When to rebuild?

[Paul in Edmonton]

How do you know when it's time to rebuild an engine?

Is low oil pressure a key factor? Or is that just the oil pump?

My tractor has good pressure when it's cold, but gets lower than I'd like when it's hot.

Yesterday I was plowing snow for a couple hours in -22°C (-8°F) weather. At that temperature, I had to use my tiger torch to heat the oil pan enough to allow the engine to turn over at fast enough to start. (It'll start without preheat at -10°C but clearly not at -22!) It then had 30+ psi of pressure. A couple hours later, it was maybe 15 psi at idle and just over 20 at full throttle. In summer it will drop below 10 psi when it warms up.

Last time I checked compression, all four cylinders were somewhere around 100.

-Paul

 

[NOXJohn]

The time to rebuild is when you have the time and money to do it. I had a 1949 8N that had an oil pressure and compression like yours and I ran it hard for another 20 years. These are tough old machines. As long as you can get them to start and maintain at least a couple of pounds of oil pressure when hot they will run a long time without any major damage to the engine.

 

[old]

15 psi when warm and at idle you should be extra happy since it is common to have one that has around 5psi when warm and those run til the cows come home. You got bragging rights there. As for time to rebuild that is when you have NO oil pressure when warm or when you start it up and walk away you can not find it due to the smoke cloud it has made or you have an engine knock or less then 90PSI compression or you just want to spend $1500 plus

 

[Dell (WA)]

Paul........ya heated the WRONG thing with yer tiger torch. HEAT yer CARBURETOR. Why? The very act of carburation draws HEAT outta the surrounding air. Ittza LAW; atomization Law.

Yer complaint about oil pressure changing with temperature is NORMAL, its called VISCOSITY factor. That is why they make multi-viscosity oil like 10-30. (which is 10wt oil plus temperature sensitive additives that make it act like 30wt oil) Me? I run 20-50wt oil all year round.

The decision to when rebuild an engine is usually made when it won't start eazily. Ford specs: 90psi min (dry) NEW engine is about 125psi. Ford oil is pressure regulated at about 35psi. Your pressure limiting spring may be weak iff'n you gitt 15psi when hot. ........HTH, oily Dell

 

[TheOldHokie]

(quoted from post at 13:33:52 12/10/12) How do you know when it's time to rebuild an engine?

Is low oil pressure a key factor? Or is that just the oil pump?

My tractor has good pressure when it's cold, but gets lower than I'd like when it's hot.

Yesterday I was plowing snow for a couple hours in -22°C (-8°F) weather. At that temperature, I had to use my tiger torch to heat the oil pan enough to allow the engine to turn over at fast enough to start. (It'll start without preheat at -10°C but clearly not at -22!) It then had 30+ psi of pressure. A couple hours later, it was maybe 15 psi at idle and just over 20 at full throttle. In summer it will drop below 10 psi when it warms up.

Last time I checked compression, all four cylinders were somewhere around 100.

-Paul

With those ambient temperatures you need a [u:46903dc6b6][b:46903dc6b6]really good[/b:46903dc6b6][/u:46903dc6b6] cold weather oil - some thing you can spin over without a torch ;-) If you can afford the $7/qt price tag a quality SAE 0W40 would make your and your tractor's lives a lot easier.

Hot oil pressure below 10 PSI is more than a little minimal and a sure sign you have excessivley wide clearances somewhere inside. It's a low RPM flathead and as such all you really need is enough oil pressure to keep the beaaings supplied and provide a modest spritz for the cylinder walls. But I would be looking at some lower end service if not a full overhauls in the not too distant future.

TOH

 

[Paul in Edmonton]

Don't worry Dell, I did hit the carburetor and intake manifold briefly with the torch as well. (Gotta be careful flaming something that's full of gasoline!) But I maintain that there's no way it would have started without heating the oil first. With a cold pan, the thing turned over *really* slowly.

And of course I know that heat reduces viscosity--that's WHY I heated the oil pan. I posted the numbers for people's opinions on whether it needs a rebuild. If people are saying 2-5 psi is fine when warm, then I'll hold off on the rebuild for a while.

-Paul

 

[Paul in Edmonton]

With those ambient temperatures you need a [u:51018231cc][b:51018231cc]really good[/b:51018231cc][/u:51018231cc] cold weather oil - some thing you can spin over without a torch ;-) If you can afford the $7/qt price tag a quality SAE 0W40 would make your and your tractor's lives a lot easier.

TOH, It already has 0W40! ($60 worth, IIRC.) Specifically chosen to make it easier to start cold but keep pressures somewhat reasonable when hot. But even that is a bit thick at -22°C for the old 6V starter. (Perhaps I should have tried starting it with 12V...)

