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Thread: Misc. pointers for swapping in an SBC or BBC cheaply-

  1. #1


    I just changed my 715 from a 350 (which it had come with) to a 427 TD. During the swap I had some help from members that came to me over PM's or e-mail and I wanted to list some of it here to help someone else.

    The motor came with a truck oil pan. I had to swap this out to a car 4 quart oil pan (Summit Racing part number SUM-G3510X) in order for it to clear the pumpkin. This gave me plenty of room from the bottom of the motor to the axle while able to use the stock motor mount horns.
    I got GM motor mounts from my local parts store that were made to fit a 1970 Chevy truck with a V-8. This is not model specific as apparenty all GM vehicles with a V-8 from '65-'72 used the same motor mounts. They fit the block perfect and with a little grinding on the motor mounts to make them flat, they fit the stock frame horns in the lower set of bolt slots. They fit the horns in such a way as to be more or less self-centering and thus level the motor almost automatically. They cost me $15.21 for 2 mounts.

    The only real problem with using these motor mounts on the stock frame horns, with the stock frame horns in the stock locations is that you have to dimple the fire wall. This shows it better:
    (Passenger side needs more dimpling)

    (driver's side)

    This gives you plenty of room to run a fan in front of the motor.

    I mated my motor (botht eh 350 and this 427) to an SM465 that is mated to an NP205. This combination is really cheap and plentiful. It's worked fine for me and I've had no complaints with the tranny of the transfer case. I had to fabricate a mount for them, but it was a simple straight-forward job. The clutch linkage on an SBC can use the pivot stud cast into the block, but I just fabricated my own linkage in a stand-alone manner that is basically just the linkage set in a bracket that is welded onto the frame. Pretty easy and stout. (if you want pics of my linkage, e-mail me and I'll take some).

    Hope this helps someone.

  2. #2
    Join Date
    Dec 2003
    San Antonio,Texas


    glad to see you got it in there B-
    67 M725 84 GW

  3. #3


    pics of the linkage please. been considering using an sm465, would like to know how you did the linkage. thanks. (

  4. #4


    I don't remeber off hand how the stock 715 linkage is. I remember that it has a pivot on the block and a pivot on the frame, but other than that I'm a blank.
    What I did was to get the linkage off my donor K truck. I had the pedal from the 715, as well as the rod that connects the pedal to the roller (?) part. That was it. The GM roller part (?) was all I needed. I took some flat 2" by 3/8" bar plate (from Home Depot) and bent it into a "I______I" shape and then put the roller (again?) between the posts of the "I______I". I welded the bracket to the frame, and used the stock bolts from the roller to bolt it to my bracket. I moved it over as far to the driver's side as I could as to give me plenty of room between it and the block.
    Here is a crappy pic-
    (This is looking down from the master cylinder)

    Then I used a stick of all tread to go between the roller and the throwout fork. Pretty simple, and really sturdy. The tricky part is that the bracket you make has to have a mount for the pivot on the front of the passenger side of the roller, and a mount from the bottom to the pivot on the driver's side. This is due to the arms of the roller being located. You'll see what I'm talking about if you look at your roller.

    Good luck,

  5. Default

    Why when you had the 350 did you run an electric fan? Did you use the stock Radiator with your 350,are you using it with your 427? Why sm465? What HP 350 did you run? I don't hate my 230, but I wasn't too happy with it today.-Thanks
    1969 M715

  6. #6


    What are you going to do for exhaust manifolds or headers. My 366 came with factory headers and setting the motor up like you have has the headers coming down on the frame mount on the passenger side


  7. #7


    love your article ! i have a 350/400th i need to swap into a stock 725 . this is going to get me on the road soon ! did the 350 quit working for you or was it enough power ? i want to do this truck as cheap as possiable . i have 3 kids to send to school and don't want to go broke supporting my 4x4 addiction ! i was given the ambulance and have a 84 suburban for a donor vehicle .

  8. #8


    Dan Archy,

    I ran the electric fan with my 350. The stock radiator would not cool it, and so I replaced it with a radiator for a Gm vehicle that had a BB. I dunno the part number for it, but can find it monday if you need it. That radiator woudl cool the 350, but not on the highway in 100 degree weather with 12* of advance w/ no shroud. So I got the electric fans. They kept it at 180* no matter what.

    I dunno if this setup will cool the 427, but I think it will. 4 row radiator, 2 puller fans.

    I am running the 465 because I got a deal on it. I wanted a new 205 and this tranny came with it.

    As to my 350's Hp- I'd guess 260 or so. I liked the power, but it leaked alot of oil and that drove me nuts.

    I have the same problem with my factory exhaust. Barry gave me a part number to soem headers that look to fit right. I'll be getting them in the next 3 weeks and if you can wait then I'll shoot you the part nubmer and a report on how it went along with some pics.

    New Guy,

    The 350 had enough power for me, and was capable of the rpms I wnated. I built the 350 myself and that palgued me since Day 1. I finally got sick of it and then this 427 came up. I didn't want more power (or torque as the case may be), but I wanted a running motor. The 427 seems to run this point.
    Good luck on your 725!

    Thanks for taking an intrest in my one and only tech article.

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