View Full Version : Cast Iron vs Aluminum Intake Manifold???

01-16-2012, 09:21 PM
What is the best intake manifold for a SBC 1987-1996 with 76cc Dart heads and 1.94" / 1.50" valves? One chapter in Small Block Chevy Marine Performance says "the finest intake manifold ever made" is the chevy bow tie 14097494 cast iron. And in another chapter it touts Edelbrock aluminum intake manifolds? What is the best? I am upgrading the exhaust manifolds from stock to higher performance manifolds with runners and at the same time could replace the intake manifold? Cam is stock. What is the best intake? (Donzi 18 2+3)

01-16-2012, 09:37 PM
fresh or salt water?

01-16-2012, 09:45 PM
fresh water/ antifreeze cooled! (run in salt water)

01-16-2012, 10:47 PM
I boat in salt water and raw water cool my engine also. These pics are from a 5 season old Edelbrock RPM airgap(2yrs on one motor, then 3yrs on next). It looks like most of the corrosion was going up, and it would have caused an external leak before leaking into the lifter valley.

01-16-2012, 10:54 PM
Makes me glad I converted to fresh water/ antifreeze cooling! What about choice of intake manifold with antifreeze cooling?

01-16-2012, 11:50 PM
air gap.
If using in salt there is coatings for the one area that water goes through.

01-17-2012, 02:07 PM
I had a SBC in my Scarab 1 back when and it had Torquer intake which blew luckily around the thermo housing. I talked to my mechanic/friend who had a Victor Jr. for $50. I was like C'mon that is a high reving intake, my redline is only 5k. He was like C'mon does that engine KNOW it is only going 5k? Marine use is hard on an engine so yes you want to go more agressive than the street as it does not matter about low rpms. Air gap or Victor, tunnel ram, etc would be fine. With my "new" Victor he gave me this epoxy that was a medium blue color that I poured through the water passages. I also used it to repair a cracked door sill on my house. Sold the boat but 10 years later that blue stuff was still holding the sill together and looked like new. I WISH I knew what it was. Lastly Merc makes an alum intake for the BBC's which has brass inlays in the water passages, do they make one for a SBC? Personally I would not worry about it with FWCing.

01-17-2012, 03:14 PM
Which intake manifold offers the BEST PERFORMANCE is really my question? I'm not really concerned about corrosion since I am FWC with antifreeze. Aluminum vs cast iron in expansion rates could be a factor, but really which is better performance intake up to 5000 rpm? Aluminum aftermarket vs. chevy bowtie 14097494 cast iron??? (my current intake is aluminum "made in China")

joseph m. hahnl
01-17-2012, 06:55 PM
It all depends on the rise of the manifold and the intake bore dias. My cast iron 350 mag manifold is slotted, to form two elongated bores instead of four bores.
an Edlebrock can have one giant square bore. The reason for this mod is to let each cylinder feed off both or all four throttle plates with out restriction. So the Edlebrock with a single square and a higher rise would have more performance. But also note that the bow tie can be machined to the same bore size as the Eddy and an adaptor riser can also be added if additional rise is wanted. Now If you have spread bore carb the bore may need to be tappered slightly below each bores tangent point.

these are Edlebrock, note* One is a spread bore, one is a standard 4 barrel, and the other with the single is a Victor Jr . I believe that a slotted iron Mag manifold has the same performance as the Edlebrock standard 4 barrel manifold.

01-18-2012, 09:03 AM
I like the Weiand Stealth.

01-18-2012, 05:52 PM
Match your components based on requirements. Stock cam with stock heads and a large volume intake like a single planeis not going to help. If your heads flow and have a complimenting cam top the motor off with a intake and carb that feeds them. Stock repalcement heads, small valves, stock cam and exhaust top her off with a edelbrock performer or comprable alum. intake. If you plan on some mods down the road like cam and exhaust a edelbrock rpm of rpm air gap would work great. Remember merc is getting 300hp from a basic sb manifold design.