-Paul

 

[TheOldHokie]

(quoted from post at 14:37:43 12/10/12)

With those ambient temperatures you need a [u:7e907fce98][b:7e907fce98]really good[/b:7e907fce98][/u:7e907fce98] cold weather oil - some thing you can spin over without a torch ;-) If you can afford the $7/qt price tag a quality SAE 0W40 would make your and your tractor's lives a lot easier.

TOH, It already has 0W40! ($60 worth, IIRC.) Specifically chosen to make it easier to start cold but keep pressures somewhat reasonable when hot. But even that is a bit thick at -22°C for the old 6V starter. (Perhaps I should have tried starting it with 12V...)

-Paul

Yes - I recall your earlier post. Sounds like you also need 12V AND a block heater to go with the SAE 0W40!! Those are some chilly numbers.....

TOH

PS> I think I'd opt for some good old fashion heat tape on that manifold and keep the open flames well away.....

PPS> My grandfather has been known to build a fire and push the tractor over it after it burned down to coals.

 

[old-9]

I agree with Dell on the heat,however I heat up the manifold to warm to touch. And it usualy started. That was before my rebuild and retirement, now when it is that cold I drink more coffee.(or CC)
joe

 

[Paul in Edmonton]

Block heater and heat tape are nice ideas. Unfortunately, there's no electricity at my cabin where I keep the tractor for plowing the drive.

The forecast yesterday said it was going to warm up to perhaps -15°C by after lunch, and -8°C by evening. Since the tractor started a week or two ago at -10°C or -12°C without any heat input, that wouldn't have been a problem. The forecast was wrong. It was -22°C when we got there, and -22°C when we left. On the bright side, it could have been worse. The min-max thermometer on the cabin said it had been as low as -38°C since I last reset it a few weeks ago.

But the drive needed to be plowed. If I let it get too deep, it'll be too much for the old 8N to handle.

-Paul

 

[Anonymous-0]

Your oil pressure is just fine. If it's going
through oil faster than you can add it or smoking
like a chimney is when to look at a rebuild. I
don't think the people on here understand what a
tiger torch is. It's a big propane torch/weed
burner that is usually used for preheating thick
steel prior to welding. I wouldn't direct the blue
flame near anything! It is very common to use a
tiger torch to heat machines in really cold
temperatures. Get a piece of pipe about 3 or 4 ft.
long and an elbow. Stove pipe will even work if
you can prop the torch not to hit it directly with
the flame. Place the elbow under the oil pan so
just the heat comes up under the engine. You'll
probably barely have to open the torch have a lot
of heat. Check that's it's not too hot with your
hand but still thawing the tractor out. Probably
only need 10 minutes or so to warm it up.

 

[Paul in Edmonton]

I
don't think the people on here understand what a
tiger torch is. It's a big propane torch/weed
burner that is usually used for preheating thick
steel prior to welding.

Honestly, I don't use a real Tiger Torch. I use a "Mr. Heater" version like this: http://www.mrheater.com/Product2.aspx?id=37.

But they're both rated to something like 300,000 btu/hr. (A heck of a lot more than a little torch on a 1 lb propane bottle.)

But whatever type of torch used, the output is seriously dependent on temperature. At -22°C, a propane tank has only 18 psi in it, compared to 107 psi at +20°C. That 300,000 btu torch is putting out only a fraction of that at the temperatures I'm using it at.

-Paul

 

[Mr. T. Minnesota]

Paul,
Do you have access to a 12 volt battery? Jump start it with the 12 volts to get it to spin a little faster. Did this on a 2n with a 6 volt electrical system. DO NOT ENGAGE THE STARTER SWITCH!!! They say it does not make any difference on polarity, but I connect the positive to ground and the negative to starter post. Let her spin. Did this on an R2 Cat 30 miles from the Canadian border last winter that had a 6 volt starting and electrical charging system.
It works!!
Hope this helps!!
Mr. T. Minnesota

 

[old]

A simple generator set up say 2500 watts or even an inverter under the hood of your truck would do well on a block heater. 30 minutes or so sure does wonders when it comes to starting a cold engine

 

[Paul in Edmonton]

(quoted from post at 03:03:24 12/11/12) A simple generator set up say 2500 watts or even an inverter under the hood of your truck would do well on a block heater. 30 minutes or so sure does wonders when it comes to starting a cold engine

Perhaps, but that means getting the generator started. It doesn't like -22°C any more than the tractor does. (And I don't have a 2500 W inverter.)

-Paul

 

[Bob Huntress]

Paul, all things considered your oil pressure isn't that bad. If it were me, I'ld consider a block heater and possible a straight 50 weight oil. Now, I am way down south, and the temp is nowhere near that cold, which may cause me to not use the 50 weight oil. You could pull a few more psi if you are using 10w30 or 15w40 currently, but, if you are not going to use a block heater, don't make the change in your oil. My point, however is that your oil pressure isn't bad.