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Well after careful consideration I made a decision to re-power my 1988 420 with a 23hp B&S Vanguard using the kit from Jim's Repair. This decision was unexpected and thought that my two 318's and 420 were well sorted for many years of light maintenance. Well the unexpected happened.

So after installing a NOS 110-3823-03 short-block in my 318, new fuel lines, pick-up filter, tie rods and a bunch of other stuff to get it working properly AND success in removing a stubborn rear brake drum on my other 318 to replace a broken brake shoe spring (M84943) I began investigating the rough running 420. For those interested I used heat, an 8" JobSmart puller and 3ft breaker bar to pull the drum. The reason why it requires so much force to remove is rust and not catching a lip on the shoe which I originally suspected. (see photos).

The 420 was my primary tractor and last used blowing snow (47" SB). I thought the engine needed valves, made the adjustments but no help. I then proceeded with a leak down test. Cylinder 2 (left side) showed 7% leak down and cylinder 1 40%. The problem, a failed intake valve seat (photo). This is disappointing as I rebuilt the P220G (700hrs) due to a broken rod (cylinder 1) 10 years ago and had only 400hrs on the rebuild. I don't think it's a coincidence that the intake valve seat failed on the same side as the broken rod. Suspect oil starvation and heat was the culprit.

I can't complain as I got 10yrs on the rebuild and paid $200 for the 420 including a 60" deck and rear PTO (sold to pay for the rebuild). Since new short blocks for a B48G (110-3824-01 and 110-3824-09) and P220G (110-3824-22) are no where to be found nor do I trust a donor block I made the decision to re-power. Well so much for being a purest but time to move on. That said, if I come across a new short block I'll still snap it up;)
 

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A good engine shop can repair/replace the valve seat. I've had a few of them repaired, it's fixable.
 

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Discussion Starter · #3 ·
A good engine shop can repair/replace the valve seat. I've had a few of them repaired, it's fixable.
Option considered but can't guarantee they will hold. Boomer only knows of one machine shop that he trusts and not worth the effort in my case. I'll likely have no interest in rebuilding this engine should it fail when approaching 70 years of age.
 

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Vbosch,
Have you been able to have a shop do the valve seat repair without removing the rotating assembly? To my non-machinists eye it would seem possible, but not sure how many phone calls I want to make chasing down the possibility if it is not realistic. - Tom
 

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I've had them done both ways. The last one I had done did have the crank and pistons in it, but all the valves and cam were pulled. This shop used to work on a lot of Onans for the phone company. His words, they had money for maintenance but not for new. The Onans were used on the power carts so they put a lot of hours on them.
 

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Good work getting the drum off without cutting it in pieces. Wow. Your 318 deck has rotable deck wheels. I've never seen on that generation.

The Vanguard is a good engine. I have it in my 400. Mine runs better with mid grade or premium fuel (89-91) especially on hot restarts. I suspect the carb fuel bowl absorbs a lot of heat after shutdown, the higher octane will tolerate that more. These also may need to have valves adjusted from factory, mine were a little off spec.
 

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Money for maintenance is fully tax-deductible in the year it's spent. Money for new is a capital expenditure usually depreciated over multiple years. I guess they didn't want to put $ into a new engine when they might not be able to fully depreciate. That's some tight cost control on cheap engines : ) Maybe they had a ton of engines so it was worth it.
 

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Discussion Starter · #8 ·
Good work getting the drum off without cutting it in pieces. Wow. Your 318 deck has rotable deck wheels. I've never seen on that generation.

The Vanguard is a good engine. I have it in my 400. Mine runs better with mid grade or premium fuel (89-91) especially on hot restarts. I suspect the carb fuel bowl absorbs a lot of heat after shutdown, the higher octane will tolerate that more. These also may need to have valves adjusted from factory, mine were a little off spec.
Thanks for the advice. That’s a 48” replacement deck. Based on my preliminary assessment it doesn’t cut as well as my other 318 with a 50” deck with a speed up pulley.

When I picked up that 420 10 years ago it was a package deal with a 300 with a non-working 23hp vanguard for $100. Replaced a cylinder head, fixed electrical issues and 10 years later it’s still running strong. This is one reason why decided to repower with a VG.
 

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I have two of those 23 HP VG's. Just the improved fuel mileage alone makes it a good decision. If I was doing a correct resto I'd go with a K532 but if it's a worker the VG is an easy choice.

Well after careful consideration I made a decision to re-power my 1988 420 with a 23hp B&S Vanguard using the kit from Jim's Repair.
 
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Why did the cylinder head need to be replaced?

When I picked up that 420 10 years ago it was a package deal with a 300 with a non-working 23hp vanguard for $100. Replaced a cylinder head, fixed electrical issues and 10 years later it’s still running strong. This is one reason why decided to repower with a VG.
 

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Discussion Starter · #11 ·
Why did the cylinder head need to be replaced?
It was a bent push rod but I don't recall the details. In retrospect I could have replaced it but I had little experience in working on JD's at the time.
 

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Discussion Starter · #12 ·
I have two of those 23 HP VG's. Just the improved fuel mileage alone makes it a good decision. If I was doing a correct resto I'd go with a K532 but if it's a worker the VG is an easy choice.
It's a worker but mechanically in top shape. Here is the 420 after the Onan rebuild and fresh coat of paint.

Curious if you installed and oil pressure and/or oil temp gauge?
 

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Both tractors have oil pressure gauges but I gotta get a couple sending units for them yet. Can't go to any stores right now because of the covid lockdown. I could order them online I guess. Not likely gonna go with an oil temp gauge. If you put one on that 420 it would be interesting if you shared the result.

After running the 23 HP VG's for a while on a 400 and a 420 I want one in my golf cart now. I like the throaty sound they make. The 8 HP (real) Honda I'm using now is the sweetest running little motor I ever saw and has lots of power for everything I need it for, but it's quiet as a mouse. It has a JD 212 muffler on it. No hotrod sound to it at all, which my wife prefers. (If she likes something the way it is I know for sure it needs to be modified :D). I always wear ear muffs with my 532's even if I'm just driving it somewhere. I put a new muffler on my nice 400 back when I did the resto but it's still pretty loud. With the Vanguard engines I only grab muffs if I'm gonna mow.

It's a worker but mechanically in top shape. Here is the 420 after the Onan rebuild and fresh coat of paint.

Curious if you installed and oil pressure and/or oil temp gauge?
 

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I've installed both a volt meter and oil pressure gauge. The volt meter died the first year, Chicom junk. Oil Guage is mechanical. I swapped the cheap plastic tubing with a braided steel line. I moved the hour meter under the hood.
 

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Discussion Starter · #16 ·
Am I reading this correctly? $200 for the 420, and $100 for a 300?? wow!
Correct. I went to a JD dealership (Miller Equipment, Robbinsville, NJ) for paint and asked if the had any attachments and discovered the 420 and 300 sitting in the yard. I didn't know it at the time but the dealership was in the process of closing shop.

UPDATE: The VG is on hold and I'll rebuild the Onan.

This morning I was chatting about the Onan seat failure with a former top fuel drag racer and to my surprise one of the best machinist on the east coast lives 6 miles away. Brought the block over to his shop and he is confident in making the repair. I believe he will fabricate a new seat using the end of an old camshaft.

Got a little tour of the shop and saw a custom jig for making bearings for a 1930 Henderson in-line 4 cylinder engine!
 
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