Cast Iron vs Aluminum Intake Manifold???

[vlbob2]

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)

[BUIZILLA]

fresh or salt water?

[vlbob2]

fresh water/ antifreeze cooled! (run in salt water)

[maddad]

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.

[vlbob2]

Makes me glad I converted to fresh water/ antifreeze cooling! What about choice of intake manifold with antifreeze cooling?

[f_inscreenname]

air gap.
If using in salt there is coatings for the one area that water goes through.

[biggiefl]

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.

[vlbob2]

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]

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.
2104.jpg2716.jpg2972.jpg

[JimG]

I like the Weiand Stealth.

[younger]

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.

[BUIZILLA]

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..

[vlbob2]

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???

[biggiefl]

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.

[silverghost]

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~~~