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Thread: Stock L31 or TPI?

  1. #1
    Fuel Injected! sturgillbd's Avatar
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    Stock L31 or TPI?

    I ended up with a cracked head after 3 years on my vortec headed tbi in my Willys Jeep. Heads were a set of EQ CH350C's that were on a burned to a crisp L31 from a junkyard. Heads hadn't given any sign of problems until the other day and I noticed some steam from driver side exhaust. Hadn't been losing coolant nor had engine been hot. Bought a new set of Promax 2151's and they are installed. I have been wanting to convert to MPFI for a while now. I have a couple complete L31 intake assemblies and also have a complete TPI setup with a new Vortec base. I run $0D with a 16197427 in the Jeep. Engine is a 350 with 4 valve relief flat tops and a Howards 180245-10 cam .500"/.510 225/230 @0.050 . Engine ran good with TBI but started pulling a vacuum above 4000 rpm at WOT. SBC TBI didn't flow enough. I would like some opinions on TPI vs L31 setups. Cam power range is advertised as 1800-5400 rpm. With TBI, it was really easy to hit the 6375 max rev limiter in lower gears in the Jeep. Which intake would you choose given the choice? Mainly the Jeep is driven on the highway. Some offroad . I got 19.5 mpg on highway trips with TBI driving sensibly. I don't want to kill the higher rpm power it has now but still would like to go MPFI. Any thoughts ?


    Thanks for any input,
    Brian

  2. #2
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    Quote Originally Posted by sturgillbd View Post
    I ended up with a cracked head after 3 years on my vortec headed tbi in my Willys Jeep. Heads were a set of EQ CH350C's that were on a burned to a crisp L31 from a junkyard. Heads hadn't given any sign of problems until the other day and I noticed some steam from driver side exhaust. Hadn't been losing coolant nor had engine been hot. Bought a new set of Promax 2151's and they are installed. I have been wanting to convert to MPFI for a while now. I have a couple complete L31 intake assemblies and also have a complete TPI setup with a new Vortec base. I run $0D with a 16197427 in the Jeep. Engine is a 350 with 4 valve relief flat tops and a Howards 180245-10 cam .500"/.510 225/230 @0.050 . Engine ran good with TBI but started pulling a vacuum above 4000 rpm at WOT. SBC TBI didn't flow enough. I would like some opinions on TPI vs L31 setups. Cam power range is advertised as 1800-5400 rpm. With TBI, it was really easy to hit the 6375 max rev limiter in lower gears in the Jeep. Which intake would you choose given the choice? Mainly the Jeep is driven on the highway. Some offroad . I got 19.5 mpg on highway trips with TBI driving sensibly. I don't want to kill the higher rpm power it has now but still would like to go MPFI. Any thoughts ?


    Thanks for any input,
    Brian
    A L31 intake and TPI will both choke that setup by 5,000 rpm.

  3. #3
    Super Moderator dave w's Avatar
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    I like tuning the 16197427 with WBO2. I've tuned the aftermarket TPI intake system designed for the stock L31 heads using the 16197427 configured for MPFI using WBO2. I've also tuned the a stock L31 using the factory L31 intake system using a MPFI modified 16197427. In my humble opinion, the stock L31 engine with the aftermarket L31 / TPI intake base is the better option, when using WBO2 tuning (if a honest 310 RWD HP is an acceptable performance goal?).

    The Howards cam specified in the post above exceeds the lift limits of a stock L31 head, but everyone reading this post knows that right?

    dave w

  4. #4
    Fuel Injected! sturgillbd's Avatar
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    Yes on stock L31 heads not being compatible with the Howards cam mentioned above. The EQ heads already had screw in studs, I added a set of inexpensive roller rockers and used this kit to overcome the lift limitation. https://www.alexsparts.com/valve-spr...ssure-vsk4h53/ It uses an offset/shorter retainer to give clearance for higher lift. Attached is a pic during the install of the heads and of the crack that appeared about three years later.

    I think I'll just use the TPI setup I have and see how it does. Thank you both for your input.

    Brian
    Attached Images Attached Images

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    Why not a EFI single plane- I once used the Edebrock MPFI conversion kit- can't remember the intake- Torker2 ?

  6. #6
    Fuel Injected! sturgillbd's Avatar
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    My main reason for not getting a new efi setup is I have too much stuff gathering dust already. I have a Weiand Stealth ram also but hate to use it since I have a new in box TPI stand-alone harness I had planned to use with it. Too many projects and plans but not enough time anymore.

  7. #7
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    Quote Originally Posted by sturgillbd View Post
    My main reason for not getting a new efi setup is I have too much stuff gathering dust already. I have a Weiand Stealth ram also but hate to use it since I have a new in box TPI stand-alone harness I had planned to use with it. Too many projects and plans but not enough time anymore.
    I grabbed a L31 marine intake off an Indmar marine engine for my project.

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