A friend is getting rid of a chevy 307, for a good price. It's in good shape but would need to be rebuilt for performance use. Are these engines any good. I was hoping for a 350 ci, but it's a good price.
It's for a weekend driver, so I would like to "push it" a little on the performance side. Is it worth it?

 

wasnt the 307 an olds motor ?

 

307 is what came stock in my 71 camaro if I remember right

think it was something like a 3.25x3.85 stroke bore configuration but don't hold that against me

don't know much about them but my dad seems to think they are throw away motors.
but again don't take my word it

 

if your wanting to "push it " performance wise then dont even think of that 307

its not that great of an engine

keep looking for a good 350....

 

don't waste your money, that 307 is only a big door-stop.

 

...unless you get it for free, then have fun doing burnouts or some equally zany thing with it until it blows up. Heck, use it as a rebuild-from-hell educational project. If it runs, it can't be totally useless, right?

 

The 307 is a great engine for what is was intended for. Family sedans. It isnt that great for performance because of the limited size of the bore. You can only fill so much air into the bore. Of course, there are probably some guys here who would say its great its great because of a short stroke, but thats BS. Dont waste your time on the swap.

 

Don't pay anymore then nothing or $-50-100, thats right make him pay you to take it. The heads will be the absolute worst, piles ever.

 

A Chevy 307 has a 3-1/4" stroke and a 3-7/8" bore. Many (most? some?) of the 307 blocks can be bored out to 4". This then becomes a 327, 4" bore by 3.25". Get a shop to sonic check the bore wall thickness. If it can be safely bored to 4" just do that and build a 327.

As to whether it can be bored to 4" the block casting number will tell the same. Just that I don't recall the proper casting number. Maybe mortec has the info.

The later year 283's were the same way. Cast as 4" bore blocks and only bored to 3-7/8". On a rebuild bore it to 4" and have yourself a 302.

RBob.

 

I don't think so, i believe that only the 283 had wall thick enough to bore to 4.0" Since the 307 and the 283 have completely different block i would say no.

 

Let me plug into the wayback machine.....................
The 302 is a 4in (327) block with a 283 crank (small journal)
except in 69 when they were LJ (about, work with me here)
the 283 is a 283..
I think the 307 is a 283 block with a 327 crank.
The 307 is a good everyday workhorse engine, it would respond to some of the same hop up stuff as other sbc but... and this is a big BUT, the other engines are inherently more suitable to hi performance use. Now keep in mind about 67-68 chevy went to large journal stuff so as I recall the 307 were all large journals.
That being said, the 307 saw a lot of drag strip use in injected rail dragsters (I don't know, the combination just worked, don't ask me why). The 283 .060 is a 301 (I think). I used to own one.

 

Look at it this way. Gm made the 302 by taking a 283 crank and sticking it in a 327 block. This was a good combo. Then after a year or two they looked around and said what are we gonna do with all of these piece of crap 283 blocks and 327 cranks? Thus was born the 307. Its all the crap left over. It sucks. Of course this probably isnt the real way it happened, but it is a humorous way to look at it.

 

Ha, thats pretty good. The explanation for the 305 must be even better

 

FWIW all 307 cranks were cast, while all 327 sjc's were forged.

 

Yes GM needed a good motor with decent performance and good emissions, ala 305. The 305 has a small bore and relatively long stroke. This makes for a more efficient burning engine and reduced emissions. It all had to do with the formation of Nox, and other oxides of nitrogen, that short stroke engines make more of. This is why if you look at most new engine designs they have long strokes and relatively small bores. The LS1 is one example.

 

maybe they were forged. The late large journal 327 cranks were cast. I have never seen a 327 small journal that were not forged but I wouldn't bet the bank on it.
I really love the explanation for the 307, that was great.

 

I thought the 305 story went like this:

A couple of GM engineers were sitting around having coffee one day when one of them said "you know, that 350 is pretty good, what can we do to screw it up?" One of the other engineers said 'I know we can change the bore to 3.75, which greatly limits its breathing capacity, and makes it near impossible to get big valves on it." The third one said "great, lets put it in the camaro!". Unfortunately, thier advice was taken

 

Hey i wouldn't complain a 305 is bigger than a 302. And the valves in 305's used in 3rd gen Camaros are bigger than alot of 350's and way bigger than Ford 302 valve sizes.

 

[/QUOTE]Hey i wouldn't complain a 305 is bigger than a 302. And the valves in 305's used in 3rd gen Camaros are bigger than alot of 350's and way bigger than Ford 302 valve sizes[/QUOTE]


would you like to bet that a DZ302 will beat the holy hell out of a 305??

 

I know they are two completely different engines, built for two completely different reasons and purposes. I was just joking that a 305 is bigger than a 302. And i was talking about the later 70's-80's Ford 302's from the same smog era as the 305.

