Rear fender oil cooler mount details, How I did it Options

[IronHillRestorations]

After I made a post about my alternate location for an auxiliary oil cooler, I thought more details would be helpful.
First let me say that this was a piece of cake for the current project, as the right rear quarter panel was removed for rust repair and chassis stiffening. Due to the difficulty in properly locating the forward mounting holes, I don’t know how feasible this is for a car with the engine installed. When I put a (slightly smaller) cooler in this same area 25 years ago, I made no notes or kept any of the measurements, I just made it work, but at that time it was done with the engine out of the car.
After trial and error fitting of a cardboard mockup, I picked a Mocal 34 row, 235 matrix cooler, which measures 260mm by 280mm, or roughly 10 5/16” x 11 1/8” which doesn’t include the -12AN fittings. This is what I think to be the largest cooler you could get in that area ahead of the right rear wheel. This cooler has a capacity of .75 quarts, which is .20 of a quart more than the kit BAT offers to upgrade a 911 front oil cooler. This is a case where bigger is definitely better.
Since airflow in the rear quarter panels isn’t as good as the front fender , I added a 7” Spal puller fan that will be mounted directly to the oil cooler with a plastic mounting tie kit, which are very sturdy round zip tie fasteners that make it easy. The fan will be wired with a relay to a switch on the dash or an automatic inline switch (to be determined later). On my old install I tried to make the fan automatically switched, but it ran too much and the fan died. A testament to this set up is that I never knew the fan died, and oil temps never got over 220* even in the hot Tennessee summers. Since this is going to be a widebody hot-rod with flared rockers, I’m toying with the idea of incorporating a scoop in the rocker flare, but that too is undetermined.
Here’s a hardware list, that doesn’t include any oil lines, thermostat, or relay wiring for the fan.
1 Mocal A34A12 34 row -12AN 235 oil cooler
2 Mocal/Setrab ABKT-235 oil cooler bracket for 235mm core
1 BAT ABKT1 cooler/fan mounting tie kit
1 M8 x 1.25 x 60mm fully threaded cap screw (13mm hex)
2 M8 x 1.25 x 50mm fully threaded cap screw (13mm hex)
12 M8 washers
8 M8 x 1.25 nylon insert nuts
1 M8 x 1.25 weld nut

Even with the fender off it took more than one attempt to get it in the optimum location, which is as far forward as possible without interfering with the outer suspension console. Using the suspension console as the baseline level plane, the cooler is tilted down at the back about 5* give or take a degree.


Just for reference

Here's what the cooler looks like mounted. It's pretty big.


I wanted to make sure the cooler could be installed and removed with the fender on, I made sure there was no interference. I had the fender on and off several times during the test fitting process.
With the fender off it was easy to use the bracket as a reference where to mark and drill the 5/16” front mounting holes, which are 70mm apart.

[IronHillRestorations]

Using masking tape I test mounted the fan to the cooler. I positioned it on the upper rear corner of the cooler, which exploits the dimple in the inner fender for the battery tray. You can also see the mounting bolts which are also used as stand offs.


The oil cooler mounting brackets have rubber pads to cushion the cooler.


The factory 911 front oil cooler uses three big thick rubber mounts that have M6 fasteners, so my choice of three mounting points with M8 fasteners will be more than adequate.

On my initial test fit I cut part of the top section of the front bracket to ensure fit around the cabin vent pipe in the quarter panel. I wasn't going to use the very outboard mounting holes anyway.

[IronHillRestorations]

This shows the cooler bracket spaced 31mm out from the inner fender in the front, using the 50mm fully threaded cap screws nuts and washers. There are washers under every bolt head and nut. For fitting purposes I used plain nuts, but for the install nylon insert nuts will be used to prevent anything from backing out. Alternately you could use lock washers, but I wanted to keep it simple.

Upper front mount


Lower front mount


For the rear I used a surface weld nut that was tacked to the inner fender. In the rear the cooler is spaced out 60mm using the 60mm fully threaded cap screw with washers. This too will get nylon lock nuts for the final install.

