I was reading some info about the poston s divider manifold and how a simple 1" spacer under the carb upped hp and torque. Should an increase be seen on the stock 350 manifold? If so please explain why. (This also assumes there is space for the spacer) Thanks Scott
More length under the throttle plates for the air stream to "straighten out". Perhaps more important is that a spacer will increase plenum volume. An open spacer on a dual-plane intake may kill low-speed throttle response because the venturis are seeing reduced vacuum pulses (but more of them) so fuel metering is affected especially at low engine speed.
jim hand the pontiac guru claimed he increased hp more with a spacer than with 15 different cam changes. he custom makes his spacers keeps a divider in between the primaries and open between the secondaries.giving idle response and WOT power. there were pics of hands intake system over at pontiac street performance.you can see a lot of thought went into smoothing air flow and keeping the air cool. crumple up some tin foil put it on top of your air cleaner and close the hood. this should give you an idea how much room you have.
A couple of years ago we did some testing with spacers. At that time my engine was making right at 500hp and my car was running mid to high 11's in full street trim on DOT's. We tested four 1" spacers, 4 hole, fully open, fully divided and sem-open (same as pictured in Jim Hand's Pontiac book). When the smoke cleared and dust settled, the quickest runs were with no spacer at all. The only spacer that came close was the one like Jim Hand uses. It ran almost 2mph faster on top end, but gave up just enough 60' that the car went .02 seconds slower in ET. The testing still tells us that we can make more power with a spacer, and I'm sure that if time permitted, I could play with shift points and tuning and end up running slightly faster with the semi-open spacer. However, back to back testing involves keeping everything consistant, and doesn't typically allow for all sorts of changes as the amount of runs you are going to get on any given day are quite limited.....Cliff
Spacers are definetly worth playing with. But you need to test for yourself to see what YOUR combination likes. If your stock intake still has the four hole opening, stick with a four hole spacer, otherwise you will have turbulance. Be aware that playing with spacers can change the Air/Fuel ratio the engine see's, so you may need to adjust carb jetting for best results.
Agreed. However, testing should involve a dragstrip, good weather and good traction. I've tested gobs of parts on the street, and to date just about every single one that "felt" faster, ran slower at the track.....LOL.....Cliff
Agreed! That meter lies to me just about every single time. I'll put on a big high rise intake, "feel" a big rush of power.....car slows down at the track!!!ou: Been doing that too me since I installed a Tarantula intake to replace my factory iron intake on my 440 powered Roadrunner back in the late 70's. It "felt" like it was going to run a half second quicker during a street test....slowed down .3 seconds at the track and ran LESS MPH as well......Cliff
What is your combination? The Buick 350 loves a 2" 4 hole spacer with a Q jet and a 2" open spacer with a Holley carb. For Race Buick 350s, not street: Bill Mah made 1021 hp but was only built to make power in the 4000-8000 rpm range using a ported iron intake with 4 inch open spacer and blow through carb. The same engine made over 500 hp at 8:1 compression.
http://www.highvelocityheads.com/ss.htm I hear good things about this spacer, the horsepower gains are dyno proven.
