Carb Spacers?
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by 1970-Bronze
Without actually putting a vehicle on a dyno - How do you determine which and what size of carb spacer should be used? 
i picked my 1/2" for a couple of reasons...i liked the idea of a heat transfer block...i knew i had limited height capabilities...
so when i looked at all the options i just took the middle path of what was commonly available....not real scientific sorry....good luck bob
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
When I had the engine on my '64 professionally built by people who drag-raced like every weekend (he in a '66 coupe w/one 4-bbl on a 10.99 index and she in an econo-dragster), I asked them to trim the divider out of the Performer RPM for a little more top end power. My mechanics said it wasn't such a good idea butchering the manifold, plus, once you've done it, you can't (easily/cheaply) go back. They recommended that I instead use a 1/2" open spacer and it's been on there since (some 20 years). The mild 331 recently dynoed at 293 hp, 293 ft-lb at the wheels, so I guess they must have known what they were doing.
Le Mans Master
Joined: Feb 1999
Posts: 6,807
Likes: 0
From: Hoosier
Cruise-In III Veteran
I have a very mild 350. I'm able to make my own spacers for little more than the cost of the material. So over time I've made and tried a 1" x 4 hole, a 1" x open, a 1" x 2 hole, and a 5/8" x 2 hole. I noticed zero difference from no spacer at all. Maybe a more powerful engine responds, but mine didn't.
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
Originally Posted by AlwaysWave
I have a very mild 350. I'm able to make my own spacers for little more than the cost of the material. So over time I've made and tried a 1" x 4 hole, a 1" x open, a 1" x 2 hole, and a 5/8" x 2 hole. I noticed zero difference from no spacer at all. Maybe a more powerful engine responds, but mine didn't.
Remember, the differences we're talking here might amount to just a couple horsepower which depending on your current configuration may not be detectable from the seat of your pants. Or, perhaps they improve driveability in a given rpm range without raising the peak hp.
The same could be said for such things as: differences between straight, H-pipes, and x-pipe exhausts, ceramic-header coatings and wraps, differences in header tube lengths, mandral-bent exhaust, freer-flowing air fliters, electronic ignition modules vs points, etc.
Taken by themselves, these minor differences may only be detectable on the dyno. Still, in the long run, an hp here and there can add up.
