Mercury Marine Vortec Dual Plane EFI Intake
 

I lucked into the chance to buy another unique EFI intake. So whats I guy to do except buy it and test it. It is basically a performer RPM with injector bungs and a 90mm 4 bolt throttle body on an adapter. I am hoping it will add low-midrange torque over the ported L31 Crossram marine intake with plenum opened up for a 90mm TB I am currently running that has runners shapped like a crossfire manifold.

https://cimg4.ibsrv.net/gimg/www.thi...0e7aa8add.jpeg
https://cimg9.ibsrv.net/gimg/www.thi...5ef963e3e.jpeg
https://cimg5.ibsrv.net/gimg/www.thi...fb05205ea.jpeg
https://cimg2.ibsrv.net/gimg/www.thi...734a058b7.jpeg
https://cimg7.ibsrv.net/gimg/www.thi...4935d2c2d.jpeg

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

If you're looking for another oddball (Mercury Marine) intake, here you go:

https://akroncanton.craigslist.org/p...887084038.html

Its been for sale for a while.

-Dave

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Good stuff!!

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

and now its gone ?

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Not gone, https://akroncanton.craigslist.org/p...907754631.html

-Dave

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

That’s the lower intake for the mercruiser 320 efi setup. The upper plenum and thrtottle body are all one piece for it.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Just thought I would show the mockup of what I am actually doing with this setup. Come to find out it has some high dollar Magnetti Marelli injectors that flow over 60 lb/hr @ 58 psi. Perfect for a ~500 hp engine on E85. I am using an Edelbrock plenum that was designed to mounted sideways by using a carb spacer designed to mount Holley carbs sideways on an Edelbrock tunnel ram. I am using a 3 to 4 bolt Ls throttle body adapter to use a drive by wire TrailBlazer SS LS2 87mm TB up front. The setup clears the accessories on my Vortec and fits under the firewall of the 97 Express van my 383 is going into. I will be using the Corvette fuel filter and running the fuel rail returnless. The distributor in the back will have a blockoff cap and be for cam reference and the oil pump drive only. All the electronics are LS based with an accelerator pedal, tach module and PCM for a 2002 8.1 Van. The PCM has the engine tune from a 2002 5.3 Flex Fuel DBW Tahoe segment swapped into it. My goal is 500 hp @ 6,000 and over 500 tq from 2,500 rpm on E85. The intake has been extensively ported to match the 210cc intake runners of the heads. I probably ground 8 lbs of cast iron out of it all together correcting the port alignment and port size to match the heads. Being a heavy cast-iron casting it had plenty of material to make the ports larger especially at the manifold face.

https://cimg0.ibsrv.net/gimg/www.thi...4e1ba99a83.jpg

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

I'm having a hard time understanding how a dual plane will help anything on a port EFI engine... :bigears

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Not to mention 60lb/hr injectors. I'm running 24lb/hr to feed 400hp. I'll soon be using 29lb/hr to feed 450hp. 60lb/hr will absolutely flood a 500hp motor. And with that intake, there is no way you're going to make anything like 500hp. Maybe with a big turbo.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

The basic principles of an intake do not change dry vs wet. Dual planes will generate more torque where the design boosts VE in the low-midrange.

As for the injectors. Those are the injectors Mercruiser put in the intake on a 300 hp 350. They have just been flowed and cleaned. I am also running E85. E85 takes 30% more fuel volume for the same HP. On gas they run fine as well. Not even close to flooding the engine. All I had to do to get it to fire up was adjust the injector flow rate and use the excel spreadsheet normall used to configure Bosch injectors to LS PCMs to calculate the injector corrections. Then fine tuned the fuel map from there.

Finally that intake ansolutely is capable of over 500 hp. Numerous 383 Vortec builds have gotten over 500 hp with a performer rpm dual plane.

Look at what a LT4 dual plane intake made with a small cam.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Here is another video of an intake test that should open ones eyes. Yes the cam is bigger in duration but the heads don't flow nearly as good and the flat tappet cam has much less area under the curve than my roller with 1.7 rockers. Not to mention the test 350 is smaller than my 383. They made 465 hp with a performer rpm dual plane intake on a 350 with a flat tappet cam.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

If those injectors are working, you must be running SFI and not batch fire. Dual planes are a compromise, using long and short runners combined to produce a wider torque curve. The RPM is not a true dual plane because the wall separating the two planes is cut down to produce a sort of hybrid dual/single plane intake that supports higher revs. The RPM may be able to make 500hp in ideal circumstances on a dyno but most engines running the Perf. RPM run closer to 425. Eddy's own Power Pack using the RPM Air gap runs 435. Racers looking to make 500hp from a small block, like the 383 I built for a buddy last year, usually go for the Victor Jr. It supports VE and torque to higher revs making that power level more consistently.

