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LS6 or L72 intake for 454


Aaronz28

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do both fit under neath the hood? 
planning to shelf the original intake and run a GM alumiunim - 

the LS6 clearly looks shorter  - but if the L72/L78 or the L88/ZL1 intake fits, i might go that route..

 

any advice on fit/best performance?

Thanks

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hey  Aaronz28,

                             i have a original ls-5 in my car with a lo rise stock manifold.i put on a edelbrock performer intake #2161 dual plane aluminum spread bore oval port to replace my original one. i used my quadrajet carb and linkage. i had to buy a edelbrock  #1935 choke kit wich bolts to the manifold. i also put on a k&n 60-1430 air filter. its 14 inches round 31/2  tall.

with a 3 '' AIR FILTER. IT HAS A 7/8 DROP BASE. I COULD CLOSE THE HOOD WITH NO PROBLEMS .I SWITHCED BACK TO THE STOCK SET UP LO RISE MANIFOLD. i was told the h.p. could increase 25 h.p. ? i also have a set of hooker headers # 2455-1 hkr competition.ceramic coated ,tube dia. 2 "" collector size 3.5 from my 454. i also have the reducers. some of the bottom of the header tubes are bent and scratched
 

 

do some research. if you are interested i want to sell the whole set up. it is very clean.   i can send you some  pics if you send me your email.    thanks joseph

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Aaron

 

Let me try to clarify what I have already said in a couple of posts. The high rise Chevrolet aluminum manifold delivered from Chevrolet on the L-78 and L-88 (and some 402 and 396 engines) clears the hood on a Monte Carlo if you use the drop top GM air cleaner base. I ran my car with this setup before I went to the 3x2. No issues.

 

The low rise Chevy4 bbl aluminum intake used on some LS6 Chevelles (used on the cowl induction LS6 cars I THINK ) and some of the last  BB solid lifter Corvettes clears the Monte Carlo hood better than the high rise Chevy manifold because it is considerably lower.

 

Because you have asked about my GM 400 HP 67 Corvette 3x2 oval port intake. It is not for sale. It will clear the Monte Carlo hood when the stock GM 3x2 air cleaner element and base is used.

 

The GM aluminum 67 Vette 3x2 435 HP intake will clear the Monte Carlo hood. I have attached pictures of this installation to another post. As I hope you can see...the 3x2 clears the hood with the 3x2 GM stock height air filter element and air filter base. In point of fact there MIGHT be room for a taller air filter element in the GM air cleaner base.  K&N will make air cleaner elements to custom heights and I considered having one made that is taller than the stock height GM foam 3x2 air filter element or the stock height K&N washable element that is currently on the car.

 

ALL 3x2 intakes from 68  and 69 will clear the Monte Carlo hood because they are low rise intakes. They are a couple of inches lower than the 3x2 high risers and as I have illustrated the high rise 3x2 manifolds fit just fine.

 

I run a cable bracket from a 68 / 69 3x2 Corvette on my installation. Just order one from any of the Vette parts suppliers and you have that base covered if you go 3x2. The same bracket works for 435 HP and 400 HP intakes. Actually to make it clearer...that bracket fits all 3x2 BB intakes ever made by GM.

 

I hope this gets all the data straight in your mind. There seem to have been a few posts from you on this topic over a period of time that indicate some confusion on what works and what doesn't. I can see where some confusion comes in when you ask a question about GMintakes and get answers about aftermarket manifolds. You are apparently interested only in GM manifolds as was I.

 

Now to summarize: ALL GM aluminum BBC intake manifolds ever made will clear the Monte Carlo hood. My information is proven thru having done it with all the high rise versions so the low risers are a no brainer. I am only speaking about using stock GM air filters and air cleaner bases on both the 4 BBL and 3x2  systems when I make that statement.

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Thanks ! LS65speed - 

 

ive been going back/forth as to whether or not to run the 3x2 vs the l72 or L88 intake.

