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307 vs.305 chevy engine

Discussion in 'The Hokey Ass Message Board' started by tajk3, Jun 14, 2006.

  1. tajk3
    Joined: Mar 20, 2006
    Posts: 6


    I have a 51 Chevy 2dr. sedan that I just want to make into a mild custom and a reliable cruiser.I can get a '72 307 for free or a '78 305 and 350 trans out of a '78 camaro for $250.I,m wondering which would be best for my low budget project.I know free is hard to beat,but I'm aware the 307,s aren,t well thought of.Both have similar mileage,80k+.I,m not one who just has to have a 350!Opinions please.
  2. Bad Bob
    Joined: Jan 25, 2006
    Posts: 23,768

    Bad Bob
    from O.C. Baby

    I would go for the 307.The 305 is good,but has NO torque.If you go on a trip it will labor on the hills.Then I would save your money for a 350.
  3. demonspeed
    Joined: Jul 22, 2004
    Posts: 517


    if it was just engines I would take the 307 because the 305 prbly has tons of emmissions crap on it. I got one in real bad condition once just to learn how to take apart an engine and then scrapped it when I was done. Neither are great engines but if you can find a free (or at least around $250), manual trans or something i would get the 307. otherwise the 305 might fit your budget better since the trans is included.
  4. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,704

    Fat Hack
    from Detroit

    Either one will be fine.

    Once again, there is nothing wrong with a 307, except that many came from the factory with unhardened camshafts that wore out prematurely, causing poor performance and mileage, and giving the 307 an undeserved bad rap.

    Slip in a quality stock replacement cam for a 350 engine and a new set of lifters and a timing set and you're good to go. The 307 is just a 327 with a smaller bore.

    The 305 is an excellent all-around performer as well. It's just a 350 with a smaller bore and makes a perfect daily driver motor.

    In stock form, you won't notice much (if any) difference between the 307 and the 305, assuming both are mechanically sound and in a good state of tune, so either one will work for what you're after.

    One thing most people overlook, though, is that the 305 will have heads with hardened valve seats for use with unleaded fuel, where the 307 likely won't, as they were built from 68-73, before catalytic converters and mandatory unleaded fuel.

    For as many miles as most people here put on their rides, the valve seat thing isn't a big deal. You can always run a lead substitiute if it concerns you, or if you plan to actually drive the car daily on pump gas.

    (Fuel quality and formulation is something that goes unconsidered by the vast majority of today's hot rodders, but it is important! The 305 was born in the era of low octane unleaded and can easily be made to perform well on today's fuels. The 307 will do okay, but it was designed to operate on moderate octane leaded fuel. It's not hard to adapt older engines (especially small block Chevys!) to work in harmony with TODAY'S gasolines, so don't let it scare you off of a free 307!)

    Of course, you could always drop the 307 crank into the 305 block and create a super low compression 285 cube motor that can't possibly run, much less make power...but I wouldn't recommend that tactic for the faint of heart!:rolleyes: :D

    Flip a'll be a winner either way! (305 or 307) :cool:
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  5. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,704

    Fat Hack
    from Detroit

    Ummm...okay. The 3.48" stroke of the 305 (same as a 350) is a now somehow hinderance to torque production???

    The 307 uses a 3.25" stroke (same as a 327).

    All things being equal, the 305 will exhibit better torque characteristics. They used the 305 (5.0) in Chevy/GMC trucks for years.

    (True, the 307 was also used in light duty trucks back in it's day, but the 305 won't be any worse off than the 307 as far as torque goes, and in fact, will likely be stronger in that department.)
  6. peanut
    Joined: Mar 16, 2005
    Posts: 488


    yea i would go with the 307! thicker heads! those 305 heads are very bad to crack. one thing the 305 has a longer stroke. and all things being equal should have a little more torque. if i had them both i would build the 307!!! 3and3/8s bore and 3and/1/4th stroke. i think that is a good combo. also with the smaller bore you have more water around the bore and sooo it runs cooler and is easy to keep cool at lower speeds anice plus.
  7. boharris41301
    Joined: Nov 8, 2005
    Posts: 42


    this may not help much but it i have a 72 swb cheyenne pickup that i drive everyday and it is has a 307 2 barrell with a 3 on the tree. I would like to have more engine a good sounding cam but anyway, i will spin good in first and a few feet in sec and run 70-75 ont he parkway and not drop on hills. for the first 307 that i have owned it isn't like i expected.
    anyway that is my 2 cents.
  8. This thread got me to thinking about Chevys 262 V8...remember those?
    I think they were in some early Chevy Monzas,or some other small bodied GM car.
    The spark plugs were an absolute son of a bitch the change.
    Question,,,what years did GM start-n-stop making the 307 SB?
    A buddy had a Nova with a stock,but headered & manifolded 307.It ran bitchen.
  9. I think I would go with the 307 also. I would add ,mill the heads a little with a valve job and maybe a little porting. Give it a 4 Barrel Intake & carb, and of course a better cam, some headers,.....anyway just tossing in my 2 cents worth as well.:D Gary 4T950 Chevy Guy:D P.S. How much of your money do we get to spend with our ideas?
  10. Eryk
    Joined: Jul 5, 2005
    Posts: 920


