What can be said about the 307 small block?

[Gregski]

I usually post in the Third Gen (73-87) section as I have a '74 GMC (which I love dearly) so don't tell it I'm looking at the Second Gen (67-72) trucks, LOL

Anyway I thought they came with 283, 327 or 350 small blocks, but then I see on the Wiki there was a 307. So I got to ask what can you tell me about this engine? It appears to have had a short life span 68-73. Honestly I have never heard of the 307, but than again I aint no expert by any means

[hamjet]

307s were popular in smaller body cars like the camaros, novas, some full size cars and pickum ups. They only came with 2 bbl carbs as far as I know, around 200 HP. it got you around town pretty well. I remember in my young years, (18-27) they were known to spin bearings, but that could be from everyone I knew beat the snot out of them. I have one in my 69 c-10 and it runs well. In my humble opinion I felt they were a fine engine that got the job done...

[hugger6933]

They were economical compared to the 350 of the time. A good bit less power but they were a small block and respond well to a slight bit of modification like a [little bit] bigger cam and headers and intake manifold with 4 bbl. Lot of guys that mod them say that it increases the gas mpg of the motor, but those same mods could increase a 350 in the mpg category as well. Jim

[MARKDTN]

Smaller bore than a 350, same stroke as a 327. Decent engine. Similar strategy as a 305 in the later vehicles. It's a small-block so same reliability as a 350 really. I wouldn't NOT buy a truck because of a 307 but I wouldn't go looking for one either.

[Gregski]

Originally Posted by MARKDTN

... I wouldn't NOT buy a truck because of a 307 but I wouldn't go looking for one either.

Beautifully summed up!!! thank you, I get what you mean

[ksshane]

I had one in my first c10, a 1970 and it ran just fine even with the 2bbl carb on it.

[GRX]

The 307 is a great engine. However, being an under-square design (bore smaller than stroke) they do not lend themselves well to performance applications. Which is why you do not see many hot 307 builds.

[turp mcspray]

Chevy stroked the 283 in search of more torque.

[TobyArnot]

Smog Motor

[FrankenCub]

I have a 307 in my truck now, it's been a real good engine. As others have pointed out it's lacking of power but I can't complain. It does what I ask of it and I do a lot of fire wood hauling. For now, it will be replaced an a couple weeks. I also had one in a '69 Chevelle that I beat the livin crap out of, the car long deceased before the engine.

[65standard]

The 307 isn't popular because it was never offered in a high performance version from the factory.


But that doesn't make it a bad motor. Just look at it as a 283 stroker and envision it with the same potential performance upgrades as any motor.

[1972RedNeck]

Originally Posted by TobyArnot

Smog Motor

1968 = probably not

[GRADYS Performance]

Actually 1968 was the beginning for smog motors. In a small block that is the year they went to PCV valves and did away with road draft crankcase ventilation.

[special-K]

The 307 is a great motor. I never heard of them known for spinning bearings. Why would that be? In fact, they have a reputaion for out lasting 350s. I have had great life from them. I threw a timing chain (actually, my boss borrowed the truck and did me the favor) before I replaced it. Bent valves helped me to decide to rebuild, since it ad 130k on it. There was no detectable ridge in the cylinders and the crank required no machining. This was in a K/20 4spd mountain farm truck with 4.57 rears that earned it's keep all it's life.
Guys who are all about cubic inches have no use for them...give them to me. It's a durable AND economical engine. When I rebuilt the one I mentioned, I put an RV cam in it, 64cc 1.94 exh heads, OEM cast iron 4bbl intake, HEI, and Holley 450 CFM carb. It pulled better than a 350 and got 13+ mpg with the 4.57s, 37/14.50-16.5s, utility bed w/pipe rack, tools, and materials. That truck turned a lot of heads when they saw it winding tight slinging four rooster tails of mud. Like I said, great motors

[Gregski]

Originally Posted by 1972RedNeck

1968 = probably not

that's what I thought, always associated the mid 70's with the birth of the Catalytic converter and the Dark Ages of SMOG

[imjeff]

Had one in my 69 Chevelle. My wife daily drove it a few years and I daily drove it a few more. Sold the car last year and the new owner loves it. Stock motor that will still twist the tires, sounds good and got good mileage. Definitely NOT a "smog" motor.

