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anyone put 305 heads on a 350?

Discussion in '1973-1991 K5 | Suburban | Truck' started by **DONOTDELETE**, May 7, 2001.

    if so let me know how you like it. i have a line on some 305 heads and i hear they have smaller combustion chambers and give good torque.

    78, 350/350/203, 3/4 ton, 4" lift, 35" BFGs
    <A target="_blank" HREF=http://bluebeast.coloradok5.com/>http://bluebeast.coloradok5.com/</A>
     
  1. northgate

    northgate Registered Member

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    Most 350 heads have 76cc or 64cc combustion chambers, while the 305's are 58cc. You will get a lot of free horsepower by bolting them on, but they are a lighter casting and therefore will not hold up under heavy use as well as a heavier casting. I have done this on "claimer" racing engines and it works good for cheap horsepower, but I don't know if I would do it for any long term use.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    You'd be better off getting some better heads, like early 350 heads or best bet (for stock) are some Vortecs. the 305 heads are really pretty bad designs from all I have ever heard. You may get good torque, but you can do that with smaller valves in better heads, so that you have torque down low, but they could still breathe once you got moving :)



    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  3. ftn96

    ftn96 1/2 ton status

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    Not a good idea!

    Will work for beer, parts and tools.
    90-350TBI-TCI700-241-33"-10/12 bolt w/4.10's,
    <A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
     
  4. i have a set of heads off a 69 350 truck motor. they have 1.74 intake valves. anyone know how to sourse the casting number to find out the cumbustion chamber size? the no. is 3832454. they would have to be rebuilt with hardend seats to work for me. i was trying to stay on the cheep theme.

    78, 350/350/203, 3/4 ton, 4" lift, 35" BFGs
    <A target="_blank" HREF=http://bluebeast.coloradok5.com/>http://bluebeast.coloradok5.com/</A>
     
  5. jimmyjack

    jimmyjack 1/2 ton status

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    sposed to use a special piston It was kind of a hot topic a few years back Kind of for racing only tho'

    "My blazer may be slow, but it goes faster at higher speeds"

    Jim
     
  6. ftn96

    ftn96 1/2 ton status

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    Blue beast go to www.mortec.com to look up the casting numbers

    Will work for beer, parts and tools.
    90-350TBI-TCI700-241-33"-10/12 bolt w/4.10's,
    <A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    as well as Mortec if they don't list the specific number you have, I have a couple of links on my page to other casting number sites...nastyz28.com is pretty good as well.


    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  8. Blazer1970

    Blazer1970 1/2 ton status

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    Beast, if those heads are 3932454, they are '68 or '69 307 heads. Not sure of combustion chamber volume for those.

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
    87 Burb 4X4 350
    01 GMC 2500HD 4X4 Duramax/Allison
     
  9. WOODYJ

    WOODYJ 1/2 ton status

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    I built up a 383 and had 202-160 heads on it. It killed all my torque. I put on a set of 305 heads and it really enhanced the torque. If you are not going to be running allot of high r's, the 305 heads are great! I have been running these on the old 383 now for 4 years and have not had an ounce of trouble. You could have trouble if you get them hot--so I have been told. I have had nothing but good experiences with the ones I am running. They do up the compression, but I have not had any trouble with it and I had it set up for 11:1 when I built the 383. Allot of people discourage this swap--but after running a set for a few years with no trouble what so ever--I Would recommend. The torque is unbelievable.

    k5woody I Don't Understand The Jeep Thing Either!!!<P ID="edit"><FONT SIZE=-1>Edited by k5woody on 05/09/01 11:08 AM (server time).</FONT></P>
     
  10. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    I would not do it. I had them on my old 350 and it sucked. I had to run nothing but 93 octane plus two bottles of octane boost just to keep it from detonating (pinging). I had more trouble because of the high compression than it was worth..

    Just my .02
    John

    '83 GMC Jimmy 4x4 ZZ4 Crate Motor
    '84 Chevy P/U 4x4 Sand Drag Racer, 578 RWHP
    '94 Impala SS
    '01 Chevy 2500HD w/8.1L & Allsion Auto
     
  11. ya know i think they are 3932454 castings. mortec says they are 69-79 350 truck heads. the motor came out of a 69 gmc 2wd. the block checks out as a 350 too. still no luck on combustion size. mortec doesnt list it. i see i'm geting mixed reviews on the 305 head swap. 83zz4 jimmy- did you did you grind the edge of the combustion chamber on those heads before you put them on? because the 305 heads combust. chamber is smaller you're suppsed to grind the edge back to match the 350 bore size. this is suposed to help decrease detonation.

    78, 350/350/203, 3/4 ton, 4" lift, 35" BFGs
    <A target="_blank" HREF=http://bluebeast.coloradok5.com/>http://bluebeast.coloradok5.com/</A>
     

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