    You've already been given some damn good advise in this thread. I can't add much more other than to vouch for the 307. I have one in my '60 Apache. I love it. It runs strong and cool. Didn't miss a beat to and from Paso this year. I've thought about swapping it for a 350, but I've really been quite impressed with this motor.
  11. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,704

    Fat Hack
    from Detroit

    Yep, the 262 was the little Monza V8 (although some Spyders came with 305s, and there was an optional 350 available in California only for one year in the Monza as well!). The plugs were only a bitch to change because of the manifolds, the 262 is just another small block Chevy on the outside.

    GM stopped using the 307 Chevy in 73, and the 305 arrived in 76.

    The 350 is the staple of the small block Chevy arena, and it is the most cost-effective motor of the SBC realm to play with as far as rebuilds and making power goes...but the difference isn't as vast as some would lead you to believe.

    (A rebuild kit including pistons for a 350 engine goes for $169 through a mail order house while the 305 kit comes in at a staggering $179. That ten dollar difference can be a real handicap, but you can take some comfort in knowing that machine work and bolt-on speed parts cost the same no matter WHAT size your SBC is!!:D )

    Power-wise, the 350 has long been embellished, while the 305 and 307 engines have long been under-rated. Many folks will have you believe that just dropping a four barrel carb, aftermarket intake, mild cam and headers onto a 350 will yield 350 to 400 horsepower, but that just isn't so.

    (One of the Chevy mags recently did a dyno test on a pretty basic performance-oriented 350 build with a good set of heads, a decent intake, cam, carb, header and ignition combo and it peaked at 318hp on the meter, just to give you an idea of what to HONESTLY expect from a warmed over 350 on pump gas today).

    Can a 305 or a 307 make 318hp? Easily. But if given the exact same treatment that the magazine 350 got, they'd probably come in somewhere around 290hp or so. Still respectable, and far more realistic than the "Fantasy Figures" too many rodders throw out when guestimating the power output of their Magic 350 engines!

    At the end of the day, ANY small block Chevy can make for a reliable powerplant to scoot your ride around town, and can be made to run decent on a shoestring budget with common sense mods and bolt-on speed parts.

    Just ask our guy Rob Fortier (RF on the HAMB), he supervised a mild 307 build for his current magazine and it ran damn good given what they did to it.

    Way back in the 80s, HOT ROD coaxed 400hp out of a 305 ("Deadly Lessons") and proved that there was plenty of power to be found in those motors without getting too exotic.

    Sure, the 350 will always be king, but these days 305 and 307 cores are much cheaper, and often times FREE! You can build them as mild or as wild as you wish, and swap parts to yeild a strong motor that will put a grin on your mug for many years! 350 steel cranks are a direct swap into 305 engines (so long as you use a two-piece seal crank in a two-piece seal block, of course), and SpeedPro offers forged pistons for them. Rods are the common 5.7" Chevy rod, so take your pick there. Head selection is a bit restrictive given the 305's bore size, but World Products offers a street performance head called the S/R 305 specifically for these engines, as they are becoming more and more popular.

    The 307 will accept any large journal 327 crank, so part number 3914672, a forged steel 327 piece is a direct bolt-in. Piston selection for the 307 is a little sparse, but they are out there, including forged offerings. The 305 heads work on the 307, as do any 1.94" valve head, leaving you PLENTY of options there!

    When it comes to manifolds, headers, distributors, valvetrain and other speed parts, the world is your oyster with a small block it a 305, 307, 350 or what-have-you.

    In the real world, taking into consideration that this IS 2006 and NOT 1964...the 305 probably represents the best overall bargain in SBC performance on current pump gas, yet can still be dressed to look vintage if desired.

    Many times, if you rode in a car with a sensibly built 305, and the dude told you it was a'd never question it. I pushed two cars into the high 14s with VERY mild 305s...and these weren't lightweights! (One was a four door 77 Malibu Classic, the other a 79 Monte Carlo). Those motors were bone stock internally with just bolt-ons and mild hydraulic cams, automatic transmissions with stock torque converters and stock rear axle ratios.

