Small Block Chevy Questions

Posted in Ignition Systems | Asked on Jun 5, 2010
  • Okay, I have a 307 engine from a 1970 El Camino. First, the heads of a 350 and A 307 the same as in bolt up to each other (a lot of parts for commercial purposes, headers, intake, sales, etc.)? What is a good way for the construction of the 307 engine, good performance (I would like to receive at least 300 horses) run with it yet in a position to 87-octane, and every day to go? I know a lot of people say, the 307′s are not worth much, but I’m a poor student, so for now, I’m just doing what I can.

    There are 15 Answers for "Small Block Chevy Questions"

    1. gregs111 says:

      if i remember right the heads are different

    2. mycle1000 says:

      the heads will bolt up (as long as they are from pre ’87 or so). a lot of small block chevy stuff is identical; that’s what makes them so popular.
      the 307 was never a favorite for performance, but will respond to the usual modifications. put a q-jet on it, nice exhaust and save up for a different v8.

    3. willy says:

      omfg dude heads hell no its not going to work I’m 13 i work on cars Ive help built lots of cars(63 corvette,camro,etc) my 4 year old cusen knows that will not work OK for the other stuff go to Ron’s or a high proformas store and ask about The intake There help u get good ones for good power then save money to get th stuff and same a little more for a tune up so that u know that your car is safe

    4. Murph says:

      Rebuild the engine block bored .30 or .60 over, use a mild camshaft not a radical curve racing cam, The 350 cyl. heads will most likely work on that block if they are not newer than 88 or 89 models and they will provide a bit of additional horses.

      Consider a fuel injection intake system that you can afford. This will be a nice reliable engine with plenty of power that you can drive everyday with reasonable efficiency.

    5. countryboy1959 says:

      I cannot stress enough to you, get out of here and go to a site called chevy talk, it is a forum, and they know their stuff, different sections for different things, and yes, the heads will bolt up, there are several things to look for, hardened guides and seats, that is after no lead gasoline, the 307 was a great boat anchor, you can make it better, and as far as a carb, do not put a gas guzzler quad jet on it, for petes sake, get a edelbrock or holley, set of headers and it should run ok, if you need more help cams and such, dont ask these people, go to chevy talk, it is free, and they do know their stuff.

    6. Skull says:

      1955 starters were bolted to the transmissions

      1956 – early 80″s small blocks haven’t changed externally, the real difference is on the inside.

    7. skip1960 says:

      All parts from a 350 will bolt on to the 307. But to get that kind of horse power you may need to have the engine bored out 30 to 60 thousandth’s and you’ll also want to put in a differant cam shaft. But you getting into a money issue. Keep searching web sites and also you should be able to get a free catalog from a performance place there are alot of bolt on parts that just may bring you up to where you want to be. It can be done and if you can do the work yourself you’ll get alot more bang for your buck.

    8. Pedro S says:

      PLEASE junk the 307… dollar for dollar for the same $ you can get350 -375 hp ina 350 for same cost as 275 in 307… go read hot rod or car craft magazines and dont do anything till then..The head change will likely do nothing.Have you computed the compression ratio change with new heads?. If you must keep 307 get edelbrock intake/carb/aliminum heads…headers…they will all fit on 350 when time comes…Go to Jegs and Summit racing.for parts.

    9. Gary B says:

      Yes, Countryboy is right, all of the parts will interchange. The only problem you might have is if you put 2.02/1.60 valves in because of the 3.875″ bore. Also, the 307 heads weren’t that bad. I believe in a ’70 they had 64cc chambers. DON’T put later 350 76cc heads on it. It will reduce the compression so much, you’ll lose power. Check your casting numbers before you pull the heads. If they have 64cc chambers, the best thing to is find a set of 305 H.O. heads and put 1.94 intake valves in them. They have a 58cc chamber and will raise the compression a little and give you hardened seats. These are a good, and cheap factory head for a small motor. EVERYTHING externally is interchangeable, including the heads. You are way better off to start with a 350. It will cost you far less in the long run. If you insist on the 307, a small Holley or Edelbrock (600-650) carb on a Performer RPM manifold, with a mild hydraulic cam (224/230 duration at .050 or similar) and 1 5/8″ headers will wake it up as long as the long block is healthy. If you don’t want to change the cam, put on a Performer intake on it instead of the RPM, and a set of stamped 1.6:1 rocker arms. I used to use .030 over 307s in a dirt track car. Good little engine with a good bore/stroke ratio. It will make power, but buying a 350 will be cheaper. We used to spend alot ($11-12K) on them, but we were running in a class where we had to weigh so much per cubic inch. If not, I’d have been running a 350.

    10. racer123 says:

      The stock 307 was built to supply maximum hp. and efficientcy for its size. Factory specs are the best in this reguard. To regain a level of modern operation you will have to retrofit this engine to burn low octane unleaded gas. Best way is to have the heads modernized(hardened valves and seats),ultra thick head gaskets and a timing chain and cam gear that will allow for a 2 degree retard in cam timing.Recurve the distributor to retard mechanical advance. A ’78 or so HEI distributor and 8mm.wires along with .50 spark plug gaps on the 1 cooler size stock sparkplugs cement a solid core of longevity to this retrofit-without the pains of preignition.I get 23 mpg at a steady 65 mph without lights or A.C. with a t-350 auto.

    11. Nym says:

      I hate to burst your bubble but getting 300hp out of a wheezy 307 is going to be expensive. You’ll most likely have to get some machining work done (porting, boring, honing) just to get your small bore engine breathing.

      I would recommend looking for a used 350. There are lots of them out there and as a result aren’t very expensive.

      350′s are very strong engines and respond very well to any upgrades. The 4″ bore makes them really deep breathers and they make great torque in low rpm’s.

      Headers, intake, timing and a mild cam will get you your three hundred horses easily without even setting foot in a machine shop ( that is if your donor engine is in good shape).

      I know this isn’t what you want to hear, but seeing as you are a “poor college student” this is by far the cheaper way out for what you expect to gain.

      Hope this helps and good luck with your project.

    12. Old man wrench says:

      For a poor collage student the best per dollar bet would be to change the rear end gear ratio to a 3.73 or 4.11.
      This will make a very noticeable difference.
      On a low budget to get any little bit of power out of a 307 is not going to happen.
      Headers will change the sound and a intake will add more air and fuel but w/o a cam good flowing heads save your dollars.
      I’ve seen many, many people put headers, intake and crab and cam and think that its faster but only louder and uses more gas and not one bit faster. Just big flowing heads and a roller cam will make more difference than all that other stuff put together.
      On the intake stroke you want the intake valve to disappear and the comb. chamber to fill w/ fuel. than on the comp. stroke in. valve to reappear. BOOM power stroke. Same on ex.stroke.
      I’ve tried headers, intake etc. and the power difference is to be laughed at, its the heads. If you can’t afford high flow heads and a roller cam,change the gear.
      Or a 100 hp nitrous kit. Might blow the bottom end out of it but you WILL feel the difference!!

    13. Jimmy says:

      a small block chevy is a small block chevy.

    14. Galaxie says:

      The 307 was the replacement for the 283, and was only produced for 5 years, 1968-1973. It was created by using the 327 crank in a 283 block. The produced decent low to midrange torque suitable for the average family guy. They were NOT noted for high performance, or high RPM capability, and generally speaking, dropping 4.11 gears in one is abuse–it’s not going to run that much better, but it will sure cost you in noise and maintenance.

      You’ve been given very good advice…a 350 has a much more favorable bore/stroke ratio, and there are a zillion performance parts available.

    15. Country Boy says:

      yea man, if you havent done anything to it, ditch it and get a 350 block and bore it over. if people ask what do you got in it? would you rather say ahh 307 or a 350??