6/carbs: ? about tall 2ndary venturi's, rich, I miss you. Options

[brant]

carbs: ? about tall 2ndary venturi's
Hi all... thanks for the help in advance.

I want to try a set of the tall 2ndary's on my IDS-3C carbs.
I'm running the stock ones and want to try the tall ones, that I've heard called "906-style"

its a race car and withoug re-hashing all of my jetting and dyno history, my questions are:

1) pierce manifold says they have 2 different types in stock a 3.5 size and a 4.5 size. I believe this measurement is in reference to bore and not height. Pierce said that both sizes are the "tall" type. Which do I want? Motor is a 1967 2.0/S motor at altitude.
(the pierce catalogue references that the IDS carbs came with 4.5 short, but I'd like confirmation before I order)

2) Does anyone know if these tall secondaries interchange on the IDA carb versus the IDS carb. I would assume so, but I once bought some F33 emulsion tubes from Pierce that do fit the IDA, and found that they would not fit the IDS. I didn't know there was that much difference between the two carbs, which surprised me. But again, before I order do people know if the 906-type tall 2ndaries will fit an IDS-3C body?

again, thanks in advance everyone!
brant

[Root_Werks]

Actually, Jake Raby had a decent write up on stack hieght some time ago. He mentioned going tall made a big difference, but you could also go too tall. I would say go with the 3.5's. I think if you go too tall, you begin to loose the effiency of the volicity effect? ..... I think anyway. (IMG:http://www.914world.com/bbs2/html/emoticons/idea.gif)

[brant]

Dan,

I think your referencing the horns

I'm talking about a different part.
the 2ndary venturi, that sits inside of the carb throat on top of the primary venturi.

the tall ones (used on the 906 motor) stick up above the carb body, and into the horns

brant

[Jake Raby]

All my testing would not apply to the six... It has different head characteristics that really impact results.

On a /4 no matter displacement I have found shorter stacks(just enough to control reversion) are mucho better for top end power and efficiency, while tall stacks are much better for low end grunt... BUT even the exhaust system will impact this-

I have seen a 18HP variance just from swapping stacks on an 8,000 RPM capable engine.

But I'll stress that my theory has never been employed on the six-

[Root_Werks]

QUOTE (brant @ Nov 3 2005, 10:06 AM)

Dan, I think your referencing the horns I'm talking about a different part. the 2ndary venturi, that sits inside of the carb throat on top of the primary venturi. the tall ones (used on the 906 motor) stick up above the carb body, and into the horns brant

Oooooooooooooooooooooooooh, those. Don't know. (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)

[Aaron Cox]

doesnt JP have tall ones on hez carbZ?

Just a lead (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[Downunderman]

I got mine from PMO.

[brant]

Howard, JP,

do you guys know if yours are 3.5 or 4.5?

(I'm assuming that is the measurement in mm's of the bore of the part, but you know what they say about assuming)

apparently PMO is out, and has been out of them for a few months. They recommended Pierce.

(seems like every opened box, has a new smaller box inside of it.)

brant

[Phoenix-MN]

I have the tall ones on my 2.5L 911, I'll look tonight if I can see what size they are.

Paul

[john rogers]

My race engine has the real tall ones and the cards are the IDS type and have the "candy canes" still in place. I used some very small brass tube from a hobby shop and extended the nozzles so they would fit over the top and I do get a tad bit of enrichment from them. Pierce Manifolds said most guys block them off but I decided to try and see if the'd work and they do above 5K RPM. They told me since I had the 906 cams the largest ones would work the best and that seems to be true.

[brant]

Thanks Paul!

John... is the 3.5 versus 4.5 a measurement of bore?
at first I thought it was height (tall) but pierce said that it was not about height, and was a measurement of bore.

when you say that you have "the larger ones" does that mean that yours have a bore (hole size) of 4.5 then?

sorry for restating the same question, just want to be sure.

brant

[john rogers]

Yes, larger bore.

[brant]

cool thanks John!

(I didn't even know there were 2 different sizes)

Thanks a TON John!

(IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif)

[J P Stein]

Oh boy, I get to post my only artsy pic....that I have taken.
I went out and measured. The height (lenght) of these puppies is 4.5 inches. Bore is a bit less (eyeball) than .5 in.

[Trekkor]

that picture makes me happy (IMG:http://www.914world.com/bbs2/html/emoticons/wub.gif)

[Aaron Cox]

gawd - what did those milled aircleaner bases set you back (IMG:http://www.914world.com/bbs2/html/emoticons/pinch.gif)

[J P Stein]

I've heard a few things about "why"....internet stuff, mostly.
Lotta salt grains here.
My carbs came to me with em' and I didn't have to "fix" anything.
whut I hear: Better mid range.
Less fuel reversion in the aux venturi (the gas comes in there) with long duration cams due to the increased height.
Used first on the 906 (with 906 cams...go figure)

Thas all I might know. (IMG:http://www.914world.com/bbs2/html/emoticons/huh.gif)
Steve Wiener could give you the straight scoop

[J P Stein]

QUOTE (Aaron Cox @ Nov 3 2005, 04:14 PM)

gawd - what did those milled aircleaner bases set you back (IMG:http://www.914world.com/bbs2/html/emoticons/pinch.gif)

Not cheep & NLA. I sold/traded them to MikeZ.
Here's an old pic.

[Aaron Cox]

whatchu runnin now JP?

ITG style?

wonder if they maketh those tall vens for an IDF

[brant]

Its the reversion issue and my 4K stumble that has pushed me into the decision to try.

I'm only running S cams, but depending upon how they are timed, they could still be a problem.

Plus I'm running such big venturi's that I picked up a mid range stumble.

brant