FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: CaptCobrajet on January 15, 2017, 05:44:52 PM
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I don't know of anyone who has bad things to say about the Ed RPM manifold. At this point, I am going to have to label it as one of the FEW parts that seems to work on just about anything you put it on. There are cases where something else would be better, but I have come to the idea that the RPM will always work, and better than most others, in a lot of cases. I have used it on many street strokers up to 482 cubes, and up to now, 670 hp was the most I had seen using it, mainly due to camshaft and cylinder heads used with it.
I had a build with hood clearance constraints, 434 inch FE, for endurance/circle track use. It needed a broad range, able to recover from 3500-ish rpm, but needed to hold it's head up past 7000. I used a healthy circle track solid roller cam. I talked myself into using the RPM instead of one of the lower profile single planes. I worked the runners about four inches in from the flange, and matched to the heads, and also spent some time in the plenums. I cut the divider down about an inch, and blended the front and rear to mate with a 1-inch transition spacer. The engine made a gob of torque for 434 inches(616 peak tq) and it made 731 HP at 6700 rpm with the dual plane!! I've been rolling it around in my head for three days. The rest of the engine was all "good stuff" but I keep coming back to the intake manifold and shaking my head. I turned one over and have been studying the runner layout. It is basically two single planes. I think when the divider is worked and they can interact a little under the carb, an otherwise very good manifold becomes a real gem. Hat's off to Edelbrock. Whether they meant to or not, the RPM continues to prove itself a really good piece. It also works on smaller, less modified builds with great success. I have seen less benefit to the plenum and divider work on smaller cam, smaller cube combos, but still, the point being.....when your combo puts you on the fence about going to a single plane, the best move, in my opinion, is to go RPM and consider mods that fit the idea.
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I always liked all their stuff it always seamed just a little better back when the f4b came out for small blocks. It ran a lot better then the offy i had.
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Funny thing. The performer rpm seems to be excellent on FE builds as you mentioned (I run one on a super mild 390 and it's great there too).
The Performer for the FE is kinda meh.
The Performer for 460's seems soooo much better while the 460 RPM is ok.... not a bad intake at all, but certainly not the equivalent of the FE version. I too wonder if it was dumb luck or some stroke of genius.
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I'm with you there Drew. My big 385-based 540 (tow rig) likes the regular Performer 460 much better, even that many inches. The air gap RPM 460 is huge......too big for mildly cammed 385 series stuff. I dynoed a 390 yesterday with an RPM and a 232/238 hyd roller. I'm going to post it in the dyno section, but it had nice flat torque, even in a 400 incher with a relatively small camshaft. Definitely different animals. I would not recommend the RPM 460 unless it was a big engine with a lot of camshaft.
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Damn that's some frisky torque, BP. What kind of compression with this bad piece?
When I did the RPM intake for my hot rod 390, I just port matched the ports that flowed the worst and left the better flowing ports alone. I found a thread some place where Joe Craine posted the stock flow of each port. So I kinda had an idea how much to port match the slow ones. It seemed kinda red-necky....... but it won a few races.
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731 HP from 434 cubic inches is a monster in my book. Congrats on a great motor. What carb did you use on that? And I wholeheartedly agree on the Performer RPM, it performed very well on every engine in my dyno tests done for my book.
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Their not the best looking intake but they sure work.
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Jay and Kevin.....that engine was 12.5:1 static. BP hand ported BBMs.....spent about 10hrs on the pair. The cam is a tight lash oval track solid roller, 270/278 on a 112, and .720 at the valve. The carb is a 1.590 venturi, 1.750 bore Holley that I sent to a really sharp carb guy. I gave the man some pertinent info on the engine, and he nailed the tune. I generally have to work on the high speeds and emulsion on the dyno, but on this one, I did not even have to change a single jet! Bolted it on and boom....12.8 A/F and no changes. Couldn't believe it.