    The days of praising the 350 while poo-pooing the 305 and 307 ought to be behind us by now, but many are resistant to change. Low octane unleaded gas is here to stay, and it ain't getting any cheaper, either! Todays world practically calls out to the 305, which was created specifically for it!

  12. dana barlow
    Joined: May 30, 2006
    Posts: 2,750

    dana barlow
    from Miami Fla.

    WOW,good run down,Fat Hack,and yes I too think same way,I would like to add if your lucky to find a SBC 400,there a good power box,I run one for some time,as they say you c an't beat in.s For the big "T"
    the Bat
    Miami fl.
  13. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,704

    Fat Hack
    from Detroit

    The 400 sbc is one excellent street motor where low to midrange grunt is the goal! I had a small stockpile of those engines back in the 80s and wish I woulda kept a few around!

    Too many people go for the 383 combo, with a 400 crank in a 350 block, but I never saw the logic in giving up 17 cubic inches to ride the Bandwagon...if you got a 400 to yank the crank out of...just build the damn 400!

    (All the wive's tales about 400s being prone to overheating are just uninformed prattle...most times, the "problem" comes from an inadequate cooling system, or careless folks who forget that 400s use specific head gaskets with steam holes in the heads. They are a siamesed bore block, but they'll run cool if the car's cooling system is up to snuff for a 400 cube mill and the heads and gaskets are correct for the engine.)

    The 400 isn't a high revving mill, but it'll pull HARD up to 5000rpm!
  14. Bigcheese327
    Joined: Sep 16, 2001
    Posts: 6,504


    Who drives above 5k these days anyway?

  15. Can't add anything to this , other than BITD, we found that 307 blocks n cranks were "soft" + wore out fast w hard use.I'd take a 305 over a 307 anyday ,but in a pinch I'd use a 307 for a street car w/o a second thought if avail cheap.(I don't beat em anymore)
  16. treb11
    Joined: Jan 21, 2006
    Posts: 2,774


  17. Bigcheese327
    Joined: Sep 16, 2001
    Posts: 6,504


    Only trouble with that story is that 307s are large-journal and all the 283s were small journal.

    The plus side of the equation is that any naked 350 block can become a 327 with the addition of a 307 crank.

  18. colorado51
    Joined: Feb 24, 2003
    Posts: 1,577


    Hack, that is sooo weird, just last night I was going through a bunch of boxes of old Hot Rod and Car Craft mags from ’76 – ‘83 that a friend gave me, and I ran across that EXACT article! I think it was from '82.
  19. Troy Destroy
    Joined: May 18, 2006
    Posts: 36

    Troy Destroy
    from Dallas, Tx

  20. gregga
    Joined: Feb 10, 2005
    Posts: 379


    I've had a 305 in my coupe for over 4 years now and it's a screamer. Performer cam and kit, performer intake, 750 Holley and Pete Jackson gear drive. Stock other than that. I can hit 105 on an on ramp and back down to 70 real easy. And 5k isn't history. My rebuilt 350 has been sitting on the stand for 2-1/2 years while this interim engine wails. I love the sound of a wound small block.
  21. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,704

    Fat Hack
    from Detroit

    Ha Ha...yeah, I couldn't remember if it was from 82, 83 or 84...just recalled reading it during one or more classes back in high school...had some dude and cute chick lwering the motor into a 'new' (for the early 80s!) Camaro in the lead photo for the article.

    At the time, my mom's car had a 305 in it, and after 100,000 miles my dad and I did a leakdown and compression test on the motor to see what kind of shape it was in and my dad was impressed! The numbers were within 5% of each other and with new plug wires and a carb rebuild, the car ran like a champ again. Made me a believer in the 305 at a young and impressionable age I guess!

    (The two 305 cars I coaxed into the upper 14s each had over a hundred grand on them as well...which is about the break-in period for a 305 I guess! Ha ha!)

    :D :cool:
  22. 6t5frlane
    Joined: Dec 8, 2004
    Posts: 2,375

    from New York

    289 !!! Oh crap that was not one of the choices....Go with the 305
  23. tajk3
    Joined: Mar 20, 2006
    Posts: 6


    Thanks to all who replyed.I know a heck of a lot more now ,about the 307 & 305 engines than I did before.Much appreciated!!
  24. Thirdyfivepickup
    Joined: Nov 5, 2002
    Posts: 6,084


    The 307 obviously makes more torque because it has more cubes... :rolleyes:

    Hack you are a 305 genius!

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