechanism or the cable type?  (I'm wanting to change to a cable type when I swap over the box)

Any problems:

• fitting the turbo under the original engine cowling??
• with the diff hitting the sump?

Diana 

[Sambo]

I dont have the model number of the box on hand sorry. It was out of an import Isuzu TWD and had direct stick shift to the gearbox. I adapted it to the existing inter linkage which also needed a custom bracket on the engine.

The cable linkage would be much better as you'll be able to locate the stick in a more comfortable position.

I had to cut and modify the sump to clear the diff.

The original engine cover does not fit with the isuzu engine.

[Diana Alan]

Hi Sambo.

Which engine cover do you have the correct Mk3 one with the low profile or the Mk4/Mk5 with the high profile.

Diana