Does anyone recall seeing data on adding a 1" spacer between carb and manifold to improve power? I'm testing a 1" spacer between my Q jet and B4B. Numbers at the track not obtained on the same day, but not seeing any noticeable change, and maybe slightly less power. I'm thinking it's not worth the trouble/height. thanks Pat
Thanks Larry - well ported iron heads and KB 118 cam with around 10:1 compression. I'm switching back to the short 4 hole insulator I had.
If you don't take into account DA then you can't be sure of anything. On top of that as Larry said a 4 hole might be better depending on how fast you are running. My heavy '76 didn't like the open spacer until I was running low 12's however as Larry said combo's vary, gearing, converter... If you are not shifting at 5500 with the open then doubtful it will help.
May also have to rejet to get the gains....it's like people who would put an Edelbrock intake on with no other changes and say they went no quicker....more air needs more fuel. Also as stated weather is different and tracks are different so unless done at the track hard to tell.
thanks for the feedback! Shifting at 5500 - haven't rejetted - looks like more testing with fewer variables is needed
Here is my testing with 1/2" spacers. Red is Qjet (800 cfm) directly on the B4B with no spacers. Blue is with a semi-open 1/2" spacer (divided between primaries). Black is an 1/2" open spacer. Semi open picked up 9 ft lb and 5 hp at the peaks over no spcaer. Open picked up 6 ft lbs and 13 hp over no spacer. B4B has center divider in place.
I doubt really if an et slip will honestly show a 10 hp change in your combo, and your butt surely won't be able to tell it. I would guess unless you had a major deficit to begin with, your only talking s couple hundredth.....a breeze or air deflected from a slightly faster car could make that much difference on its own. I can tell you since I have some first hand experience with those heads, I ran a 2" open spacer onto of the ported sp1 with a 950hp holley when I ran them. I bet I have tried every combo of spacer out there from open, tapered, short, tall, etc. Hell I even goofed off with my tapered HVH super suckered and flipped it upside down and still no real change. I liked the 2" plastic not because it gained anything, but the carb stayed cooler and the air cleaner fit better
Great stuff! Thanks all! I appreciate the info. If I really want more power, a cam and intake change would be next step to help feed the heads. Someday maybe. For now, back to launch optimization with the stick - huge gains in the 60' with the Viking shocks.
My seat of the pants dyno says the wide open half inch moroso wood spacer under the qjet on stock iron intake is a long time winner. I also run that cam and some garage ported heads, plus eight pretty, chrome pipes.
Doesn't a plastic or composite spacer also help keep the fuel cooler and transfer less heat from the intake manifold to the carb base plate?
yes that’s the only consensus, a plastic or wood spacer to insulate the carb from intake heat. All the other spacer options, heights and styles are hot and miss for each combo. Some combos like an open or closed spacer, other combos don’t care.
When I was on the dyno with my 350 the 1 inch spacer needed 1 more jet and the 2 inch open spacer needed 2 jet sizes. But it also raised the rpm where peak power occured. The 2 inch spacer had the engine getting peak torque in a bigger spread. I used a wood open spacer the whole time I had the engine running I never used a 4 hole as my engine could spin to 6400 The Holley 750 double pumper had 30 more hp than the Carter AFB 750 I was trying to use 365 hp with that carb and 395 hp with a Holley 750 dbl pump. I would use the 4 hole taper spacer that Wilson Manifolds use a 1 inch should do it but I bet the 1 1/2 -2 inch would be the ticket on a modified engine. This will fit with a drop base air cleaner and the TA dual plane intake You can only put a 1 inch spacer with the SP3 as this intake is as high as the DP intake with a 1 inch spacer same height there. I use a 16 inch drop base Flo Control air cleaner 4 inches high with the SP3 and 1 inch spacer and the 1/2 inch nitrous spacer and it just makes it with the hood closed.
