[Cliff R]

I've back to back tested the RPM against T-II's with 1" spacers on them for years and even thru the Victor into the mix on occasion.

At the track I've tested the RPM against a T-II, Street Dominator, and Tomahawk and with and without spacers. I've done the same testing against my factory iron intake. The track reflects exactly what we see on the dyno. The car runs quicker short times and give up some top end charge. In most cases the best ET are with the dual plane intakes even though you may run 2mph faster on top end with a Tomahawk using a 1" spacer, for example. For the most part we are just shifting power, not really making more of it as ET's are always pretty close with the extreme spread less than a tenth and most runs usually just a few hundreds of a second difference.

The T-II, Street Dominator and Tomahawk require a 1" where the RPM does not. If you try to test one of those single plane intakes w/o a spacer you are probably going to get your feeling hurt. Well, at least on any 455 or larger build capable of making over 500hp or so. Adding spacers to the RPM is hit and miss. They typically do NOT like fully open or 4 holes spacers. The best I've tested on them to date were fully divided or semi-open (allowing the rear openings to see a good bit of each other).

I will also put a warning out there about the RPM. I had one custom try to use on over 700hp and he kept spinning the same rod bearing. Can't remember at the moment which one, but one of the runners in the RPM is chopped off a bit where another one lays over it so may have been leaning out that cylinder.

After pulling the engine twice to find the same rod bearing toast and the rest in good shape he switched to a single plane intake with a spacer and never had any more issues........FWIW.....