01-18-2012, 08:28 PM
Match your components based on requirements. Stock cam with stock heads and a large volume intake like a single planeis not going to help. If your heads flow and have a complimenting cam top the motor off with a intake and carb that feeds them. Stock repalcement heads, small valves, stock cam and exhaust top her off with a edelbrock performer or comprable alum. intake. If you plan on some mods down the road like cam and exhaust a edelbrock rpm of rpm air gap would work great. Remember merc is getting 300hp from a basic sb manifold design. good, sound advice..

01-19-2012, 12:26 PM
Will the PERFORMER AIR GAP 2604 (3.72-4.92") fit under standard rear deck lid of Donzi 18? Or, does it have to be PERFORMER 2104 (3.50-4.60") Boat not at house. Comments???

01-19-2012, 01:45 PM
Marine engines do not generate the heat a car engine does. Is an air gap really necessary? Being a "performer" is it really any more High perf than the stock Steel or are we just shaving 20lbs? From all my car building days a performer was basically an aluminum stock intake. Dissipates heat better and weighs less but no real performer. I would personally want something more agressive if over 300hp like the Weiand or the Edelbrock Torquer. I was never a holly manifold fan. In my Corvette I am running a 383 with over 400hp but unfortunately due to hood clearance I am stuck running a slighlty modded performer style intake....polished of course.

01-19-2012, 01:47 PM
If you have got better aftermarket free flowing heads & good exhaust manifolds you might consider the Edelbrock Performer RPM .
It is a mild highrise dual-plane design.
I like a dual-plane design intake becuse it runs & idles better at very low RPMs in my opinion; yet still flows very well up to 5500 RPM or so.
A dual plane has a faster, better atomized intake charge velocity at lower running speeds up to 5500 RPM.
I have had good success, and super all spped performance with the Edelbrock Performer RPM on several performance boats.
I always block-off it's center heat riser passages with a special intake manifold gasket that blocks it's cylinder head & intake manifold exhaust carb heater passage.
This heater passage is only used to prevent carb iceing in cold conditions .
Block this cross-over passage unless you intend to go boating in very cold weather conditions.
At the 140-160 temps a typical carb boat engine runs at ~~the manifold with the blocked heat passage does not get very warm at all.
I also use a sheet metal lifter valley baffle pan to keep hot oil off the bottom side of the intake.

Never used the Edelbrock RPM Air Gap intake~~~
Is it also a dual-plane design ?
It does not appear to be cast as such from the posted photos ?
There is also no center carb bore dual-plane style baffle.

I like dual-plane high-rise intakes for most high performance boat applications.
They are a very good at "all speeds" & a great all around design for the RPM speeds our performance marine engines rum. 0--5500RPM .
The Performer RPM is a very low profile high-rise intake because it is a dual plane design.
It should easily fit under any Donzi "Classic" style hatch cover without mods, or alterations, as long as you don't install a very large & high flame monster sized arrestor on your engine's carb.

Just my opinion~
Other opinions can, & will most likely, vary~~~

01-21-2012, 05:06 PM
Edelbrock Performer RPM might be the obvoius choice, but I can't find Edelbrock Performer RPM for 1987 to 1995 cast iron heads??? I can find for 1986 and prior, and 1996 vortec and newer. Now what for 1987 to 1995 non-vortec?

01-24-2012, 02:10 PM
As far as I know there is a manifold with 8 or 10 bolts and one with 6. The 6 is for Vortec or center nut valve cover engines. I believe the 86+ all use the vortec style manifold but it depends on the number of bolts that hold it on. I could however be wrong as I never modded a 1986-95 SBC. My 1980 Vette block has been modded with stage 3 Vortec heads off a 325hp Mercruiser. Intake is aftermarket.

01-25-2012, 07:30 AM
Although you are running a closed loop cooling system with antifreeze, others who read this may not. As Maddad's pics show corrosion is an issue with aluminum in a short period of time.

DART Coatings does a phenomonal job and has several coatings for this application. New Aluminum can als be Jet Hot coated , tumble polished and offers the same corrosion protection.

Mario L.

Just Say N20
01-25-2012, 08:45 AM
Mild Hi-Jack.

