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Discussion Starter · #1 ·
I'm working on installing the cooling system in a TJ-8 (sort of) and trying to fit the biggest intercooler and smallest radiator that I can get away with in order to provide room for the intercooler plumbing. I've spent hours going through all of the threads on here that have anything to do with radiators and coolant systems. I found a ton of helpful "this worked" and "that worked", and based on the dimensions of those this's and that's, I thought I'd found the perfect solution... but... then it showed up today and DANG it's tiny. Its a mishimoto aluminum performance rad, MMRAD-K20-EGR, 2-row single pass (tanks on top and bottom). Core size is 16.73x15.04 inches (roughly 425 x 382mm) and 1.57 in (just under 40mm) thick. The physical fit, of course, is beautiful. Not so sure about the performance fit, though.
Engine is moderately modified, spec'ed to make around 400 lb/ft (roughly 200 hp).

I'm about a month away from first-start on this setup. What say you? Is this egregiously too small, or should I just try it and see?

Thx!
~
 

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When doing engine swaps especially on old style engines like the 4bt and 6bt etc we always try to have a coolant fluid capacity of a similar size to the vehicle the engine came out of.
The surface area of the radiator is also a consideration and again will affect the systems ability to shed heat.
Your location and climate will also affect the systems ability to shed heat.
For example when I removed the 4 cylinder Perkins engine from the Oka and replaced it with a 6 BT I also increased the radiator from 2 cores to 4 cores with the same surface area. The systems coolant capacity is around 25 litres.
 
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Discussion Starter · #3 ·
I understand what you're saying. But then I'm back to the counter-point that the original vehicles were a lot heavier and way more frontal area than a lifted, aluminum bodied TJ (should wind up ~4500 lb).
If I had worlds of grill room, I'd would put the stock size TJ rad in and plumb the intercooler to the side. Technically speaking, I could make it fit I guess, but at the expense of room for the CAC. I've seen so many threads talking about how cool the 4bt runs and once I got to figuring frontage area and depth, the numbers indicate that it'll do the job... just wondering if anyone out there has actually done it. Sometimes the math and what goes on in the really-real world don't completely jibe.
 

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I think you'll find the 4bt is a cold running engine. It doesn't need a giant radiator. The intercooler on the other hand should be as big as you can fit. That's one area where bigger is better. You want the engine to put most of it fuel usage into mechanical energy, not wasted heat. That's where a proper turbo and injection pump adjustment come into play.
 

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While that radiator is kinda small, you've got a moderate power goal. What region do you live in?

I have to block off nearly all of my factory Toyota FJ60 Land Cruiser radiator (15-3/4 x 24 x 2-7/8 core based on a quick search) in the cold months (NC) to get the thermostat to open at all. In the summer, the fan kicks on occasionally, but certainly does not run all the time.

I think the radiator is large enough, but plan on having a good fan with (more importantly) a good shroud behind it, and you'll most likely be fine.
 

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I ran a 16x16 3 core in a 5000lb bronco in LV,NV summers with no issues but dont think I was at that hp level. Like Johnny says a shroud and good fan are important. I run mech fans.
 
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Discussion Starter · #7 ·
I live in Northern Ky at about 700 ft altitude (or what passes for altitude in the east). Though, I do have an evil master plan to semi-retire sometime soon-ish and roam. The truck is being built as a home-away-from-home in a minimalist overlanding sense. I expect it'll come in about 4750 lbs fully burdened. I saved a lot of weight with an aluminum tub and the fact that it's just a two-seater cab with an aluminum flatbed.
I've got a ton of room front to back behind the grill, as the engine is about as far to the rear as I could get away with and I'm running electric fans.
Thanks all for the insight! I'll let the forum know how it works out. Should be firing her up by end of January.
 

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OK HERE'S YOUR OLD MANS ANSWER. I HAVE The 4bt in my 72 Bronco . & Stock 4bt ... Mine has a cheapo .. ebay Champion 3core Radiator on it.
I don't run a fan blade. But I do have an electric fan in place .. It's hooked to a toggle switch.. All I need to do is fli[p that fan on every 5 minutes for a few seconds & I'm good to go.
My Gas motor would not keep from running hot. So I put in the new aluminum radiator .. STILL HOT. SO then in went the 4BT . & aLL IS FINE.
.. I EVEN RUN Mine on the farm .. Like pulling a hay rake on a summer day. Just flip the toggle switch.
oR Pulling a Grain Drill in the fall.
.. I don't know where you live but Im in hot ol'e TEXAS .. So I say just give it a chance. .. TRUST your 4BT.
 

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If you look at the first gen 6 CYL Dodge Cummins trucks without the intercooler, their radiators were really small. The B-series Cummins are very efficient engines and down wast a lot of heat into the cooling system.
 

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1978 Jeep CJ 5 Cummins 4BTI
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Sure would be curious to know what intercooler you're using for your TJ--I have a CJ--that's my next addition but I have to find one that'l fit in front of my radiator.
 
