Hey guys,

I'm considering replacing the engine in my 1966 F-100 and I thought I would ask the forum for some advice on some replacement options. She currently has a 300 I6 in her that has been running very reliably, but the coolant system seems to be rotted out (judging from what I've seen replacing thermostats, etc) and she runs very hot when she has a load in the back, especially on warm days. The 300 I6 seems to be a (almost) bullet proof engine that gets decent gas mileage and will tow a little bit, but there must be some other bolt on options out there. Suggestions? And what are your reasons for the suggestion?

Thanks!

James

 

351w crate engine! (at least that's my dream). i don't have a reason. i just used to have a 63 with that engine and ran forever. mine has a 302 in it now. i'm still trying to get it going.

beautiful truck, btw.

 

The engines that will bolt up to your existing transmission are the 240-6, the 302 and the 351W.
However, you will need to consider accelerator linkage and exhaust issues (assuming you do not wish to downgrade to the 240).

If you want to change the entire drivetrain, all engine and transmission options offered in Ford trucks 1965 - 1979 will bolt into your '66 with minimum work.
You will be looking at exhaust, accelerator linkage, engine perch (mount) and driveshaft issues, depending on what option you choose.

Frankly, it sounds to me that you like your 300, and it merely has cooling problem. For all the time, trouble and money, it would be a lot simpler - and cheaper - to put in a new radiator, new water pump (check for rusted out impeller blades), and possibly a new engine. Or, just disassemble yours and have it hot tanked to remove internal rust and scale.

You can put a new 300, with new radiator and carburetor (as an example) much more easily than changing the drivetrain.

Having been there and done that, I think you are satisfied with what you have, it just needs some repair.

Best of luck.

 

Banjo Picker,

That's a really good point. I'm happy with the truck and totally spaced on the fact that an engine change would require new exhaust headers, more $$$, etc...I currently have a new water pump and a F-250 radiator (used) in her that I was told was in good shape. Looks like my only option left is hot tanking or replacing the engine. Will hot tanking remove scale and rust in the coolant lines in the block? That's what I think the problem is. I looked in there while changing the thermostat/water pump and it just looks like a rusted mess. I do not see heat leaving the block efficiently with that much rust in there.

Anyways, I can get a "re-manufactured" long block 300 I6 for $1150. Any idea what an engine installation would cost? (Assuming I remove the old 300 and replace it with a new 300.)

 

If you go the route to R&R the engine, I would shop around if you do not do it yourself-I can't really tell what local costs would be near you.

Some rust in the system won't cause any problem, unless you can wipe fingerfuls of sludge out of the cooling passages. It hurts the cooling more if the crud is in the radiator than if it is in the engine.

Some questions:
Is the thermostat installed correctly, with the spring side facing the engine?
Have you checked the temperature? What leads you to believe it is overheating? (Temperature gauge versus boiling over, for example.)
Are you using 50/50 mix of antifreeze and water? (100% antifreeze causes overheating.)
Have you checked coolant flow in the top of the radiator once the engine reaches operating temperature? You should see the coolant moving pretty quickly across the top of the radiator (with the cap off) once the engine reaches operating temperature.
Has the radiator been checked and-or boiled out for free-flowing cooling tubes?

Have you tried using a coolant cleaner and then had the system backflushed?
Have you tried this until the water runs clean after several attempts if necessary?
If there is accumulated rust sludge or silt in the radiator, that will hurt cooling more than if it is in the engine.

One more possibility - does it boil over and doesn't even seem to reach full operating temperatures? If so, then you have a different problem, one that is not a coolant or overheating one. Post back, though. It would be caused by compression gasses being forced into the cooling system, which over-pressurizes it so that it "blows" - but that's from the engine gasses, not heat. This is caused by a blown head gasket or cracked head (or something similar).

Hope this helps.

 

Keep the 300-6. It's the most reliable, long lived, service friendly engine Ford ever made. It's got plenty of torque for towing and they can be a gas sipper. I had a 78 E350 once with w 300-6 that got 18 mpg. I owned it 20 yrs ago and it is probably still running.

 

Couldn't agree more. Why not just get your current 300 I6 rebuilt? I currently have a FE 360 in my truck and I would swap it for a 300 I6 in a heartbeat if it didn't involve so much work / time / money.

 

I used a bottle of that prestone cooling system flush on mine not too long ago - the engine had set for at least two years with little use before I bought it a year ago. In any event, I put some in and drove it around a while and then flushed. I ended up repeating that process 3 times before semi-clear water came out. The first couple of batches were just flat out nasty. Remember this is not just cleaning out stuff in the engine, but probably the heater core as well.

 

I second the idea of performing a system flush over and over until you get clear water. Vinegar will cut rust but it takes a while but if you've got time and not a lot of funds, that might be a cheaper way to go and just buy 2 or 3 gallons of vinegar and replace whats in the engine now with it and run it that way for a week or so.

 

I have had 2 300 sixes (78 E150 and 91 F250 4x4). The mileage fell of on the 78 as it got older I think because of the carburetor (down from 22 to 17). I have been told that a 4 barrel intake and headers will really wake it up without a severe mileage penalty. They made the 300 six up until 96 or 97 so look for one in the wrecking yards. The newer ones are designed to run on unleaded gas.

 

I would absolutely stick with the 300 six, I personally have one in an 84 F150 that has nearly 500,000 miles on it and the only trouble I had was the timing gear has worn out 2 times over the course of that 500k. BUT if you really want a V8 I had a 66 F100 step-side in highschool that had a 351 cleveland in it and boy that thing was fast yet the fuel milage wasnt bad maybe 12-15 mpg.

 

Thanks for the input guys. I think the winner is a new 300 I6 if I can't figure out a way to get my cooling system to improve.

The mechanics of the coolant system are functioning correctly. The thermostat is installed correctly (you can feel the upper radiator hose heat up after the engine comes up to temp), I use a 50/50 mix of antifreeze/distilled water, and normally the temp gauge is right in the middle once the engine comes up to temp. Its only under heavy load or on hot days the system can't dump enough heat, so its a capacity issue.
I know there's a lot of scale build up in my block and in my mind there are a few things I could try before buying a new motor:

Flush the system with a cleaner or mild acid - Very good suggestion guys. I'll try a system flush prior to doing anything. I've been looking at white vinegar (some other guys mentioned it).

Replace the $50 used radiator with new - Since its possible the guy I bought it from was lying to me about the condition, I should try buying a new one before I change the motor.

If both of those fail to help (I wont know until summer), I'll start getting quotes for dropping a new 300 I6 in her with a new radiator.

Thanks!

J

 

Another option for a serious flush is Calgon Automatic Dishwasher soap (powder). Sounds crazy, I know, but I've used it a couple of times and you'll be surprised how well it works. Flush normally the best that you can, then drain and fill the system with water and 4oz of Calgon (half a cup). Run it a couple of heat cycles and then drain it and refill with fresh water. It'll be brown. Drive the truck for a day and then drain and refill again. It'll be brown again. You'll have to do this several times to get all the crud out and fully rinse the system. You may still need a new radiator, but either way, it'll cool better as the coolant makes better contact with the block and carries away the heat.