I am having a 450 hp/406 built. Ported/polished 202 double hump heads (I know, new Vortecs flow as well stock, but this is what I have), mechanical roller cam/lifters. I spoke with the tech help @ Edlebrock yesterday, and was told the 2701 dual plane will flow a 350 @ 5,500. Because of the heads, and 406 displacement, I was told the Performer RPM 7101 was what I should get. The block is a 1972, so I'm in the pre-1986 mode.

But the comments about aluminum corrosion have got me a little concerned. I boat 100% in fresh water, with open cooling. I have owned 8 engines with open cooling, and have never had a problem, but they have all been cast iron intakes. How worried should I be?

Dr. David Fleming
01-25-2012, 01:53 PM
Intake and exhaust manifold design came about in a couple of ways. The cylinders were designed to all feed off of one fuel source or to each have their own source. In the case of v-8 engines with carburators you had multiple carburators or a carburator for each cylinder all linked together with a gang throttle linkage, or you had one carburator with a manifold feeding all cylinders.

The Eldebrock Performer is a 180* manifold design which came about to prevent some cylinders - those that fired next to each other from suffocating each other. In the firing order of the engine 18436572 number 4 and 3 and 6 and 5 pull fuel at about the same time. By dividing the manifold into 180* instead of 360* fuel distribution was improved. 180* manifolds are often called "duel plane" because the division puts the fuel passages one above the other. The 360* design is called "single plane" because the whole fuel passage arrangement is on one level.

The late design Torker and Victor manifolds by Eldebrock which came out in the 1970's are an attempt to capitalize on engineering being done by Chrysler Corp. in "ram tuning design" of intake and exhaust systems. This whole effort by Chrysler was to give each cylinder its own intake or exhaust pipe. When the cylinder draws fuel or exhausts a pressure pulse is created which travels up or down the tube causing an inertial effect to fill the cylinder with fuel or draw out the exhaust with greater effect. "Ram tuning" by Chrysler was four individual cylinders fed by long 36 inch intake tubes looped over the top of the valve covers. A four barrel carb was located over each front tire of the car. The throttle linkage was a long bell crank. Eventually this was shortened when the tubes were cut in half and a plenum chamber was created to feed the tubes.

In short this is what the Eldebrock Victor/Torker is - a ram tuned manifold with the tubes bent to feed off of a plenum chamber under a single four barrel carb. It is a "ram tuned" manifold. The other Eldebrock Performer "duel plane" manifolds are an entirely different engineering concept. Just as headers are different "ram tuned" engineering concept than exhaust manifolds on the exhaust side of the engine.

joseph m. hahnl
01-28-2012, 09:41 AM
Dual Plane Intake Manifolds

Dual plane intake (http://www.jegs.com/c/Fuel-Carbs-Intakes_Carburetor-Intake-Manifolds/11937/10002/-1) manifolds are named for their split plenum opening in the intake where the carb sits. Each side of the opening feeds 4 cylinders on a V8. Dual plane intake manifolds are the most popular for high performance street and mild racing because they generally build power across a wider range and start at 1,500 RPM, depending on the dual plane manifold. Each intake manifold (http://www.jegs.com/c/Fuel-Carbs-Intakes_Carburetor-Intake-Manifolds/11937/10002/-1) has its own performance characteristics. It's best to know how you'll use your vehicle and select from there. To be clear: Dual plane has nothing to do with the number of carburetors that the intake will accept. You can have a dual plane manifold that accepts 1 or 2 carburetors.
Single Plane Intakes

Single plane manifolds are named for their intake opening where the carb is bolted on. A single plane intake has one "hole", in the plenum where the carburetor sits on the intake. Fuel from the carburetor enters the intake through one opening with no separation. That single hole feeds all 8 cylinders on a V8. They are typically less restrictive and work best to build power between 3,000 and 8,000 RPM's. Because of the RPM range, the single plane intake manifold is best suited for racing applications.

So, How do I select the right manifold for my application?

