There is no way to tell. You have to try it and see how the engine responds.

 

ive used one for years and not only do they tend to keep the fuel cooler but as you say itll move the torque curve and horsepower up a bit.
ive done a test awhile back on and engine dyno with one and gained some good numbers.
aint nothing wrong with getting more volume on your intake!

 

Thanks

so, do you remember what your difference was in terms of numbers?

I kind of agree that nothing ventured is nothing gained, but a nice comparison would be really helpful if you still have the info.

Arn

 

There is no way to tell. You have to try it and see how the engine responds.

*********

correct.
The spacers work "primarily" becasue they alter the flow pattern below the carb itself and also into the runners. Often making that turn more gentle changes the flow and fuel suspension so noticeable power increases are seen. Sometimes it's more due to fuel atomization than actual air flow increases.
You never can tell what will make more power. Remember, adding a spacer might require rejetting for a true apples to apples comparison.

Remember those "turtles" that used to placed inside the plenums? They did a similar thing by changing the flow patterns.

 

if i remember correctly I gained about 8 horses and moved the torque curve up about 200 rpms.
that before i did jet changes.
after jet changes etc. I saw 21 hp increase at roughly the same RPM with torque curve relitively the same.

 

Spacers & Power

A spacer is going to be used to either fix a problem in the intake tract (plenum length, size, etc) or to help with a heating situation. If the engine was designed and built properly the use of a spacer should actually hurt power and performance. That being said most people cannot afford to have a custom manufactured induction, or valve train systems made. So a spacer will allow you to taylor off the shelf intakes to meet your demands.

Spacers as a rule of thumb.

As a rule of thumb an open plenum spacer will decrease your torque, and throttle response while increasing the engines power band. A 4-hole spacer will generally increase your torque, and throttle response, but move your power band down. The thicker the spacer the more of an affect it will have. Meaning you should see more change from a 2" spacer vs. a 1/2" spacer. Bottom line it's a matter of trial and error to see specifically what your combination wants. I suggest building a combination without a spacer, driving it, and then use a spacer to move the power band where you want it.

 

Hey tech i,am surprised you did not tell him what effect it would have on his carb signal and jetting.

 

Thanks again

The carb is jetted with #49's on the primaries.

I am told the 3.4 liter v6's work best with either the #49 or #47. My .050 over 2.8 is working pretty good right now, but I am looking for more dig out of the hole.

If I need to re-jet after installing the 4 hole, will it normally be up or down? Logic is telling me probably up.

Arn

 

Jetting with spacers.

Again as a rule of thumb

Normally a 4-hole spacer will increase the air velocity going through the carburetor, requiring a decrease in jetting size, while using an open spacer will decrease the lower speed air velocity requiring an increase in jetting.

 

smaller jetting - better fuel metering?

So if I can reduce my jetting a bit it sounds like better performance in the street range and potentially a bit better fuel consumption on the highway. Am I right?

Arn

 

smoother throttle response

Well it is in, and although I haven't run it much today, the throttle response is better and there is a smoother torque application at the low end.

I suspect I have gained but I'll know better tomorrow.

Thanks to tech, dawg and xntrik for the help

Arn

 

Pretty good response

Well, the 4 hole phenolic did as advertised. It definitely improved low end torque a bunch and moved my usable rpm down a wee bit.

From the look of it without a dyno, the car was pulling hard to 6000 rpm but now appears to be pulling hard only to about 5600 rpm. But, that is ok because the cam is really intended to do up to 5500 rpm, so the match is good.

The idle circuit did need leaning out a bit, and I am still testing my jetting.

I'll have the car out to the track in October so we'll see how it does.

Arn