SP1 dyno testing with carb spacers

Discussion in 'Street/strip 400/430/455' started by 436'd Skylark, Dec 5, 2017.

  1. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Mark Demko and 300sbb_overkill like this.
  2. Mark Demko

    Mark Demko Well-Known Member

    Interesting results from Cliffs testing for sure!
    When I get my GS back to the track, I'm going to try spacer/no spacer. Hopefully it likes no spacer due to height issues it causes:D
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Mine runs fine with just the 1/4” gasket. Don’t know if I would pick up Power with a spacer as I don’t have the hood clearance to try it.
  4. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    that's the ass kicker Larry. We are all in the same predicament with the hood. It would have to be a pretty good game for me to mess with the hood. I'd like to see some numbers to make an informed decision
  5. sriley531

    sriley531 More Luck than Skill....

    Happened to me once. Just cut a hole in the hood. Easy-peasy..... haha
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  6. Jim Weise

    Jim Weise GOT AIR? Staff Member

    I am crazy busy right now finishing and engine build, but I can offer this.

    Yes, I have tested spacers on all manifolds, many times. As of today, I have dynoed over 100 different combos of 455 based engines, and very few of them got off the water brake without having a spacer or two tested.

    Generally speaking, the SP-1 likes a 1" dart cloverleaf or 4 hole to open transition spacer, (HVM Super sucker) under a Holley. Don't test a ton with Q-jets on a single plane intake, but I am sure I have done it. I like Q-jets on dual plane manifolds, the stronger vacuum signal for the "smarter carb" make them work well.

    Typical gains are that it spreads the torque numbers out, which makes more upper end HP.. 8-12 more HP is not uncommon, I have seen it in the mid to high teens, but that is fairly rare.

    Every combo is a little different, if I recall we tested a spacer on Larry's motor, and it made very little difference.

    I will dig up the numbers later.

    In my experience, spacers are actually more effective on the dual plane manifolds, saw over 20HP with an 4 hole spacer under a 1000 TQ on a 500 HP iron 464 years ago.. I remember it because it was such a big improvement.

    One hard and fast rule is this. Airflow does not like "shelves".. do not put an open spacer on a dual plane intake, with an intact center divider, and expect to pick up power.. it's more likely to go the other way. Simple common sense here. Using multiple spacers, a 4 hole under an open spacer is obviously wrong..

    Later on, hopefully this evening, I will dig up some numbers and sheets for you to look at.
    Skippy597 likes this.
  7. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    I had no problem with hood clearance when using a TA SP1 with an 850 Holley, 1" Moroso 4-hole spacer (ran better than the Moroso open spacer I tried), Aluminum heat shield, and 3-gaskets between it all. That was when using a Corvette drop base air cleaner bottom and a 4" K&N filter too boot. That Corvette drop base will work just as well in a Quadrajet application (the 2 carburetors are the same height). If using the Stock GS "Cold-Air" air cleaner system then that would be a completely different story.

    Bluzilla's 14.56;1  Stage 1.jpg Bluzilla's Engine Bay 1992.jpg

    Last edited: Dec 6, 2017
  8. Robs455

    Robs455 Well-Known Member

    Drop base air filter robs power compared to a flat one..
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  9. Mark Demko

    Mark Demko Well-Known Member

    Same thing they noticed on the dyno on Engine Masters
  10. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    Informative video! According to that dyno session the flat base (place #7) did make more power than the drop base (place #9) with the same K&N filter and solid lid. A whopping ..........."2.3" Horsepower on a ........."752"Horsepower Engine! Too bad they didn't test the GM engineered Corvette (umbrella) drop base. Notice that the 4" tall K&N (place #5) made "5.2" Horsepower over the 3" tall K&N (place 7) with the same flat base and lid. Given that information, using a (drop base 4" K&N) VS a (flat base 3" K&N) and the same solid lid, the (drop base 4" K&N) should net a "2.9" Horsepower increase. Add that to the Horsepower you're gaining by allowing the use of the carburetor spacer (which is the main reason of this thread) and you should end up with a worthy Net-Horsepower gain. That fortifies why I noticed on my dyno (the drag strip) that my Corvette umbrella drop base with the 4" tall K&N filter and solid lid worked the best for my Skylark. My take on all this, ..... which I tested over 25 years ago,.... is the taller and larger diameter the filter.... the better, (given the same base style and lid).

    Last edited: Dec 7, 2017
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