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Discussion Starter · #1 ·
Hello fellow 4BT Swappers!
I got Jeep JKU with 4BT VE pump all stock, 700R4 trans, will be tuning it in a month or two, would like to know what really works what not.
Did you dino your rig? What do you have at the wheels?
Thinking to start slow, just with fuel pin, 3200 spring and pump adjustments and than see if I want to add injectors, turbo upgrade and 60lb springs with 3800 pump spring...
My goal is 250-275 hp, 400-500 lb/ft torque.
Appreciate any advice!
 

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That power will require compounds IF it's gonna be a daily driver, 250 could be attainable with a super HX30 but you would not get the same power where the 4BT is at it's best.
The really great things about compounds is having all the boost you need/want starting around 1,200/1,300 this enables you to really add fuel cleanly and coolly on the frons end of the torque curve. The 3,200 spring is good enough in the years I've been driving mine I don't think I have ever exceeded 2,800 and have not seen signs of defueling to that RPM, there is no need with my early fueling rate. I'd "think" that stock injectors would be fine to around 250hp beyond that 5x.012" work well.
If you are gonna be at that power level a big I/C along with a big air box/filter and cold air intake will be needed, I would still think about 60# springs even if it will never see above 2,800/2,900 RPM just for piece of mind and incase you decide on an exhaust brake.
 

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Discussion Starter · #3 ·
That power will require compounds IF it's gonna be a daily driver, 250 could be attainable with a super HX30 but you would not get the same power where the 4BT is at it's best.
The really great things about compounds is having all the boost you need/want starting around 1,200/1,300 this enables you to really add fuel cleanly and coolly on the frons end of the torque curve. The 3,200 spring is good enough in the years I've been driving mine I don't think I have ever exceeded 2,800 and have not seen signs of defueling to that RPM, there is no need with my early fueling rate. I'd "think" that stock injectors would be fine to around 250hp beyond that 5x.012" work well.
If you are gonna be at that power level a big I/C along with a big air box/filter and cold air intake will be needed, I would still think about 60# springs even if it will never see above 2,800/2,900 RPM just for piece of mind and incase you decide on an exhaust brake.
Thank you for sharing!
Any thoughts on Super HX30W vs HE351CW?
What would be good compound turbo setup?
I am not trying to build 500hp monster like these guys:
 

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Having never ran either I only know from others here that the super 30 is the best single turbo for good solid boost across the RPM band there are others that make good boost lower with a trade off on the at higher RPM's my experience with the 4BT has shown me that you get the most bang for the buck by running a turbo that gives you the highest boost on the front side of the torque curve so I prefer one that builds good boost by 1,500 seeing as you will spend most of your time between 1,500 and 2,000 which is where the 4BT is at it's best. Big boost will require a quality head gasket on a block/head with a good clean, flat surfaces and head studs are also needed for peace of mind.
In my rig which tips the scales at 8K I see 30+ psi starting about 1,400rpm with it running clean and cool this is at 5,000' so it really moves a load with ease, ever since getting it up and online too much boost has been my issue and I have been tuning to lower boost and drive pressure to get better mileage and have had luck doing so without sacrificing power. The closer to "ideal" I get the more time it takes but there are worse tuning issues to be dealing with, looking back compounds would be worth the work/cost even if you only needed 30 psi to meet your power needs just for the fact that it is there from 1,400 up...$.02
 
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I'd guess 275/500+, I can pull a 6% grade at 15,000# CVGW and hold 70mph without any drama, that is with a close ratio ZF5 3.55 gearing and 33's as I sit now it's on par with a 24 valve 5.9 as far as how it works.
 
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Question, what is the intended use of this vehicle?
Will the driveline survive in that use with that sort of torque?
 
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Blackduck brings up a good point after the compounds were installed my new 11" clutch disk that was fine with a single was completely overpowered, I'm very careful
about power application as I think my 1350 U joints and 44/60 axles as well as the ZFs5-42 would tap out should I get rough with them where the tires had good traction.
But with that being said with the early and abundant torque the truly is no reason to do so, on trails it just chugs along happily at 1,300-1,500 with zero drama.
 
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Discussion Starter · #9 ·
I'd guess 275/500+, I can pull a 6% grade at 15,000# CVGW and hold 70mph without any drama, that is with a close ratio ZF5 3.55 gearing and 33's as I sit now it's on par with a 24 valve 5.9 as far as how it works.
Very nice!
I would be happy with stats like these.
 

