Intake manifolds
 

Witch is better for top speed dual plane or single plane intake manifolds? I have a zz502 502hp and I'm not sure what to put on it.

Single plane .

what he said

Merlin Single plane.

but has anybody actually swaped a performer rpm air gap for a single with no other changes to see the real diff ??

6000 rpm and under the performer rpm air gap will out perform the single plane is for wot all day your lower rpm and idle will be like sh!!ty you want the engine to perform from idle to wot unless you are racing all day @ wot you will be loosing alot of performance every where else I run the performer rpm air gap on my 502 580 hp and I have the put you back in the seat performance all the way to wot.:evilb:

thats what all the dyno intake shoot outs I've seen said to...just wondering if anybody actually flogged them on boat...now how about the diff from a stock merc alum high rise vs a rpm air gap ?? Rob

Air gap all the way the runners run cooler! The runners are not part of the valley cover they are a little higher and have longer runners than the stock manifold The stock one the runners are the cover for the valley and the runners will run alot hotter.

Hot Rod magazine does a lot of dyno testing and a recent article stated very plainly that an Edelbrock RPM Air-Gap was the best intake they've ever tested for engines smaller than 500ci turning less than 6,500rpm. It gave up only a few hp on the top end vs the single plane but retained the low end like we all know dual planes do.
http://www.carcraft.com/techarticles.../photo_16.html

http://www.carcraft.com/techarticles.../photo_15.html

Your head/cam combo (assuming it is 100% ZZ502 stuff) will be fine with the Air Gap RPM.

Now, for 502's with better heads (AFR/Dart/etc) and cam's utilizing the better heads (say .600" lift or bigger) the Air Gap RPm will step on the airflow the other parts will flow and engine would otherwise get. These will have much better top end with single plane intake like Edelbrock Vic Jr and really not much loss/if any at lower rpms.

Note: The Air Gap RPM's intake bolt holes inbetween the runner pairs will be exposed when the intake is put on must aftermarket aluminum heads since their port roofs are higher that the GM heads and thus the RMP Airgap.

that second graph was misleading as it was showing the victor jr making more hp from 3900 and took a while for the air gap to catch up....I think they crossed the intakes there..made no sense...any way my basicly stock 509 with the factory alum intake, wonder what i would see by changing the intake ?? thansk Rob

N:rolleyes:thing more than likey are you running a stock carb if so that's the frist thing I would change.

no, actually running a 750 DP, have a flowed 850 that I'm going to try next season...just put this engine in at the very end of the season, only have about 2-3 hours on it...have few things to try next season, just wondering about the intake so I could look over the winter...Rob

what I seen in other threads.... I seen guys have good luck with the stock merc alum high rise manifold that's why... I think you will not see much if you change out to the air gap think the only things you might see is a cooler air charge due to the runners are out of the oil maybe some hp possible it's like fliping a coin is worth 10 hp for 265 dollars for a new intake what are you running for a flame arrestor I'm running a 14" dia 4" height filter from k&n it is a marine flame arrestor if you are running the small merc arrestor that is a big problem. Have you tuned the carb to the engine can you read air fuel ratio or a exhaust temp. what camshaft are you running are you running the stock exhaust manifolds ?Tell me more about your engine spec's :cool:

http://www.knfilters.com/marine/boats.htm

running the tall K&N velocity stack w/5" filter on top, breathing thru a open scoop(am going to seal that off so breathes only outside air) engine is a fresh 509 stock roller cam w/1.7 roller rockers, full custom marine headers, just got the boat running after pulling my bower motor, boat ran over 80 with no tune time and handling was a big issue(no ext steering) so I pulled that engine, also running a 1" spacer under the carb, Thanks Rob

That's kinda a small filter element you might be a the max air flow the best gain for you at this point in time would be to replace the camshaft and springs and a good set of 10 degree locks and retainers I'm running a ultradyne bullet racing cams 228/236 @ 50 .601 int/exh lift 280/288 with the stock rollers lifers and gm roller rockers and eddie marine exhaust with stainless risers with my setup is a good 580 hp + 5000 rpm

thats 5" tall, it's the biggest velocity stack one that K&N makes, I could use it because I already had the room from the blower that I ran before... not looking at changing the cam anytime soon, just tuning on what I have...thanks for all the help..Rob


http://i227.photobucket.com/albums/d...r/100_3760.jpg

The stock cam is like a broom stick that's where you would gain alot of good power if changed it..

