I've played around with a 3/4 inch open hole carb spacer on my 401 and got some fairly even increases across the rev range using my 1976 800cfm Q-Jet. This time I have a new 72 BBB 800cfm Quadrajet which was rebuilt and modified by Scott (ex-Cyberbuick) before being sent to me. He did a good job and it seems to have more power but over a narrower range (probably a topic for another thread) but I don't mind because it's kind of comes on with a surge which I like. I installed the same spacer (open hole 3/4 inch) under it last weekend and noticed a further increase not only in power but in the sharpness of it's delivery. It's fun but I've also noticed that I've lost a lot of my beloved bottom end. No more smokey takeoffs like my avatar to the left any more with this setup but that's ok because I'm not finished yet. I have a machinist who can make me any kind of spacer I like for about $50 so I'm thinking of ordering a 4 hole spacer this time to try to get back (or even increase) some of that famous Nailhead bottom end push while maintaining the rushed flow of air that should also increase my mid range and top end as well. Does anyone have any suggestions as to what height it should be? At the moment I'm at the limit of my underhood space with a 3 inch air cleaner and the 3/4 inch spacer but I was thinking if I could get the same flow from a 2 inch K&N filter (they do flow better...right?) then maybe I could go as high as using a 2 (or 1 3/4) inch spacer. I know I should probably leave well enough alone...but I can't. I love getting the most out of any combination and I'm just a hot rodder at heart and why leave something alone when there might be more power (or experience) to be gained - right?
Lots of views but no comments. So, can I presume that the higher the better and that a 4 hole is better than an open hole for maintaining bottom end? Can I also presume that any 4 hole is not going to be as good as an open hole for top end? If I still get no comments then I'll just have to experiment and work it out myself.
Leave the big air filter on the carbie, the 2 inch will end up restricting carb inlet air flow. If you must spacer, 4 hole, pin or dowel it to the manifold to get the holes lined up, no more than 1/2 inch thick. Holes no larger than the ones on the intake manifold. Remember, don't park that car for too long, you mates are up-side-down on the globe, and we don't want the gas leaking out the top of the carbie.
Thanks Dave. I think I might just lay it back down on the intake and be done with it. I am getting annoyed with all the suction noise I'm getting with the open air cleaner though and I'm noticing that it runs a lot better on cool mornings and evenings so I might put my energy into creating a cold air induction system which should add a little more power and shut the thing up as well. Can't believe the induction noise this thing makes especially with the windows up. Sounds like 50 vacuum cleaners all running at once.
