another engine question

[americanhorses]

My 73' 302 it original. It has been redone 3 times. It's now at .40

I've been told that's it...your done. It only has 10k on it, but I'm looking into the future. Is this motor really done when it give out this time?

 

[cldonley]

Some motors can go to .060" over, I don't know if your 302 is one of them. It depends on the cylinder wall thickness, and whether it will have a smoot finish after machining. In other words, even if there's enough material to .060" over, the quality of the casting may not be good enough. Rebuilding doesn't mean you have to bore the cylinders though. Most times you can just hone, replace rings and go another gazillion miles. There's also no need to bore for performance, the gain would be minimal. Also, if you don't bore you don't necessarily have to replace pistons. As long as you keep it full of oil and don't overheat, our Ford motors will go a very long time. So, in short, no it isn't done!

 

[70_Steve]

I'm sure you'll get all kinds of responses from this.

What I got from my machinist is that the the issue with going larger than .040 is that, if the cylinder sleeves were not installed in the block exactly square with the deck, or just a hair off-center, then when going .060 over, a part of the cylinder sleeve may be too thin. This can be checked with an ultrasonic scanner before boring, to make sure there's enough material to bore safely to .060.

 

[Rustytruck]

Its Done or should be done. The government is killing your old design engine with bad fuel and now bad oil. Your better off upgrading to the new 5.0/5.8 roller cam motors when the time comes to spend big bucks. Those motors are going 200,000 miles on todays gas and oils. You can spend big bucks upgrading your block but why redesign the wheel when Ford already did it?

 

[americanhorses]

I was thinking that might be the case about the fuel being bad for the old motors. I've read some threads about the ethanol. Hell...in CA no telling what else...except water maybe.

 

[cldonley]

Ethanol is no good for seals, hoses, gaskets, nozzles and the like. Because alcohol is more likely to entrap moisture it can be harmful to metal parts if your vehicle does a lot of sitting. Water entrapment is bad for fuel line freezing too, which is why we've been able to keep it out of aviation gas (imagine fuel line freeze up at 21000 feet in a reciprocating engine airplane). But I haven't heard of any real evidence of damage to engine internals due to our government regulated gasoline. Bottom line is, if you take care of that 302 it'll go a very long time, and you will likely be able to rebuild without punching out the cylinders. I've honed and re-ringed many engines, airplanes and trucks, and run them long and hard without over sizing anything. Not that going to a 5.0 roller motor is a bad idea, it's just not the only option.

 

[Timmy390]

Unless the block is sonic checked, no one can say for SURE if it's done ot not. Thin is bad as it will run hot and easy to crack.

If it's all about having the original block, then sleeve that bad boy back to stock bore.

Tim

 

[englewoodcowboy]

If you are pressed to keep that block, you always have the option of getting it bored and having the cylinders sleeved. That would bring it back to its stock diameter. It's an expense but it's up to you and your preference and is another viable option.

 

[americanhorses]

Unless the block is sonic checked, no one can say for SURE if it's done ot not. Thin is bad as it will run hot and easy to crack.

If it's all about having the original block, then sleeve that bad boy back to stock bore.

Tim

I don't care about the orig. block being kept the Bronco. My thought was to get one of those fancy motors everyone keeps showing pics of. And dropping this one in an old ranchero.

 

[savage]

I just had mine rebuilt, and the machines bored it .60 over and said it would be fine, I question him about going that big, he check the block and said it would be fine.He's been building fords for over 40 plus years. But the block is a Mexican block so maybe that the reason it fine. So far its not running hot, and has a lot of low end torque.

 

[Rustytruck]

Ethanol is no good for seals, hoses, gaskets, nozzles and the like. Because alcohol is more likely to entrap moisture it can be harmful to metal parts if your vehicle does a lot of sitting. Water entrapment is bad for fuel line freezing too, which is why we've been able to keep it out of aviation gas (imagine fuel line freeze up at 21000 feet in a reciprocating engine airplane). But I haven't heard of any real evidence of damage to engine internals due to our government regulated gasoline. Bottom line is, if you take care of that 302 it'll go a very long time, and you will likely be able to rebuild without punching out the cylinders. I've honed and re-ringed many engines, airplanes and trucks, and run them long and hard without over sizing anything. Not that going to a 5.0 roller motor is a bad idea, it's just not the only option.

Prior to 1975 Ford used unhardened exhaust seats. With the removal of lead in gasoline in 1975 the absence of lead doesnt protect the hot exhaust valve seats and unhardened seats get accelerated wear. When rebuilding those heads it is recomended to move to hardened exhaust seats and stainless steel exhaust valves. Some motors have rotators on the exhaust valve retainers and those too are recomended to be removed. This work is expensive and unnessary if you move to a more modern engine. You can get a 5.0 core for less than the cost of upgrading one stock early head.

 

[73azbronco]

You can make any engine go another 100-10,000 miles, for under $500, but is that what you want? That's what crappy engine rebuilders shoot for, the 90 day wonder motor.

Best bang for buck is as low a mileage explorer 5.0 long block you can find. Check under valve covers, if it looks clean and or slightly yellowish, they used synthetic and I bet you can get 200,000 miles out of it. If it's full of gunk, move to next block.

 

[Broncobowsher]

.040, I would be done with that block. Doesn't mean it has been redone 3 times already. Often the first overbore is .030 and if that doesn't do it hit for the .040 overbore. Nowhere does it say you only get .010 per rebuild. I have had engines that more taper wear then that and were still running.

Not all shops, really not many, have the sonic thickness checker. These blocks were Fords thin wall castings to keep weight down. Means there isn't that much meat in the walls to start with. Add in 70's lacking of quality control and the core shift that these blocks got, those walls are getting pretty thin.

I find it funny how people call the modern fuel so bad. If you look back the old engines were 100k wonders. Typically by 100k they have already had one valve job and were ready for a rebuild. Odometers only went to 100k. As time goes on engines lasted longer. 100k is no big deal, often the factory crosshatch can still be seen on the cylinder walls. Oh, this is suppose to be the bad fuel and oils that kills engines? But they last so much longer now? At the same time the engines are more stressed, pushing higher and higher levels of HP for a given size and pushing heavier and heavier vehicles. Ah, your 40 year old rubber hose is rotting out, must be the modern fuel causing that.

 

[matts460]

Oh yes Mexican blocks are thicker metal. I have an Ford book that mentions them good score!

 

[cldonley]

Lead prevents detonation so you can have higher octane fuel. Unless you want to build a racing motor. Avoiding boring a block at rebuild is a good idea...the ones who say you have to bore it when you don't are the ones ripping people off, selling machining and parts you don't need

 

[matts460]

Ya I just got my 390 FE back together. My new donor was a complete 360 from a junk yard here in my town that only has 70's and back cars/trucks. It was 100k virgin complete engine. My machine shop tried to clean it up at .020 but it had to go .030 the ridge was just to deep. It was cool to tear it all down and find all original Ford componets, gaskets and bearings.