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4JH1 transplant

Getting the best performance from your Isuzu, the in's and out's

4JH1 transplant

Postby Fargof » Tue Jul 14, 2020 7:32 am

Hello All,
Newbie to this forum and the Isuzu engines,but no newbie to diesel conversions. I’ve always leant towards the ever faithful Cummins in my past conversions,but for my latest acquisition I need something a bit lighter than the 4BT or 6BT that I’m used to playing with.
The latest pick up is a ‘59 Dodge Fargo,running a 245 Hemi and 4 speed,I’m looking to do something a bit different with this one. I’ve got access to a couple of RA’s,one running,one with a shot pump. I’ll want to be going full custom mechanical pump,
What I’d like to know is,if chasing a reliable 250+ hpwhat would the gurus recommend when rebuilding one of the 4JH1’s?
Fargof
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Re: 4JH1 transplant

Postby isuzurob » Tue Jul 14, 2020 7:28 pm

Use custom pistons, change exhaust and inlet manifolds, big potting on the head, different valves, big turbo and 12mm pump like mine has, goes really well
isuzurob
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Vehicle: 1990 Isuzu Bighorn 2.8t/d, 3" extended shackles, 2" body lift, 33" silverstone extreme tyres, Front+rear bars, winch with 40m dyneex rope, 21/2 inch exhaust, lokka's front+rear, custom turbo, emissions removed, injector pump modified and more

Re: 4JH1 transplant

Postby paulthepilot5 » Wed Jul 15, 2020 7:48 pm

To be honest, 250hp and reliable is a bit of an ask. A few of us are working on performance JB1/JH1 engines, as far as I know no one have reached figures that high yet. They are a strong engine, Even though the JH1 has weaker gudgeon pins compared to the JB1, it has better piston oil cooling galleries. Biggest limitation is cylinder head, which struggles with the high mass flow needed to burn the fuel required and subsequently EGT and drive pressures will suffer. Short duration power runs are manageable, sustained power not so much. As isuzurob has said, head work, valves, exhaust and intake manifolds are needed then a pump and injectors to supply the required fuel
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Vehicle: 1995 Isuzu Rodeo 2.8d
Compound twin Turbo
12mm fuel Pump
+50 injectors
Water/meth injection

TF Rodeo ute 2WD short wheelbase
2.8 4JB1T
Inline injection pump conversion
+50 injectors
Borg Warner s200 turbo
300hp, 650nm

Re: 4JH1 transplant

Postby isuzurob » Thu Jul 16, 2020 7:31 pm

I have done the above work on my 4jh1 with extensive fueling mods, distroyed first set of pistons, hence custom built, never had on a dyno but will absolutely leave a tuned 3.2 ranger behind 0-120kph but runs out of legs, I'm running 36psi and high ish egt
isuzurob
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Posts: 1775
Joined: Mon Jun 07, 2010 6:12 pm
Age: 25
Country: New Zealand
City: Taupo
Vehicle: 1990 Isuzu Bighorn 2.8t/d, 3" extended shackles, 2" body lift, 33" silverstone extreme tyres, Front+rear bars, winch with 40m dyneex rope, 21/2 inch exhaust, lokka's front+rear, custom turbo, emissions removed, injector pump modified and more


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