I didn't mean to sound like a d**k about all this. I am opinionated but I also believe we each built it our own way. That's what hotrodding is all about. Have fun with your project.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Ahhh...Dual planes were created to make a stronger signal at the carb/booster. It is that feature that helped with low end tq. Now I'm sure that most dual planes have smaller runner cross section than most single planes...since single planes were built specifically for higher RPM, but the major contributor to "more tq" at lower RPM is/was due to the carb working better at low RPM on that style intake.

With PFI...or ANY FI, ya don't need or care about velocity through the throttle body at low RPM; there's no booster, no "signal" and no need to have velocity in order to draw fuel from a float bowl. So...I'll say it again: I'm having a hard time understanding how a dual plane will help anything on a port EFI engine...But keep us posted. I'm :bigears


A few things here:
1. The intake on that LT4 is much different than the Mercruiser one
2. The LT4 is achieving that "489" number from a GROSS hp rating...so not 489hp in the terms that we're used to discussing
3. You feel that Mercruiser's intake choice for a 300hp engine will also support "500hp"?

And the second vid: also GROSS hp. Nothing wrong w/a dual plane...they work -especially the good ones like the RPM/Air gap....but they're to "fix" a problem that carbs have and EIF doesn't. You don't need two planes w/EFI so why limit yourself w/a dual plane intake? Us an intake w/the right runner length, runner cross section and plenum volume for your combo. KISS.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

I have had both intakes in hand. Very little difference between the mercruiser and the GMPP LT4. Both are high rise dual planes with about the same runner dimensions. The designs are nearly identical. The intake is ported to match the heads.

500 hp I am talking about is gross HP. Its already made 376 to the wheels through a locked 4L85E and 5.13 geared 10.5" 14-bolt. While spinning a clutch fan and full accessory setup. Running the full air intake, filter and through the high flow cats and muffler. If the drivetrain is only eating 25% its still making ~500 hp. A stock 340 hp 8.1 only makes 230-240 rwhp through the same driveline.

And you bring up a good point. The dual plane runner length and dimensions fall more in line with this build which is a grunt engine. Peak power is at 5,900 rpm and I shift it at 6,200.

Booster signal is only part of it. The dual plane intake has a resonance effect between cylinders that are 180° apart that help boost VE in the low-midrange. The resonance makes the runners function as if they are 2x as long in a dual plane. It has to do with the pressure waves being created by other cylinders in the same divided set of runners.

I have run a single plane with a TBI on top and a dual plane. I did not notice any low-end loss with a 2,800 stall in that application.

This 383 sequentially injected dual plane mpi intake runs smoothly down to 1,200 rpm where the least rpm the single plane TBI liked was about 1,500 rpm.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Is there a mag/net article about that resonant tuning? I know that a dual plane draws from each "side" with 4 evenly spaced/timed pulses....never heard or read anything about resonant tuning. You're feeding the thing w/a single TB anyway from a common chamber. (?)

Second part, Help me out here; my LT1 runs smoothly down to...500 RPM? It's a single plane intake (the stock LT1 intake). Shouldn't any reasonably cammed and properly tuned EFI engine run smoothly down to 1200 RPM...or lower?


IDK. It's cool that it's different. I don't see how it will be an improvement over a single plane that features similar runner lengths/cross section and plenum volume.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Idling or running with no load is one thing. I am talking about lugging it down under a load. As in high gear with the converter locked while driving uphill. The LT1 does not have much torque in the 1,000 rpm range.

GMPP parts themself even stated the LT1 dual plane intake is worth +30 ft/lbs over the LT1 EFI intake on a stock LT1. With a Q-Jet, GMPP HEI at 32° total advance, the dual plane intake and a set of 1-5/8" headers a stock LT1 made 396 ft/lbs of torque on an engine dyno.

The intake I am running is Single plenum but the intake still has divided runners.

