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420 repower or rebuild

1047 Views 12 Replies 8 Participants Last post by  TempletonJDguy
My '91 420 is a great tractor that gets lots of use with a blade, FEL, blower and tiller. I'm in no hurry to replace it but the Onan is blowing oil past the rings (per a recent leak down test) and has 75-80 psi - so it's only a matter of time! I've read different forums about Vanguard repower options including SEW, Jim's Repair, Harbor Freight and others. The Vanguard seems to get pretty good reviews overall so that's where I'm looking at this point. I live way up north in the western part of the UP of Michigan. It's a great place to live but pretty limited with machine and fab shops which means that if I do the swap myself, the kit has to have everything as there's nothing close by where I can pick up whatever else is needed. I've read through the posts and can see this topic has been discussed quite a bit, but the posts are several years old. Does anyone have experience with the swap from SEW? Does the kit have everything that's needed? I'm just looking to make this as simple as possible without having to chase down other parts so any comments are greatly appreciated. Thanks in advance!
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You'll get the standard replies to rebuild your Onan ... only you can decide if that is the right choice. Parts are still available from certain sources, so it is in the realm of possibility. I'll be interested to hear from recent repower projects as well.
You don’t even have to rebuild it. Just do the rings if your lucky. Myself I would go the couple hundred dollar route vs the couple thousand dollar path. Now if it had thrown a rod snd I couldn’t find another block then a repower could be justified. The more I use the 420 the more I like it!! 👍🏻
Just finished rebuilding the Onan in my 420. It is definitely less expensive than a repower, but it may take a little longer if you're not experienced (like me). I would do the rebuild over though. I got all my parts from Onanparts.com and rented a three stone hone from AutoZone.
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The biggest reason to re-power vs re-build is the fact that the key component of the tractor is 'new' - expected reliability is increased, the risk of "Now What" issues decreases, and they are better on fuel.
A lot of the members have > 1 tractor; so if one begins to act up, they have a back up plan to maintain normal routines. I wasn't in a position to own two tractors, I had to know the 318 was ready to go when it was needed. So for me, it was a question of upfront costs, and the resulting useful life of a tractor that was already 25 years old.
I decided to re-power. At this point, I am 10+ years in to my '15 year' useful life estimate, and happy w/ my decision - the engine has performed perfectly, w/ absolutely no issues (starting to get a little nervous about the now 36 yr old wires connected to TDCM though). It sounds like you use the your tractor for multiple tasks, so your 'useful life' timeline might be different.
Something else to consider - how much longer will other (non-engine) parts be available for these tractors, and at what cost ($$ and also 'time'). If you went the route of re-powering, would you have a plan B for the engine if your useful life estimate for the tractor came up short? If no, a re-build is probably the better option.
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I understand were you are coming from. My guess, is you don't have a machine shop nearby who can measure and service the crank & cylinders for you and get the correct parts ordered in between the times you will need to use the tractor. Also, time and workspace isn't always available to do these projects in. If you are a 1 tractor family and the money is available, You should call SEW and Jim's and price out the kits that would take the least amount of time and trips to the local parts store to install and remember that milage and time cost money. Ask ahead of time what is in the kits, get a copy of their Bill of Material for the kit and installation instructions. I remember the kits for some tractors from one of the vendors was said to have been wired before it was shipped by the vendor. I have never done a kit from either of these 2 suppliers, so I am not an expert, but I have tried to put together odd cars in the middle of now where in lousy weather while trying to get parts in a short period of time. Research is going to be your best friend.
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Also, once you have your new engine in place, you can take your time and rebuild your old enginefor fun and put it one the shelf or sell it to get back some of your money.
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It's pricey to do a rebuild so I probably wouldn't do that myself. I'd really want to though. I'm keen on always having a plan B.(y)
Also, once you have your new engine in place, you can take your time and rebuild your old enginefor fun and put it one the shelf or sell it to get back some of your money.
Or plan C. Rebuilding an engine is fun when you don't have to do it on a deadline. I just got pictures of a friend of mine who just finished the annual rebuild on his vintage british racecar that now can wait until the season starts this spring.
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The biggest reason to re-power vs re-build is the fact that the key component of the tractor is 'new' - expected reliability is increased, the risk of "Now What" issues decreases, and they are better on fuel.
A lot of the members have > 1 tractor; so if one begins to act up, they have a back up plan to maintain normal routines. I wasn't in a position to own two tractors, I had to know the 318 was ready to go when it was needed. So for me, it was a question of upfront costs, and the resulting useful life of a tractor that was already 25 years old.
I decided to re-power. At this point, I am 10+ years in to my '15 year' useful life estimate, and happy w/ my decision - the engine has performed perfectly, w/ absolutely no issues (starting to get a little nervous about the now 36 yr old wires connected to TDCM though). It sounds like you use the your tractor for multiple tasks, so your 'useful life' timeline might be different.
Something else to consider - how much longer will other (non-engine) parts be available for these tractors, and at what cost ($$ and also 'time'). If you went the route of re-powering, would you have a plan B for the engine if your useful life estimate for the tractor came up short? If no, a re-build is probably the better option.
At least with Deere’s something that new probably has atleast 20-30 years of generally abundant part supply, the older 60-early 70’s machines I think are starting to hit the beginning of NLA land on some more idiosyncratic stuff but even then they’re still pretty dang good on availability compared to pretty much everyone else.
My hope is that parts will remain available and become more available. An abundant following of these tractors has remained and increased partly due to the wealth of information online. I noticed a similar thing happen with old Stihl chainsaws. Parts that were very hard to find, nla, are now being made (coils, sprocket covers with chainbrake ect).
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My hope is that parts will remain available and become more available. An abundant following of these tractors has remained and increased partly due to the wealth of information online. I noticed a similar thing happen with old Stihl chainsaws. Parts that were very hard to find, nla, are now being made (coils, sprocket covers with chainbrake ect).
Yeah have seen that for some odds and ends, my 185 really needed a new carb when I bought it but aftermarket was nonexistent and Deere/Kawasaki wanted a fortune. Over half a decade later their everywhere on EBay and Amazon.
Ya but don’t buy them. I’ve had bad luck with the kawi carbs for the 100 series. Those carbs I like to find original that works. Most of the knock off carbs are good though.
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