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Discussion Starter #1
perusing Vizard's "tuning BL's A-series engine" recently, i was reminded how much stub stacks improve flow over the bare carb inlet. when i look for stub stacks for the DCOE, well, there are none. the shortest ram stack i found is a 16mm one, which does not appear to be fully radiused, which would seem to limit its flow improvement.

does anyone know about a stub-stack available for the DCOE carbs?
has anyone made their own?

-jason
 

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Try TWM Induction. On their website they show a 12mm tall "shorty stack" that's probably what you're thinking of.
 

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Discussion Starter #3
thanks, 73gtv. those are close to what i was thinking of, though the radius looks like it could be a little more generous...

any experience with those?

-jason
 

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I don't at this point. Was thinking of making a fiberglass airbox with these on the carbs buts that's a "down the road" project.
 

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Gary, if you look at the TWM site they have what they call a shorty stack which is around 12mm high. Basically a ring. I'm assuming that's what Jason is talking about. K&N makes a dish with four radiused holes that fits inside the aircleaner for Holley carbs and that's where the "stub stack" term comes from. The purpose of the "stub stack' being to smooth airflow into the carb.
 

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Thanks. I appreciate the explanation, but not the reference to short stacks. Now I'm desperately hungry for a plate of pancakes covered with butter and syrup. :)
 

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I'm doubting syrup would improve the taste, but anywho, here ya go.....

Stub (called 'shorty type' @ TWM) :


Conventional (called 'full raduis type' @ TWM) :


Oh, and a closup picture of Gary's stacks from off the TWM site :)

 

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I use an ITC foam air filter, not an air box, and I'm not sure about the clearance measurement. The specs for the ram pipes and air filter were provided by a manager at ITC, who dug into the company parts bin so he could test his recommendation before emailing me. I thought his service above and beyond the call of duty. Here are excerpts from what he wrote:

"We do have a distributor in the US who deals with the kind of filter you will be after, Coast Fabrication over at Huntington Beach. They may be contacted on 714 842 2603 or via e-mail at [email protected] - this may have recently changed, if you don't get through on this address drop me a line and I'll get it sorted for you.

"Before you get in touch with them please send me some details of your engine, carbs and clearances etc and I should be able to give you some further insight into which components you will require."

Email #2: "The 22JC50 is the standard baseplate we list for your Alfa engine, the hand written 22 part denotes the specific application and is hand written because we are still a relatively small firm and are too tight to get lots of different labels printed. ;)

"I pulled a 22JC50 and an old TWM ram pipe off the shelf to do some checking and I reckon it might be quite tight on no. 4 ram pipe when the filter is actually fitted, full radius ram pipes throw up loads of problems with internal clearance, typically 80 -90mm od compared to 60mm od for standard style ram pipes. As you are cutting your own plate this should not be a problem, it looks as though you still have a bit of space at the back of the engine bay and you would only have to move it back by around 10mm to get the necessary clearance inside.

"If you can fit the JC50/S/75, that will be the better filter to go for, the extra height will always be a help, especially on no.4 cylinder where the domed part of the filter will curve slightly over the rampipe. This filter should cope with about 500bhp so the extra airflow available won't really make a difference - it'll just help with the clearance inside and make sure all four cylinders can breathe easily and evenly."

Best regards,
Andy Jackson
Parts Manager, ITC

I did use the JC50/S/75, as noted here: http://greend.com/Specifications.htm
 

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What is the HP gain of this setup compared with a standard AR airbox? Does it shift the peak torque RPM? I have CB 47 cams and 34mm venturis in 40DCOE's.
Thanks,
Ed Prytherch
 

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Hi Ed. Sorry, but I don't know the answers to your questions. If the motor was in a Spider it would definitely go 135 ... no wait, that's a whole other thread. Let's not go there.

I can only tell you that I have a very strong 160-165 horse motor that likes to rev, yet will still putt around town. I have no data to indicate how various ram pipe- air box and/or air filter setups compare. Perhaps the people at TWM can help you.

Also, while I like the ITC air filter, if I were to do it all over, I'd use an airbox that brings in cold air.
 

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Weber 40 DCOE Stub Stacks

Recently saw some sidedraft Weber stub stacks on Ebay. Item Nr. 270227608690. They appear to be identical to those we used on a 1600 Giuletta at Sebring.
 

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Stub stack (12mm) clearance issues??

