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Big Block Talk! Everything about swapping a big block engine into your cart! |
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01-06-2022, 04:29 PM | #1 |
Not Yet Wild
Join Date: Oct 2019
Posts: 23
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EZGo ST350 Redux
This all started about 3 years ago... My then 83 year old dad started complaining that the walk to his hunting blind at our ranch was getting a bit rough. I then began the search for a suitable cart that he could use for the trip to the blind. I was first searching for an electric cart but I ended up purchasing this nice used ST350.
st350-1.jpg st350-3.jpg This cart was bone stock at the time...and this was good enough for a year or so. He really did not like the peddle start (nor did I) and the rough ride due to the lack of a "real" suspension. Right after hunting season was over I decided to hauled the cart back to my house and began the BIG transformation of the cart. For now I'll jump to the final product....but I do plan to post multiple threads showing the journey... Attachment 226568 Attachment 226569 Attachment 226570 Hope you folks enjoy. |
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01-09-2022, 08:16 PM | #2 |
Not Yet Wild
Join Date: Oct 2019
Posts: 23
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EZGo ST350 Redux-overall plan
As stated in the post above there were two main complaints about the stock cart. First being the peddle start and second the lack of suspension. In addition to not caring for the peddle start...the stock Robin 350cc just didn't have enough power. This cart was intended to be a ranch cart...not just a hunting cart, so part of the Redux plan was a big block conversion to increase the power.
For the big block power plant I went with a Predator 670. I was able to pick up a slightly used 670 (it was practically brand new) off of FB Marketplace for less $350 back in the summer of 2020. The big block would solve the power issues, but there was still the suspension to deal with. The stock leaf spring/shock setup, both front and back, needed to go! For the front end my first thought was to fab up an A-Arm front suspension from ATV components. For the rear suspension I really wanted to go with a multi-link setup with coil over shocks. I researched these ideas and found several folks who had done both of these exact things...so I started the design and plans for for my cart. As I got further into the designs, it became apparent that my desire for a multi-link rear suspension wasn't going to work out. Given the space needed for the engine cradle there just wasn't going to be enough space for a properly fitted multi-link...the engine cradle would be in the way of the triangulated links. The builds I had seen from others who had done this were using electric carts...so no issue with an engine cradle. Additionally after estimating my time, effort, cost of the ATV components as well as all of the material needed to build the support structures for the front end, it just didn't make economic sense to for me to build it myself. Due to these realizations I went back to the drawing board for the whole suspension. I ended up deciding to go with a RHOX BMF 7” A-Arm front end....which worked out great (with a few modifications needed to fit my cart)! For the rear end i ended up designing a trailing arm setup with coil over shocks that incorporate a pan-hard bar to control lateral movement of the axle. I will post separate threads for each of the main build groupings as well as several other custom designs that went into the overall build. Hope you guys enjoy the build story...and maybe get a few ideas of your own from it. |
01-09-2022, 09:12 PM | #3 |
Not Yet Wild
Join Date: Oct 2019
Posts: 23
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EZGo ST350 Redux - engine cradle and trailing arms
The ST350 wheel base is longer than other EZGO gas carts like the TXT, etc... This fact contributed to the design of the trailing arms and engine cradle. Having a little more room made the build easier, in my opinion. Even so I still made a small modifications to the frame in my build, most notably i removed the central cross member where the stock front engine mount was attached. This allowed me to have the front of new engine cradle attached at the same lateral pivot point as the trailing arms.
I adding a 1/4" thick 2" x 2" piece of angle iron along the full length of the front cross member as enforcement and as an attachment point for the trailing arms and the front engine cradle mounting tabs. For the engine cradle itself, I had mulled over purchasing one of the various cradle kits available on the market...but once again economics played out for me. I had almost all of the material already on hand to build the cradle, only needed the front heim joint and a bung. As i was already ordering heim joints and bungs (and rod ends for the other end of the trailing arm setups) i just added one more to the order. craddle-0.jpg craddle-1.jpgcraddle-2.jpg craddle-3.jpgcraddle-4.jpg The trailing arms as well as the front bars on the cradle are made of 1-1/4" diameter, thick wall tubing. I also incorporated the stock rear yoke into my design which made the attachment to the axle "like stock". Im not a welder or fabricator by trade, so please don't judge the look of the welds! LOL I added the parallel c-channels with the slots cut into them as the actual mounting points for the Predator engine (after much carful measurement). The piece that attaches to the stock yoke is 1/4" thick 4"x4" angle steel and is welded to the base plate which is also 1/4" thick. |
01-09-2022, 09:43 PM | #4 |
Not Yet Wild
Join Date: Oct 2019
Posts: 23
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EZGo ST350 Redux - rear suspension
Due to the reason stated previously, I could not use the multi-link design i had wanted. Instead I ended up with a trailing arm design with coil over shock and incorporating a pan-hard bar setup. This pan-hard bar was needed to control any lateral movement of the axle. Had I been able to use a multi-link design instead the triangulated links would have accomplished this task.