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I wholly agree on the RPM intake. Almost a "can't lose" piece. I've had a bunch of them (like one every other week) and they always make way more torque than a Victor and rarely give up anything significant at 6500 or less.
They seem to be pretty reactive to carb spacers, but it's a "try it and find out" sort of deal, where one combination will want open, while another wants a 4 hole. So far my best guesses revolve around seeing a side to side variance in A/F on the dyno. If you see a big difference - like a full "ratio" - the open seems to even things out and you can get more aggressive & find some HP. If they are fairly even the gains are small. I've seen a 4 hole add a ton of torque down below peak, but not always. Probably changes in the car.
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We dynoed two engines this week with identical heads and manifold. That 434 solid roller wanted the 1" transition spacer. The 390 with a much more docile hydraulic roller did best with only a 1/4" insulator gasket. The open spacer hurt it, and the transition spacer hurt it down low, did nothing in the mid-range, and only made 1-3 hp up top. I think the spacer thing is combo and cubic-inch specific, no doubt about it. We pulled that 434 incher well past peak, and it really never fell off a cliff, just gradually lost power. The intake was not giving up, even past 7000.....really surprised me.
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I wish that the Performer RPM intake was designed to work with the factory shaker hood but it puts the carb about 3/4" too far back.
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Hey guys would the RPM work as well with port/runner injection EFI?
I have not seen an Ed supplied port equipped version as in the Victors. Could make one I'm sure but.....?
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I wish that the Performer RPM intake was designed to work with the factory shaker hood but it puts the carb about 3/4" too far back.
Actually there are some slots in the shaker assembly that will let it move the scoop back and forth a little, and might allow the Performer RPM to work. I've read that some people have done it successfully...
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Hey guys would the RPM work as well with port/runner injection EFI?
I have not seen an Ed supplied port equipped version as in the Victors. Could make one I'm sure but.....?
Have not done an RPM.
I did a BT dual plane and it works very, very well.
Put 16 bungs into a BT 2x4, but that was for a 600HP CNG project that has only run on carbs so far.
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Hey Jay, In your GFEIC book, on the 410 & 425 HP 428 CJs, did you ever figure out why the Performer RPM was so far down on lower RPM torque? I am going to be putting in a almost bone stock 428 CJ in my 59 Ford 2 door sedan. It was a low mile engine that I had laying around in the garage for 25 plus years. It is still standard bore, with the original "428 Super" cast pistons, stock iron CJ heads etc, the only changes are a small Oregon Cam solid flat tappet cam, similar to a Comp 270S, a set of FPA shorty headers designed specifically for 57-59 Ford cars with a FE engine, and an aluminum intake. I am kinda torn between the Streetmaster and Performer RPM. I have both on hand, both untouched. In your book, both seemed to work quite well unported on a mild engine, but since the 59 will be fairly heavy, the RPMs lack of low end concerns me.I will be using either a 3310-1 Holley 780, a factory 780 from a 70 Torino 429SCJ, or a 4779 750 DP. Again, I have all these carbs on hand, so I am trying to make use of parts taking up space in the garage.
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Rory, I am baffled to this day by the low end torque performance of the Performer RPM on those two engines. I remember playing all kinds of games with the carb trying to get those numbers up where they should be, without success. It seems strange in the face of a lot of reports about engines in vehicles, where that manifold seems to have a lot of low end torque. I have no explanation - Jay
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Jay, think it could be the low vacuum at WOT during dyno testing, vs in use at higher vacuum levels (part throttle?) especially with a vac sec.
Regardless, the RPM ports are big, so you'd have to expect some slowing of movement, but I also haven't seen anything in use act like the curve on the dyno. Even in some overcammed, under-compressed, uncer-inched applications it seems to do OK, or at least can be tuned to do OK with a little timing
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Well, if that were the case you'd expect to see the same performance from some of the other manifolds, right? Like the Blue Thunder intake, which has even bigger ports and runners? Yet it wasn't there on the other intakes. Strange...
