FNG/ Heads Selection Assist Needed

Discussion in 'Street/strip 400/430/455' started by Matt Ennis, May 12, 2019.

  1. Matt Ennis

    Matt Ennis Well-Known Member

    Hi guys,

    New guy here, I purchased a 69 custom deluxe with a 350/st300. It came with a 68 400 block bored to 430 with 10:25:1 forged pistons with custom file fit rings. The heads have stage 1 valves and the cam was pretty stout,510 lift custom ground by Scott Brown,flat tappet lifters,hi volume blueprinted oil pump B4B intake...th375. I will hopefully be making the swap in the next few months.
    Heads are the high flow ones from a 68 430. Would the TA head's give more HP?
     
    Donuts & Peelouts likes this.
  2. TrunkMonkey

    TrunkMonkey Well-Known Member

    FWIW. I had a 430 with tall ports from an Electra and went with TA Stage 2 and their headers.

    Figured the cost of getting iron heads ported and built up, it was more cost effective and greater flow/durability to go the TA route.

    (I have everything ready to assemble, did all my oil mods, and deck mods for the heads, extra bolt holes, blocking oil ports and near zero deck, but have been finishing a few mods to my '64 'lark before putting the 430 together for the '68 'lark, so I cannot speak to it running, yet...)

    But, I do not think I will be disappointed in the least.

    If your heads are in good shape and the worl/parts were done well, then you may be in a good place.

    Either sell them and by the TA, or run it and see what you get. You can always buy them later, and you won't be out much spending in the process.
     
    Donuts & Peelouts likes this.
  3. Matt Ennis

    Matt Ennis Well-Known Member

    Also does anyone know if I'll have to modify driveline with that setup?
     
  4. TrunkMonkey

    TrunkMonkey Well-Known Member

    Will you keep the ST300 or swapping it out?

    You will need the correct frame pads, for the small block to big block and you may be looking at yoke/drive shaft length, but nothing too tough.

    Cooling will be another area and some wiring mods to the front/engine harnesses, and a few other small things.

    But enough people have done this, that the wealth of information and parts you will need are not out of reach.

    If you have not thought of it, evaluate your braking and suspension, as you will find things like understeering in corners, vehicle stance and stopping will become "things of excitement" when you first encounter then after the swap.
     
  5. Matt Ennis

    Matt Ennis Well-Known Member

    I'll be swapping to the th375. I just had the frame pads and motor mounts delivered. Front brakes are already swapped and was thinking about doing the back.

    Where would i find the info on the wiring and the other things needed?
     
  6. TrunkMonkey

    TrunkMonkey Well-Known Member

    If you have the service manual for your car, it will have the wiring diagrams for the GS. That will be a good place to start.

    Make a list of things you have already done, or have the parts and info to do, and post it. You will get replies either proving info or folks asking questions about the things/items that are "missing" in the discussion.

    It's fairly organic in the process of "filling in the gaps".
     
    Matt Ennis likes this.
  7. johnriv67

    johnriv67 Well-Known Member

    Best resource is the chassis service manual for that year. I sadly forget where I ordered mine from, but they’re out there

    TM beat me by 3 seconds:D
     
    TrunkMonkey likes this.
  8. TrunkMonkey

    TrunkMonkey Well-Known Member

  9. Donuts & Peelouts

    Donuts & Peelouts Life's 2 Short. Live like it.

    Hey FNG welcome to the site.
     
    Matt Ennis likes this.
  10. Thumper (aka greatscat)

    Thumper (aka greatscat) Well-Known Member

    Noticed you mentioned hi volume oil pump, some attention needs to be done to minimize any possibility of cam gear or front cam bearing wear. Watch cold oil pressure, run only 10w30, check what oil pressure spring was installed. A stock spring is usually enough. Also were oil passage mods done?
    gary
     
  11. LARRY70GS

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

    Will it make more power with the TA Aluminum heads? Yes, without a doubt. If you do go with aluminum heads, measure everything and determine your static compression. Aluminum heads need more compression. Get it to at least 10:1, maybe even 10.5:1 but that will depend upon your cam. Just because your pistons are rated at 10.25:1 DOES NOT mean that is what you have unless the pistons are at zero deck, they probably aren't. That's why I say measure everything and calculate what you have.

    X2 on the HV/HP pump. A blueprinted stock pump will give you all the oil pressure you need and not load the front of the engine.

    http://www.v8buick.com/index.php?threads/oil-pump-clearances-and-oil-pressure.326597/
     
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  12. LARRY70GS

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

    This might help,

    http://www.buickperformanceclub.com/conversi.htm

    I would look around for a 400 instead of the THM375. The ST300 has an electric kick down like the 400. The THM375 uses a cable like the THM 350.
     
    Last edited: May 13, 2019
  13. Philip66

    Philip66 Well-Known Member

    Where are you located? If we knew that someone close to you may have a Trans for you. I've got a couple but pick up only, not shipping one.
     
  14. Matt Ennis

    Matt Ennis Well-Known Member


    Larry, correct me if I'm wrong but I thought the 375 was essentially a 400 just in a 350 shell? Doesn't the 375 have an electronic kick down as well?
     
  15. Matt Ennis

    Matt Ennis Well-Known Member

    Spokane Washington area. The transmission i have had been built for the motor and i would like to run it if possible
     
  16. Bens99gtp

    Bens99gtp Well-Known Member

    the th375 is basically a 400 with a 350 27 sline output shaft instead of the normal 32 spline of most 400.

    you could have the output shaft changed.....but if mostly street driving doesnt make much since to do this
     
  17. Matt Ennis

    Matt Ennis Well-Known Member

    So basically just have to get a new yoke?
     
  18. LARRY70GS

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

    I thought the 375 had more in common with the 350 than the 400. Is the 375B different than a a 375? In my 72 Buick chassis manual, the 350 and 375B are covered in the same section, and the pictures show modulator position and pan/filter the same as a 350.
     
  19. LARRY70GS

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

    Looking at my transmission books, it seems that the 375B is a 350 derivative and the 375, a 400 derivative. That's where my confusion came from. Matt, which one do you have?

    If it is the THM375, it should have a longer extension housing with 375-THM cast into it on the bottom.

    THM375.jpg
     
    Last edited: May 13, 2019
  20. Bens99gtp

    Bens99gtp Well-Known Member

    these also came in the early 90s ss pickups, not sure if they had s special length housing, but I did go through one for a customer and all the parts and trick I use on a 400 went to it. but gear vendors took a few times to get me the correct stuff.

    I'm almost positive that a th350 yoke fits it
     

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