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I found 68 Impala with 307 engine that's for sale. It is all original car with A/C. Nothing has been rebuild or changed (which is good and bad). I have browsed thru posts here but I do not see a lot of info about 307 block. Is it any good? I have no funds now to replace engine and having close to stock car is ok with me but if this particular engine is no good, I will probably just move on. Are spare parts easy to find just in case it needs a rebuild?

Thanks.
 

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If the motor runs it is. A 307 is a 283 bore with a 327 crank. Because this is a 1968 block it uses the large journal so if you replace the block with a 350 4.00 inch bore block you can build a 327 instead of a 307 which is better than a 307 because it breathes better with a bigger bore. The 307 crank in a 400 cubic inch small block (you would need to sleeve the bearings) would give you a 350 cubic inch motor the way the general should have built it. 4.125" bore, 3.25" stroke. Makes for a zippy motor. None of these can be rebuilt as cheaply as buying a crate motor, but they are fun to think about.

Big Dave
 

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The 307 is actually my least favorite old type engine, BUT they are still good engines. The same engine builder friend of mine that I mentioned in the other post, convinced me (again) that they are good. After mentioning that they weren't my favorite, he then pointed out that they are the exact same engine as the 327 except they have a little smaller bore. Well he was right again. I bought my '72 C-10 Pick-up with a 307, 3-Speed when it had 95,000 original miles. That was just about 9 years ago and it now has 152,000. Still runs great.

The only thing I would say about it tho, is don't abused it and maintain it regularly. Changing the oil and filter often is very important.

Parts are no problem to find for any Small Block Chevy.

Bill
 

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Discussion Starter #5
Thanks for all the replies. If I get the 68 Impala, I am not going to turn it into a performance car. My goal is to have nice daily cruiser with sort of good mileage. So my concern is mostly if the 307 engine is capable of moving the 3700lbs car. And by that I do not mean spinning tires but decent acceleration would be nice :)
 

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Now we are talking about two mutually exclusive things, unless you are going to install a new LS-3 Cadillac engine with displacement on demand technology in your Impala. It takes it from a fire breathing 6.2 liter motor down to a 3.1L four cylinder by turning on or off cylinders on the fly. The motor only uses as much engine as it needs to meet the requirements of your right foot. That coupled with an overdrive six speed transmission and you have the best of both worlds performance and economy.

Big Dave
 

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Discussion Starter #7
Yeah, but I would need to keep the car stock (307) due to lack of funds for engine transplant. By "decent acceleration" I did not mean fast but just decent. I can't express it more clearly. I currently drive 6 cyl. Buick with 3800 engine and 205 hp under the hood and this car, even for being in "grandma's car" category is fast with good pickup. On the other hand, I used to have 93 Pontiac Sunbird with 2.0L engine (something around 115hp) and this car was slow as molasses even with its 4 speed manual transmission.

So if 307 after rebuild can get me around 16-18mpg with decent acceleration I am all set. I just do not know if it is possible with this engine.
 

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Me either. I would not rebuild it unless it needed a rebuild as you can buy a brand new 350 cube crate motor for the price of the rebuild.

Big Dave
 

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If you do keep the 307, which of course will keep the car all original, the engine should bring you enough accelleration to be happy and should bring the mileage that you have listed, especially if you keep it "super-tuned" and drive it sensibly. The 307 in my truck can pull a good load and I am all around satisfied with it.

As a side note, the 307 can sometimes get confused with the newer 305. I don't think too many will dis-agree when I say the 307 is a much better engine.

By the way, if you buy this car, bring it out on the Hi-way for a test drive first.

Bill
 

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The only motor worse than the 305 is the 262 cid V-8 they built for one year and stuck in an Impala. The bores in that motor are the size of a quarter, which isn't a problem if we are talking a V-16 motor, but in a V-8 it is the pits. Like I said the 307 is just a stroked 283 which was one of Chevy's better motors. Not too strong on torque, but it would rev to the moon so it was quick with the right gears.

Big Dave
 

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The 307 with a 2 barrel carb is a good set up. Easy on gas, enough pep to get you around. It is a vast improvement on the 283 regarding the PCV system it offers. I always liked them left alone bone stock, very reliable and smooth running as well.

Bob
 

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I have had three cars with a 307 and everyone of them had the intake manifold gasket go out on them in under 70,000 miles. The cars were low mileage extremely well cared for cars. The 80 Cutlas Supreme and the 84 Buick Electra woody wagon were repaired in a repair shop and were never the same. The 35 Chevy truck I repaired myself and had no problems afterwards. If you don't want a shop to get their hands on your car and ruin it forever you might want to think twice about the GM 307 in my opinion.
 

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Biggest problem with a 307 Olds engine is the block. It is very weak and has been known to split in half through the lifter valley yielding two separate four cylinders that share a broken crank. If you want to see it happen more quickly than a life of dragging around a 5300 pound Olds just add nitrous. The 5A head is better than the smog head 7A that dropped the compression ratio below 7.6:1.

I haven't seen a lot of leaking intake gaskets, But if I had to guess it would be due to over heating on a low mileage engine and the 70,000+ miles on an older engine from heat cycles. The engine was designed to improve Oldsmobile's CAFE numbers but because it was under powered for the load it ran wide open most of it's life (not recommended for better mileage). In fact I would bet if you pulled the 307 and installed an Olds 455 your mileage would improve.

Big Dave
 
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