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Well Jay is that not something you could test the next time around?
IIRC, you wire up the secondaries on any vac. secondary carb when on the dyno. If so, maybe don't do so and see if low rpm torque picks up. Just a thought......
On edit: 'Course you've probably already tried this, eh?
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When you go to Mc Donald's they better not screw up a hamburger conversely when you bolt on an Edelbrock Intake manifold they better not screw up on that. Manifolds are what put Edelbrock on the map they know exactly what their doing. Blair metioned the RPM's intake is like two single planes but personally I disagree the lower section is indeed like a single plane but the upper plane much more closely resembles a common dual plane.
Bravo on Blair providing some details on how he modified the RPM. I've long wondered how the pro "builders" handle enlarging the runners of an RPM because the RPM has extremely uniform runner dimensions from essentially the plenum to the flanges. If one ports an RPM it's a given the runners will end up sort of hourglass shaped somewhere because there are areas a mortal can not get to. Typically runners on intakes are tapered and "porting" a common intake is simplified by only needing to do the area adjacent to the flange. Not so the RPM to enlarge a runner the full length is pretty much impossible to do unless you happen to have a 4" tall little buddy you can send into the runners to get to the "blind" areas/sections that you can't get to or even see with a die grinder and burr. Realistically short of cutting apart a RPM the only way to truly open up the runners from plenum to flange on an RPM is perhaps Extrude Hone. Making the big power with an RPM sure says it's not necessary to have large runners
One of the wackiest manifolds you'll ever see is the Edelbrock F427 which almost uniquely* has enormous funnel shaped runners. To port match a F427 only requires an inch if that at the absolute most since there is so much taper.
* The FoMoCo Sidewinder also has highly tapered cavernous runners
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Well, if that were the case you'd expect to see the same performance from some of the other manifolds, right? Like the Blue Thunder intake, which has even bigger ports and runners? Yet it wasn't there on the other intakes. Strange...
Good point, dunno LOL
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Well, if that were the case you'd expect to see the same performance from some of the other manifolds, right? Like the Blue Thunder intake, which has even bigger ports and runners? Yet it wasn't there on the other intakes. Strange...
A quick look at the camshaft you were using, and its lobe centers, and installed position would be a good indicator of why the torque was low on the RPM intake. Also, if I remember correctly you only used a 1/2" open spacer for the dyno testing, and the spacer can be part of the problem with the RPM, and not other intakes. I know the cam was the same for all tests, but there again, it proves that different intakes like different camshaft specifications, and one "cam fits all" does not work. The more I dyno test intakes and spacers, the more I find that each engine combination will like something a little different to get the maximum torque and horsepower being sought after. When you throw in a mix of different headers, the game completely changes. You can test every conceivable combination of heads, intakes, camshafts, headers on a given shortblock, and many will be similar, but one will finally prove the best combination of all of the tests, and it will not be the one you expected. Joe-JDC
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All I can say is WOW on JDC pointing out: "if I remember correctly you only used a 1/2" open spacer for the dyno testing, and the spacer can be part of the problem with the RPM, and not other intakes."
With the Perf RPM having the unique (2) single plane arrangements it's obvious there's some serious Edelbrock voodoo going on. What get's me is I'm pretty sure Jay was once posting info on his making a removable plenum spacer on I'm thinking it was on a Perf RPM?....
It's always interested me on people removing part of the plenum divider which essentially turns a dual plane into a single plane with funky long runners. I think I recall more than one of Barry R's EMC Motor's ran a highly modified Perf RPM with major surgery on the divider
The current SHELBY FE Intake is obviously an exceptionally close copy of the PERF RPM with the exception the SHELBY has a significant cut down of said plenum divider.
