Holden Ecotec Intake Manifold

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bubba2533
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Holden Ecotec Intake Manifold

Post by bubba2533 »

Hey all,

I’m looking for an intake manifold for a Ecotec VS Commodore

I don’t need the upper sections or throttle body. Only the lower piece of the intake manifold as pictured below.

I’m located in the United States and we don’t have these style manifolds in any factory vehicles.

Any help would be appreciated.

Thanks,
Branden
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vlad01
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Re: Holden Ecotec Intake Manifold

Post by vlad01 »

Is there a reason for wanting one of these? We found the US ones to outperform those by quite a bit so we did the opposite and imported a series 3 banana manifold.

These ecotec ones are too restrictive due to the runners being cast so small and no meat to improve via porting. They are about low 30ish or high 20mm diameter ID just above the injector bosses. The US ones were huge in comparison and flowed on the bench something like 40% more iirc.

The only disadvantage is the US ones have very long runners and not ideal above 6000-6500 or so for NA but still way better than the ecotec ones and are great for boost. I think you can get inserts for the US ones to make the runners shorter so prob a non issue anyway.
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bubba2533
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Re: Holden Ecotec Intake Manifold

Post by bubba2533 »

Hey, that's some really good information. I didn't even think about the US manifolds not being available over there.

I haven't seen any data testing all the manifolds (including a holden ecotec one). This video is the best testing that I've found to compare some of the US manifolds.

My factory manifold is pictured below (2000 Pontiac Firebird), which I haven't seen any direct comparison between other US manifolds. I 3D printed an adapter to test fit a 92mm LS style throttle body, which I would make out of aluminum.
IMG_7145.jpg
I'm thinking this is the US manifold you called the banana manifold:
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I might just go to my local junkyard and grab an aluminum FWD intake manifold.
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vlad01
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Re: Holden Ecotec Intake Manifold

Post by vlad01 »

Yes, that's the one!

The one you have now also isn't too bad. I read years ago an engine builder who raced a car like yours got something around the 270hp at the wheels with your intake.



You will need the lower section too and new runner insert/seals like this.

https://www.ebay.com.au/itm/32530731334 ... ctupt=true

EDIT: Couldn't find the runner insert on ebay, hopefully it can be reused?

I have seen some people replace the insert to the ZZP HV3 moulded insert which shortens the runners a lot and depending on your cam it can improve power a bit mid to top but if the cam doesn't suit it will make it worse.

I found the link to those but holy crap! what's with the price? Gareth bought one from them for like 100 bucks or so when I was helping with his race engine development.

https://www.ebay.com.au/itm/13204788539 ... ctupt=true


This is what the ecotec lower intake looks when cut, You can see it's shitouse, compare the cross section area with the injector bung size and then you realize how tiny they are and no room for porting improvements.

IMG_1649.JPG

And now compare the L26/L36 lower intake. The port matching is not great but very quick and easy to grind out to match and the runner only opens up to much larger sizes from the gasket face upward.

Also the L26 alloy upper intake has a nice large round throttle opening. Iirc it was like 75mm? or bigger? which is plenty for these engines.
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bubba2533
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Re: Holden Ecotec Intake Manifold

Post by bubba2533 »

Wow it's deceivingly small, but really easy to see how small they are when cut open like that.
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Re: Holden Ecotec Intake Manifold

Post by vlad01 »

It's quite funny seeing lots of racers and engine builders make custom and big plenums for the ecotec LIM thinking the throttle size and/or the volume is a problem. Volume helps with small throttles but neither is the issues with these and the LIM is always completely overlooked.

The initial idea and design is good, throttle is decent and the volume is ideal for many combos, so is the length of the runners, very much ideal for a moderate to hot motor but geez they skimped on the runner size. I suspect this was for low speed air velocity to help with emissions and economy at low engine speeds.

It's apparent that for 1000hp builds of these engines here in Aus, people need to push high 40s PSI boost to get there, there's your problem!


The only thing I don't like with the US manifolds is the thermostat is at the rear for a RWD car, though our L67 engines were the same and had piping plumbed from the rear from factory. Also these L26/L36 banana manifolds needed a section cut out and welded up to clear the timing cover as they normally have the throttle facing the flywheel. PITA but doable.

Gareth built his race engine with the alloy L26 bananas in mind and it did work and very well! There is a thread on here somewhere with pics here and there. If I find it, I'll post it. Iirc he used the Dorrman china copy LIM and it was decent quality and modding was easy as it was not oil soaked for welding but used one should be fine. Upper was a used genuine one.
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