LSx - Weber Intake Manifold

[Terry Oxandale]

I'm always keeping an eye on an LS1 ITB intake, but I've yet to find one under $1400 (and up to $1600). I understand the cost MAY be justified and hope you can beat out your competition, but I've resorted to a plan that uses the Edelbrock Pro-Flow XT, cutting the top off, welding in a Weber mounting plate, and be done at roughly 1/3 the cost of these other intakes. Below is my idea of what I'm wanting to do. It will take a little bit of filler rod here and there for the round to retangular port transition (that's seen on any weber-to-head intake), but the current prices for a simple direct to head intake is outragous. My plan is to eventually go with the EFI, but they all use the same Weber pattern.

 

[Wolfgang]

Re: LMP to fit ZFQ in new Can am car

Seems like a great idea for an economic solution but I wonder how the width between the Weber bores will fit that of the Edelbrock runners. So quite a bit of massaging to do.

I will CAD model an intake based on your idea and consider our own castings. Not sure where we end up with price yet but will place a separate thread once I get the model and casting costs.

 

[Randy V]

Re: LMP to fit ZFQ in new Can am car

((Guys - I have moved these posts to a new thread and placed it in the proper forum))

Terry -

As long as you're in Fabrication mode on this manifold - you may want to consider a common plenum for the carbs to mount to. Would not have to be very thick (maybe 1" total height) with maybe 5/8: inside height. This will balance the vacuum signal across all the carbs and reduce the amount of intake reversion from valve timing/overlap.
I'm currently working on plans similar to this for my own car..

 

[Randy V]

Sorry folks - I fat-fingered the MOVE of this thread. I have now UN-Fat-Fingered it ((I hope)) and put it in the Induction/Exhaust forum...

 

[Terry Oxandale]

The difference between bore centerline (IDAs) and runner centerline is roughly 8mm (or 4mm per side). This is really no different than countless Weber intakes that offset the round mounting flange into a rectangular shaped intake port, and is unavoidable unless one is using individually mounted single bore ITBs or carbs where the spacing is not "set" by paired castings (such as Extrudabody products).

Thanks for your help Randy. In regards to a plenum, I've spend hours (really!) on this site's Weber carb posts regarding maximum HP and the restriction the Weber carbs may pose to high horsepower. I do not want to rehash this very enlightening topic, but have considered this in my design. My thoughts about a common plenum are as Randy described above.

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I hope I'm not repeating the concept here, but I also want to provide more throat area available per intake event. We all know the small 4-ventury carb can supply the needs of V8 induction due to the common plenum allowing access to all four venturies simultaneously and accomplishing what Randy describes in smoothing the vacuum signal. My thoughts on the plenum would be to allow multiple stacks to see the same intake event, which allows smaller chokes, while simultaneously allowing a larger displacement under the intake at a higher RPM. To do this efficiently though, I would think the plenum would need to be of little restriction. What I did not see covered in the preiously mentioned data, is what the cons of such a plenum would be. I've never done anything on a car that was not a compromise of getting this for the sake of that.

Ideally I'd like to have four separate plenums that join 180º intake events, but this would criss-cross all over the top of the motor, and would be difficult to fabricate toward adequate cross-sectional area. But then...I could avoid most all of this and just go with ITBs rather than carburetors.

 

[Jonathan Strain]

If the plenum is big enough to allow full flow you have over 1,000 CFM of carburetor. The engine will lean out and die every time you start to open the throttle due to a loss of signal. If the plenum is very restrictive between cylinders it will be ok.

 

[Kelly]

Terry - As long as you're in Fabrication mode on this manifold - you may want to consider a common plenum for the carbs to mount to. Would not have to be very thick (maybe 1" total height) with maybe 5/8: inside height. This will balance the vacuum signal across all the carbs and reduce the amount of intake reversion from valve timing/overlap.
I'm currently working on plans similar to this for my own car..

IMO it’s not a compromise that usually comes off very well. The answer to top end starvation for IR carbs is bigger IR carbs. Problem is bigger than 48 IDA are scarce to nonexistent (58mm IDAs, Inline Autolites, etc). I think what is being described is achieving a compromise response characteristic somewhere in between IR and an ordinary open plenum intake. As you diverge from IR you lose the ability to achieve the optimal state of tune possible with totally isolated. As you increase the communication between runners, you approach the characteristics of ordinary open plenum 4 barrel induction systems and at that point, why bother with the cost and complexity of the multiple carbs? Both approaches require purpose selected cams for optimal performance. Drag racers find some merit in improved fuel distribution in approaches similar to what you describe and this is why you see split dominator carbs on top of tunnel ram plenums. Doubt these benefits would come through over broader rpm ranges and benefit a road course car much though.
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Having said all of this, the most unique approach I’ve seen to the compromise approach is the 351c intake below. Would you believe that intake started life as a 4-barrle open plenum Edelbrock Torker? –No kidding. It’s all aluminum and there’s a ton of work sitting there. The plenum section is essentially a laminate of plate. Easy enough to fab up the laminates, just weld the perimeter and then finish/detail. If you get tired of it, you can remove it and you haven’t to hack up your IDA intake. I didn’t fab this one but I think it’s pretty clever and the work was skillfully executed. This approach to the plenum could be adapted to any IR intake. I think it would best serve what you are contemplating if you adapted something similar and added the ability to install removable orifices to each runner in order to achieve your desired state of tune.
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You’ll notice the approach to the intake itself also turns the IDAs in a manner that simplifies linkage and is reminiscent of the ultra rare 58mm IDA SOHC intake immediately below the pictures of the 351c intake.<o></o>
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Thought this might stimulate some thought. Hope it’s helpful.<o></o>
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Kelly<o></o>

 

[Terry Oxandale]

Nice explanation, and what I anticipated. Thanks for the unique photos. This helps a lot!

