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Discussion Starter · #1 · (Edited)
hey everyone,
first post here.
i recently picked up a 4b (did a s/n# check on it to make sure it had the squirters) and i want to do a performance build up on it. I know the owner of the local cummins shop and they gave me the green light to purchase the engine knowing what i wanted to do, so i'm going to ask them to do me up a build list but i want to here from you guys who have done this already what it would take exactly for me to get 300rwhp, thats the number im set on, i have no issue over building it then detuning it back to 300 as im sure most people would prefer to do that for piece of mind.

so basically i wanna know:
*should i just use genuine cummins internals or aftermarket?
*will i need the block plate for any flex at 300rwhp?
*waist gate turbo vs variable vain turbo, single vs twin or charger plus turbo (ive seen a few posts saying a single will do it but twins are better for driveability im not too concerned about how much of a pig it is to drive as it will be mostly offroad use and rainy days when i cant ride my harley)
*injectors?
*head, ports and in&out manifolds?
*and ill get a custom cam (they did one for me once before in my little old ford festiva i had... miss that little **** box lol)
*and ofcourse the much debated VE vs P pump? i saw a post some where saing a VE can do 300+ but ive seen more saying it cant :confused: so even if its only temporary can the VE do it
*one more thing ive seen there is a "stroker crank" i think it might be a crank from another engine that fits, but it bumps it up 4.5ltrs is that a good avenue to look into "more cubes less stress" isnt that the usual saying?

also being in aus ive chosen to use a nissan patrol gearbox and transfer as my stock boxes are definitely not up to the task for the end result of this build. if i use the chevy conversion flex plate and fly wheel kit then get a (chev to patrol) bell housing adapter kit to suit the patrol gearbox (chev conversions into patrols here are pretty common so its basically an off the shelf kit) that should work fine right?

lots and lots of thanx in advance :beer::beer::beer::beer::beer:
 

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Use the Search function. It's been done.
 

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Only thing that I haven't seen done is put a patrol transmission behind a 4BT.

What specific transmission is it? What motors did it come behind?

I honestly think you're going to have a hard time coming up with what clutch to use.
 

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Stock engine will do it. Get a P-pump, it's just easier. Upgrade valve springs and pushrods. Head studs with the cylinder head o-ringed. HX30/HX40 twins. Mild injectors. Decent sized intercooler. Pretty much any exhaust manifold and intake manifold setup would work. Pump and twin tuning should get you to an easy 300hp.
 

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*one more thing ive seen there is a "stroker crank" i think it might be a crank from another engine that fits, but it bumps it up 4.5ltrs is that a good avenue to look into "more cubes less stress" isnt that the usual saying?
I don't know what it would cost but I'm sure it would get you more power. After my checkbook heals up I think I am going make my 3.9 into a 4.5.
 

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I think the "stroker" uses the 4.5l block with the 3.9 pump and lines. I believe there is about 1/2 inch more deck height on them blocks.
 

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Discussion Starter · #8 ·
Stock engine will do it. Get a P-pump, it's just easier. Upgrade valve springs and pushrods. Head studs with the cylinder head o-ringed. HX30/HX40 twins. Mild injectors. Decent sized intercooler. Pretty much any exhaust manifold and intake manifold setup would work. Pump and twin tuning should get you to an easy 300hp.
what psi would i expect to be running in that set up?
im basically taking a crash course on all this as i go. up untill a month ago i had never even considered one of these engines let alone heard of them :p and here most guys wouldn't even dream of running 30psi through there worked 4.2l diesels let alone the numbers i've been reading so this is definitely a learning curb
 

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To put a 4.5 crank in a 3.9 block requires custom rods. You're talking big money. There is a 6.7 stoke kit for the 12 valve which is the same stroke as the 4.5, so it would take the rods and pistons from that set up to make it work. Be easier and cheaper to use a 4.5 engine and add the other parts to it. Just don't see as many of the 4.5's available. The one to look for would be the QSB4.5-30 which is the 8 valve head but uses an electronic injection pump.
 