I would change the flame arrestor to a gaffrig,, the K&N are not made for a boat ,,,because they actually cloog up ,,,there is no dust on the water,,,they will take all the grease ,oil and belt wear and cloog the airflow.:eek:
tests proof that they are better then stock for about an hour of running time then they are worse then stock.
The only thing the flame arrestor should do is keep little kids out and keep the flames in when backfire.

Gaffrig gives u alot more airflow.

Thanks for the input on the flame arrester, but I don't think so...when I had the blower motor in this year, I had a eddie marine unit on, would not make any boost..none at all...called weiand and they told me to pull off the arrester, I was not believing but ?? removed it, made 4 psi no problem, took my 10+ year old K&N's off my gibson, have not been cleaned in years..still looked ok...tried one of them..3.5 psi boost, so not believing they are that bad...sorry..just what I found in my own testing...Rob

that kn velocity stack can really mess with your float levels especially if you are using the marine j-tubes. These carbs are designed to get their airflow from the sides not from the top.

We made about twenty five pulls just changing air cleaners, stacks and sub stacks and two carbs . Best combination was the hp carb design with a fairly low profile air-cleaner that hugs the top of the carb.

The worst in any combination was the velocity stack and j-tube combination.

using a milled top 750 DP std vents, used the v-stack because it puts the filter into the scoop opening, going to try a flowed 850 I have laying around next year

Yes = swapped an RPM air gap for a 4150HP for a Brodix single plane for the same carb
No = changed cam to complement the increase in air flow

Why change. Dual plane and original cam squashed the air flow capabilities of the heads and exhaust. Not all the fault of the intake, but it has it's limitations.

If you have a STOCK ZZ502 motor, keep the stock manifold or a minor upgrade would be to use the Performer Air Gap. From my experience, for marine use, get rid of that ridiculous vacum secondary carb and purchase (JEGS or Summit) a Holly 4150HP 950 mechanical. Minor jet change to your motor needs. That and the intake change will net you some additional power without major motor work.

5500 rpm or less the biggest carb you want is a 800 cfm 5000 rpm stay with a 750 cfm jetted right any thing bigger cfm carb is just over carbing the engine in that rpm range the engine will never flow anything bigger.and you will have very slow sloppy air signal for the carb to funtion right. slow ventury means weak lag throttle responce = Sh!!ty performance.

Sorry to disappoint you, but RPM only plays a small part in what the motor needs for a carb. It's air flow. That dictated by the heads, cam, intake and exhaust and then RPM. I know, the cam in part dictates the RPM.
Second, check out what really makes up the 950 #4150HP carb. You will be surprised. Hint: Just because it flows 950cfm doesn't mean that it contains those exact parts.

Ok! you make no sense........think about it no rpm = no airflow your a friggen genius! rpm = airflow the faster it spins the more air flow you need per cycle and yes the cam is what makes up the time per cycle on the amount of air per revolution per cycle.if you need more information I would be gladly explain to you on airflow needs per cycle.:drink:

Carb Sizing formular is:
CARB CFM = Cubic Inches x Max RPM's / 3456 x VE%

VE is Volumetric Efficency. 100% is not likely
A good built motor is around 90%

502 x 5200RPM /3456 =755.32 CFM Carb
755.32 x 90% = 679.79 .

502 x 5600RPM /3456 =813.43 CFM Carb
813.43 x 90% = 732.09


The HP 500 used a 800CFM

If I'm not mistaken the 950 holley is just a race version of a 750 not actually a 950 cfm carb...

