Results 1 to 8 of 8

Thread: vortec head 89 tbi engine

  1. #1
    Carb and Points!
    Join Date
    Aug 2016
    Posts
    4

    vortec head 89 tbi engine

    hello all, I have been reading this forum and have enjoyed it. I am a veteran engine builder, sprint cars and drag, for years. I am currently embarking on a engine for my sons 89 chevy pickup. Frame off restoration, nice piece. I have been concerned with the efi. Plan to use stock system. Vortec heads, vortec pistons, block decked to zero, Scat 4340 crank (no cast cranks here) and Crower sportsman rods. The aim is a everyday driver that runs good, torque and mileage and not over 5500 rpm. Plan to use GMPP manifold, new exhaust with improved y pipe, converter, muffler ect. My concern is the compression ratio. Quick calc says 9.4, although I have not cc the parts yet, and I will soon. I have the ability to machine the pistons to change that if needed, cnc is my business. Programmer for 35+ years. I have d cupped pistons for many custom builds for street friends in the past. As far as cam is concerned my understanding is a very wide LSA is required with this system, and am planning on that. So that leaves me with a relatively high dynamic CR. I want this thing to run on 87 and will do what is needed to make that happen. Have several stock roller cores for regrind (Crower) and will go that route. So my Question is, where do I need to be on the CR without a big tuning rodeo that I don't have time for. Thank You 2424

  2. #2
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    6,268
    I use the decimal point rule for compression ratio vs. octane, which goes like this:
    8.7:1 = 87 Octane
    8.9:1 = 89 Octane
    9.2:1 = 92 Octane

    Quench is key! http://www.superchevy.com/how-to/eng...earance-guide/

    dave w

  3. #3
    Fuel Injected!
    Join Date
    Oct 2013
    Posts
    1,022
    What kind of LSA do you consider very wide?

  4. #4
    Carb and Points!
    Join Date
    Aug 2016
    Posts
    4
    Quote Originally Posted by lionelhutz View Post
    What kind of LSA do you consider very wide?
    I consider 114-117 wide. Thanks for the reply

  5. #5
    Carb and Points!
    Join Date
    Aug 2016
    Posts
    4
    Quote Originally Posted by dave w View Post
    I use the decimal point rule for compression ratio vs. octane, which goes like this:
    8.7:1 = 87 Octane
    8.9:1 = 89 Octane
    9.2:1 = 92 Octane

    Quench is key! http://www.superchevy.com/how-to/eng...earance-guide/

    dave w
    I figured about 8.8 to 9.0 but maybe you guys know something about the vortec head I don't. More tolerant because of combustion chamber? Thanks for the reply

  6. #6
    Fuel Injected!
    Join Date
    Oct 2013
    Posts
    1,022
    I've run very well with 110* to 112* LSA. You don't need over 114* for it to work.

  7. #7
    Carb and Points!
    Join Date
    Aug 2016
    Posts
    4
    Quote Originally Posted by dave w View Post
    I use the decimal point rule for compression ratio vs. octane, which goes like this:
    8.7:1 = 87 Octane
    8.9:1 = 89 Octane
    9.2:1 = 92 Octane

    Quench is key! http://www.superchevy.com/how-to/eng...earance-guide/

    dave w
    Zero piston to deck with .039 gasket

  8. #8
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    6,268
    A quench of 0.039 is a touch to tight for me, I favor a quench in the .042 to .045 range.

    The Vortec head is a fast burn design, allowing for more spark advance compared the pre-Vortec factory heads.

    dave w

Similar Threads

  1. Vortec Head swap on my '92 TBI 350. Tuning questions.
    By jdyates in forum GM EFI Systems
    Replies: 73
    Last Post: 09-22-2016, 03:50 PM
  2. Replies: 14
    Last Post: 03-17-2016, 01:04 AM
  3. Please Help TBI Vortec Engine
    By andy@e-t-d.at in forum GM EFI Systems
    Replies: 8
    Last Post: 11-22-2015, 02:18 AM
  4. 94 K1500 TBI / Vortec head swap - Cam question
    By dispoejoe95 in forum Gear Heads
    Replies: 17
    Last Post: 10-30-2015, 03:54 AM
  5. Vortec head 355 TBI
    By dmsdak in forum GM EFI Systems
    Replies: 1
    Last Post: 07-20-2015, 03:58 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •