When to run a stall converter?

Discussion in 'Small Block Tech' started by Reidk, Nov 16, 2020.

  1. Reidk

    Reidk Well-Known Member

    I'm getting ready to pull my 1970 350 2 barrel engine. I plan to freshen it up with new front and rear main seals, front cam bearing from TA, sp3 intake, ta 284 88h cam, hooker super comp headers, edelbrock avs2 carb, and thinner head gasets, also very minimal DIY head porting.

    Should be 10:1 compression with the thinner head gaskets. The 284-88h is supposed to be a torquey cam, the edelbrock AVS2 is supposed to have incredible off idle response but the sp3 is the gray area for me...should I consider a stall converter with this combo? I will not be drag racing this car but I would like to be able to roast the tires. The stock 2 barrel 350 has just enough power to light up the tires for a few feet.
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  3. alec296

    alec296 i need another buick

    A 2 barrel engine with stock piston and thin head gaskets is 8.5 actual compression. I would advance the cam 4 degrees to try to get some low end torque up.
    or look at a crower level 3 cam, advanced 4 degrees. Will have more torque.
    the 284 a 2400-2500 small block rated torque converter will be decent, alittle more will make it more fun.
    The abs carb will need to be rejetted and other internal changes. Get an air fuel meter for that or you could be leaving lot of power on the table. Any carb is good for off idle response in tuned right. Not just an AVS .
    the 284 isn’t really in theory the right intake for a torque cam. Which can cause a need for a higher torque converter rpm. Dual plane is more for low end. porting, stick to valve bowl short turn and raise roof slightly. When diy porting, a 2 inch pipe with a 1 inch outlet isn’t going to increase flow. So opening the intake side without getting the valve side doesn’t make more flow.
    If you really want roast tires, get a 3 series rear gear like 3.42 -3.73. And possibly a 2.75 first gear set for transmission
     
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  4. Reidk

    Reidk Well-Known Member

    I really don't know the gear ratio. The fact that it's a bone-stock 2bbl 350 and does have some burnout power makes me think it may be slightly lower ratio than some. It struggles to hit 100 mph. That could be due to a number of things though.
     
    ceas350 likes this.
  5. Reidk

    Reidk Well-Known Member

    The parts are already on their way. The 1970 350 2 barrel is spec'd at 9:1 compression. What year was your motor? I know it dropped in 71. I don't have to maximize every last bit of off-the-line power necessarily. I just want to make sure I'll be able to do a nice burnout with this combo. If I go to step on it and it doesn't roast the tires. I'll be pissed I didn't run a stall converter.
     
  6. Reidk

    Reidk Well-Known Member

  7. alec296

    alec296 i need another buick

    I’m gonna suggest you research/or pull rear cover and get numbers. You would have to be a 3.73 - 3.90 to struggle at 100.
    not common for a 350-2 to have deep gears.
    The 9.0 compression is only advertising. It is not actual measured. Just a number the put in brochures. Hers a picture of the 70 pistons. The shallow dish is”rated 10 to 1” the other is rated “8.5” or 9.0 or 8.0. Depending on the year. If you mill .030 off head it should be near 50 cc head, and with thin gasket work net about 9.1 compression.
    Yes I have seen the cam, have the 455 version in a 430 with efi. Lots of torque in that. On a dual plane intake. A custom converter and a 2004r transmission with a 2.75 first gear
     

    Attached Files:

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  8. Reidk

    Reidk Well-Known Member

    When it comes to the heads is there any benefit to just cleaning up the edges of the ports?
     
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I suggest you measure everything so you know EXACTLY what your static compression will be. Factory ratings frequently mean nothing. It is likely lower.

    What you want to avoid is "cheaping" out on an off the shelf converter. You pay more money for a built converter, but it is well worth it. You don't want the converter to have a loose feeling, you want it to be efficient with good throttle feel at lower speeds. Read the thread I linked for you. I don't think I have ever read anything negative about Jim's converters.

    Stock 350-2 gearing was usually 2.56 or 2.73. I think you want 3.08 or higher gearing.
     
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  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  11. Reidk

    Reidk Well-Known Member

    As of right now my budget is pretty much maxed out. I plan to have the motor out and back in within a couple of weeks. The converters being recommended above are pretty expensive. The guys at ta said I really wont lose anything on the bottom and with the sp3. anybody else have enough experience with the sp3 to confirm that? I just want to make sure I have some nice burnout power with this combo LOL
     
  12. alec296

    alec296 i need another buick

    You would get more from recontouring the valve guide. And smoothing the valve area. if your gonna clean up the port opening, leave the floor. And raise the roof slightly.
     
    Reidk likes this.
  13. Reidk

    Reidk Well-Known Member

    The cam I bought specs 9:1. Hopefully the thinner head gaskets get me close to that. Buick advertises 9:1 stock...
     
  14. Reidk

    Reidk Well-Known Member

    Not sure on the terminology. I'm new to this
     
  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Like I said, that 9:1 figure means very little. If you are going to pull the heads off, just measure everything and you will know for sure.

    As far as the SP3 intake, I would start a thread titled, Who is running an SP3 intake? Then ask for their combinations and their impressions.
     
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  16. Reidk

    Reidk Well-Known Member

    Since I am struggling at a hundred do you think it's possible there's something else going on? maybe transmission?
     
  17. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The engine is running out of breath, probably because of the smaller carburetor and exhaust? Do you have a tachometer?
     
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The cam description recommends 9:1 compression. The reason for that is the subject of the article I linked for you,

    http://www.empirenet.com/pkelley2/DynamicCR.html
     
  19. Reidk

    Reidk Well-Known Member

    No I dont
     
  20. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    If you did, you could get a good idea of your rear gearing. 2.56 gearing will rev about 2000 RPM at 60 MPH
     

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