 

I say if you can get the 307 for a good deal, then do it. You can use the crank for a 327 build if you want to. You can use the rods for lots of sbc setups, and you can take the cam out and throw it on the ground. I get some kind of strange pleasure from breaking camshafts..........

*slap myself in the chest while biting my shoulder and rocking back and forth*

 

Hey i wouldn't complain a 305 is bigger than a 302. And the valves in 305's used in 3rd gen Camaros are bigger than alot of 350's and way bigger than Ford 302 valve sizes[/QUOTE]


would you like to bet that a DZ302 will beat the holy hell out of a 305?? [/QUOTE]

my grandpa has a 68z with the DZ motor...well actually 2 DZ motors...the original is in a temp controlled storage room and the one hes got in it is a fully balanced and blueprinted trans am series race motor...about 450hp..its pulls like a MF'er all the way to 8,500.....not to fun to drive on the street though lol


personally i wouldnt touch that 307 with a stolen credit card

 

The 307 was a 283 block with a 327 crank (while the 302 was a 327 with a 283 crank). Depending on the casting, they could be bored.

Compared to a 305, I'd rather build a 307. The 307 gets no respect because they all had crappy heads and 2bbls carbs. They were never given any "performance options". And, in those days when 327s were plentiful, why build a 307?

But as with any SBC, you can build them with the right heads, cam and intake. It's just (as in the old days), do the same work on a 327 (or a 350 today) and you make even more power. So nobody builds a 307.

 

They did not share the same block, look at the casting numbers. No 307 ever used a 283 block, it had its own block that happened to have the same bore.

 

a 307 is like a 305 "just dont expect to much"

 

This is the answer I was looking for. I know why they did it I was just looking for some humor.

 

No problem, shifty. Anytime you need it!

 

No, no the story goes one day the GM engineers started thinking the Ford Mustang really sucks a big one, how can we make our Camaro more competitive with the mustang. We don't want Mustang owners being too depressed, for buying a ****box. So they got to thinking what makes the 350 so good, the bore. Now what can we do to screw it up so it is more comparable to the Mustang. I know make the bore much smaller. Boom the tough acting 305 with a 3.735" bore was born.

It was all done to be more competitive with the horrible mustang. Ford actually paid them to make the 305 suck so that the mustang would not be slaughtered in the "Pony car Wars."

 

307 and performance useage should not be used in the same sentance. It's like non acholic and beer, just wrong.

Now if you happend to need an engine to replace a bad one on the cheap, then theres nothing wrong with it.

 

IMO, A 307 is a better engine for performance use than a 305. I do not think it is better than a 302 or 350 by any stretch. I just wanted to keep that clear. I was mowing it over with my engine advisor, (DAD), He confirmed my thought about a 307 having a large journal 327 crank. That means you could find a 350 block that spun a bearing or something that ruined the crankshaft and or rods, and drop this 307 crank and rods into it and have yourself a large journal (maybe even 4 bolt main) 327. Nothing wrong with that.

So I guess what I am trying to say is that you could use this 307 for a while and since it has a better rod ratio and bore/stroke combination than a 305 (for hot rodding), it would IMO be an upgrade from a 305. Then you could keep your eyes peeled for a crippled 350 and use the crank out of your 307 to make a 327.

 

Just rememer that the 307 cranks are all cast.

 

Lots of SBC's have cast cranks. My 350 has cast crank, running a lot of power through it, haven't broken it yet. I shift at 6900 RPM.

IMO, you would have even less problem with the 327, less rotating mass, shorter stroke, better rod ratio.

 

My buddy's '69 Camaro had a 307 in it. It was a complete dog. I wouldn't waste my time on it.

 

Yeah like your l69 is real fast...

There was a chp a few years ago, i have the issue somewhere, about building up smaller engines. They built up a 283 and something else. The 283 made close to 300hp, with no head porting and minor work. Aint that bad.

 

I am not condoning building a 307. That being said, it was probably a stock 307, and worn out at that. The same thing applies to most thirdgens with 305s.

 

I have a 307 in my 85 berlinetta.. i run the **** out of it and would have to say that a 350 treated the same I dont think would still be here.. it has double hump heads on it according to the internet 64cc 2.02 1.5 or 1.6 .. hooker headers edelbrock performer intake, holley 600 vs carb. fastest time 9.8 1/8th with peg leg rear and slush box. the tach pegs at 7 and the motor still goes... yea the tach is accurate. I wont say its the best motor for performance but like the other guys said swap it in if its cheap and dog it lol. I plan on rebuilding mine and trying to get 300hp at the crank.. but thats just because I like the motor. not asking for another war but I think the 307 is an improvement over the lg4.