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Very nice!
I would be happy with stats like these.
My goal was pulling a loaded car trailer comfortably at interstate speeds and I have met that, in all honesty the 4BT is more capable that the truck itself is with it being a 1968 3/4 ton even with the other upgrades I have done.
 

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First off, a 700R4 won't come close to living with a 4bt at that power level. A 200 HP 4bt will have over 400 lb ft of torque. 250 HP will put it past 500 lb ft and that torque comes on near 1700-1800 RPM. The 700R4 is a TH350 and will not live with that kind of torture. If you stay automatic, you'd need something like one of the Dodge units that came behind a Cummins. As Steve said, 250 HP is pushing the limits on a single turbo. Don't even think about an HE351. Way too big for a 4bt to spool. The Super HX30W is the biggest single the a 4bt will tolerate. People have tried every imaginable turbo on these engines and the HX30W series or the HE221W series are just the best out there. Stock 4x.012 injectors will get part of the way to 250 HP but you'll need 5x.012 to get there. That's the size that came on the 250 HP 4bt marine engine. They would need to have the correct body and pop pressure for a VE pump.
 

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One other thing when you reach this power level engine cooling starts to become an issue for the 4BT, in general the consensus is the 4BT does not need a lot of radiator but beyond 200HP it starts to and for me coolant temp is more of a limiting factor that anything else when I'm working it hard.
 

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I don't care what you do to a 700R4/4L60E or how much HP/TQ a builder rates it for. A very mild 4BT will kill one in a short time. Figure on a rebuild every 10K miles.

700R4 cannot make the line pressure at lower RPM's to handle the torque a Cummins makes. A 700R4 barely holds behind a stock 6.2 diesel in a light 2wd pickup.
 

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Steve, that is a good point. More power creates more heat. In general, a stock radiator is fine for a 4bt but push the power to higher levels and you may need a bigger radiator along with a big intercooler to tame the heat from around 40 PSI or boost.
Snuggletough, you are correct on those transmissions. It has been proven too many times. The one main issue on the 700R4 is it doesn't build pressure enough to keep the clutches from slipping at the low RPM where the Cummins comes full on. It might be possible to build one that would work but most don't want to spend a big chunk of money to get there. The only GM transmission that a few have used with success is the 4L80e or 4L85e. Even those may get iffy above the 200 HP Level. That's one reason GM went with the Allison 1000 in their Duramax diesels. Even those were updated 3 or 4 times for more torque handling and adding a 6th gear. Not a practical transmission for a Jeep due to its size. That's generally a problem for most heavy duty automatics in a vehicle with limited room.
 

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I've dynod 200 whp and just shy of 500 ft lbs with an single hx35, but I much prefer my compounds hx30 over hx35. I'm in the same boat as Eggman, but I've never tried towing as much weight as him up a mountain pass!!
My 7200 lb ford expedition hauled my 7k trailer around town fine, never tested it in the mountains

If you don't want to change that 700r4 I'd stick to fuel pin, governor spring, timing advance and light fuel and boost increases.
 

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The HX35W is not a good single for a 4bt. Most of it's power is on the top end and EGT's are pretty high. It is the perfect turbo for a 6bt which is where it was used. An HX30W or a Super HX30W can easily do 200 HP alone. Twins just make it easier.
 

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The HX35W is not a good single for a 4bt. Most of it's power is on the top end and EGT's are pretty high. It is the perfect turbo for a 6bt which is where it was used. An HX30W or a Super HX30W can easily do 200 HP alone. Twins just make it easier.
Im not sure if the op was specififying wheel hp or crank hp, but the Hx30 super is close to 200 whp but no one here has hit those numbers, let alone a smaller hx30. I think it's running out of steam and egts are too high at that point
 

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Don't know what your numbers show, but HP loss through the drive train can vary quite a bit. With a manual transmission it seems about 20% loss is a fair number while with an automatic it can range as high as 40% depending on the transmission. So, if you have a 20% loss you'd need 250 HP at the flywheel to achieve that. Yes, that is pushing a single turbo past its limits. Better have twins and one size bigger injectors for that. Engine dyno numbers may or may not account for things like alternator, cooling fan, power steering pump, or ac. All those are HP drains as well. Just think, that a base 105 HP 4bt at normal operating speed you may have had 80 HP or less at the rear wheels.
 
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