What's involved in rebuilding a 420 Dozer motor?

[Cardinal]

Like the title says, what is involved in rebuilding a 420 dozer's motor?

Understand that I’ve built (and rebuilt) MANY small block Chevy motors, am a qualified small engine tech, and worked as a industrial shift mechanic for more years than I’d like to remember.

BUT, I’ve never built (or rebuilt) a John Deere 420 bulldozer motor.

Supposedly, the engine ran but burned oil but didn’t knock. What parts do I need to rebuild it? Pistons with sleeves or just pistons? How big an over bore can be done to the block (I assuming that it’s been rebuilt once before although that may be a bad assumption as it may be a “virgin” and never been apart before)?

Does the crank usually have to be turned or are they usually OK?

Are the valves in block or in head?

Do you reuse the cam and lifters or do you install new ones?

Do you reuse the oil pump or do you install a new one?

Any and all guidance will be greatly appreciated.

Sincerely,

John

[Willyr]

Overhead valves with mechanical adjusters at the rocker. I think (not certain) lifters are tappets like on a Briggs and Stratton. Generally speaking as to the crank, just do a clearance check and replace / rebuild if scored.

You will probably be more than able to get away with pistons and rings. Do valve job wouldnt be a bad idea. I dont remember if the engine can be reuilt infram or not. Since some one rebuilt my bellypan I know I can.

[Cardinal]

I wish that I had paid more attention to what was going on at the John Deere dealer that was across the street from us in Deposit, NY when I was a kid in the 1950's to mid 1960's! I remember brand new B's and A's along with those mechanics tearing apart EVERTHING in there from small bulldozers to HUGE tractors with horizontal cylinders you could stick a man's head into!

What was a big innovation was the "shift on the move" transmissions! A driver could really put the HP to use with that!

[H-D]

I think that most will agree that the foremost 'tool' required is the service manual. All the specs & service limits are found there. Tractor/crawler engines are more forgiving than their higher revving cousins, but the manual is THE authority. This board is a priceless resource for researching possibilities & probabilities as well as 'recommended methods' like tying cordage to your clutch adjustment wrench to prevent your crawler 'eating' it . I have the 440 IC & ICD manual on disk & appreciate the utility of being able to print the necessary sections for trips to the shop.

[Cardinal]

+1 more that shop manual is the way to go.

When I bought my first car, a 1964 Chevy II 2dr sedan for $400 in 1969 (you can't buy the hub caps for that much now!), THEE first thing I bought for it was a set of Helm Manuals. I learned how to do EVERYTHING from rebuilding an engine, rebuild Muncie four speeds, suspension replacement, wiring, etc.

Where is the best place to get manuals for John Deere equipment. EX: for a 350 or 420, or 1010 dozer?

Sincerely,

John

[Tigerhaze]

Manuals for the newer machines (350, 1010) can be bought online from Deere or a number of vendors on sites like Epay.

I believe there is a person on this that can sell you the 420 manuals on CD. You can do a search of this site to find the names and links to these various sources.

[Lavoy]

Pretty much all of the internals are available, no problem there. In probalby 20, 30 or who know how many engines, I have never found one that did not have a tapered bore. Most will clean at .045, .090 covers pretty much all of the rest.
Cam and lifters are normally good, only had a few bad ones. No new cams or lifters available, but never had one that could not be reground.
Oil pumps by and large do not bother, take it apart, check for damage, and reinstall.
ALWAYS magnaflux the head. On any head I do, they are magged, trued, new valves, guides, springs, and keepers. I also have hard seats installed.
Cranks almost always will have a scar on them at the oil port, but usually mains will clean at .010, rods .020 at the most as long as there is no damage.
If you plan on keeping the crawler, do it right. Even if you don't plan on keeping the crawler, do it right. If you sell it, do you want to advertise it as an overhaul, or a rebuild?
Lavoy

[Cardinal]

Lavoy: My father was of the faith: any job is worth doing right the first time. I agree with you 100% on everything you said too. Some parts are reusable (cam and lifters, oil pump) IF they are cleaned, inspected and found to be OK. Cranks need to be checked for wear, concentricity (round), taper, among other things. Cylinder bores need to be mic’ed with a taper gauge (my neighbor has one of those). Pre-unleaded gas engine cylinder heads need hardened seats put in for the valve to ride on (otherwise, the original valve seats will wear out MUCH faster).

I've built (and rebuilt) dozens of small block Chevy engine (from 265 to 350 cubic inch engines) from bone stock "rering & rebearing" builds to all out racing engines. THEE things that make a build successful are: attention to detail, cleanliness is next to godliness, VERIFY everything, using the correct gaskets and sealants, prime the engine before starting, and be patient (especially when putting the rings on the pistons!).