As with many situations in building an engine, it should match your intended purpose. Everyone wants the big tunnel ram dual quad intake sticking out of the hood, but it may not be practical, or best, for maximum performance. All intakes (http://www.jegs.com/c/Fuel-Carbs-Intakes_Carburetor-Intake-Manifolds/11937/10002/-1) advertise an RPM range that identifies where they are most efficient. As an example, the intake may advertise "1,500-6,500 RPM". This RPM range must be considered and is the easiest guide to choosing the right intake for you. Street cars work best with a dual plane intake, most advertised "idle to 6,000 RPM" or "1500-6500 RPM". Race cars that work more in the upper RPM ranges will require a single plane, ?2,500-7,000 RPM? or "3,500-8,000 RPM". Next, the intake and camshaft selection should go hand in hand. The camshaft will also state an RPM range for its best performance. The RPM range of the camshaft and intake should match or be very close. A minimal low RPM difference of 500 RPM is acceptable, but should not exceed 1000 RPM. If this is the case in your selections it is better for the intake RPM range to start lower than the camshaft. The reverse may cause low end instability, thus an off throttle hesitation. Lastly you need to consider the physical fitment. Most obviously, be sure to select the appropriate part number for the engine and cylinder head design. Consideration for engine vacuum ports, water coolant ports, carburetor flange fitment, and be sure to check for proper hood clearance.


http://www.musclemustangfastfords.com/tech/mmfp_0901_single_plane_or_dual_plane_intake_upgrad e/viewall.html

01-28-2012, 04:31 PM
If your Big Block Mk IV, or V, engine has large oval intake ports the performer RPM , or Performer will work just fine in this application.
If the heads have the later small oval peanut ports, for high torque applications, they will also work just fine~~~but they were really designed for the large oval port heads as there will be a small port size mis-match..

01-29-2012, 09:44 AM
i used an alum dual plane weiand stealth the 302 motor was a raw water salt boat like maddad's and showed very much the same corroision issues. the thermo housing was severly pitted. the refreshed motor will be a raw fresh water cooled and will only come as close to salt as the pretzels in my lunch box. corroision is an issue i have concern with, the motor was ingesting water from either the intake leak or rain water draining into the carb from the hatch joints in the off season.in the pic the older stealth with the pitting in yellow on the left and the newer stealth on the right

Dr. David Fleming
01-30-2012, 06:39 PM
Even though headers are almost universally used on performance engines for exhaust the use of "ram tuned" intake systems with carburators is more infrequent. Elderbrock was very sucessful with their Torker "ram tuned" design and this is a testament to how well they did the engineering on it. They also produced a manifold called the STR - Street Tunnel Ram. There was a version for Chrysler engines called the "Rat Roaster" designed to make the big Chrysler outperform the Big Chevy. These were copies of the Chrysler factory Super Stock duel quad ram manifolds that were so successfully built for drag racing. The ram tuned "Rat Roaster" was notorious for the fuel distribution problems causing crazy carburation and fuel puddling in the manifolds at various temperature and humidity conditions. I think that the success of the Eldebrock Torker is fantastic considering that it offers this successful fuel induction system for those who want carburated ram tuning.

Fuel injection is an entirely different system. Most cars and boats today use a "ram tuned" manifold because the fuel injection systems elimiate all the carburation problems with fuel distribution. 454/502 MAG MPI - 500/524EFI all these Merc engines use "ram tuned" intake and the computor fired fuel injection gets the mixture right every time. Most car engines have used the "ram tuned" intake for the last 15 to 20 years. First "ram tuned" Detroit auto I had was a Mercury with a small block Ford engine 289/302 with a huge fancy "ram tuned" fuel injection setup - thing had ram passages that curled around the inside of the manifold - man that was 1988! - could have called it the ram's horn manifold. Latest Chrysler fuel injection in my car has a bridge that swings out of the way giving the engine long or short intake runners depending on the engine speed - pretty trick.

Headers with the right length tuned pipes and intake with the right length tuned runners - a matching cam - this was an awsome power producer. Really went past the old exhaust manifold and 180* intake system which worked so well back in 1950. This exactly what 500/525 EFI Merc Racing engine is. Great 1960's engineering with 40 years development time. Now I just need an intake from Merc with a bridge that changes the length of the runners across the operating speed range!