Help me design a 350

Discussion in 'Small Block Tech' started by vonhef, Jun 24, 2018.

  1. vonhef

    vonhef Active Member

    I have a Buick 350 originally out of a 72 or 73 Skylark or similar car. It is stock with a 2 barrel. I wish to perform a complete overhaul and am needing some advice on upgrades.
    This engine is in an old Ford pick-up and will be used for street-rod use... so low RPM drivability is important. I do not want a poor idle or high stall converter.
    Horsepower? All I can get with-out sacrificing street cruising.

    1. Would using the 10:1 compression cast pistons be safe with pump gas or should I choose a lower ratio?
    2. I would like to use a hydraulic roller cam & lifters, but don't know which grind specifications to choose.
    3. Fuel delivery... carb or throttle body fuel injection?
    4. Duel plane or single plane manifold?
    5. I have been waiting for the aluminum heads, but may go ahead and order the cast iron heads from TA and revisit in the future when the new heads are released.
    6. How much difference in HP can I expect from TAs $1000 roller rocker shaft?

    Thank you for your input!
  2. DBS

    DBS Well-Known Member

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  3. MrSony

    MrSony Well-Known Member

    9:1, comp 268 cam kit, headers take em or leave em, good valve job on the heads, would be a perfect street engine.
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  4. hugger

    hugger Well-Known Member

    10 to 1 cast pistons don't exist.
    Dual plane manifold
    Cam, probably the 212 in roller form with some added lift
    Throttle body injection is great if you have the coin, but a good working Qjet is hard to beat
    Roller rockers, I would expect maybe 10hp but if you decide you may want to do something different more performance oriented in the future they'll be there.
    The exhaust side of stock heads are absolutely terrible open them up and make sure you get a quality valve job with good ring seal.
  5. wovenweb

    wovenweb Platinum Level Contributor

  6. 10:1 cast pistons DO exist. Technically may not be exactly 10:1 without proper head gasket thickness and minor head resurfacing, but on paper they do exsist. TA advertises them.
  7. Paul Stewart

    Paul Stewart Well-Known Member

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  8. 70skylark350

    70skylark350 Well-Known Member

    I am in the process of building a 72 350 as well, its at the machine shop now. A lot of guys have a lot of good advise on here. I went with custom JE pistons to get 9.5:1 compression, they are pricey. definitely doing the oil system mods. Im thinking of going with the SP3 intake but it does not respond well to a Rochester carb so need to research that more. maybe 212 cam or one step up? not sure yet. gearing and proper converter are just as important from what I read. Plan on dropping twice as much coin as you are expecting!!!!
  9. 70skylark350

    70skylark350 Well-Known Member

    Yes, Jim Weise here on the board can sell you 10:1 Autotec pistons for $795.00. does not include rings, and the wrist pin is not factory size. My engine builder did not recommend this high compression for the street but Jim builds them all the time so???? I went better safe than sorry... Oh yes, the pistons I mention are forged not cast.
  10. Swagon

    Swagon Well-Known Member

    the cast "high comp" is 10:1?? they've been around for awhile. but like any piston even the autotec piston it all depends on head CC, head gasket thinkness, and deck height..
  11. Swagon

    Swagon Well-Known Member

    Im at 10.5:1 compression with the factory high comp piston, and a .040 head gasket. the head and block was milled of course.
  12. alec296

    alec296 i need another buick

    Some decent choices. The cast 340p is about 9.2-9.3 depending on overbore. With the roller 212 cam as long as it’s not much over .500 lift , you can use stock rockers. A standard 212 with a sp3 isn’t really taking advantage or the potential. If going flat tappet, go 413, or custom Scott Brown
  13. vonhef

    vonhef Active Member

    A lot of great comments!
    So it seems that to be safe a 9.0 - 9.5 compression ratio is probably best with pump gas.
    Brian, I appreciate the link with your dyno numbers! Your 400 HP engine is impressive indeed... all because of your special heads. That is why I wish the new aluminum heads were available now.
    It looks like for lower rpm torque, the duel plane manifold would be the better choice?
    Thanks guys for the advise!!!
  14. MrSony

    MrSony Well-Known Member

    Basically unless you want to rev past 6k (wouldn't advise much past 5, rods can take it, crank can take it, but it was never meant to, plus it'll probably make peak hp at 4500rpm anyway, but GOBS of torque for a small block under 3500), the SP3 is largely unnecessary. Hell, besides weight savings, the dual plane is not entirely necessary either.
  15. Dano

    Dano Platinum Level Contributor

    I'm no 350 expert like some on here, but my last build ('70 "SP" 350, M-21) ran pretty well. I did several mods initially (in order as I recall: headers, 2-1/2" exh. 3.42, 3.73, dual plane, KB MKII) all of which helped with the biggest gain probably from the 3.73, but IIRC the intake did noticeably help maybe .1-.15 sec. I never ran it @ the track prior to installing the headers.

    Then did a complete rebuild (major changes: .030 over 10.25 measured SCR w/ Hypereutectic pistons, '73 rods, big valve ported heads, KB C118, balanced) and that rebuild gained about another second. Hard to say exactly how to portion that out, but it all seemed to work well together and I'd suspect the heads were a big part but then they probably allowed the cam to really work. The compression was only marginally higher given the common consensus that the factory 10.25 was prob. closer to 9.5. I'm not sure if today's pump gas will support 10.25?

    There were other little things I did (plenum, open element air cleaner come to mind) some of which were also done on the attached KB build. The KB build seemed to show, and corresponded to my anecdotal evidence, that the 350 seemed to respond well to rear gears, headers/exhaust, cam/heads, and I assume because the rpm's are kept up, the 4-sp. I'd have loved to tried 4.10's with the M-21 and an M-20, and/or a 200R4 w/4.33/4.56, but for whatever reason the 350 seems to like the M-21's ratio spread.

    25 years later and I'm building a 350 automatic car and afraid I'll be disappointed with the TH 350 even with a higher 1-2 planetary and 3.73's. May try it anyway or just go right to a 200R4 w/ 4.56's

    Attached Files:

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  16. 36racin

    36racin Platinum Level Contributor

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  17. 70skylark350

    70skylark350 Well-Known Member

  18. Dano

    Dano Platinum Level Contributor

  19. Dano

    Dano Platinum Level Contributor

  20. 36racin

    36racin Platinum Level Contributor

    Sealed Power 340P makes a 10:1 cast piston. They are what I put in my rebuild.

    Vonhef where are you from? I know of a rebuilt short block in Texas. May be something to look at especially if you are looking to save some dollars...I'm in for about 4k right now with machine shop and parts. But I needed an replacement block, and I ordered some extra(future use parts) like headers, intake and pre bent exhaust tail pipes. Which will now all be installed during the reinstallation of my motor.

    I'm no engine expert by any means. Those who are please remember us that aren't may need additional information or assistance to understand the ins and outs of building engines or what would be best for our Buick engines.
    TorqueMonster1 and 70skylark350 like this.

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