The Garage - Throttle Body
Modifying the OEM Magnum Throttle Body!

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Last Updated: 12/3/2013
Throttle Body Mod

Harbor Freight
Address: Harbor Freight Customer Service, 3491 Mission Oaks Blvd., Camarillo, CA 93011-5034.

PHONE: 1-800-444-3353
Mo- Fri, 5:00 am to 6:30 pm PST

Technical product questions, please call 1-888-866-5797, Monday thru Friday, 5:00 am to 7:00 pm PST.

FAX: 1-800-905-5215 or

Click here to visit their website.

The fabrication, modifications and designs you see on this web site are completed by myself. If you duplicate these modifications you do so at your own risk. I do not endorse or make any claims to their safety, performance, On-road or off-road worthiness. Any "Product Reviews" are my sole and personal opinion. These reviews are on items purchased from or provided by reputable aftermarket suppliers. All registered trademarks belong to their respective owners.

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My Magnum engine needed more air and the solution is buying fully machined performance throttle body from Hughes Engines or BBK or modifying the OEM stock throttle body.
I decided to mod the OEM which involves opening the TB intake from 49mm to 53mm, making two new butterflies and mount them to the OEM shaft. The original horns don't have the thickness to support the larger bore andneed to be shaved off.
It's an easy mod for me because I have a small machining setup utilizing a MiniMill and a 9x20 Lathe which I purchased quite some time ago from Harbor Freight Tools. This machine is not really the expensive part, it's the required tools and tooling can end up costing quite a bit of money. Without them, you can't so anything.

My small Machine Shop setup
The basic procedure of this project is to remove the old throttle body from my vehicles Magnum engine, modify it, and reinstall it.

The first picture to the right shows my old OEM throttle body
before the disassembly, although the sensors have already been taken out.

1. I began by uninstalling the throttle body (TB) from the engine and completely dismantling it. I wrapped all sensors in a piece of shop towel to protect them while removed. I also had a second throttle body on hand which I won on ebay some time ago which I used for this project. This was cheap insurance in case I would screw up.

2. I then machined the throttle body out to 53mm, including removing the horns and then had a friend blasting it for me. I made two new butterflies on my lathe from quality brass which I purchased from OnlineMetals.

I then re-installed the shaft, butterflies, and the rest of the components. In the picture to the right you can see the OEM throttle body all finished just waiting for the sensors and re-install.

3. Now I gasket matched the opening on the intake manifold using a Dremel tool with a stone grinder bit and afterwards 3M wet/dry 600 grid sand paper for the finish. I stuffed shop towels into the intake to prevent any debris to get into. After I was done I used a heavy duty shop vac to clean up.

My intake manifold currently on the Durango although looking stock, is a modified OEM barrel with longer runners and thus having a more on the low end. This is likely one of the reasons why I needed more air for it.

4. I purchased a new gasket from RockAuto and installed it between the manifold and the throttle body. I then began re-installing all cables and vacuum tubes and finally mounted my Mopar Performance air filter on top. This pretty much concluded the install and this mod.

Finishing up!
It's time to start the Durango up and listening for any vacuum leaks at the throttle body, but everything checks out and I don't hear any unusual noises.

The entire project took about 10 hours and thus was accomplished on a single day but if I had a small Portable Soda Blaster like the one a friend of mine purchased from Harbor Freight Tools for about 100 bucks, it would have taking even less time as I wouldn't had to wait until he had time to do this. Definitely on my wishlist though ;-)

This mod was a lot of fun and for the cost of about $10.00 on material definitely one of the more affordable ones. I can definitely tell that there is a lot more power after modding the throttle body and response to throttle is a lot faster too.

I am more than happy with the outcome and I would do it again without hesitations with the nice bonus of being one of the cheaper mods I have done. This is a must do performance mod for this engine! This mod gets my stamp of approval!

This project was completed on 06-10-2008

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