BUT every brand of engine has nuances. EX: there are THREE distinctly different 3.8L Buick engines. EACH one of them use a COMPLETELY different intake gasket set. Small block Chevy's have three different crankshaft main and rod diameters AND a 400 SBC BETTER have the steam holes drilled in the head or it WILL overheat!

That's why I asked for all of your inputs about rebuilding the 420's motor: to avoid any pitfalls that you all have learned the hard way (or know from reading the John Deere manual(s)).

Better to have good information from you all than to guess my ways through rebuilding a 420 JD motor only to have it not run well at all.

Any and all advice will be greatly appreciated.

[Lavoy]

With few exceptions, here is what I do to any engine I do.
All components washed in a wash cabinet on tear down, and will get washed again by the machine shop as work is done.
Head is magged, trued, new guides, valves, springs, keepers, and hard seats.
Block is trued, bored, new cam bushings installed.
Crank is ground.
Rods are cut and resized, new wrist pin bushings.
New pistons, rings, pins, and retainers.
All new bearings and seals.
Tap all head bolt holes, and chase all head bolts.
All new bolts other than head and rod unless required.
Head gasket installed with Copper Spray a Gasket (Hylomar will work if you can find it)
Everything torqued to spec and assembled with Lucas oil stabilizer.
Spin engine, no plugs, no ignition until oil pressure registers.
All new plugs, points, coil, wires, condenser.
New water pump.
If I have the crawler here, engine is run in on the dyno for at least an hour, typically on Deere Break In Oil.
Set timing, RPM, carb, and such while on the dyno.
Lavoy

[Cardinal]

Lavoy:

EVERYTHING on your list is what I would normally do on a SBC )small block Chevy).

One thing that I learned is to be very careful when "chasing" the treads out with a tap is not to try to inadvertently cut new threads. It is VERY important to keep the tap aligned to the hole/threads so that you don't under cut (make the threads too deep) which can weaken the threads.

One point that escapes most people is putting hardened valve seats in under the valves. It cannot be stressed enough that with the original valve seats will NOT last very long against today's unleaded fuels. Years ago you didn't need hardened valve seats because the TEL (tetra ethel lead) lubricated the valve seats. Now that we have unleaded gasoline, the seats are erroded away = poor valve seal = lost power.

[Cardinal]

Head gasket installed with Copper Spray a Gasket (Hylomar will work if you can find it)

I've used both Coppery Spray A Gasket and aluminum paint on steel head gaskets (SBC's use Felpro 1904 http://www.jegs.com/i/Fel-Pro/375/1094/10002/-1or GM originals are all steel). It is MANDITORY to use some form of sealant on them or eventually they'll leak.

[Lavoy]

Back before I used anything on head gaskets, I pulled a head on our 40 three times in one day trying to get it to seal. Both the head and block had been planed so they were flat, but still no luck. Shot a coating or Hylomar on both sides, never touched it again. Hard learned lesson, but never made that mistake again.
Lavoy

[Cardinal]

Lavoy:

Been there, done that, and HATED it! Back in the dark ages when there were only steel head gaskets (no composite gaskest back then), my parents had a 1959 Rambler American with a flat head six in it.

Dad blew the head gasket on it and had a local yokle fix it instead of letting me have a crack at it. The "professional" charged my dad for planeing the head along with a head gasket.

Wouldn't you know it, I'm driving the car and went to pass someone, shifted it into 2nd (three on the tree) got just up to where I was beside the car I was passing and the head gasket blows AGAIN!

This time (because I had the car when it blew, dad told me to fix it. BTW, I was 16 at the time (a couple of weeks ago! LOL!).

I could NOT get the head off of the block! Went next door to Wheeler's Collision and asked Dave Hartz (their head mechanic) what I was doing wrong. He said, "put the nuts back on the head studs, and start it up. The compression will blow the head off of the block". Did and done.

I looked at the head and it had the OLD head gasket on it with shelack (sp?) all over it AND it hadn't been planed at all!

I took the head to Rose Units, they planed the head, sold me a new steel shim head gasket, and told me to spray it with aluminum paint on both sides.

Put that all back together and MAN would that little flathead six run with that shaved head on it. You might say that was how I got started in building fast cars and busting my knuckles on cars and trucks.

[Lavoy]

It's funny, you hear about all the disreputable mechanics nowaday, looks like they have been around for a long time.
Lavoy

[Cardinal]

Disreputable mechanics have been around since Grogg invented the wheel and had to find somebody to fix it! LOL!

The "problem" with today is that everyone is out for the fast, easy, and "cheap" (not to be confused with inexpensive) fix.

My dad firmly believed that ANY job worth doing was worth doing right (the first time). It makes me laugh when you see companies say "our new policy is to do it right the first time". That tells me, "then you were doing a half aXX job till you got caught so now I'm supposed to trust you to do what you should have been doing in the first place". What a way to run an airline!