 

[Wolfgang]

Many thanks for the usefull information. My respect to those guys who are able to manually create these manifolds. Eventually we decided to model a manifold which can take the 48 Webers or just a throttle body and is symmetrical to be used for both cylinder heads. In addition we opted for additional bosses to place the original injectors into the manifold if needed. We have chosen for individual runners for our Can Am MKIII car as we tune it for track day usage anyway. If a plenum is required that can be accommodated by a sandwhich plate.

Looking into the design it is actually not as easy as it may appear. the bolt pattern for the manifold to the cylinder head need to be matched to the Weber throttle body. In addition we nneded to avoid collision with our rear bonnet in terms of total manifold height and width. Last not least we wanted to have a smooth runner migration from the rectangular port to the throttle body.

We will finetune the manifold a bit and then start getting the model and castings. Any interest from other folkes let me know.

 

[Rick]

Kelly: The manifold you show looks very similar to a few made for 427's and accepted the GIANT 58mm Webers which were mounted front to back instead of across from each other. Much like a V12 Ferrari.

Who is the manufacturer/vendor for the Aluminum stacks???

 

[Kelly]

Kelly: The manifold you show looks very similar to a few made for 427's and accepted the GIANT 58mm Webers which were mounted front to back instead of across from each other. Much like a V12 Ferrari.

The third picture is in fact a picture of the 58 IDA SOHC intake. The first two pictures are a 351c intake that was a fabricated one-off.

Who is the manufacturer/vendor for the Aluminum stacks???

I don't know where those stacks came from. The pictures were forwarded to me by a friend because of my IR induction fetish.

Best,
Kelly

 

[M.L.Hearn]

Here is another option if you are looking for a EFI type or you could make adator plates to fit also.

Hilborn Fuel Injectors

 

[Terry Oxandale]

I had thought about that as well, using a 10º plate to keep it all vertical. But once again, the the injector bosses are already cast in the Edelbrock set-up, so if (or when) I go with ITBs, perhapes I can find throttle plates only. TWM used to offer thottle plates only using Weber bolt patterns. They were very short, and very affordable, but they discontinued this product (old 3000 series product), and focused on the injector housed ITBs only (the new 3000 series product).

 

[marc]

Here is another option if you are looking for a EFI type or you could make adator plates to fit also.

Hilborn Fuel Injectors

View attachment 45204

You missed the part at the bottom that quotes 6500 to 7000 for the kit. that is alot

 

[Terry Oxandale]

Spoke with Doug at TWM yesterday and he pointed me to a new product they have. It is an ITB plate that has 4 throttles spaced to match the OEM bore spacing, have no injector bungs, and used the OEM injection assembly on the manifold itself. Pretty neat, but still a little pricy at $2500. This will allow me to still use my own intake if I want to stay with an EFI.

http://www.twminduction.com/ThrottleBody/gm_ls1_ls2_fr.html

 

[Wolfgang]

I have seen that manifold but the stacks are not vertical and the Weber style look more period authentic. The total price from the website is 4995 USD which I agree is still enough for us to justify our own manifold for the LS and combine with a jenvey IDA or IDF throttle body. I think we could make a set of 2 manifolds for one engine for 500 € or about 750 USD. Decision to make them will be easier if there was some interest from others.

 

[Thomas Rouw]

at those prices you could actually buy a second hand CNC milling machine, material and parts to build your complete own system......

by the looks the TWM system must be to short to do any good on a stock LS1 it's not like the things scream 8Krpm out of the box. cant really see form this angle, but it seems that you cannot fit any larger tubes than the ones on there in the picture. Mr Helmholtz won't really like it methinks.


Grtz Thomas

 

[Terry Oxandale]

It's embarrassing! Once again I'm looking to the Brits for parts. First, the Image wheels, now it's Jenvey ITBs. Where will it all end?

Anyway, I finally spoke with a Jenvey rep in Canada. Sorry guys, after asking the UK rep to repeat himself many times, I finally decided I needed either an interpreter, or instead, speak with someone from this side of the great pond. So I talked with the guy at Emerald in Florida (ugggg) that wasn't interested in listening to a customer, but rather on telling me what I wanted and needed...period! With that bad taste in my mouth, I diverted my energy to the Canadian dealer, and was very pleased with his knowledge and ability to listen to what my needs and desires where, and to address those needs.

So long story short, it's almost a cinch that Jenvey's SF ITBs (no injector bungs) will be sporting the LS2. So, if any body is interested in a set of 48 IDAs with larger chokes, let me know.

Thomas, you are so right. This was one reason the modified Edelbrock intake was so appealing in that the runners alone are 6" long before adding the ITB and horns. But in all fairness, all of these new market manifolds are designed with a hood over the engine, which will not exist in my application.

Ox

 

This is an option that might interest you. I spoke to these guys at the SEMA show and the quality of there product is amazing!!
Chev. Manifolds

 

[Andrew Robertson]

You missed the part at the bottom that quotes 6500 to 7000 for the kit. that is alot

Hilborn EFI pricing is not what it seems. If you buy just the stuff in the picture at the link below (i.e. no ECU, no injectors, just the intake base casting, ITBs, rails, TPS, throttle linkage, manifold vacuum kit for MAP, and stacks) the SBC kit runs to about USD$2700 from memory. It's much cheaper than the listed kit prices of $6200-$7000 to buy it this way then spec it up with your own sensors, injectors, loom and ECU. That's what I'm doing.

Hilborn Fuel Injectors

Cheers, Andrew Robertson, New Zealand