Hey Einstein, put your reading glasses on. I never wrote "no rpm". I wrote "only plays a small part".
Your VE graph is just that, a graph. Uses only the Cubic displacement and the rpm. Hey Einstein, according to your graph, the heads, cam valve size, intake manifold don't matter. Hell, just use your graph and slap on what cfm carb size your graph spits out. No I don't need to explain air flow. Take some useful information from some professional head tuners. They are NOT using the flow bench information as in the past. It's TEST, TEST and more TESTING.
I have a name for your graph theory slap on bolt it up motor build-up: Cookie Cutter Engineering

Bingo. Carb numbers, or model numbers for that fact are sometimes misleading. Talk to a carb professional before you jump into the fuel pool heads first.

Seriously though, I do understand that for general purposes, the VE to CFM sizing does work. My point is that for today's motor with so much really really good performance stuff out there, general terms in many cases just doesn't fit. Example: Look around. Several 496 marine motors builds making max. HP at 6000 RPM are using a 1050 dominator.
496 x 6000RPM / 3456 = 861.11 and that is at 100%. The days of using poor flowing peanut port heads are few. And that is a good thing. We all benefit from the aftermarket desiging and building great performance products.

Why you crappin' on Rotax ? he makes many valid points.

Here's my quicky opinions:

Holley's cfm recomendation chart is very conservative. This is is so the general public doesn't get themselves into trouble. Yes, it is easier to hurt power/driveability with 'too big' of a carb vs 'too small' but what is too big today with modern cams, heads, and 500cid's ?

Many engines with modern cams, intakes, and heads will have good driveability and very good top end with a carb sized somewhere around 120% with a single plane and around 150% with a dual plane.

Yes, carb #'s are all monkeyed around. The Hp950 is closer to 830cfm. But they work well because it's metering is very good. Not because of big airflow. Why does the HP500's 800cfm carb work well on bigger motors ? It meters fuel well.

If you had a more airflow capable carb and kept the good fuel metering, then bang, the engine would make more power. The trick is to find an off the shelf holley that meters fuel as well or to find a carb tuner to build one for you.

Sometimes, the airflow demand makes a carb not meter so well, but more often than not, a carb that does not meter so well is because the carb metering system suks.

Don't always blame a poor performing carb by saying 'it's too big.'

BTW: as long as there is vacuum measured under the carburetor, it is restricting airflow to the engine. It's almost impossible to make a carb big enough to cause absolute 0" vacuum. A 1250 won't even do that on a 502.

Got out my dyno sheets from my session with 502 ci with custom cam and 305cc AFR heads.

Stock (old) 500HP blue carb with choke and stock dart intake-563 hp at 5400 rpm, peak tq at 590lbft at 4400 rpm.

Switched to Holley 950 cfm Racing with 81 primary jets and 82 secondary jets up from the 79 square-586 hp @ 5400 rpm, peak tq at 605lbft at 4500 rpm.

Switched to Edelbrock Vic Jr. intake with 1" open spacer-595 hp @ 5500 rpm, peak tq 613lbft @ 4600 rpm.

These are corrected numbers, CF was .99 that day.

I think that Wags382 massaged a stock 500HP carb and did well with it by removing the choke along with some additional work.

Edelbrock intakes are also much less expensive than the Dart intakes.

On my 548, on a dyno, using a massaged Victor manifold, my motor made 12 more ft/lbs of torque at 3000 rpm with a 1050 annular discharge carb, than it did with a 950HP. The 950 laid over and died by 5000 rpm. The 1050 was up over the 950 by 31/hp at 5000.

The motor made 685/tq at 4600, and 682/hp at 5750.

Thankyou Bob Madera aka RMBuilder.

Chris

we kinda got off the post here... how about with stock rect heads and cam ??

For all out top end on a 502, I would pick a Victor Jr. It will probably beat the RPM air-gap by 10-12 hp at 5200-5400 rpm. The RPM air-gap will beat it untill about 4500 rpm.

I would use a Holley HP1000 carb, which is just a 850 DP with the choke horn removed and better metering circuts.

Been there... tried all that... on a dyno... with that motor.

Chris

P.S. I would have a cam done by Bob Madera aka RMBuilder. The guy really knows his stuff !

thanks....some good info from this thread....Rob