Hi folks,

I'm interested in fitting the stub (12mm) stacks reference in this thread on the 1750 motor that's I recently installed (but haven't yet started) in my '63 Giulia Spider restoration project. I plan to use the off-the-shelf K&N filters with this application. In your experience, is there enough room within the filter housings to do this - without interfering with the face plate (fender side plate) of the filter? And will there be any airflow restriction issues??

Thanks much!
Jim Caldwell
Coralville, Iowa (where the floodwaters are just receding)
1963 Giulia Spider #AR372591
 

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Discussion Starter #15
I plan to use the off-the-shelf K&N filters with this application. In your experience, is there enough room within the filter housings to do this - without interfering with the face plate (fender side plate) of the filter? And will there be any airflow restriction issues??
Jim-

Places like Advanced Performance Technology sell 16mm ram stacks suitable for use in 1.75" (44.45mm) tall K&N filters, so the 12mm ones you're thinking about should present no problems. It seems fishy that having a ram stack eating up 36% of the filter height doesn't impact the flow, but I have no quantitative data to indicate that it does or doesn't. It would take a couple of back-to-back dyno runs without and with the ram stacks to get the answer.

Just eyeballing it, those 12mm stub stacks look to have about a 6mm radius, which seems a little small. The idea is to present a nice smooth flow path around the corner of the carb inlet, and the smaller the radius, the less nice it is. The ASHRAE Handbook of Fundamentals gives a loss coefficient for various inlet radius (r) to pipe diameter (D) ratios ranging from 0.5 for a sharp corner to next to ~0.025 for r/D = 0.25. The pressure drop across the carb inlet is the product of this loss factor and the dynamic pressure, one half the product of the air density and the square of its speed. For a ratio of 6/40, it's about 0.07, so maybe 6mm isn't too bad after all.

It's too bad that there aren't many alternatives available for short ram stacks, or data providing the benefits. I'm still toying with the idea of having some stub stacks with a larger radius machined from aluminum stock, but that's not in the cards this year. Also, if I remember Vizard's comments correctly, the flow benefits of stub stacks are not as great on multi-weber carb setups as they are on, say, single SU carbs.

Good luck!

-jason
WA, USA
 

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Jim Caldwell had asked: "I'm interested in fitting the stub (12mm) stacks reference in this thread on the 1750 motor that's I recently installed (but haven't yet started) in my '63 Giulia Spider restoration project"

Jim:

As an old Iowa City resident, I'm glad to hear that you and your Giulia haven't floated away!

My sense is that no one on the Internet can predict whether this will fit - it will depend on what sort of motor mounts you are using, header-column clearance, etc. If your carb-fenderwell clearance is anything like mine, you'll be lucky to fit any sort aircleaners into the space. However, the intake manifold on your 1750 sits a few mm higher than the one on my 1600 so that should help a bit, since the fenderwell slopes away toward its top.

Here's a shot of the cut-down Weiands on my car. This is with normale motormounts & headers. You can see where even these shallow cleaners have worn some paint off the fenderwell.
 

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Hi Jason and Jay - thanks for your responses to my ??? about stub stack applications and fit. Jay -- We're high and dry, and I'm immensely grateful for that...but I guess if a USGS Hydrologist (me) built a house on a flood plain and was flooded out, he'd have no one but himself to blame. We're about 100 feet above the elevation of normal stage on the Iowa River. I'll quit on the Giulia project and start working on an Ark, if the water gets within 5 feet of my house. Yesterday, the Coralville Reservoir ceased flowing over the emergency spillway. Barring any major precip events, the Iowa River should be back within its banks in Iowa City in 2-3 weeks. But, what a MESS here in eastern Iowa.

Re: clearance for aircleaners in my project. I'm using NOS Veloce mounts in my 1750 conversion. Strangely, the Centerline mounts, engineered specifically for this conversion didn't work out. Despite widening and lengthening the slots in the chassis for the mounts, the C-Line mounts skewed the back of the motor an inch or so toward the passenger side of the car. The NOS Veloce mounts cured that problem. With the Veloce mounts, there's about 11 degrees of engine tilt toward the steering column-- with about 1/4 to 1/2 inch clearance between the generator pulley and the steering box (hopefully, that'll be enough). This setup gives decent, but not generous, clearance between the Webers and the inner fender. Hopefully, it'll be enough!

Jason - thanks for your comments on stack design and efficiency -- and the link for the APT site. I'll let y'all know what I come up with.

Best regards,

Jim
Coralville, IA
1963 Giulia Spider #AR372591
 
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