Keep what you got? Path of least resistance
rvator51 said:
After coming back from Oshkosh, I found several more cracks in my front mounted oil cooler support brackets. I have had to repair this area several times and keep beefing it up more. I am thinking about moving the oil cooler to the back of the engine behind the #4 cylinder. Doesnt look like there is as much room to mount it there as on the RV-6s.
You are right but it's doable.
1. I wonder if anyone has changed oil cooler locations on their RV-4 and how the the oil temps work with the rear mounted oil cooler? My temps are always great with the front mounted oil cooler.
The RV-4 is known to run cool. I don't know why, but compared to say a RV-6, a RV-4 just always cools better. My old O-320 RV-4 ran cool as did 10 to 15 other RV-4 buddies. Never had the cooler up front but moving to the back will not cause a oil temp issue, at least if you make a good installation with a good quality cooler. Keep in mind almost everyone who mounts cooler off the baffle, whether front or back end up with cracks at some point and than obligatory reinforcements and bracing. It's a common issue and there is one solution which I mention below.
2. It looks like the oil cooler will have to be mounted a lot lower on the back baffle than on rv-6s etc. Does anyone have pictures of their installation process?
If you physically mount the cooler off the back baffle, typically the left-rear #4 cylinder, you can run into baffle cracking problems there as well (plan on it). People often need to reinforce and brace from what Van plans show, to make it work. I would consider just repairing and reinforcing what you have? If it works it works. Cracks in baffles around the cooler is par for the course.
If you change cooler location you will need new oil lines, replace & repair fwd baffle, modify the rear baffle, mount the cooler and make ducting in some cases. When a cooler is full of oil it weighs a good bit. When mounting direct off the baffle, most builders find they need to reinforce & brace the baffle & cooler to take the fatigue.
3. Any comments, good or bad about the front or back locations?
Consider if you do move the cooler, firmly mount the cooler to the engine mount with Adel clamps and run a flex duct to the cooler (avoiding baffle or cooler cracks). Email me for pictures, I have dozens of cooler set-ups I'll send you. Van makes a firewall oil cooler kit (third pic from left). I'm not keen on Van's cooler kit, for a few reasons, but it works OK for 320's, not so much for 360's.
These are all random pics of other builders work I have, sorry I don't have the credits, but nice work guys who know who they are. I had a RV-4 and made an installation similar to the first pic on the left, but the cooler was more vertical and angled. Your min dia for duct should be 3" (3.5"-4" dia for large coolers), and consider smooth and curved shapes verses wedges and box shapes for the air box. Pics below show two boxes with corners and two with smooth transitions. Which one works better? Smooth
The fwd left is a great cooler location; the only down side is the longer oil lines, which you already have. If you repair it, use 2023-T3 to 6061 aluminum and increase the gauge of metal, add doubler's and braces; it'll likely last forever. Don't forget to reinforce the cooler flanges with a *nested filler strap*, spacers and use washers and long bolts to use both cooler flanges not just one (pic above right). * Nested filler strap (radius filler) fits tight in the flange bend radius and runs the full length of cooler flange. Some times when the baffle is reinforced, the cooler ends up cracking. I know.