[special-K]

Originally Posted by Gregski

that's what I thought, always associated the mid 70's with the birth of the Catalytic converter and the Dark Ages of SMOG

The dark ages of smog began to end in '65 for California and by 1975 the Fed mandated catalytic convertors on cars and 1/2t trucks. We hate to be regulated, but no one thought of air pollution when they started making cars. Our air is much better now, thanks to emissions control. Grady is correct with his statements. I always figured all V8 displacements increased due to added emissions/drop in compression to compensate.

[Sammys70]

got one if your looking

[gvw5400]

For what it's worth , the 307 is an over-square engine design. The bore is 3.875" (283 bore) and the stroke is 3.250" (327 stroke). It is a good engine that can be built up like any small block. In fact the 307's bore is larger then the bore of a 305.
307= 3.875"
305= 3.736"
All the Best , Dirk

[Robznob11]

Boat anchor... But every back yard has a good 350 to replace it with

[Gregski]

Originally Posted by special-K

Our air is much better now, thanks to emissions control.

I must disagree, I think the air is the worst it has ever been,

now would it have been worse without these mandates sure, but its not better than in 1965 nor how it was in 1975 or 85 for that matter

[special-K]

Originally Posted by Robznob11

Boat anchor... But every back yard has a good 350 to replace it with

Please shre your experience so we can all learn...or at lest know what yu base it on, other than rumor and hear-say. In many ways the 307 is a better motor than a 350 and I have facts to back it up. Bigger power? Hell no! That should be obvious to anyone. Enough power? Hell yes! From my experience, the smallest displacement engines of same design are the most durable. That is important to some of us.

Originally Posted by Gregski

I must disagree, I think the air is the worst it has ever been,

now would it have been worse without these mandates sure, but its not better than in 1965 nor how it was in 1975 or 85 for that matter

Waiting for facts. I "know" the air is cleaner and so do the experts in the sciences. Smog was terrible before these mandates. That's why California did it first. They had to. Ask anyone who was around before and ask them if it's better. And, you do realize how much the population has grown and how we have now become a dual-income society, right? Or, maybe you noticed how much worse traffic has become in the years since the regs were introduced...with all the expanded roadways and a completed interstate system. Start multiplying the '60s figures and just imagine how bad the air would now be.
I'm not in love with the regulations either. and, I have always known the Fed hits us little people with this stuff while overlooking larger sources of pollution by "the money". Want to know how much I like living with emissions regs? I have never owned a vehicle where it is required. Between old vehicles, diesels, to late models old enough to fly under the radar, I have never rolled through a test station in one of mine. My daily driver I bought in December, registered it historic in January as soon as it qualified for historic. I carry regular insurance on it. Yes, when I was married my wife had new vehicles that ran through, but no worries with those. I also live far from the city in the fresh(er) country air at a higher elevation than the city and burbs.

[motorcritter]

The only reason the 307 is coming out of the '70 C10 is that it's tired and smokes, plus, I'm done with carburettors. I haven't decided what will go in there, I've got a TBI setup, another TPI engine, an LT1 w/ 4L60E, and a couple of Benz diesels (OM 616 & OM 617). If I could get a driveline out of a Benz Sprinter van for less than the giant money they command, I'd do one in a heartbeat. No problems with a 307, or a 305, for that matter. An LSx is a whole 'nuther thing, altogether. I just want more power, no carbs, and 'newer stuff'. Everybody's got their own preferences, and that's what makes this group of folks great!
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[Robznob11]

Well you hit it on the head, no power and with the restraints of the design of the motor there is no reason to throw money at it. You may as well fork out 500 bucks for a solid 350 foundation. Also the heads and intake that come on them are not good for anything. If you want a stock motor that lacks power but is reliable ok they will work. But most guys always wish they had a little more zip and there is no use in spending money on a 307 when 500$ can double your power and options.

[67 cst swb]

Every 307 I have ever had, I took apart, kept the crank put it in a 350 block and built a large journal 327. Ok, so maybe twice I have done this.