V8 difference 307 or 350 ???

[brawley]

Im looking at a 1971 parts truck , I was told it has a V8 in it, before I take the ride over to look, how can I tell by looking at the engine weather its a 350 or 307, I can look up numbers, but wanted to see if you can tell by looking at engine??

[landy]

Since the same block is used for the 307 and 350 (and for many other small blocks as well), I don't think you can tell just be looking at them.

[jocko]

not that this will help you tell by looking - but if there is no engine listed on the SPID (and it has an "E" code vice an "S" code on the SPID), the base V8 was the 307. If it came with a 350, it would be listed on the SPID. Again, this doesn't guarantee the motor hasn't been swapped, just helps you confirm what it "should" have in it - or, at least, what it would have had from the factory.

[Mikeeal33]

Did any 350's come with a 2-barrel? I know the 307's did.

[brawley]

thanks for the info about the SPID, that helps....any info on the 307's im thinking about swaping out my 250 inline, not sure if that's much of an improvement or not....

[King Cary]

Look at the harmonic balancer, there is a size difference. Google 307 harmonic balancer and 350 harmonic balancer, that way you will see what I'm talking about and be able to spot the difference.

[69GMCLonghorn]

Someone touched on the carb... There were 2 barrel 350's, but NO 4 barrel 307's. So if it appears to be all stock and has a 4 barrel carb, it is a 350 (or something other than a 307).

[69GMCLonghorn]

Originally Posted by brawley

thanks for the info about the SPID, that helps....any info on the 307's im thinking about swaping out my 250 inline, not sure if that's much of an improvement or not....

Lots of people consider the 307's to be boat anchors because they're not as powerful as a 350. I'm not in that "boat" so to speak. No, they don't have the power of a 350 but they are good engines, and will definitely be a big improvement over a 250 I6. You can put a small 4 barrel and headers on a 307, get decent power, and better mileage than a 350 (maybe close to what your I6 gets since it won't be working as hard!). Just food for thought.

[54blackhornet]

I have a 71 C/20 with the original 307. It sat for twenty years inside a grain elevator building before I bought it. After rebuilding the two barrel carb and installing a HEI the engine runs like a sewing machine. Does not smoke or burn a drop of oil in 3000 miles. I believe the 307 receives bad reviews because the 350 is so much more common today. It’s also very easy on fuel. I use the truck strictly for bringing in fire wood. The low first gear in the original four speed is perfect when it’s loaded with wood.