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Discussion Starter · #11 ·
I'll let ya know as soon as I figure it out! :) I'm going to get everything else placed and then get one as wide and tall as will fit in whatever room is left. I'm going with an electric fan behind the rad and the engine is mounted as far back as possible (both to get the weight a bit more centralized and to provide as much room in the engine bay for the intercooler. Nothing is mounting to the stock grill so I may be able to "cheat" that forward a smidge. I really think the width is going to be the limiting factor... spearco makes a 13x17, but I'd like to make use of every bit of vertical space I have (just in case I decide to try to fit a second turbo down the road.
 

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If twins are in your future plans a good intercooler is definitely needed. When you do the fan or fans, be sure to build a good shroud. Fans just sitting in back of the radiator don't do a lot without a shroud. Of course the intercooler will be cooled mainly by the incoming air from the moving vehicle. Fan will be mainly for the radiator. Also, with twins, your power output will be significantly higher. Usually think on twins in the around 250 HP and up range. Need to start out with a good turbo if you plan to transition that direction. The HX30W 44mm would be the preferred unit there. Also, a very good single turbo when not using twins. That one can support 200+ HP with no issue. Main thing you have to consider is the rest of the drive train. A 200 HP 4bt will have 500 lb ft of torque at around 1700-1800 RPM. That's more than most big block gas engines will have. With twins pushing 300 HP you're at 750 lb ft. Weak parts can start to break at both of those power levels if you get too abusive.
 
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Discussion Starter · #13 ·
Great info... Thank you! I think the only reason I'd consider a compound setup is if I find I'm having EGT issues at altitude. I'm truly hoping to run this thing all over the continent. If I can keep the temps in check with a single turbo, I'd rather do it that way, as the first design principle when I filled out the dream sheet for this truck was Simplicity. Its by no means an unlimited budget build, but I remember what my daddy said about boots "you'll never regret buying the best you can afford."
I took a lot of design notes from the 60's Unimogs... My '66 404s has never had any serious mechanical issue. I attribute that to the balanced engineering. Everything downstream is stronger than what's upstream.
 

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Your dad gave some good advice. We all try to stretch the money to our best advantage but in some things you can't cut too many corners. Nothing wrong with doing twins and I personally think they are ideal on the 4bt. There would be some engine mods needed for safety sake. Head studs would be #1. Possibly having the head O ring'd would be #2. HD valve springs aren't really required but not a bad idea since they aren't expensive. If you read some of the builds with twins you will see that a bit of tuning is required to get it just right. Best keep the boost level at 40 PSI or lower. Otherwise those O rings I mentioned become a necessity. You have to work out the exhaust manifold you want to use for twins since you have twice as many turbos hanging on the side of the engine. Another possible update would be the oil pump. Guys sometimes change to the 6bt size pump which has more flow rate. If you tuned the engine to the 250-300 HP range, that is one heck of lot of power. My old F250 7.3 only has 180 HP on a 6000+ lb truck and I've crossed the Rocky Mountains 5 times. Do you have any plans for updated axles? All that torque can wreak havoc on weak axles. Have to be careful how you use that right foot on the pedal. Get reckless and you'll have broken differential gears or U joints or twisted drive shafts, not to mention what it can do to a transmission.
 
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Discussion Starter · #15 ·
The engine was spec'ed out with pretty hefty guts to begin with. No studs or fire rings, but I'd definitely do that if I find the compound setup necessary. Truck has 1-ton running gear, kingpin 60 up front and a 14 bolt rear, both NOS mil-spec. Kinda hoping she'll play nice with the single turbo. Passenger side of that engine is crowded and have the goofy horizontal oil filter setup.
 

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You mentioned "Fire" rings. Those are not the same as O rings. Fire rings are generally not recommended for a normal street vehicle. They are usually found on very high performance diesels like drag racers or sled pullers. If you are anticipating a boost level needing those you'll have a whole lot of other mods to do.
 

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I second char on fire rings not being a good choice for street. They just don't hold up to repeated heat cycles in the long run.
 
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Discussion Starter · #18 ·
No competitions for me! No fire rings either. I fully intend to keep it on the single turbo so long as the EGTs are in control. Don’t even really have a horsepower mark in mind, other than as a general spec for the builder. Engine was built to be in the 200 hp range, which is more than my ‘91 12 valve had stock. Never felt the need to turn that old girl up, so I’m oretty certain this (8 valve ?) one will be fine in a 5000 pound truck. More than anything, I’m just trying to be prepared as I hear “oh, you’re definitely gonna want compounds” all the time.
 

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200 HP is a good number for a 4bt. Not overly stressing the engine and easily achievable with a single turbo. Main thing on controlling the EGT's is get you air/fuel in a good balance, a good intercooler, and advance the timing just a bit but not too much. No need for big injectors or a turbo other than one of the HX30W's or an HE221W.
 

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1978 Jeep CJ 5 Cummins 4BTI
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So I just decided to go for it in my CJ5--I put a Isuzu D9 (3.1L Diesel?) intercooler in. Plumbing here is temporary. It is sort of behind the radiator--I know not the best but there just isn't the room in front without major modifications. I took it out yesterday in testing and was very pleased. It has it's own fan so when I know the engine is really loaded I can flip it on. This was an easy installation and is better than none at all. INTERCOOLER.jpg ETA--Those twin radiator fans rarely ever come on.
 
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