spekbikes

when im reading magasines i find that they all have differnt opinions on how carb spacers affect an engine, 4 hole deisgn, open design, a radius'd 4 hole, and how some sizes are 1/2" to 2 " , can anyone explain how htey each work and why they make power on certain engines, so i can figure out if its right for me and how big of one to start out with. thanks

RB83L69

They do 2 things: they add volume to the plenum; they add length to the throttle bore, which straightens out the air flow in there a little bit. Those 2 things have completely different effects on how the engine runs. Which effect predominates, and as a result whether a 4-hole or an open one or a transition one or none at all produces the most power, is highly dependent on everything else about the whole induction system. It's also dependent on gearing; converter, gears, transmission, tire size.

There IS NO one-size-fits-all "put a so-and-so spacer on and pick up x HP" rule. Anybody that tells you that, is either inexperienced, or is reaching for your wallet.

Think of it as a tuning aid. If you want to use that method (like, if you have hood clearance, for example) you might want to get your hands on one each of a few designs, and see what effect it has on YOUR combo. I can guarantee, it won't be the same as somebody else's combo. Some magazine will put some one of them on some motor they're building, and pick up amazing unbelievable numbers; but it'll make your car go slower. Or vice-versa.

Night rider327

iTrader: (13)

I agree 110% RB83L69.

Carb spacers should never be thought of as a speed part (like you would a cam, intake, etc), They should be looked at as a tuning tool/aid that may or maybe give you the results you want.

No way of saying which is better and which you does what really.

The old gen idea was 4 hold spacers moves the peak down in the RPM band, and gives more low end torque

and the open spacers moves peak up in the band and gives more top end.

As a gen rule only that still applys, but you have to try and see.

Been time I though a 4 hole would help and turned out an open one worked better.

been times where I lost alot over 4 MPH in the 1/4 with any and every type spacer

Best thing to do is, buy 1 of each, and head to the track. Make a few passes launching the same and shifting the same, then switch to a spacer and make some more passes, switch to a diff spacer and make more passes.

Forget ET, you dont care about that at this point. Look at you speeds. MPH is a better way of telling HP than ET. ET is just power + traction + gearing + stall speed.. MPH is power

Look at see which runs had the highest MPH's.. Then you'll know which if any spacer works best on your combo.

On my 88, I found a 1" open spacer helped me a good bit in a few ways. I was blowing the times off at the tree, with the spacer I guess it moved my torque up the RPM curve some cause with it I 60 footed better (less wheel spin) and my trap speed picked up a bit. It helped my top in cause i'm running a 'small' intake for my combo. Just a performer intake and 600 cfm carb

Now it may be diff when I finish the suspension and put better tires on. I'll re try the spacers again then to see.

Tech @ BG

As said before spacers should be used as a tuning aid, not an end all be all you need to have one or not. A Spacer can crutch having something too small or too big in the intake tract (carburetor, intake, cam being too small or too large).

As a rule of thumb a 4-hole design spacer will add bottom end torque, and throttle response. It can move the power band down lower in the RPM range. An open spacer can have the opposite affect decreasing the torque, while increasing the top end HP, and moving the power band up higher.

The thicker the spacer the more of an affect it will have. i.e. a 1” or 2” thick spacer will have more of an affect than a ½” thick spacer.

Bottom line with any spacer, you must test it on your actual vehicle to see what it needs to perform best.