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Discussion Starter · #10 ·
To put a 4.5 crank in a 3.9 block requires custom rods. You're talking big money. There is a 6.7 stoke kit for the 12 valve which is the same stroke as the 4.5, so it would take the rods and pistons from that set up to make it work. Be easier and cheaper to use a 4.5 engine and add the other parts to it. Just don't see as many of the 4.5's available. The one to look for would be the QSB4.5-30 which is the 8 valve head but uses an electronic injection pump.
this is where i found reference to the strocker crank idea, i dug a bit further but not a great deal turned up:
dieselworldmag. com/ cummins-4bt-101-4bt-basics-performance-options
don't mind the spaces wouldn't let me post the link
 

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I see you have already purchased a 4BT, but you haven't said what injection pump it has VE, or P7100.

Your power goal is going to be easier with the P pump.

The 4BT is not common in Aus, and the parts required to upgrade to a P pump will probably have to be sourced from the USA, or has your local Cummins shop indicated they can do this within your budget.

In Aus, the Isuzu 4BD1T, 4HE1, or Toyota 14 or 15BT are worthwhile/suitable alternatives to the Cummins 4BT that should be easier to find.

My experience is with the Isuzu 4BD1T, they are very similar bore and stroke to the 4BT, and arguably more robust, smoother, rev harder, better VE and BSFC and breath better.

The stock 4BD1T injection pump with simple screw adjustments and a little over 30 psi boost (from compound turbos) can get you 300HP at the crank at 3000 rpm. With a modified pump and extrude honed or edm injectors, you can get 500HP no internal engine mods. With an engine balance and valve spring upgrade they will rev to 5000 rpm (with stock pump). The stock head gasket will hold 50 psi, or a safe 60 psi boost with just ARP head studs.

You would certainly need the strongest version of the available Patrol boxes with the torque these engines put out. Comparing a Nissan td42 to a 4BD1T is chalk and cheese, the td42 looks like a weak dinosaur in comparison.
 

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Discussion Starter · #12 ·
I got the cummins engine because of the connections I have, I can do all the work needed no worries (except any machining) and a budget for 300rwhp is no issue.
It currently has the VE pump I'll build the engine and if I can't change to the P pump at the same time I can do it at a later date.
If the patrol box doesn't survive I'll drop an auto from wholesale autos no biggie, hell might just do that straight up
 

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what psi would i expect to be running in that set up?
im basically taking a crash course on all this as i go. up untill a month ago i had never even considered one of these engines let alone heard of them :p and here most guys wouldn't even dream of running 30psi through there worked 4.2l diesels let alone the numbers i've been reading so this is definitely a learning curb
50-60psi boost is probably what you would see.
 

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what psi would i expect to be running in that set up?
im basically taking a crash course on all this as i go. up untill a month ago i had never even considered one of these engines let alone heard of them :p and here most guys wouldn't even dream of running 30psi through there worked 4.2l diesels let alone the numbers i've been reading so this is definitely a learning curb
And nor should they dream of running 30 psi boost with those Nissan diesels. They are a light duty indirect injection diesel, compared to a direct injection diesel designed for much higher peak combustion pressures.

Indirect injection diesels loose out on efficiency and produce low torque. Because the fuel injection and combustion process is so much different they can rev much higher. However they are much more fragile.

The 4.2 Nissan needs a lot of work on the internals and injection pump and rev a lot higher to produce big power numbers. An increase in Torque and Power comes from burning more fuel and the indirect injection diesel can do that by running at a higher speed (volume of air is a function of displacement and rpm's).

A direct injection diesel like the Cummins 4BT engine produce higher torque and power at much lower rpm's. So the method is to inject more fuel and use high boost pressure to cram more air into the cylinders with no increase in the revs.

I got the cummins engine because of the connections I have, I can do all the work needed no worries (except any machining) and a budget for 300rwhp is no issue.
It currently has the VE pump I'll build the engine and if I can't change to the P pump at the same time I can do it at a later date.
If the patrol box doesn't survive I'll drop an auto from wholesale autos no biggie, hell might just do that straight up
Thats good. There is a lot more support for performance increase with diesels that are more popular in the USA market.
 

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Compound turbos (HX30/HX35 or HX30/HX40) will do it with a maxed out stock VE pump if you get everything right.

Otherwise a modded pump or P pump will give you more head-room. You'll need about 40psi boost.
 

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Discussion Starter · #17 ·
With the twins set up would they both be waist gated? I've seen a few builds where the second turbo has the gate sealed. So I'm not sure what I'd do in that regard
 

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