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Exhaust Size

This is a discussion on Exhaust Size within the GTO forums, part of the Vehicle Specific category; We are now in an era where small block CI capacity is the same as a big block. So, what ...

  1. #1

    Exhaust Size

    We are now in an era where small block CI capacity is the same as a big block. So, what is going on with small block exhaust system to keep up. Most 500 CI BBs have 2 1/4-2 1/2 in. exhaust tubes and 3 1/2-4 in. collectors. So, the issue I am kicking around in my mind is: how far can we go with 1 and 3/4inch exhaust tubes and 3 in. collectors?? This especially important for FI motors

  2. #2
    Nitrous Tuner LS2Tuner's Avatar
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    Aug 2006
    WestCoast AZ-CALI

    05 Goat SMASHED

    Well the main issue your going to run into is the major loss of TQ when you step up the size. Plus with the major loss of back pressure it tends to make it worse on FI motors with reversion.

    If you are staying stock stroke save your money for a few hp gain your loss 20-30 tq which you'll feel in drivabilty. The few ponnies you won't even notice.

    Also if you plan on spraying it then a little bigger is also so better.

    The only quality big tube headers I know of that fit well are the Kooks 1 7/8" Primary and they have a 3" collector.

    What are your plans?

    Are you going to buy a LSX block and build a 454ci LS motor or are you just making a general ?...........
    Don't be afraid of the bottle!!! Be afraid of your tune!!!

  3. #3
    Yes, you raised some good points. Some years ago I used to race CBBs and know we needed large pipes to aid the flow. But the SB problem concerns the small heads which are OK for motors 400 CI and less. 500 CI are BB numbers and you need the bigger heads and ports to handle the flow.

    I am not an automotive engineer, but 500 HP, whether generated from a SB or BB have almost identical calorie requirements. In otherwords, the SB heads have to handle the same amount of air and fuel to get the same results.

    Actually, I was considering putting a BB in a GTO. The motor's height is OK, but devising an exhaust system is a PIA. BTW the babe in your signature has an a...s sent from heaven.

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