Dominator/Holley 4150/Demon 850 -SP1

Discussion in 'Street/strip 400/430/455' started by DasRottweiler, Oct 17, 2020 at 7:52 AM.

  1. DasRottweiler

    DasRottweiler -BuickAddict-

    Ok, I am thinking of going with an SP1 intake manifold with a Dominator flange. Can I bolt a Holley 4150 /Demon 850 to it? It does have two bolt patterns...JIM
    Last edited: Oct 17, 2020 at 8:37 AM
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"


    BQUICK Well-Known Member

    You can run an adapter....
    DasRottweiler likes this.
  4. DasRottweiler

    DasRottweiler -BuickAddict-

    Ahh, plenty of room to go up, (Stage 2 Scoop)
    Notta fan of adapters....gonna hafta make a decision...
    Thanks all for the replies...JIM

    BUQUICK I'm your huckleberry.

    I’ve been looking into this exact same question myself. I want to replace my E85 Dominator with a 4150 gas carb since I lowered the compression from 13:1 to 10.5:1 but I want to keep my old KB Wildcat intake which has a 4500 flange.

    anyway, I see that there are a few 4150 carbs out there that have a dual pattern baseplate pattern. No need for an intake adapter for either application.

    this is just a single example:

    Or depending on which 4150 carb you have, you can swap the baseplate with something like this:
    DasRottweiler likes this.

    BUICKRAT Torque Rules!

    if the sp1 has 2 bolt patterns, one may well be for a 4150, but yer gonna have to measure or try it yerself
  7. DasRottweiler

    DasRottweiler -BuickAddict-

    Apparently, you need an adapter to go from 4500 to 4150. Not sure ifya can go the other way, if ya follow...
    I'm buying an SP1 square bore off the board and I'll be using my Demon 850 on it. The Dominator may go up for sale after a going through. Just can't see doing all that wrenching , heads, cam etc. and bolting my old Offenhauser 360 back on....
    Hey, did you toss yer old felpro head gaskets when ya went thru your motor?
    Could use if if ya got em hanging on a nail for mockup on your old block. J
    Last edited: Oct 17, 2020 at 6:03 PM
  8. BrianTrick

    BrianTrick Brian Trick

    Yes,you will need an adapter,or weld and machine the intake. I am running a ported 4-hole adapter with my intake,so I can run a 4150. I pin the adapter to the intake to do any needed blending. I have the part number for the adapter at work. I can post it Tuesday.
  9. hugger

    hugger Well-Known Member

    a simple 1/2 in adapter is all you need,. And when going from a 4500 to a 4150 there is no real work or interference whatsoever

    When goung from 4150 to 4500,..yea you create a bottleneck if yiu use the adapter but it would only show up WAY up in rpm range that a buick will never see, could argue it may would even benefit a combo,. Serving a venturi effect

    To "properly" go from a 4150 requires machine and hand profiling

    The dual bolt pattern on tge 4150 sp1 is qjet and 4150
    DasRottweiler likes this.

    BUICKRAT Torque Rules!

    Pretty sure I tossed them, but I'll check later today...
    DasRottweiler likes this.
  11. BrianTrick

    BrianTrick Brian Trick

    I have one of those 1/2” adapter spacers. Yes,it would “work”,but the transition will leave potential power loss. Mock it up and see how it looks.
  12. hugger

    hugger Well-Known Member

    You're only creating more plenum volume,...the short turn under it wouldn't cause any issues in my mind as the air isn't sitting its hitting the floor and being pulled,..path of less resistance imo,.."I" would just go with a dominator and call it a day ha
  13. DasRottweiler

    DasRottweiler -BuickAddict-

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