So, 2014 JKU with a 5.9 Magnum swap. I'm using the OE 5.9 HD Hayden clutch fan and modified OE 3.8 fan shroud. My 5.9 isn't built for max power - just a solid truck engine with a bit bigger truck cam, stock manifolds, Holley 2bbl Sniper, etc.

The theoretical question of 'will a stock Wrangler 3.8 radiator cool a V8' is still out there...and I wanted to ask if anyone has retained a stock JK radiator after a v8 swap, and how is it working out?

Apparently a JL 392 radiator is nearly identical in size to a JK 3.8 radiator...which really begs the question. To help enable the stock 3.8 radiator to cool my v8 I'm mounting the trans cooler behind the t-case, no A/C, so the radiator will 'only' have to cool the engine.

Ideally, if I need a replacement radiator I want to be able to just go to the nearest parts store and get one - easy - no custom radiators or waiting for one to be built/arrive. To that end, if necessary I'll install an engine oil cooler to enable the OE stock 3.8 radiator to to the job in the worst of conditions, like Moab in the summer.

So, who's done a JK v8 swap and retained the stock radiator...and how's it working out?

Thanks

 

In my case with a 2016 Chev 5.3LT Direct Injected I use the 3.8 rad that was in the Jeep prior to install. 100F days slow wheeling no issues and stays at 190F. Highway cruising at 75mph no issues either. Hint: turf the carb and do the Megasquirt junkyard FI and distributorless system. Friend had a 440 Roadrunner that had 587HP and diid about 8-10mpg then did the same with Megasquirt. After some playing around they got 21mpg and another 50HP out of it on the same dyno. He used a Jeep cam positioner, Ford Taurus tone ring, Chev LS fuel rails and injectors sized to suit and a Holley TB with Megasquirt Software.

 

thanks for the info - it's very helpful . Where do you have your trans cooler?

No carb on mine - 2bbl Sniper is awesome

- Sam

 

Well I finally have some results from my JKU build. To recap, I'm building a '14 JKU, with a 5.9 Magnum and 1-ton everything else, and yesterday, after 16 months and about 1300 hours of building, we fired it up for the first time. My #1 unknown was whether or not the stock 3/4" off-the-parts-store-shelf Murray JK radiator would be 'big' enough to cool the 5.9 Magnum engine, and I'm very happy to report that apparently...so far...it is - at no time during the initial break-in or subsequent drive-around afterwards did the engine get 'hot' - not even 'warm' - it has a 180* thermostat and it never went north of 185* on the Sniper display, with the dash gauge matching suit.

I didn't want to introduce any more heat into the radiator than necessary, and to that end I placed the trans cooler behind the transfer case - the power steering cooler is however up front as low as possible.

Lots more testing to come, but the initial hour of running it around looks very good. One thing to mention - I'm running the stock '02 Dodge Dakota mechanical clutch fan inside a modified OE JK fan shroud, not the OE electric fans, so the fan is always spinning/drawing air through the radiator, not just turning on when things get 'hot'. The entire time the inlet side of the radiator was hot, but the outlet was cool enough to lay your hand on the face of the radiator no problem, and that was awesome.

Anyway, just for what it's all worth -













trans cooler -


P.S. cooler -


- Sam

 

Sorry for the late response but my tranny cooler is behind the transfer case and up in between the driveshaft and the left chassis rail. In front of the Emissions canister. Very much the same as yours. What will you switch the fan with?

Where's the Jeep ECU as you don't need any for the motor and tranny?

 

my trans cooler is activated automagically via a 190* thermostatic switch - no manual toggle switch - haveta wait until it gets hot enough to know if it'll switch on.

All of the Jeep's OE wiring and computers are long gone, with just a simple Painless Performance wiring harness handling all wiring. The only computer is to control the Holley Sniper EFI.