 

The problem i'm dealing with at the moment is regarding which air cleaner i'd run if i go 4bbl.   My stock LS5 air cleaner will work with a 3/8 spacer (which i've tried) but looks kinda silly with that obvious performance intake.... and i can't run a LS6 chevelle air cleaner as I don't have the hole in the hood...

 

i want the car to look factory even though it might not have come that way :D

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Thanks ! LS65speed - 

 

ive been going back/forth as to whether or not to run the 3x2 vs the l72 or L88 intake.

 

The problem i'm dealing with at the moment is regarding which air cleaner i'd run if i go 4bbl.   My stock LS5 air cleaner will work with a 3/8 spacer (which i've tried) but looks kinda silly with that obvious performance intake.... and i can't run a LS6 chevelle air cleaner as I don't have the hole in the hood...

 

i want the car to look factory even though it might not have come that way :D

Didn't I just say that as long as you run a stock GM air cleaner with a drop base you are gonna be OK? Hole in the hood??????? Just decide on a manifold and get the appropriate air cleaner and element and you are done. There is no need for a hole in the hood. The drop base, open element chrome top GM air filer with a stock height (3 inch +/-) paper air filter is going to clear with room to spare on the 4 BBL setup if you chose a 4 BBL. The stock 3x2 foam air filter element, chrome top and base are going to clear and there might be room for additional height above the height of the stock foam 3x2 element.

 

You are making this WAY more difficult than it has to be.

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No, i'm talking about an air cleaner that looks correct - the Chevelle LS6 air cleaner was designed for a cowl induction - hence the hole in the hood - 

i don't want an air cleaner that seals to the hood -  and the single snorkel LS5 is probably too restrictive.... and open element style doesn't look stock was my point.

 

at least with the 3x2 there is no confusing what it is.

 

Didn't I just say that as long as you run a stock GM air cleaner with a drop base you are gonna be OK? Hole in the hood??????? Just decide on a manifold and get the appropriate air cleaner and element and you are done. There is no need for a hole in the hood. The drop base, open element chrome top GM air filer with a stock height (3 inch +/-) paper air filter is going to clear with room to spare on the 4 BBL setup if you chose a 4 BBL. The stock 3x2 foam air filter element, chrome top and base are going to clear and there might be room for additional height above the height of the stock foam 3x2 element.

 

You are making this WAY more difficult than it has to be.

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No, i'm talking about an air cleaner that looks correct - the Chevelle LS6 air cleaner was designed for a cowl induction - hence the hole in the hood - 

i don't want an air cleaner that seals to the hood -  and the single snorkel LS5 is probably too restrictive.... and open element style doesn't look stock was my point.

 

at least with the 3x2 there is no confusing what it is.

I don't know what more to say. I don't have pics of the car with the GM aluminum L-78 / L-88 Hi Riser and the GM drop base with the chrome top. JUST GET THE OPEN ELEMENT DROP BASE HIGH PERFORMANCE GM Air Filter and stock height element set up for the aluminum hi rise intake and you are ready to roll. Forget the cowl induction stuff above the carb, it won't work w/o a cowl hood and you don't have one. There is no confusion here on the 4BBL. I can't explain this any better than I have. It is a no brainer with the parts I have outlined. You say you want the Hi Performance look. Get the open element filter element and the drop base and the chrome top (if you go 4BBL)  and you can move on to whatever is next in your build.

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Why would you put a rectangle port intake on a engine with oval ports?

Most likely because you have a Rectangle Port intake and you don't have an oval port intake.  Just kidding Just kidding.

 

People do it all the time, back in the day it was done for the visuals of having an aluminum high riser and a Holley on an engine with otherwise milder internals that should have run a Q-Jet. As to performance gains...I have no idea, in fact I doubt there are gains. I am reasonably sure based on my research that there is nothing to be lost on the street with such a combo.  I have researched this with a great many folks who have actually done it and have been assured that it works fine. My LS6 454 is now bolted together with Edelbrock Oval heads and a 67 Vette 435 HP (Rectangle Port ) 3x2  intake. I have yet to drive it set up this way and I do have a 67 oval port 3x2 GM intake on the shelf just in case.

