Is a carb spacer really worth it in power? How does it curve the hp/tq power band?

 

Basic theory on carb spacers:

4-hole spacer increases the vacuum signal to the carb when you're over-carb'd. Better low-RPM torque.

Open spacer increases the effective plenum of the intake when you're short on intake for the upper RPMs.

One could almost say, if you need a carb spacer to make your engine work better, you didn't get the combination right to start with.

 

the reason they have them is for air/fuel atomization (not shure on spelling) when the air and fuel come from the carb and hits the botom of the plentem it atomizes, but you dont want it to hit the plentem at full force or you will create a slight pressure in the intake runners (not allowing for as much flow), harming your performance, so you raise the carb enough so that when it hits it is forced sideways into the runners

 

Sounds like band-aiding an improper manifold choice.

 

I'd have to agree. The manifold/carb setup should work correctly, or else the mfgr would have raised the mouth from the factory.

 

Those are very broad and poor assumtions esspecially for those that dont have access to engine dynos to try EVERY conceivable combination ouot there to find your "optimum combination" so as not to "band aid" the problem. Without starting a pizzing match I understand your concepts, but realistically it's not possible.

They are used as tuning aids, just as jetting, timing are used. I'm willing to bet there is'nt a motor out there that will not see some gain somewhere by using a certain type of spacer, and that's just the plain truth of the matter. If your stubborn about it, so be it and hopfully your happy with what your running. In our truck's engine while it was on the dyno we tested a number of different spacers and all produced different results weather changing the torque curve, gaining/dropping hp, etc...until we hit the one that netted us the best numbers and the best power curve.

If nothing else ESPCIALLY on a street driven car, the added insulating factor from the hot intake to the carb base helps keep the fuel cooler. I've personally been victom of testing an aluminum spacer and later in the round robin racing car started to stumble, changed to a plentonic spacer for next race, same round robin in later rounds and car ran great. After talking with many other racers they too had expereinced the same results using metal carb spacers and conditions went away with a less conductive material. and these are only 1/4 mi bursts...think of what going on under the hood with daily driven high under hood temps these car have.

 

Heat insulation is a different issue than altering the carb height and/or plenum volume with a spacer. It is a good idea, though. I had the Holley heat shield with the thick gasket on the Action + manifold, when I switched to the RPM Air Gap, it was just enough higher that I couldn't use the thick gasket and close the hood. The manifold itself stays enough cooler that the heat shield with thin gaskets on each side works just fine.

 

So there is absolulty no way to know if you need one unless you are dyno tuning right?

I am writting a list of parts I need to finish my car and want to know if I need to toss in a spacer, apparently non-metal one.

You guys seem to know what you are talking about, do you know what kind of gasket is the best?

-headers/ collector?
-carb?
-valve covers? ect.,..

 

The past 4 yrs I've dont all my spacer testing at the track and for the layman that's the cheapest way to do it unless you get a great rate for engine/chasis dyno time which would be the IDEAL way to tune. One thing to keep in mind also when jumping upto taller spacers you will also ned to jet up a little to help compensate for the new carb signal. On my old 355 I found the best was a 1" 4hole spacers, tried a 1" open, a 2" open and a 2" 4 hole. The 1" 4hole delivered the best 60's, mph, and had really good street response also.

On my 388 in sig I did'nt even bother with the 1" stuff since the Vic jr has such short runners I needed to help the engine gulp in more air and give a better signal so I just went right to the 2" open for a taller plenum. The 383 in the truck we picked up 20hp by switching from a 2" open to a 2" tapered 4 hole spacer...things like that you'll never see at the track cuz the increase is too little and ambeant temps/weather will often cover up any gains/loses that small...so if you have acess to some dyno time, just have all the spacers on standby and have a jet kit and you'll find the best combo for your engine.

As far as gakset.
Carb-always just used the cheap Mr.Gasket ones, 4 hole and open centers depended on what my stack consisted of under the carb.

Headers and Collectors I've tried the paper gaskets in the past, but have GREAT luck with copper at both ends and I tried the aluminum this year, again with great results. No leaks, blow outs and just a typical check your nuts/bolts a few times a year to make sure they're still snug. I do not recommend Earls replaceable insert gaskets-they are a one time use and then you have to buy new inserts when putting things back together.

Valve cover-no brainer-moroso 1 peice rubber with the steel inside. reusable and no leaks/blow outs. Just be sure to use valve cover studs as it makes life soo much easier. Costly at $31/set, but it's the only pair you'll ever have to buy with no leakage issues.

 

As usual IHI. Thanks for your help.