[IronHillRestorations]

So it’s all mounted nice and tidy, but how can I pass this on for future use? I used the vertical surface upper cross member on the firewall as a reference point, and butted my ruler up against the lip of the side panel. This is where you’ll measure from to make your reference marks to drill your mounting holes. Flush against the vertical edge of the firewall and the upper stop is the lip of the side panel.



From the upper reference point measure down 176mm and forward 61mm. This is where it’s a little tricky as I wanted a repeatable method that you could use. Keep the ruler flush against the vertical side of that panel and hold it against the inner wall, and set the sliding square at 176mm, this is your down measurement for the top hole. Then I used a shorter scale (ruler) measure a perpendicular straight line from the edge of the vertical ruler 61mm toward the front of the car. I didn’t bend the scale. This is the spot for your top hole. I must confess that this was easy with the battery tray not yet installed.
Continue down that same vertical line to 345mm, and then another perpendicular line 75mm forward for the lower mounting hole. Before drilling any holes measure between your two marks and make sure you’ve got 70mm. You can enlarge the holes a bit if you have to, and in a worst case scenario, you could employ some oversize washers.


The rear mount is very straight forward, which I’m not going to detail. The pictures tell all. You have much more access to install this mounting point.
After it’s all installed I’ll make a stone shield from some black plastic inner fender material, and make a follow up post.

This is how it measured out on this 914-6 chassis, I can’t promise that there isn’t a difference in a later style chassis, or some variance in your chassis. Double check and measure, check and measure again.

I’m not going to get into the front mounted cooler, or rear mounted cooler discussion. This is just how I decided to go. I know this might not be the best choice for a track car, and it’s not “GT correct”. My own opinion is that the trunk space a 914 provides is one of the more practical aspects these cars have to offer. I also am a fan of a full size, fully inflated spare tire. This approach preserves both.

You might get halfway through doing this and decide I’ve caused you more grief than help. Clearly, your results may vary.

[mb911]

Looks great.. If I ever build another project this will be an option even though I have the GT lines this does keep things simple.

[IronHillRestorations]

Another shot of the rear mount


Inside the fender. The fan is taped on the cooler, but you can see how it fits in the recess of the inner fender

[IronHillRestorations]

The cooler, the brackets, the fan, and the (not shown) thermostat were all purchased from BAT, a great supplier of oil lines and oil cooling components.

[burton73]

Do you think a Boxster vent would work with this? Thinking of my V8 car that needs external oil cooling for its 930 Trans. It is set up for it and I have a new Telton gearbox oil cooler pump that came with the V8 car. Looks like a very clean way to mount instead of putting it under the rear trunk. It seems like it would be cooler where you are putting it.

Can you set this up to pull outside air?

Bob B

[amfab]

Awesome! I am planning to put my cooler there on my build. So nice to have someone work out details ahead of me. I am curious what motor you are running?

[DRPHIL914]

boy that seems so tight! not sure that you will get enough air flow across the coils even with the fan, atleast not with out the scoop in the side like previous poster was asking, like cayman or boxster. I don't really like the scoop by itself but in this case it makes sense, but its functional,

[mepstein]

There is probably still an oil cooler on the engine so I'm sure this will work for most situations. Many people get by without an auxiliary oil cooler. Some 6's run hotter than others, location and driving style come into play.

I removed the engine oil cooler on my 3.2 so I have no choice but to go to the front for max cooling.

[tomeric914]

boy that seems so tight! not sure that you will get enough air flow across the coils even with the fan, atleast not with out the scoop in the side like previous poster was asking, like cayman or boxster. I don't really like the scoop by itself but in this case it makes sense, but its functional,

(IMG:style_emoticons/default/agree.gif)

I played with different locations for the oil cooler and found that the only location that works is in front with air forced through the cooler at speed.

The fan is too small, the assembly gives no room for airflow and the hot air from the cooler will continually recirculate within the fender doing nothing more than heating the fender.

[IronHillRestorations]

Awesome! I am planning to put my cooler there on my build. So nice to have someone work out details ahead of me. I am curious what motor you are running?

