Rebuild Advice
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Rebuild Advice
I am prepping to rebuild the 300 in my 1980 Explorer. The truck has a bad leak at the rear main which I think began a few years ago when the choke stuck open and dumped a lot of gas into the system. Anyway, I need the ol' girl back on line to help with my business and have been looking for a rebuild guide for these motors. I can find lots for the big and small block V8s but info on the 300. Any advice? I am looking to put it back to stock -- fuel efficient, dependable and fun is all I am after. For some reason this truck is the only that truly makes me smile when I take it out.
My folks have always said that the truck got 25-29 on the highway when new (the speed limit was slower then too) so I am hoping to get something close to that.
I also want to go through the brake system (new lines mostly) and change out all the fluids since it has been sitting for about 3 years.
My folks have always said that the truck got 25-29 on the highway when new (the speed limit was slower then too) so I am hoping to get something close to that. I also want to go through the brake system (new lines mostly) and change out all the fluids since it has been sitting for about 3 years.
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Joined: Dec 2007
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From: Boise, Idaho
Sounds like a fun project, and a great engine to do it with. Not sure on a guide for rebuilding it (although there's plenty on here that rebuild them, so they may be able to guide you).
However, I wouldn't hold my breath for 25 - 29 mpg for anything. There's been lots of discussions over the years on fuel mileage and the consensus is generally 20 - 22 is the mark to beat, no matter how slow and steady you drive. If you hit that, you're doing great. Still commendable considering that the V8s shout for joy at 12 - 15.
The only mod I'd recommend on a "stock" rebuild is some head work. They were sand cast and made as fast as Ford could put them out, so they suffer from a lot of casting junk and such. Some cleaning up and smoothening out may merit a little gas mileage and some free power, as well as less work on the part of the engine.
Have fun!
However, I wouldn't hold my breath for 25 - 29 mpg for anything. There's been lots of discussions over the years on fuel mileage and the consensus is generally 20 - 22 is the mark to beat, no matter how slow and steady you drive. If you hit that, you're doing great.
Still commendable considering that the V8s shout for joy at 12 - 15.The only mod I'd recommend on a "stock" rebuild is some head work. They were sand cast and made as fast as Ford could put them out, so they suffer from a lot of casting junk and such. Some cleaning up and smoothening out may merit a little gas mileage and some free power, as well as less work on the part of the engine.
Have fun!
Elder User
Joined: Feb 2010
Posts: 546
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From: Reading, PA
i second the fuel mileage comment that abandoned bronco brought up. On top of higher speed limits the formulations of fuel have changed greatly over the past ten years. The addition of ethanol alone is enough to reduce fuel economy in and of itself by about 10% on most engines (some exceptions may be flex fuel vehicles designed to run gas ethanol or both).
22 mpg would be a happy place for me however mine even with 3.08 gears and an AOD my old girl is getting up in years and hurting in that respect (although i hope to remedy it soon myself).
Might i suggest if you don't need to do a full rebuild (i.e. if it's not really bad AND not making any horrible noises) just pullin her apart and checking her out. You may be able to simply replace all your gaskets and rering and get some good life out of her yet. These engines are tough and have been known to go (with proper maintenence) 300,000 miles without a rebuild. It would save you some money at least depending on the condition.
22 mpg would be a happy place for me however mine even with 3.08 gears and an AOD my old girl is getting up in years and hurting in that respect (although i hope to remedy it soon myself).
Might i suggest if you don't need to do a full rebuild (i.e. if it's not really bad AND not making any horrible noises) just pullin her apart and checking her out. You may be able to simply replace all your gaskets and rering and get some good life out of her yet. These engines are tough and have been known to go (with proper maintenence) 300,000 miles without a rebuild. It would save you some money at least depending on the condition.
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Mike,
I like your thought on giving the motor the once over and seeing what it really needs before doing a full blown rebuild. Is it possible to do a solid job of this with the motor in the frame? I have been reading on how to change the rear main and I am thinking this might be a better use of my dollars right now. My thought is pull the pan, change the rear main, oil pump (I have a new one in hand), and the gaskets then fire her up and see what I have left to look at.
I like your thought on giving the motor the once over and seeing what it really needs before doing a full blown rebuild. Is it possible to do a solid job of this with the motor in the frame? I have been reading on how to change the rear main and I am thinking this might be a better use of my dollars right now. My thought is pull the pan, change the rear main, oil pump (I have a new one in hand), and the gaskets then fire her up and see what I have left to look at.
Lead Driver
Joined: Mar 2008
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From: Near Los Angeles
Depending on the miles on the engine, I would proceed. If it has a lot of miles, then you may go to all that work and find things start going out one by one, burning oil, needs a valve job, rod knocking ...etc. Doing a complete rebuild would be insurance. And remember the radiator. Poor cooling is the #1 cause of rebuilt engines failing.
If you do the partial option, I'd be sure to check the bearings while down there. Plasti guage a couple and see what you have. Check the end play on the crank, and that will tell you the condition of the thrust bearings. Spray the oil pump bolt holes with brake cleaner, blow them out with air, and use thread locker on the bolt threads when re installing. Torque to spec. Note: It is a bitch to change the rear main with crank in. Learn to curse in a foreign language, then no one will complain.
Good luck.
If you do the partial option, I'd be sure to check the bearings while down there. Plasti guage a couple and see what you have. Check the end play on the crank, and that will tell you the condition of the thrust bearings. Spray the oil pump bolt holes with brake cleaner, blow them out with air, and use thread locker on the bolt threads when re installing. Torque to spec. Note: It is a bitch to change the rear main with crank in. Learn to curse in a foreign language, then no one will complain.
Good luck.
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Joined: Feb 2010
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From: Reading, PA
x2 on while you have it open check everything out. I wouldn't proceed to spend ANY money on it untill you know what you've got. But if it is low mileage and looks good internally you can make your decision based on what you feel is best. It's all about how much money you want to put into it now. If you have the money and you would like to have the insurance rebuild it anyway. If you are a little tight on funds and you wanna see what happens then i would change what you need and check to make sure there isn't anything catastrophic already in the works and run it till it NEEDS to be rebuilt. but that's just me because i'm a cheap *** LOL.
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Before '84, I believe, Explorer was a truck badge, like Custom, Ranger, etc. When they went to XL, XLT, etc., they made the Explorer and Ranger vehicles of their own.
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