[Cliff R]

I've also tested a pile of intakes and carburetors on these engines, track and at the dyno.

To 500hp my "modified" factory iron intake is a solid 6HP better than the RPM (no spacer on either one). At higher HP levels the RPM will start to show it's colors, probably worth at most 10hp over a stock intake at past 550hp or so, but it woln't really outrun it by much at the track, since low and mid-range power will be very close.

For the few extra HP one gets on the dyno with some of the aftermarket intakes, I'll take the stock intake as the fit is much better.

For really high HP levels, up and over 700hp, I would NOT use the RPM. They have at least one runner than is deficient and can lean out that cylinder and pound down the rod bearing. Can't remember which one it is, but one of the runners gets a tad restrictive where another one lays over it or under it, and it's pretty difficult to access and not enough material to effectively correct the issue without busting thru into the other runner.

A few years ago I removed the RPM intake from my current engine and went to a ported factory HO intake. I HATED having to use a shorter Shaker top and custom air filter in the opening, and wanted to put all the stock parts back in place. The car was well under the roll bar rule anyhow, so I didn't care if it gave up anything. I also installed full length mandrel bent 2.5" tailpipes at the same time, to "tame" down the exhaust note some past the straight thru 3" mufflers.

To my surprise the car still runs 7.20-7.30's in so-so air at our local 1/8th mile track, around 95-96mph. I just figured the last two modifications would slow it down to 7.40-7.50's which would put the car around 11.50-11.60 at a 1/4 mile track.

Also keep in mind I'm comparing these intake on an engine in excess of 550hp/600tq. I have to chuckle a bit when I see folks "hacking" up or buying "special" parts to install an RPM intake on a low compression 400 engine making under 400hp. IMHO, the RPM is a complete waste of time/funds for most of the set-ups we see them end up on over here in the Street section.

I've also ran into fitment issues with them, but they are easily corrected. We find a lot of them not wanting to sit down on the heads, which only involves removing some material from the bottom of each flange all the way across them. Same deal with many of the BBC Edelbrock intakes I've installed.

I have seen a few Pontiac RPM intakes with very poor port alignment, and have had to open up the bolt holes a few times to get all the bolts started.

In the FWIW department, I wouldn't even look at that intake unless you are over 500hp and/or don't have a decent stock intake to work with.......Cliff