 

There will now likely  be no end of discussion and point counter point about this. Folks who have done it will swear it works, folks who likely never have tried it will have all sorts of reasons that it won't work. The word that will come up more and more if this discussion takes off is "reversion". I am just not going to get too deep in this discussion of the pros and cons. Soon I will have my car on the road and I will know one way or the other if it works or not. If it doesn't on goes the oval port 3x2 and the rectangle port 3x2 gets sold. If the rectangle port intake on oval port heads works well the oval port 3x2 gets sold.

 

We will see what we will see.

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To my knowledge it was commonly done the other way around.  Oval port intake on a rectangular port head to build velocity and increase the low end since the rectangular port heads were so big.  Going the other way around will work, but the main issue that has been seen is the step from the rectangular port intake to the oval port head since the intake port is bigger then the head port it will cause turbulence in the air flow coming in unlike when you do it the other way around. 

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"To my knowledge it was commonly done the other way around.  Oval port intake on a rectangular port head to build velocity and increase the low end since the rectangular port heads were so big.  Going the other way around will work, but the main issue that has been seen is the step from the rectangular port intake to the oval port head since the intake port is bigger then the head port it will cause turbulence in the air flow coming in unlike when you do it the other way around." 

 

You are mistaken...off by a country mile. At least in terms of using Chevy intakes you are off by that country mile. Some aftermarket oval manifolds reportedly were cast in such a way that there was sufficient material on the oval manifold to cover the "roof" of the rectangle head port. The Chevy oval port intake manifold port is so small and the rectangle port is so large that there is no way to seal the point where the manifold meets the head. In the case of both the rectangle port head and the oval port head the bolt patters are the same. This is why the bolt together aspect of this swap works.

 

With a Chevy Oval intake on a rectangle head you would have a HUGE vac leak OR nothing but gasket material to cover the huge upper opening at the top of the rectangle head port roof. Get a pair of rectangle port intake gaskets and a pair of oval port gaskets, line up the holes and look at the gap you will have. The rectangle intake works on an oval head because the rectangle gasket has head material to seat on. The oval Chevy manifold on a rectangle head has no such material...sealing the runner is impossible. The oval (Chevy) intake cannot use either the oval gasket or the rectangle gasket if used on a rect port head.  Maybe with the aftermarket manifolds cast for such a conversion...maybe it works, but with Chevy parts....you just can't get a seal between oval manifolds and rectangle port heads.

 

Another point on this velocity discussion. I did not study much fluid dynamics in Engineering School but it seems to me that the following analogy holds true. In long run HVAC ducting it is common to start with a large size duct and neck down the duct cross-section as you get farther and farther from the source of heated or cooled air. This necked down duct cross section change is to increase velocity at the extremities of the ducting. Any velocity gained upstream of the oval port manifold openings would be lost immediately once the air flow encountered the increase in port cross section that accompanied its entry into the rectangle head. Air flow would fall flat on its face and the engine would in effect be right back there with rectangle port velocity numbers. With the exception of the aftermarket oval intake manifold mentioned earlier I doubt this oval on rectangle head combination would even run. As to the increased velocity....I would have to dig out some books from way way back when I was in school but I think the velocity increase theory is just that a theory. I am not saying that people did not try it and believe it worked.  If I had more time I would research this theory which for now is firmly in the urban legend category for me.

 

post-193-0-33706900-1459813092_thumb.jpg

 

Attached is a pic of a Chevy aluminum 3x2 oval intake up against a rectangle port Chevy intake gasket. As I hope you can see there is no way that combination is gonna seal. It won't work the way it is in the Pic and it won't seal if you try an oval gasket & oval manifold on the rect head. 

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My mistake was in not thinking stock Chevy intake.  Sorry, I'm mainly knowledgeable in aftermarket performance parts, which in that case it works great.  I've done a oval port Holley Strip dominator intake on rectangular port Dart merlin heads. 

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