Switched to 3.73 gears and not loving it

Discussion in 'High Performance Modifications' started by sinnyz_me, Jul 7, 2018.

  1. 1978 Z/28

    1978 Z/28 Veteran Member Gold Member

    Messages:
    105
    Likes Received:
    27
    Joined:
    Jul 17, 2017
    Location:
    New Brunswick
    with 3.73s with stock tires at 60 mph rpms were 3000 when I went to 4.56s rpms went to 3700. now I am going with 3.42s
     
    sinnyz_me likes this.
  2. muscl car

    muscl car Veteran Member Lifetime Gold Member

    Messages:
    21,726
    Likes Received:
    638
    Joined:
    Jul 8, 2001
    Location:
    High Desert of Hesperia Calif
    Im running 3.73's with 28" tires with no problems and with a built sbc and 4200 stall converter
     
    sinnyz_me likes this.
  3. sinnyz_me

    sinnyz_me Veteran Member

    Messages:
    104
    Likes Received:
    7
    Joined:
    Jul 23, 2006
    Location:
    Des Moines, IA
    What motor are you running with that? I have a gm good wrench 350 so nothing wild with horsepower. So with the 3.42's is that still good for quickness of the line and burnouts?
     
  4. 1978 Z/28

    1978 Z/28 Veteran Member Gold Member

    Messages:
    105
    Likes Received:
    27
    Joined:
    Jul 17, 2017
    Location:
    New Brunswick
    I am going to run a 350 bored 40 over, flat top forged pistons, 292 turbo heads giving a 9.9 cr, victor JR intake, Holley 750 double pumper and a XR282HR cam. I am running a wide ratio m22 with a 2.52 first gear instead of 2.2 the overall first gear is 8.61 with 3.42s compared to 8.2 with 3.73s. So with the 2.52 first gear there is enough gear ratio for off the line. I ran a flat tappet crane cam with a .488/.508 I/E lift 234/236 degrees duration @ .050 with the 3.73s ran 13.08 @108 mph closed exhaust and street tires
     
  5. wiseryder

    wiseryder Veteran Member Lifetime Gold Member

    Messages:
    2,109
    Likes Received:
    49
    Joined:
    Sep 11, 2004
    Location:
    belding,mi USA
    They sure are. My buddy just purchased a 4L80E, with controller, almost 4K, they said it could handle 1200 HP ,Hes around 800Hp
     
  6. NYH1

    NYH1 Veteran Member

    Messages:
    1,594
    Likes Received:
    12
    Joined:
    Feb 27, 2010
    Location:
    Central New Yorkistan
    You might get better results with a high rise dual plane intake like the Edelbrock Per. RPM or Weiand Speed Warrior and a 650 vacuum secondary carb.

    NYH1.
     
  7. 1978 Z/28

    1978 Z/28 Veteran Member Gold Member

    Messages:
    105
    Likes Received:
    27
    Joined:
    Jul 17, 2017
    Location:
    New Brunswick
    Before picking the cam, talked with comp cams about the setup and this is the cam they recommended.
     
  8. 1980RS

    1980RS Veteran Member

    Messages:
    3,418
    Likes Received:
    597
    Joined:
    Jun 17, 2006
    Location:
    MN
    Switch those 292 heads to some Vortec's and an Air Gap and watch that car go easy into the 12's. The 292's unless really, really ported are a very poor head on the intake side, they are also crack prone. The have a real bad flat floor that hurts power and it's for the short side radius for air to make the turn.
     
    NYH1 likes this.
  9. 1978 Z/28

    1978 Z/28 Veteran Member Gold Member

    Messages:
    105
    Likes Received:
    27
    Joined:
    Jul 17, 2017
    Location:
    New Brunswick
    not worried about et times and 292s have more metal where previous heads cracked bought heads new from my uncle's Chev dealership and intake was port matched to heads by an old machinist and myself in 1979 where we worked one friday afternoon, also daughter in law painted the lettering on the intake and valve covers. keeping them sentimental reasons

    IMG_3126.JPG
     

    Attached Files:

    camaro71/holland likes this.
  10. jeff swisher

    jeff swisher Veteran Member

    Messages:
    1,375
    Likes Received:
    416
    Joined:
    Apr 26, 2018
    Location:
    Yukon Oklahoma
    I feel all these stories of crack prone heads are due to heads that have been mistreated..Like ran with wrong octane or too much timing or got too hot too many times.

    I used to drive more than 70,000 miles a year and tested all kinds of "myths" and all kinds of cams also.
    9 years of that and you put a lot of that weak or crack prone talk to rest.
    Not to mention I have build many sets of heads for buddies.
    624 castings were said to be crack prone. None of mine were.. 305 heads were said to not flow any air.. not in my testing and measuring..and another Crack Prone head. Only time i ever had a cracked head was when i first purchased the head and found it was already cracked.

    Do not think I am easy on my stuff either.
    Here is my MPG build to get the bugs worked out of a 1947 dodge I just put on the road.
    305 heads with 1.84-1.50's and 268H on 106LSA in a 350" sweeping the tach to 7000 rpm.


    2.75 gears in that one but it made a lot of low speed TQ so did quite well for a highway gear.
    On a very conservative wheel dyno Not corrected it made 261 HP.
    That same dyno would show 220 Wheel HP on the 5.3 Gm engines.
    Not too bad for a mileage build 18+ MPG with spirited driving tossed in.
    TH350 . It ran 14.0 with mud and snow tires and 13.5 with sticky tires. Today it has a little more spunk and i hope to improve that ET.
     
    Last edited: Jul 10, 2018

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.