Talk about an interesting dyno comparo a PERF RPM vs a SHELBY
https://www.shelbyengines.com/products/shelby-dual-plane-intake-manifold
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https://www.shelbyengines.com/products/shelby-dual-plane-intake-manifold
The Chelbee intake has those square bumpsies on the plenum floor. Do they really do something, and what can be done to replicate them on a smooth floor?
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There's been a bunch of work done on what are often referred to as 'turtles' or 'stuffers'. Some are installed using epoxy and others are made to be bolted to an otherwise smooth plenum floor.
KS
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There's been a bunch of work done on what are often referred to as 'turtles' or 'stuffers'. Some are installed using epoxy and others are made to be bolted to an otherwise smooth plenum floor.
KS
I'm well aware of those. But what's the scoop on these?
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The picture of that Shelby bothers me as-is. Sharp edges have no place in that area and will likely shear fuel (I hope that is the right term) as it passes over those edges.
Although at first glance that looks exactly like how I do FE RPMs, I'd knock those edges down on the divider and in the roof of the plenum. All sharp turns need to be rolled back a bit. We reached pretty deep into the ports as well, but in my opinion, the big money areas are all the sharp edges at every turn point.
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Not trying to change the subject, but I guess I kind of am. Have anyone of you engine builders used the Edelbrock 7505 2x4 air gap manifold. I know there is the issue with carb choice, but was wanting to go with a dual EFI setup that will fit on that manifold. Seems like a BT 2x4 MR is hard to come by nowdays.
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The Edelbrock RPM Air Gap 8V intake needs a little work on the #8 port down below the carburetor area to help with the turn towards the port, but overall, it flows well with simple gasket match. Worked well enough to break a C-6 bellhousing on a customer's roadster. I have been looking for one for a while now, but they seem to be non-existent. Joe-JDC
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I had good luck with mine on the dyno, despite the Edelbrock carbs. I'm surprised they are not available; maybe they flopped in the market or something? ???
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jayb, Did they show the same low end torque issue as the RPM on those couple of engines.
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I only tested that intake on the 425HP 428CJ, but it did not have the same low speed issues; it started off with 400 ft-lbs right at 2500 RPM.
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I have used one of those per the customer's request. It showed me about 40 less hp than the same build with a Ford 2x4 MR. After that, I never tried it again. Some of that was the carbs, I feel sure, but my assessment was that it was not on the same planet with a MR 2x4 with two good Holleys.
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My guess is that at least half of that difference was the carbs. Here's a little data from my dyno testing:
427 Sideoiler dyno mule:
Ford MR 2X4 Peak HP - 577.8
Ford MR 2X4 Peak Torque - 526.6
Edelbrock Air Gap 2X4 Peak HP - 566.7
Edelbrock Air Gap 2X4 Peak Torque - 504.2
The Ford intake was run with Holley 660 center squirter carbs, and the Edelbrock manifold was run with Edelbrock 1405 carbs. For power production I think the Holleys are head and shoulders above the Edelbrocks. I'll bet that Edelbrock manifold would work just as well as the Ford intake if it was fitted with some decent carbs...
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All I will say about the Edelbrock RPM Air Gap 8V is that it does out flow the MR intake both in unported and after porting condition. It was possible to balance the runners to within a couple of cfm each. I personally would like to see a well ported MR vs RPM AG comparison on the same engine at 482 CI or larger. I think folks would be surprised. I agree, most folks use the small Edelbrock carbs, and there are two large Edelbrock carbs available that are rated at 750, 850 cfm. I have not seen anyone compare those carbs to the 660 Holleys. The ported BT MR was within a few horsepower of the Tunnel Wedge in your testing. Personally, I don't think anyone has spent the time to try to get the maximum out of the RPM AG because of the carb spacing. Until someone does a maximum effort on the intake for testing, it will always get a bad rating. Joe-JDC
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I was hoping to find an aftermarket 8V intake to use with a dual efi setup. There aren't many options. How much time was spent working on the ed ag to get the flow right. As far as carb spacing, to get the looks of the traditional oval filter could a custom base be made?