I started by removing the original axle mounting brackets from the axle. This gave me room to weld on the lower mounting tabs for the coil over shocks as well the trailing arms. The most challenging part of this design was how to add the pan-hard bar setup and not make it look like an afterthought! The design I came up with was to weld a 2"x3" rectangular tube across the wheel well opening of the frame and then attach the drop bracket to it. This gave me some adjustability in the pan-hard bar configuration. I found the drop bracket online at some "off-road" suspension store. The other end of the pan-hard bar is attached to the axel with a bracket I fabricated from leftover pieces of that 4"x4" angle steel that was used for the engine cradle. The pan-hard bar itself is made from the same 1-1/4" diameter thick wall tubing as the trailing arms. I re-enforced the existing top shock mounting points with 3"x3" 1/4" thick angle and then welded mounting tabs to them. This gave me the top mounting point for the coil over shocks. susp-1.jpg susp-2.jpg susp-3.jpg susp-4.jpg susp-5.jpg |
01-09-2022, 10:39 PM | #5 |
Not Yet Wild
Join Date: Oct 2019
Posts: 23
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EZGo ST350 Redux - front end
As is plain to see the front end is a RHOX BMF 7" A-Arm kit. There were a few modifications I had to make, both to the RHOX kit itself as well as my cart, to get this to work.
First off the RHOX kit is designed for the post 2001.5 year models that have the 4-bolt steering column mounting. My cart was made pre 2001.5 when EzGo was still using the 3-bolt design. So this design change was more significant than just adding another bolt to the column...the entire steering assembly was changed, from the steering column mounting, steering rack, idler arm, tie rods... everything was changed in the later models. For me to use the existing steering column with this kit, I had to fabricate a custom mounting bracket that the steering column could be bolted to. In the post 2001.5 year models EzGo increased the spacing of the mounting holes where the top of the shocks are bolted to the frame. The RHOX kit uses these holes (along with the mounting points of the front leaf springs) to attached the suspension to frame. I had to cut and re-weld a portion of the mounting bracket on the RHOX kit so that the holes would line up with the older frame. This was relatively simple and the material I use was actually thicker, and therefore stronger, than the factory bracket...at least in theory. The front wheel axles (and therefore the hubs as well) of my ST350 are quit a bit longer than the ones that came with the RHOX kit. The RHOX kit expects you to reuse your original hubs, since my would not fit I needed to order a set of front hubs. Ones from a post 2001.5 TXT model worked fine. The only other mod I had to make to the front was the addition of 2" wheel spacers. The RHOX kit is designed for wheels that are 12" is diameter...mine are 10". Not wanting to spend more money on a set of larger wheels I just added these spacer, which worked great. Without the spacers that smaller wheel would not clear the spindle arm that attaches to the tie rods. f-susp-1.jpg f-susp-2.jpg f-susp-3.jpg f-susp-4.jpg |
01-09-2022, 10:49 PM | #7 |
Not Yet Wild
Join Date: Oct 2019
Posts: 23
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EZGo ST350 Redux - engine & alternator
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01-09-2022, 11:01 PM | #9 |
Not Yet Wild
Join Date: Oct 2019
Posts: 23
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EZGo ST350 Redux - exhaust
I fabricated the exhaust header and the muffler mounting bracket. The exhaust tubing is 1-1/4" and comes into a 1-1/2" collector.
The muffler is a Walker Quite-Flow model 22229 which has 6" outer diameter. The clamps are TOTALFLOW 6" TF-600SS 409 Stainless Steel Single Bolt AccuSeal Exhaust Muffler Clamps. The whole exhaust system is relatively quite... which is what i was going for: exhaust-1.jpg exhaust-2.jpg exhaust-3.jpg |
01-09-2022, 11:17 PM | #10 |
Not Yet Wild
Join Date: Oct 2019
Posts: 23
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EZGo ST350 Redux - electrical control system
Since this project was turning into a total makeover... I did not want to forget about a new electrical control system. In addition to the mechanical upgrades I ended up stripping out the entire electrical system from the old cart. I don't have any pics of the new relay/fuse box, other distribution boxes or wiring harness... but I do have several of the new dash panel.
The only "old" parts that stayed were the fuel gauge, fuel sender unit, head lamps and tail lamps...every single wire, connector, switch, etc was removed from the cart. I custom fabricated the dash panel from a 1/8" thick sheet of aluminum. I added the swirl pattern by attaching a 2" abrasive sanding pad to my drill press and just used it to scratch the surface in the overlapping pattern. I did also add some LED fog lights as well as LED light bar for the cargo area..which can been seen in the pics for final finished project. dash-1.jpg dash-2.jpg dash-3.jpg |
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