I think you'll are failing to realize the dual plane sits lower and I do not have room for a taller intake. It would hit the bottem of the firewall and stick into the wiper cowl area.

I would have to see if I can find the David Vizard article on resonance tuning of a dual plane. In one of his books he even explains how to build a plenum divider in those "X" style single planes and explains its worth about 40 ft/lbs of torque with no top-end loss. IIRC it is in Max performance small blocks on a budget.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Somewhere burried in there is a 5.7 Vortec, lol. Not much room up top to work with. The narrow accessory spacing also limits forward facing intake choices. To retain the factory accessories and keep the upper plenum from being too tall I had to find the best flowing intake that would work in my RPM range, with my heads and still make decent power.

https://cimg6.ibsrv.net/gimg/www.thi...a9879c7855.jpg

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

EDIT: Yeah....^^that^^ looks like no fun. :(



It makes about 300 ft lbs at 1000 RPM ...about the same as most EFI 350 SBC's. I wasn't talking about Idling either. I was talking WOT. See here, I actually started the pull at ~500 RPM....unfortunately the dyno op didn't hit the "go" button until ~1300...
https://cimg5.ibsrv.net/gimg/www.thi...eb6108f90d.jpg



On this one (my "tork monstah TPI") I started at idle also....but they didn't hit the "go button" until about 1100 RPM.
https://cimg7.ibsrv.net/gimg/www.thi...c2d5000ac4.png


...either way, they both pulled seamlessly and w/o issue, just like I'd expect.




1.That sounds impressive. But couldn't you get the same +30 lbs from a same length runner single plane/EFI intake? Or even more from a longer single plane/EFI intake?
2. What about a Cross Ram intake? You'r right that there aren't a lot of low profile options. I wish that there were more SBC cross ram style intakes with dual plenums/TB's; low, but gets you a nice mid-long runner intake. Like the early Viper intake. Still, I'd bet that the Mercruiser intake/spacer/TB and elbow is about the same height as a TPI and all of it's variants (Super Ram, etc).
3. I'd LOVE that. Any reading I can find on topics that I've not read before...the better. I'd appreciate it a bunch if you find it. Thanks!

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

I had the marine crossram for years on the 350. The problem with it is the restrictive inlet elbow to the throttle body that practically touches the firewall. No room for a taller elbow. The top of the elbow is only about 1" off the top of the throttle body and the air does not flow very smoothly through that 90" turn. It works ok up to about 350 hp but as you get toward 400 hp it really becomes a noticable intake restriction. Even the taller version used on a truck/suv becomes a noticable restriction over 350 hp compared to the smooth radiused inlet of the Volant CAI setup.

https://cimg1.ibsrv.net/gimg/www.thi...592127fc88.jpg
https://cimg6.ibsrv.net/gimg/www.thi...973d23cf00.jpg

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Yep. I had that same elbow on my '96 Silverado. I had thought about heating it w/a heat gun and "blowing UP" the roof of it for more flow. Never did it though....and I hear you...no room in the van.

If you could bell mouth the entry to the TB....but not worth it.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Except the ones on a truck are 2x the height from the factory. The 4.3 Astro/Safari vans use the same intake bonnet as the 305 and 350 Express/Savanna vans.

The intake setup I swapped to was not a ton of money and is a helluva lot better than what it was. Especially with the 87mm DBW throttle body compared to the BBK 80mm I had on it.

The new intake fits well and seems to work very well. The new 383 makes ALOT more torque than the 350 it replaced. I am very happy with it.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Huh. Didn't know that. Even the truck one looks way too pinched above the TB. Especially when you look at all the air space above the thing.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

I agree. The van one is so tight I can barely fit my fingers inside between the floor and roof. I have not measured it but it is probably barely 1" gap.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

When I put the volant in a 99 Suburban with a LT1 F/Y-car cammed L31 with 1.6 rockers and long tubes it picked up 3 tenths and 2 mph in the 1/8. Same night, same track, same weather went from consistent 9.5s at 75 mph to 9.2s at 77 mph. I had both intakes and swapped from the stocker to the Volant back to back. Took about 5 minutes to put the Volant on. Back to back heat soaked passes.

https://cimg1.ibsrv.net/gimg/www.thi...f7bfa1ad0.jpeg

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

I don't get the obsession over big injectors being unable to idle. Running MS2 (batch fire) with 55s and an HSR in my 383 w/276HR cam. Idles at 14.5" and I think I can get it a bit better after some ignition improvements and engine repairs. Yeah I have a wide band and all that but still. They're not even modern 55s they're decapped Turbocoupe Injectors.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

^^^^ Now THAT'S interesting!
What would you top it with?

