How To for Heaterbox Motor Modification

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May 22, 2008, 04:05:20 PM

The heater motor is actually a Stock Motor that I have recessed into a modified heaterbox housing.

Here are the steps to do the heaterbox modification.

1 - Remove heaterbox from the car.

2 - Place heaterbox facedown on a towel or soft surface with the motor facing up.

3 - Find a drill bit JUST SLIGHTLY larger then the small rivets that hold the sheetmetal back to the fiberglass housing. (1/8" I think)

4 - Carefully drill out all of the rivets, dispose of them and remove the sheet metal back.

5 - You will find that the heater motor is held on to the heaterbox mounting bolts on the rear plate by four nuts.
5.1 - The mount studs SHOULD each have a small spacer tube on them , remove and save them and the four nuts for use on reassembly.
5.2 - Remove the four nuts that retain the heater motor and remove the motor and squirrel cage fan assembly and carefully set aside Be careful that you do not bend or damage the fan.

6 - You should now have a flat piece of sheetmetal with a hole for the fan and four studs for mounting the fan.

7 - Now take the sheetmetal back and turn it over. You will see the original mounting studs are spot welded on to the back. Find four 1/4" X 1" bolts with threads all the way to the head of the bolt and center one bolt on top of the head of each of the original mounting studs and weld them in place. Let cool then proceed to next step.

8 - Now take two or three 1/4" nuts and thread them all of the way to the head of each of the bolts you just welded on. These are used to space the fan assembly away from the back plate the desired distance. I believe that I used three nuts on my final assembly.

The motor set back can be varied by the number of spacer nuts used, Just be careful not to space it to far in or you WILL hit the heater core

Find some 1/2" wide self adhesive weaterstrip and cut to length and place between the bolts to seal the motor to the plate. (you may have to stack the weather strip for a good seal)

9 - Now place the fan assembly on to the bolts and use four more nuts to hold it in place. The fan should now be on the BACK side of the sheet plate.

10 - Now take a high speed die grinder and bit and enlarge the cone shaped hole in the heaterbox to about 1/2" larger then the squirrel cage fan diameter. You want between 1/8" and 1/4" clearance all around.

11 - Now find seven 6 X 32 X 3/8" machine screws and seven 6 X 32 Nyloc nuts. Enlarge the holes in the plate and heater housing just enough for the screws to fit and put the screws in from the sheetmetal side and the nuts on the fiberglass side and reassemble the sheetmetal plate to the fiberglass housing.

12 - Now place the four spacer over the original studs and a nut on each and put the heater box back in the car. DO NOT add more spacers here or the heaterbox will not line up and seal with the vent hole in the cowl. Now is a good time to replace the weather-strip between the heaterbox and cowl if it is damaged or compressed too much.

While you have the heaterbox out and apart, add a reinforcement to the cable control mounts by drilling or grinding the rivets out/off and cutting and drilling a 1/8" X 1" steel or aluminum strap to match the rivet holes. replace the rivets with 6 X 32 machine screws and nyloc nuts, put the plate on the inside of the box and tighten things up. This will keep the cable mounts from breaking off at the most inopportune time.

I have been running this modifacation for over six years now and it works and heats great.

I hope this will help a few people with their heater motor and valve cover clearance troubles.

Herb - Dart67

Hopefully Bill will make this a part of the Tech Section for everyones help in the future.

Thanks Herb! This DEFINATELY should be made a permanent post/addition to the tech pages!!

Ryan

Great idea and thanks for sharing

how much to you gain?

jamesdart,

Here is a photo of the modded fan motor and valve cover clearance.

How much you gain, depends on how far back you space the motor in the heaterbox.

Herb

sweet idea!
Looks like I have another porject lined up to do. thank you

Beautiful, I know what I'll be doing this winter. Anyone wanna buy a Mopar Performance valve cover with the some of the fins ground off? It'll make your car lighter!

Tim

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maybe add a little custum and have the ring around the fan chromed or powder coated. just a thought brain fart

The ring and the mounting nuts are powder coated.

Herb

do u know foa trick to get ur heater to actually work better?

My header works fine. Maybe your core is partialy plugged.

Herb

Quote from: Dart67 on January 20, 2007, 12:52:23 PM

My header works fine. Maybe your core is partialy plugged.

Herb

my heater is brand new!

Do you have the iron water pump housing? When I took mine apart, it had so much rust in the heater hose tube, it was clogged 100% solid, I have never seen one like that, but it was a south Texas car that probably had not seen Anti-freeze since it left the factory.

This post really caught my eye, so I decided to dive in and accomplish this mod. Well for anyone reading this, know that this mod is for NON-AC cars, because my Dart was an original AC car, and the heater box is very different than the one in your pictures. The hole in the firewall is different for an AC car as well, much larger. So scavenging a non-AC heater box out of the salvage yard still presents a problem with the firewall. Even the fan motor is bigger for the AC vice non-AC. Not to mention that I had all my dash pieces replated and I have the AC controls in my 67 Dart. So after finding out about the diffences, I had my work cut out for me. It is still possible to modify the AC version, but it takes a bit more fabrication and some welding since the blower motor housing is metal, and alot of trimming off of the retainer ring for the fan motor, and cutting off the inner steel cone at the rear of the housing is required so that the motor can be set into the housing to gain the recessed distance required. I haven't finished just yet to see how this is all going to work out in the end. But just thought I'd post this so if you want to try this be aware of the differnces between an AC car and a non-AC car. Good Luck.

Awesome,

I read about this mod in my Mopar mag then I made a crucial mistake and lent it to a buddy........gone.

Thanks for posting it. I was afraid I was going to have to figure it out the HARD way!

VV

Has anyone tried using the short motor from a rear defrost kit to replace the heater motor? They look to be the same diameter and have a very similiar appearance. I plan to try this before putting the 440 in my Dart.

Great Info! I'll have to re-read it a few times and follow it very closely. Removing my heater is not an option and I refuse to modify $100.00+ aluminum valve covers.

Thanks Herb! The retrofit was easy. I had to set my motor back 1 1/4". It works great and still moves alot of air. The biggest hastle was cutting the copper pipe off of the new Mexican made heater core and soldering on the pipes on from the old one. The new heater core was close but not close enough to fit; poor quality control.

Tom

Hey I am new to this site, I have a 69 R/T SE Charger and have always been a B-Body fan but I just ran accross a 72 Dodge Dart and now I am starting to be an A- Body fan also, I am looking at picking this one up and build a low deck bigblock car and I was wondering on your heater blower modification is that necessary if you are running stock valve covers with a low deck motor? Right now I am doing alot of reading and soaking up information for my next car project.

Kevin

Not needed on low deck

So the modification isn't needed on low deck motor with stock valve covers....
What about low deck motor with Mopar Performance cast aluminum valve covers?

Dart67, Thanks for the post. Great info.. Beautiful engine compartment. thank you

Quote from: jbarker on January 06, 2008, 12:43:42 AM

So the modification isn't needed on low deck motor with stock valve covers....
What about low deck motor with Mopar Performance cast aluminum valve covers?

I would like to know too. I have a low deck, factory a/c car, and I want the mopar covers.

Has anyone done this modification on a 60-62 Valiant or 61-62 Lancer?