Usually, the 4 hole spacer on a dual plane is your preferred method for maximizing low-mid range power. The inverse is true when using a single plane intake using an open spacer and mid-high range. More plenum volume = higher powerband; the more spacer height you use, the more plenum volume you'll get. Using an open spacer on a dual plane will usually raise the powerband with the two planes being connected, though sometimes this will hurt overall performance depending on the combination and spacer design. Using a 4 hole spacer on a single plane can improve your upper low-mid range power due to increased velocity the 4 hole spacer can provide, as well as help with reversion turbulence beneath the carb to help keep the fuel atomized. I hope this helps.
I remember when Mike Phillips at AMP built and tuned my engine on the dyno it made more power without the open spacer. This is a holley 850 with a KB Wildcat manifold
We installed one of Dave Visner's (VED) tapered 4 hole spacers on my engine while on the dyno. No real increase, or loss, in torque or HP. It did however, bring lower RPM torque numbers up and flatten the curve. Lower HP gains were minimal. It's still on the engine. Stamped "Dyno Room" LOL.
I've been using tapered 4-hole on everything,with great results,like the one from Wilson Manifolds,or the HVH Supersucker.
The dyno didn't lie. My dyno experience on the fresh build went as follows: 462 CID, Stage 2 TASE heads flow 340/240, Bullet Hydraulic Cam @'050" = 228*/520" x 233*/525", 108. Edelbrock Peformer with center divider plenum cut down and blended. MSD Locked out 34* btdc. TQ@4200 HP@5400 Changes Made: Pull # 15 510 450 Northcut Race Prepped Qjet Carb Pull #16 525 472 Swapped for Proform 950 and added 1" RV spacer (open) Pull #17 536 489 Added another 1" RV Spacer Pull #18 540 490 No Change Pull #19 550 500 Add another 3/4" RV Spacer to simulate future N2O plate Not bad for a 9.7:1 CR,small RV cam BUICK. I have since changed from a 2" open spacer with the 3/4" N20 plate to a Wilson type of tapered sapcer and the N20 plate and notice a significant improvement. I wish had dyno info on this change, but, there is no doubt the spacers improved how this set up performs.
2" spacer and the N2O plate. You simply can not beat this one for the money. Be aware you may likely have hood/clearance issues, hence the Stage 2 hood scoop. http://www.ebay.com/itm/301939905041?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
I believe the spacer I had on at one time was a 2" open aluminum spacer. I have the air cleaner that drops around the side of the carb with k and n top and sides and it did clear the hood
My Skylark was having none of it even with dropped Base K&N 2" element. I decided to go 4" full open element with the dropped base and force air down it at speed. As it sits, it sits proud of the top of the hood 2".
What carb you running Chris? Maybe the qjet would clear since it has more compact throttle set and can get away with a lower dropped base?.
I gained a little more clearance by taking a drop base,and trimming the excess carb flange down. The base was already clearance for the Holley bowls,but I had to dent them a little deeper,and massage the area over the throttle lever. I then ran a filter top. Some years later,I learned of a base that was made for a 70's Corvette that had all of these clearances,and was dropped even more.I have included a picture of the Corvette base. You do have to watch how much clearance you have between the underside of your aircleaner lid,and the top of the carb. If your carb has an air horn,then you need to go from that. You need at least 1.5" clearance to allow enough air to flow into the carburetor.
thanks for all the info guys. going to a cowl induction hood. body man said he to lower cowl induction because????? have not got hood back yet. I do not leave my car at all. running 2" KN + top 14" filter., sealed from bottom of carb to top of hood.750 dp with holleyfull flow main body no choke or air horns. polished high sheen( not that it makes any difference)but it sure looks good. main question is ?--- minimum clearance from top of scoop to top of ccarb? running 2"spacer now-- could drop to 1" if needed. thanks for all the response.kenny462.
I ordered a Chinese Re-Pop of the lid that Brian shows. Couldn't get it to fit worth crap! Seems like everything hit, starting with the long fuel-filter inlet. But that wasn't the only thing. Been a coupla years and can't remember what else but I ended up throwing it away, after various attempts at "massaging." Best, Ranger Aiken, SC
Mark, I take it you like the Wilson copy? I run that L88 Corvette drop base also, it has the most clearance of all drop bases.