 

Only the early 283's could be bored to 4". The 60's 283's typically had thinner walls.

The 307 was not a 283 block, as stated. It had the same bore, but the crank was LG - different casting. And, it too had walls that were too thin to bore to 4".

The 307 has a better bore/stroke ratio, for higher RPM power, than the 305. It will give up a little lower end torque to get there, but when RPMs get going, the 307 will absolutely take over.

There wasn't such a thing as a performance 307 from the factory, because they were all small port, low compression, small cam, 2bbl, single exhaust wonders. However, with good heads, good cam, good intake, and good exhaust, it will out-perform a 305.

The Popular Hot Rod Engine Masters small block competition a couple of years ago, limited to 370 cid or something weird like that (forget the exact #), had one entry that used a 307 block with 3.75" stroke crank - obviously custom pistons. Since they used "average HP" between certain RPMs as the winning criteria, I believe it was 3500-6500, it did very well. Only a dyno day hitch, IIRC, and strict repair rules, kept him from winning the thing.

If I had a 307 block in good running condition, with no 350 in the immediate future, I wouldn't hesitate to put my parts around it. I'd certainly want a little more stall, though.

 

A friend of mine got rid of a 307. It was a good price. It was not in good shape. We also use it on weekends. We use it for performance also.It came with a lot of extra parts. I paid my friend , the Sheriff, $1200. for it. It had headers, Vacuum Holley 600, 350 tranny, 8.2 10 bolt rear, 2.73 gears. peg leg,, 0 psi oil pressure at idle, bearings rattle a little on cold start ups. Oh, almost forgot,, all this was setting in a "70 Chevelle". Took it to the 1/8 mile track,, high 11's, 66 mph,, added 2500 stall converter, eaton posi, 400 springs,, 4.56 gears,, zz4 intake, zz4 hei.,holley spreadbore 650 dp, high 8's,, 78 mph,, 2.75-50-15 cooper cobras,, spinning alot, gets sideways in second,, fun to drive,, many hours labor,, should have just dropped in a"572", also added 416 heads, 1.94x1.5 valves, unshrouded, polished chambers, self ported, 170cc intake runner, flow about 200cfm at 400 lift, milled .030, 58cc, 10-1 compression, stock cam,, for now

 

Has anybody else noticed that jonb is AWOL??? He hasn't posted on this thread since starting it. I want to know, jonb, how much does your friend want for this 307??? Did you buy it??? Are you planning on it??? I just want to put my official vote on the matter. If it is a good deal like you said, BUY IT!!! After reading what others wrote, and thinking about what I said, it would be worth getting if it wasn't too expensive. I think a 307 would make a good engine even if you just put your 305 top end on it. I guess that would depend on what pistons it has.... You know, Compression Ratio.

 

It was a sbc with a 3.25x 3.48

 

Better than the 305 if you swap the heads out for a smaller cc chambered head and machine the block deck down revs good and can build horsepower.

 

The biggest problem with the 307 was the used large cc chambered heads on every variant.

 

Thread is almost old enough to legally drink hard liquor.

 

NO it was NOT. Please don't register just to revive 20-yr-old threads and post INACCURATE GARBAGE in them.

It had the 283 bore, which was 3.875"; and the 327 stroke, 3.25".

Butt I'd agree, the heads the factory used on all of the 307s were CRAP. Much like most of the 305s, particularly the earlier ones (late 70s) and the L03.

The 305 has its own bore, 3.736"; and the 350 stroke, 3.48". In fact the same crank casting was used in lots of 305s as in many 350s, the 442. The actual crank as installed was not "the same" though, to the point that they can be directly interchanged, as it had to be balanced differently. Same casting, different machining. Much like the 307 crank; even though it had the same stroke as the 327, the machining was different.

As far as the 307 being "better than the 305", that's kinda moot nowadays. About like arguing over which kind of animal plop is "better"; horse or bull. Both of those engines were GM's attempts to create an "economy" "emissions" POS to deal as cheeeeeeply as possible with the constraints imposed on them at the times. Neither is "good" for what we'd consider performance, in 2025, no matter what heads you put on them; in the sense that you can spend EXACTLY THE SAME money time and effort on a 350 short block and come up with something VASTLY superior to either one, or even $100 more or whatever to make the 350 into a 383, whatever their merits in an information vacuum might be. Wasn't "A Good Idea" in 1970 or 1980 either.

 

Am I the only one who just LOVES how Sofa sticks pins in old wives tales myths, , , so we can all get to watch em pop like overinflated party balloons?

 

Nope, you're not the only one...

 

I just don't get how people dig up these 2 decade old threads with a response to a comment like it was posed recently. Then the whole thread is peppered w some silly *** comments mixed w serious commentary. It's a trip.