This is scheduled to get a 230hp 2.7 with EFI.

[burton73]

Suck the fan air through the vent. The only way to test it to try it but I do not think that the ways guys are hanging them next to the exhaust and under the trunk would work as good as it is much hotter there. Vent and sealed duct will force outside air into the cooler. It will need to be tried to see for sure. Take and idea and test. isn't that what the factory does. That is where all of technology comes from. Yea fancy testing in a wind tunnel but the fan will pull air from the outside if set up that way


Bob B

[tomeric914]

... but I do not think that the ways guys are hanging them next to the exhaust and under the trunk would work as good as it is much hotter there...

Under the trunk works on 4 cyl cars with oil coming from a spin on adapter between the filter and engine. That oil is more liquid than on the 6 coming out of the engine. It's also on an engine with ~100hp. I ran one under the trunk with my 4 at track events for a couple of years and was successful at keeping the oil less than 220 deg F even on the hottest of days.

When I tried the same thing with the 3.0 six and a 12x12 Setrab cooler with a 12" diameter puller flowing a noticeable amount of air, I was seeing 260 deg F. Location was part of it; the fact that the oil is really foamy at that point (especially close coupled) was the other part of it.

That same 12x12 cooler in front laying flat keeps my oil temps at the track and street at about 190 deg F using a 200 deg F thermostat. I would theorize that the distance from back to front along with the many turns to get there reduces the foaminess of the oil.

Also consider the weight of the cooler, fan, oil and lines attached to the whole assembly. The 4 studs holding it on may not be enough in the long run, especially after hitting a few good bumps.

By no means am I dissuading the OP from what they are doing. Your mileage may vary, etc., etc.

[billh1963]

I've often wondered if a scoop around the sail panel or even one down low would look good?

The C7 Z06 has both (they are functional) and look good in my eye. A scoop down low would not be intrusive and would probably get a lot of air.

[Dave_Darling]

I believe you guys are talking about the difference between "best" and "good enough". In Perry's experience, the large cooler in the fender has worked well enough for the car it is in in the circumstances that he has had it in. It might not be good enough for a 24-hour race, but it doesn't have to be.

Likewise, the under-trunk-floor setups are not optimal but can be good enough for at least some uses.

--DD

[billh1963]

Found an old thread with pics:

http://www.914world.com/bbs2/index.php?sho...=62387&st=0

[IronHillRestorations]

On a street car, I'd add another cooler under the rear trunk before I'd put one up front, for reasons already stated.

For a track car, I wouldn't put it anywhere else than up front.

All the information I've been able to find says 210* is what you want, which is when the water in your oil will vaporize. Over 240 for extended periods isn't advisable.

A fresh tight engine will always run cooler than a tired one needing a rebuild; the old engine will have more blow-by in the case which will raise oil temps. So the fresh 230hp 2.7 going in this car will run cooler out of the box, than your old 2.0T engine that burns a quart every 500 miles.

[DRPHIL914]

On a street car, I'd add another cooler under the rear trunk before I'd put one up front, for reasons already stated.

For a track car, I wouldn't put it anywhere else than up front.

All the experts that I've spoke with have told me 210* is what you want, that's when the water in your oil will vaporize. Over 240 for extended periods isn't advisable.

Mine is up under the rear trunk with a good angle to it and seems to allow a sufficient amount of air to move thru it. I didn't have that fan wired up for the drive in Helen, and up the hills I topped out right at 230-235 but never went over that, and only hit that as a max during long steep hill climbing. Last year on the same hills and the year before in Banner Elk, NC, with the fan kicking on at about 220, it never went over 220 , verified with dip stick thermometer. I used to also see some pretty high oil temps here in the summer heat in SC just on the highway and this was why we put the aux oil cooler in in the first place, but with the aux it stays a good 20 degrees cooler. so I can see your point about not requiring a front cooler unless you are racing. I don't plan on tracking the car, and its cool to see that your set up in the rear is good enough even for a nice /6 motor! How far out are you from actually having that car on the road? have you posted a build thread with details of the rest of the restoration?