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

That right there, is some serious bang for the buck. $124 for a mid-length runner intake!?

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

You could always get creative and make a lid with throttle body.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

^That^

Just fab an aluminum box w/a TB flange on one side/end/top.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Not to derail Fast's thread but that would be an interesting addition to a 383 in need of a little more induction.
Getting back to the earlier mention of induction length tuning, I'd be curious to know what those runner lengths are. One could really dial in a spicy little engine package if the target were a fixed RPM range (such as might be the case for someone wanting to build an open road event engine).
Hmm.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

indeed the port volume looks really generous. You'd have some stuff to figure out but I can't imagine that thing not running real well with some big heads feeding a larger cubed engine.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Unlike an RPM Air Gap, those runners appear to be the same length. With that information it wouldn't be difficult to calculate the RPMs where a given combination would make peak power. Vizard's Torque Master program or PipeMax could handle that kind of data and produce a result.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Not only that but the angle into the head is pretty darn well straight. HUGE benefit there.

As a question, could you fit a Stealth Ram under there? Not really curious about your opinions on it functionally just trying to figure out your clearances to mine. I swear that you have less room than I do somehow and I find that interesting.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Here is another one for vortec heads..
https://www.ebay.com/itm/133363902315

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Perhaps making a TB flange with a mandrel bend on it that extends the TB out from under the top of the doghouse. As a bonus you get plenum volume which probably isn't huge on that intake anyways.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

https://cimg6.ibsrv.net/gimg/www.thi...5f00c0d734.jpg
I already set the dual plane up a long while back. Has a 1200cfm 4bbl throttle body and a spectre low profile 4" inlet bonnet. (Carb only used for mockup for spacing before the TB arrived) I bumped the cam in the 383 to a 232/244 @ 0.050, 108 LSA. Makes around 525 HP @ 5,700 rpm and 540 TQ.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Which heads?

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Assault Racing castings ported by Lloyd Elliot.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Sound clip of it at idle? How does it drive?

How did you arrive at "525 hp"?

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Actually several ways.

Airflow in GMS/SEC x 1.2

Fuel injector duty cycle vs injector flow vs typical BSFC of a performance small block

Also RWHP / by HP loss through a 4L85E and 10.5 14 bolt.

On a conservative tune it hit 410 hp at the wheels. I plan to get much more aggressive on E85 after I upgrade the fuel pump. So far the stock Vortec pump is holding steady pressure at WOT with only a Racetronix Hotwire.

Also HP calculations from an 1/8 mile vs weight calculation.

​​​​​​At 6,400 lbs it ran an 8.50 @ 82 in the 1/8 mile on a flat section of "track" via the performance app in my OBD2 logging.

Idle sounds alot like my 350 with a hotcam.

Idles perfectly at 750 rpm in Drive

Cam idles like you would expect a 212/224 @ .050 cam to idle in a 383. Rhoads VMax lifters knock about 20° duration off it.

Drives around as well as any mild cammed small block until you put your foot into it.

I really like the progressive feel of the 4bbl throttle body. It starts picking up the secondaries around 65% throttle opening. Drives about like stock until you really boot it.

When I actually get it registered and on the road again will post some new videos. Let it lapse before the Covid19 stuff while I was working on a few problems I found (almost new but bad lower ball joints, AC Delco Professional suck, FWIW) and have it parked in my shop.

Based off the calculations made it may actually be making close to 550 hp but I will be conservative and say 525. I know without a doubt it is over 500. I know it would ET a little better than it did on that run. I didn't stall the converter and rolled on it slowly from the start to keep from spinning the tires and skewing the results. I was probably 30-40 feet into the run before I matted it.

Re: Mercury Marine Vortec Dual Plane EFI Intake
 

Trap is what matters. You think you lost 115hp through the drivetrain, huh? O.K. WallaceRacing calc shows a more realistic 438 hp, FYI.

I thought you said that you had a 232/244 @ 0.050, 108 LSA cam. (?)