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Carb Spacer ?'s

Discussion in 'The Garage' started by Mr. Infinity, Apr 4, 2003.

  1. Mr. Infinity

    Mr. Infinity Registered Member

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    Carb Spacer ?\'s

    I am swapping my carter afb for a quadrajet 4mv tonight. I have a 1" 4 hole spacer now and since I am going to have to buy a new spacer I thought I would try a different one.
    My truck has a shiot load of HP and torque, so someone suggested going with a 2" open spacer for higher RPM's. Anyone got any thoughts or suggestions? This is what I am running now. 383 64cc aluminum heads, froged aluminum flat tops, comp cam x4262h(I am thinking about switching to the x4270h this summer), edelbrock performer intake. sm465, np205, detroit locked 5.13's front & rear turning 44 boggers.
     
  2. Mr. Infinity

    Mr. Infinity Registered Member

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    Re: Carb Spacer ?\'s

    Come on guys, I can't be the only one that uses a carb spacer. I am leaving work at 2:00pm to get my carb, so can someone throw some ideas out before then? /forums/images/graemlins/confused.gif
     
  3. Thunder

    Thunder 3/4 ton status

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    Re: Carb Spacer ?\'s

    Well basicly the 4 hole spacers are for low end torque.
    The open spacers move the torque curve toward the upper RPM range.
    A four-hole spacer under a carburetor that's too big can help pick up air speed and signal. It makes the venturi think it's longer and more efficient. This builds low end power.
    An open spacer adds plenum volume which helps on the top end.
    Use wichever spacer that matches the way you want your engine to run.
    In a truck with 5.13s & 44s I dont think is makes a whole lot of diference.
    On a drag strip they are handy to fine tune your engine to help lower your ET. Some people stack them and use combinations of both kinds.
    There is really no set rule of thumb with spacers except, Whatever works. They are just a tuning aid to use when you have everything else right.
    I like the open stackable kind. That way you can add or subtract height till you get things the way you want them.
    Because I have plenty of low end power.I am running an open 1/2 " spacer on my modified TBI 350 it works ok. I can easily peg the spedo on my K5.
    I have used all kinds of spacers on carbed engines I have built.
     
  4. Mike's '84

    Mike's '84 Registered Member

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    I'm about to swap a stock Rochester with a new/rebuilt from National Carburetor for my 84 350. Would a spacer hurt my chances of acing my next appointment with the Smog Cops? Everything else is stock.
     
  5. R72K5

    R72K5 Banned

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    technically you would think that exhaust would be cleaner since a spacer would give fuel air mix more time to mix and therefore would burn more completely

    but maybe that actualyl would increase no2

    but would be less raw fuel in exhaust at least

    and id go with 4 hole unless youre engine is badass solid overlap cam high stall required and big time bored and such

    good luck
     
  6. bigblock44k5

    bigblock44k5 1/2 ton status

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    You might not see anything but a decrease in power due to the fact that the open spacer is going against what your intake is for. Open spacers work best with single plane intakes. You are basically making your performer a crappy single plane intake. You could possibly see a bit more in the upper rpms, but you will lose more than that down low.
     
  7. diesel4me

    diesel4me 1 ton status Premium Member

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    no way to tell but by trying it....

    I bought both style spacer/adapters when I put a carter AFB on my 400 small block in the 74 K20,on the stock Q-jet manifold--it ran ok with the 4 hole spacer,but I was curious as to how it would go with the open one that has a thin divider in the center of it,so I swapped that one in,and WOW--what a difference!--it felt like just changing the spacer and flipping the air cleaner lid over to expose the element made 50 more horses!--the 4 hole spacer didnt feel like it added any low end torque at all--if anything,it felt weaker!--with the aircleaner in its stock form,with the 4 hole spacer,it was not very impressive at all,despite the claims it makes more low end power--didnt in my case---.

    When I had the Edelbrock on my 250 six,I found the 4 hole spacer helped that motor run stronger at low speeds though--I guess the open spacer made the plenum have too much volume,and slowed the velocity of the fuel air mixture down to a crawl when you openned the throttle,causing the motor to "flatten out" and nearly bog out--it was much more responsive with the 4 hole spacer--I guess the smaller the motor,the faster the fuel air mixture needs to flow thru the motor--bigger motors have enough "suction" to pull enough air thru the open adaptors,and can burn all the fuel you can pour in...:crazy:

    Every motor is different,whether stock,mildly built,or full race--I think trying each spacer is the only way to tell which will work best in your case...:)
     
  8. Mike's '84

    Mike's '84 Registered Member

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    You all have given me a few things to think about....thanks!! I assume the plate in there now is stock. What about height? If you have a larger chamber would that not atomize the fuel more efficiently?
     
  9. diesel4me

    diesel4me 1 ton status Premium Member

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    how high is too high!

    I used a one inch spacer on my truck--I've heard more height is better in some cases,but not all..its all trial and error,as I said before--if I had an aluminum aftermarket intake instead of the stock Q-jet one,I might have had very different results with the spacers.....too high,and the hood wont shut!(not usually a problem on GM trucks though..)

    One thing to keep in mind is the added height and thickness of the spacer will block a lot of heat from going into the carb base--great for more power and a richer mixture in the summer--but all the vehicles I've had spacers on suffer in the winter from carb icing and stalling,making it hell to drive in lousy weather(theese problems are worst when its snowing,or a cold rain,humid days under 50 degrees).which unfortunately is quite often here where I live--we have discussed this at length in other posts recently,and how to remedy this problem..:crazy:
     
  10. bigblock44k5

    bigblock44k5 1/2 ton status

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    Whether or not a spacer is going to give your more power depends on the intake and cam you have in the motor. Right now you have a dual plane intake set for very low rpm's. dual plane intakes have very small plenums which are divided so 4 cylinders use each plenum. Adding an open 2" spacer is going to change the manifold from stricly dual plane, to a mixture of single and dual. So basically your manifold isnt going to be as good as a stricly dual or single plane. The thing that is going to make the difference to whether this will make more power or not, is the rpm range that your cam was made to be run at. I dont know your cam specs so its hard to say what will happen. I would expect a little more power if you should be running a performer rpm instead of a straight performer based on your cam specs.
     

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