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Thread: County V8 to 4BD1turbo conversion.

  1. #1
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    County V8 to 4BD1turbo conversion.

    I recently converted my 1988 V8 County from a 4.2 litre Rover V8 to an Isuzu 4BD1turbo which came from a truck, and also intercooled it. I took lots of pictures during the process, so I thought posting them here might be of help to anyone thinking about doing the same conversion. There are several different parts and minor modifications needed for the job.
    I'll be brief in my description as the pictures will hopefully explain themselves to a certain extent.

    I started by buying a damaged truck with a good motor in it. In this case it was a 1988 Isuzu NPR59, 7 ton GVM with the factory turbo engine. I was very fortunate to pick up this particular truck as it was only written off for front suspension and body/chassis damage to one corner. The mechanicals were perfect, even the radiator was unmarked. In fact, it was still quite drivable. The best part was the engine had only done 3000 kms since a full rebuild at a cost of more than $6200 and came with the receipts.

    The first stage was to strip the truck, remove the engine and give it a good clean.



    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


  2. #2
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    Next........Find , purchase and fit the various components needed to fit the engine to the County.

    Bellhousing ------ (not pictured) In this case, needed to mate to the Lt95 4 speed gearbox.

    Flywheel housing ------ The Landy bellhousing will not mate to the truck flywheel housing. The starter motors and clutch slaves are also in different positions. This is the army spec housing without the inspection plate. it's totally sealed except for the wading plug. There is a breather at the top of the bellhousing.

    Flywheel ------ The landy flywheel will not fit in the truck housing. The offset may be different too.....this is one thing I forgot to measure.

    Starter motor ------ The Landy starter is 12 volts and has 3 mounting holes. The truck starter is 24 volts (like most trucks) and has 2 mounting holes.

    Clutch and pressure plate ------ Completely different to the truck clutch. I picked up a NOS clutch and pressure plate for a good price, but it was to suit a 'non-turbo' Isuzu Landy. I fitted this kit thinking that the pressure plate would be ok for the turbo motor as the kit was brand new. I was wrong. After a few weeks on the road, the turbo motor was powerful enough to spin this clutch. And before anyone asks, the master cylinder and pedal adjustments were triple checked. I replaced the pressure plate with the one specified for the turbo engine........problem solved.

    Clutch throw out bearing spacer ------ The throw out kit is the same as the V8 except there is a metal spacer for the Isuzu.

    Clutch push rod ------ The push rod for the Isuzu is quite a bit longer than for the V8




    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


  3. #3
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    Spiggot bush ------ The truck has a spiggot bearing, the Landy version is an extended housing with a bronze bush insert.


    Last edited by rijidij; 14th April 2008 at 07:47 PM.
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


  4. #4
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    Mounting pin for clutch rocker arm ------ The pin and arm are the same as for the V8, but the pins can be known to 'chew out' where they fit into the alloy bellhousing. My second hand bellhousing was chewed out, so I drilled it out and sleaved it with steel.....and after a suggestion from a friend who has worked on many of these, I drilled and tapped the end of the pin and bolted it through the bellhousing using some loctite to help prevent any further movement of the pin.

    Spacer for oil filter housing ------ The turbo engines have a filter housing which takes 2 spin-on oil filters. When fitted to a Landy the housing must be spaced out from the block so the front prop shaft doesn’t make contact with the bottom filter. Another spacer must be made for where the oil feed tube connects above the filter housing. The spacers can probably be purchased as a part, but I chose to machine my own (with the help of a friend with a milling machine). There is no room next to the chassis to get the 2 long bolts in to connect the filter housing so I got some high tensile threaded rod (not cheap) and used loctite to secure them in the block.

    Engine mounts ------ Although you could get away with using the mounts off the truck, with some minor modification (2 bolt stud pattern is slightly different), the Landy Isuzu mounts are actually bigger and stronger, so I chose to buy new ones.



    Last edited by rijidij; 14th April 2008 at 12:58 PM.
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


  5. #5
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    Next……..Get the County in the shed and start stripping it to remove the V8.
    Important : Before removing the V8, take accurate measurements of the exact position of the gearbox. When the new engine is fitted, the gearbox must be in exactly the same position as it was before. The reason for this is that you can’t buy the engine mounts that are a part of the chassis, so you have to fabricate your own.
    I then dummy fitted the engine and bellhousing to the gearbox and made sure it was hanging in a way that the gearbox measurements were correct. Then the new mounts were measured and fabricated and tacked into place. The engine was removed and the mounts fully welded on.
    This is the only time I needed the engineer to inspect anything apart from the completed project. He wanted to see the raw (unpainted) welds.




    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


  6. #6
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    Fit starter ------ When I fitted the starter motor I found the oil return pipe from the turbo had to be bent slightly to miss it.

    Exhaust header ------ There is not much room between the engine mount and the starter to fit the exhaust through. Some turbo manifolds point straight down, which would make it a bit easier. I chose to run a 3 inch system right through so I fabricated the header pipe while the engine was still on the floor. It’s highly recommended that a flexible joint be fitted to the exhaust not too far from the engine to allow for some harsh vibration from the diesel.

    I also fitted an ‘Endless Air’ compressor where the A/C used to be fitted when in the truck. (not pictured)


    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


  7. #7
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    Radiator ------ I used the V8 radiator, but I had the outlets swapped over so I could fit standard hoses if I wanted to.

    Air filter ------ The V8 air filter can be used with the turbo motor if you flip it over and relocate the dump valve.

    Intake manifold ------ Because I intended to fit an intercooler, I removed the pipe which normally goes over the top of the engine and fabricated a small stainless one with the fittings for the dump valve and the small hose which goes to the boost compensator on the injection pump. I also spun the alloy housing of the turbo around so the outlet pointed away from the engine.


    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


  8. #8
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    While the front of the County was stripped, I took the opportunity to fit some soundproofing. I also fitted it to the underside of the bonnet (not pictured) and gave the chassis a clean and paint.

    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


  9. #9
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    After fitting the engine and the front guards, I could now go about fitting and plumbing the intercooler.

    There were many more tasks during this project which I either haven’t mentioned or have forgotten…….for example, cleaning the fuel system etc etc etc etc .

    After many months, I finally got to the stage where I could turn the key.



    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


  10. #10
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    The verdict ?

    Well, I’ve had it on the road for several months now, and I can honestly say the only thing I miss about the V8 is the exhaust note. The turbo motor out performs it in ‘almost’ every way, especially off road.
    I generally don’t like comparing diesel engines to petrol engines because they deliver their power and torque in completely different ways, but they will always be compared……..all I can say is, after having a 4.2 litre V8 in the County for 12 years, I’m more than happy with the performance of the Isuzu turbo engine. And I have good fuel economy for a change.
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


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