[stinky jinx]

I am sorry that I am slow to understand carburation but.............are you all saying that in most situations a 4 hole spacer will give you more low end power ? If so does it matter what thickness it is ? Let me put this another way for anyone new to my questions.........for a 350 chevy motor with a mild cam, a duel plane air gap intake manifold, shorty headers, 350 B&M trans, 343 posi and a 650 single pump carb, should I put a spacer on, and should it be a 4 hole if I am wanting more low end power?

[stepside454]

if your wanting more low end yes, a 4-hole. How thick? cant say itll very from 1 engine to another. basically the way it works is, it decreaseses the plenum volume boosting the signal, so the engine reacts like it has a smaller carb. smaller carbs generally give more low end & thoratle response. I asked you before & you never answered.... what max RPM do you run this motor ?. John

[stinky jinx]

4500............sorry about not replying. I am new to how this forum works.

[sune]

Originally posted by stepside454
if your wanting more low end yes, a 4-hole. How thick? cant say itll very from 1 engine to another. basically the way it works is, it decreaseses the plenum volume boosting the signal, so the engine reacts like it has a smaller carb. smaller carbs generally give more low end & thoratle response. I asked you before & you never answered.... what max RPM do you run this motor ?. John

Sorry to instrude with my own questions....

I have been wondering if you can go the opposite way, and make the carb seem bigger to the engine with a open spacer..?

Sune

[stepside454]

if your staying within 5000 RPMS Id recomend a smaller carb than a 650, or...a Q-jet, even though a Qjet is actually more CFM than 650, because of its spread bore design, they make greal loe end as well as top end.
If staying with aftermarket square flange for a 350 that never revs past 5000 RPMs Id use a 570 Holley Street Avenger. There are going to be a few in here that call me crazy... but within that kind of RPM thats all that motor needs & it will respond well, infact it would even better with a 4 hole spacer.
Sune... yes an open spacer has the oppisite effect, makes the engine think it has a lil more carb. John

[Tmod]

Most spacers that are available are 1" thick, You can get other thicknesses but the availability is not as abundant as the 1".

Some people don't like the software Dyno program but I have several different programs as such and one takes into account the spacer height and I found that a 1" gave me the best powerband down low then either a 3/4" or a 1 1/4" spacer.

I also build my own spacers as most of the available spacers are for carbs with a bore size of 1 11/16" and if you have a spread bore the bores of the spacer don't match with the bores of the carb. The primary spacer bores will be bigger then the bore of the primary throttle plate.