Refresh costs 71 307 vs 86 305

Discussion in 'Engine Topic' started by Matt T, Sep 29, 2016.

  1. tom3

    tom3 Veteran Member

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    Wouldn't it be nice if GM would build a vortec roller 350 crate for the price of the Goodwrench crate, $1400 or so?
     
  2. Matt T

    Matt T Veteran Member

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    Thanks for the input!
    I'm taking the 305 out of the equation. I'll pull whatever parts make sense, but it smokes too much to run as-is and I'm not spending money on it. The goal is to have something that runs fine (reliable, not fast), looks OK, and could stay in for several years but only cost a couple hundred--so hone, rings, bearings, seals, etc.
    The 307 was supposedly running OK when pulled by the PO 25-30 years ago. I could throw it in or fire it on a stand just to check before wasting money.
    Someone mentioned putting the 305 heads on the 307 along with the other parts. What would that get me besides hardened seats (does it matter much with stock spring pressures)? Anyone care to explain?
    I'd rather take the time and do the 350 right--name brand parts (not a ??? kit), magnaflux, and proper machining. Heads are 1.94/1.50, but I haven't checked numbers. This all takes time and money I'd rather put into safety and bodywork first.
    This isn't a final decision, just enough to keep moving forward stripping the '86 T/A for now to get it out of the yard.
     
  3. fester

    fester Veteran Member

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    You need hard seats for today's fuel. The tetraethel lead in the days of the 307 lubricated the valves and protected them from wear. Unleaded will cause the valves to burn and then you will need new valves and hard seats installed. A good set of Vortec heads with matching manifold will add 40-50 hp and cure your head problems..
     
  4. 70-camaro

    70-camaro Veteran Member

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    The 307 heads are 70 cc combination chambers, 305 HO heads are 56 cc that will up your compression considerably. Be sure to use the 305 head gaskets.
     
  5. fatkid_racing

    fatkid_racing Veteran Member Lifetime Gold Member

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    Freshen up the 307, quick dingle ball hone, use the 305 heads freshen them up with new seals and a quick relap of the valves and some steel shim gaskets.

    Summit gasket kit minus head gaskets
    G2660 $16.97
    Mr. Gasket steel shims
    1130G $20.38 each
    Summit brand (king) main bearings
    172000 $15.97
    Summit brand rod bearings
    171000 $14.97
    Summit brand oil pump/pickup/drive combo 3-60-08-003 $49.97
    Sealed power rings
    E-245X $41.97
    Summit cam & lifters
    1102 $103.99
    Summit timing chain
    G6501 $14.25

    Grand total $298.76.

    Not bad for a backyard rebuild that will likely run forever, and run fairly strong for what it is.
     
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  6. Highlife

    Highlife Veteran Member

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    I had a 307 in a daily driver firebird years ago, built very similar to the way fat kid is describing. It had the 305 heads off the stock motor in the car, a PAW RV cam, an aluminum Z28 intake, stock hei out of the 305, and shorty headers topped off with a 625 carter afb. It wasn't the fastest car ever, but it wasn't a slouch either. One night after a bunch of persuasion from the guys at work I was finally convinced to put it on the local 1/8 mile track. Where it ran a 10.01 at 68mph. Not bad for a 307 in a heavy tank with 2.41 gears. That roughly translates to a 15 second quarter mile and all the testing for the 305 formula birds netted 17.90 quarters, so my little 307 shaved 2.80 seconds off the best they could get the car to muster when it was new.
     
  7. BUSHY 409

    BUSHY 409 Veteran Member

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    build A KILLER 350 YOU KNOW480 480 SUMMIT CAM ,resize the big end . good rod bolts , over bore , use dish pistons , with them]305heads you will have 10-1 maybe 3 angel valve job !!!! Phase 2 good set of pistons and heads ..now u are big dog ! Good luck
    OLD CHEVY NEVER DIE THEY JUST FASTER


    [ you will have a
    lest 10-1
     
  8. ratpatrol71z28

    ratpatrol71z28 Veteran Member

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    If time isn't problem and it sounds like you want something just to get it moving... why not just run the 305 for now, by all means it is running, then slowly build and invest into the 350. When you are ready swap it all. Don't go backwards playing with engines you don't plan to keep for very long. Goodluck
     
  9. rockheadrocks

    rockheadrocks Veteran Member

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    I agree with Fatkid on everything but the cam. The 307 is basically an underbored 327 (or more correctly, a 283 bore with 327 stroke) so I'd cam it like one. Because the smaller bore limits the engine's breathing, the VERY old school GM 151 cam (L79 327) will work very well. .447" lift on both sides and 114 degree LSA. The 305 heads (assuming they're not the completely lame LG4 heads) will have 58cc chambers and if memory serves, 160 ish intake port. Great port velocity, not much high rpm breathing. In this case, because of the 307's smaller size, an old 2101 Performer and Q-Jet will be all that engine will ever need. El cheapo headers to finish it off, and enjoy.
     

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