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I'm just in the end stages of bolting in a 351W in my 78. I was wondering if I should go with the stock carb spacer. I have a factory 4bbl intake and a Holley 600 carb, my buddy says an aftermarket carb spacer would greatly increase horsepower.Is it worth the $ to get an aftermarket spacer? What the heck does a spacer do anyway?
Most spacers give more plenum volume and offer some heat disapation that help to cool the carb and the air fuel mix. A 1" plastic or wook spacer usually work well. As for the extra power, you'll probably see some but not much, but keep in mind this is a $20~30 upgrade so 5 HP would be a bargain! I've got three different ones and I'm expermenting on mine.
According to my PAW catalog, an open spacer will generally increase upper rpm power. It is difficult to predict what a 4 hole spacer will do, but the consensus is that it will usually help bottom end power. I am running a 1" 4 holer on mine and it SEEMS to make the bottom end a little more responsive. The only way to know for sure is to try them, and then the power difference may be so slight that you would never notice it.
DannyP
89 F-150 4x4 former EFI I-6 now carbed 351W, Edelbrock heads,cam,intake,carb.
MSD 6A, ZF, Sterling 10.25 with 3.55L's.
The new composite, plastic and wood spacers are supposed to reduce percolation of fuel mixture and are heavily marketed this way. Manufacturers claim that these new age spacers reduce heat transfer by up to 10X compared to metallic spacers. Heck, for $20, I got one that is a divided type to sit atop my Performer RPM.
My Edelbrock heads have no exhaust crossover, so during the winter the aluminum Edelbrock intake just barely gets warm. I think the carb does it's job better if it is nice and warm, but not hot. I think one of these phenolic spacers would be OK in the summer, but not the winter. I am running an open element filter right now, but am considering rigging up a thermactor type air filter so the carb gets some heat in the winter.
DannyP
89 F-150 4x4 former EFI I-6 now carbed 351W, Edelbrock heads,cam,intake,carb.
MSD 6A, ZF, Sterling 10.25 with 3.55L's.
Well DannyP knew what it was, Hey guys those spacers arent wood and they arent high tech they are phenolic and we have been making gears and other stuff out of it for atleast 50 years
Otto, the materials used for the spacers are relatively new for this particular type of application, hence the descriptive words like "high tech" and "advanced." And, yes, several manufacturers make them out of wood. Check your references then check with Edelbrock.
Do what I did. Use a stock air cleaner in the winter so that you have the heater and also reduce the cold air flow too. If you don't reduce the volume of cold air the heater will be worthless.