I was looking on ebay and they have alot of different kinds of spacer blocks 1 inch, 2 inch, aluminum and some other kind of black material supposed to stop heat transfer. How much difference do these make and can you tell a difference after putting one on. Thanks to all who have responded to my many threads.


Keith

 

If you're talking about carb/throttle body spacers, then yes, they do help. But are they really worth the dough? Usually not. Most of the time a spacer is good for about 10 horses, but these horses often don't come until 4000 rpm, so in a normal truck, I'd say save your money.

The Law
1989 F-250 HD 4x4
460, C6, BW 13-56
Almost Stock

 

Depending on your intake configuration, you could gain as much as 4" of vacuum at idle, which will really help your low end pull as well as your fuel milage. I did a vacuum test on my setup, a 302 with a dual plane aluminum intake and an Edelbrock 600 carb. I hooked up a vacuum gage, and found 17" of vacuum at idle, not bad. Then I threw on a 1" tall, 4-hole spacer, and it made 21" of vacuum at idle, with a steadier signal, indicating less turbulence. Low end torque was noticably better, high RPM performance seemed the same, possibly better.

The point is, you'll never know how your setup will react until you try it. 4" of vacuum will probably end up giving at least another 1-1.5 MPG. I personally gained 20 miles of range per tank, out of a 19 gallon tank. The quickest and easiest way to get the immediate response of the spacer is with the vacuum gage. Make sure you get a 4-hole spacer though, the open plenum designs are for High-RPM engines with large carburetors, as pointed out in the previous post. TK

'77 F100, 302 (the aftermarket Prodigy), C4
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing

 

Which one would be better the 1 imch or 2inch?

 

No easy answer to that either. The only way to know is to buy both and test them both. In reality, I've found that almost every combination except a gross mismatch between carb and intake manifold preferred the 1". An example of a mismatch would be a 289 wearing a 750 cfm carb with a dual plane intake. Not a good idea. a 1" 4-hole seems to be ideal for street use.

The real principle that guides this is the phenomina of turbulence, which imparts a head loss to the fluid, therefore reducing it's velocity. That intake runner velocity is critical to low RPM torque. Sometimes the spacer will create more turbulence than it reduces, but there's no way to predict this, except with unreasonably complex computer models, and that can consume 12 hours of a supercomputer's time to solve (solving the Navier-Stokes equation for millions of points in 3-d Cartesian coordinates). Yeah, I saw this in the Clemson University Mechanical Engineering Department when I studied fluid mechanics this summer, it's ugly.

Bottom line is, you'll probably be best off with the 1" 4-hole, but to be sure, buy both, test them both, and keep the one that makes the best vacuum at idle, or take them both back if they don't help. TK

'77 F100, 302 (the aftermarket Prodigy), C4
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing