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305 heads on a 350???

Discussion in 'The Garage' started by bigcat44, Mar 18, 2005.

  1. bigcat44

    bigcat44 Registered Member

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  2. mr_clean

    mr_clean 1/2 ton status

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    I heard someone on here mention that 305 heads have a 57cc combustion chamber which could raise the compression up to high to run pump gas...

    I don't know for sure, but that might be something I'd look into first.
     
  3. sled_dog

    sled_dog 1 ton status

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    305 heads jump your compression up quite a bit and flow like crap. All in all they are no good for a 350.
     
  4. Thunder

    Thunder 3/4 ton status

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    Pass on those heads
    No good on a 350. 350s and 305s have diferent size bores. Stock 305 heads are designed for the smaller bore of a 305. Putting them on a 350 shrouds the valves screwing up the flow on a head that already does not flow very well. Also only have small 1.84/150 valves. They can be made to work good on a 350 with machining the combustion chamber, larger valves(194/160 will fit no problem), and a good port job. But you can buy a good set of aftermarket 350 heads or vortecs for what that costs.
     
  5. Z3PR

    Z3PR Banned

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    I'd go for a set of World Products S/R Torquers for a truck.
     
  6. bigcat44

    bigcat44 Registered Member

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    awesome, thanks all for the advise, I'll pass on them.
     
  7. 4xcrazy

    4xcrazy 3/4 ton status

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    BUT they do work fine as a daily driver,,, i had to put some on a rebuilt 350 block,,,cause it's all i had at the time, and needed it to run, runs and drives great,,has good power, would most definately have better with 350 heads,,,but hey, they work.
     
  8. American84K5

    American84K5 1/2 ton status

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    i have 305 heads on a 350 bored .030 over runs great :grin:
     
  9. LittlecountryK15

    LittlecountryK15 Registered Member

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    when I bought my truck I drove it for about a month and then all of the sudden it was like the timing or something was outa wack...well we messed around with it for a few days and we still couldn't get it to start..then we got it to start and it had so much compression that it broke the starter bracket in half...so I had it towed to the shop and sure nuff it wasn't the timing but it had 323 heads on a 350.....I ended up haveing the whole top end rebuild b/c of the idiot that put them on.
     
  10. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    305 heads have 58cc combustion chambers but there is a piston specially made so that you can run 305 heads on a 350 without raising the compression ratio. Without tearing the engine apart you would never know this though.
     
  11. beater_k20

    beater_k20 Banned

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    actually, you've got it reversed. a set of 350 heads on a 305 would shroud the valves. as far as valve shrouding, 305 heads are ok on a 350. better than they are on a 305 anyways. but, they still dont flow for crap.

    there is no piston made "specifically" for this application, just different style and displacement pistons. even still, the 305 heads are inferior to ANY 350 head.
     
  12. truckinprogress

    truckinprogress Newbie

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    im running 305 heads on my 350. works good i have great power. flow is not a problem cause i only have a 425 propane carb anyways :laugh: next time id get some close chamber ones tho....
     
  13. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Maybe you better do a little research before making a statement like that. Silvolite pistons makes a 350 piston for use with 305 heads and it is part number 1472 and is intended for use in 1969-1990 350ci engines.

    I copied and pasted the info directly from their website.

    General Motors
    V 8 350 / 5.7L
    1969-90
    Chevrolet


    STD. BORE SIZE
    4 / 101.6mm


    COMP. HEIGHT
    1.54


    PIN DIAMETER
    0.9273
    offset


    COMPRESSION RATIO(s)
    8.4

    Part
    Number 1472


    SIZE AVAILABILITY


    VIN CODE



    RING PACK
    2-5/64
    1-3/16


    NOTES
    For Use With 305 Heads. 3.300' Dia. Head Recess .270' Deep.



    WRIST PIN P/N
    LOCK PIN P/N
    APPROX. OVERALL LENGTH


    RECOMMENDED FINISHED BORE DIAMETERS
    PISTON MAJOR AXIS MUST BE MEASURED PERPENDICULAR TO THE PIN CENTERLINE AT 70 DEGREES FARENHEIT 3.710" DOWN FROM THE PISTON HEAD

    Piston
    Oversize Piston Major Axis
    Diameter +.0000/-.0005 Recommended Finished
    Bore Diameter







    Silvolite Pistons

    Here is a link to the exact page. http://kb-silvolite.com/spistons.php?action=details&S_id=253
     
  14. beater_k20

    beater_k20 Banned

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    yeah? its a dished piston, it will work just as well with any head as it will with a 305 head. there's nothing "305 head specific" about it. i see them used all the time with 76cc heads on blown street engines. nothing special there.
     
  15. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    If you look at the specs on the piston you would soon find out that the dish is 3.300" in diameter and .270" deep which results in a compression ratio of 8.4/1 with 305 heads, if you used that piston with 350 heads you would have a compression ratio of only about 7.4/1 which is too low.

    Also turbo or blower pistons are made much differently from naturally aspirated pistons. The top of the piston is much thicker, the first ring land is farther down the piston, and the piston is made of a different material and also forged.
     

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