Dellorto velocity stacks

bottomend · Post by **bottomend** » Fri Apr 09, 2004 2:32 pm

What size are you guys running...and why?

I have a set of 40 DRLA's that I'm gonna rebuild. I've got the book, the rebuild kit, the update kit, CB linkage/filters( I've got the 6" filters) I need to know whats recommended for stacks.

jloh · Post by **jloh** » Fri Apr 09, 2004 2:48 pm

my 40's have the 2" stacks and 31/2" filters.

reason: thats how i bought it!

yetibone · Post by **yetibone** » Fri Apr 09, 2004 3:00 pm

...Back when new DRLA's were available, a local VW shop turned me onto Dellorto's 'cause he said they were less expensive, and performed better on the street than Weber IDF's. I can't say there's any truth to that 'cause I've never run IDF's on anything of my own.

I still use Dellortos 'cause that's what I know the best.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Fri Apr 09, 2004 5:15 pm

Dells ARE the best... More power and easier to tune...

bottomend · Post by **bottomend** » Fri Apr 09, 2004 6:34 pm

You guys dont have to convince me of anything.... I'm really excited to rebuild these and get 'em in my bus.

I have a set of 4" stacks on order and I was wondering if those would cause me to loose power. I read the thread over at the 914 web site and there seemed to be some differing results.

I've got one of the carbs almost completely torn down. The only thing remaining to remove is the butterfly valve shaft. Any tips on this?

Bobby74 · Post by **Bobby74** » Fri Apr 09, 2004 7:51 pm

4" stacks are perfect....

IMO anything above that, pretty much defeats the purpose. Its supposed to funnel the air in and increase velocity (duh), by straightening the air. However, if you have the carb way below the stack the air will tend to be turbulant as it bounces down the walls of the stacks. Where if you have a stack between 2-4" it will straighten the flow right before its drawn past the spray bar (in your case). Just my opinion, I don't own a dyno.

-Bobby

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Fri Apr 09, 2004 8:36 pm

The higher the RPM capability of the engine, the more it is impacted by the height of the stacks....

jloh · Post by **jloh** » Fri Apr 09, 2004 9:49 pm

once you have the butterflies out, tap the shaft through with a hammer until its even with the a bearing. then tap the other side and the first bearing will pop out. then take the shaft and remaining bearing out of the throttle body and over to your sturdy bench and use a box end wrench (10-13mm) slide it down to the bearing and tap on the wrench with a hammer.

getting them back in the FUN part! two sets of hand swould be nice.

the dell tech book says to take them to a shop "equiped" for this job...but you can do it.

this is how me and dstar did it...so dont flame me if its not the "right way"! lol

914 Ghost · Post by **914 Ghost** » Sat Apr 10, 2004 10:50 am

Velocity Stacks are good.
From the TECH BOOK:
"USING TALLER VELOCITY STACKS HAS SHOW A MARKED IMPROVEMENT IN MID RANGE TOQUE AND UPPER END POWER"

Also, says you need to consider different moving the main jets up a step to take advantage of the increased power 'potential'.
I've compared Dell's and Webers side by side, same car (1.8L 914) same day.
The 40 DRLA's were MUCH nicer than the 44 IDF's= biggest difference was all around smoothness- I almost can't tell the difference between Dellortos and the stock F/I. The Webers are the "tough guy carb" they sound throaty and make you wanna punch the throttle at stoplights to get power out of them. Weren't so great at lower engine speeds- they did work, and I'd use them on a dune-buggy, but the Dellortos were more better'er.
My $o0.02
Bob O

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Sat Apr 10, 2004 11:15 am

My dyno graphs on TIV engines do NOT show this...

I thought the same thing for years till I tested 4 different lengths of velocity stacks on the same engine, and then did the same test on 3-4 more that were of different tune.

The TIV head design changes this equation in my opinion.

Books are great, till you buy a dyno and start spending money on fuel. The dyno doesn't lie...

BTW, The engine was optimized with each stack change before getting a power pull, typically the jetting changed very little, I think we had to make one air corrector swap and one main swap thoughout the test on one engine.

For High RPM I tend to like short manifolds and short velocity stacks, if you se my conversion video you'll see what that can do on my 2316 in the 914, and those are just 40 dells.

914 Ghost · Post by **914 Ghost** » Sat Apr 10, 2004 11:33 am

Teh tech book was great when I knew nothing, I I believe you're right about the dyno.
They didn't dyno every engine combo with their carbs, so the proof is in the puddin'.
Also the tech book never once mentions a Type-4 or 914.
Just Bug. So maybe the type 1 engine when "built" gets some advantage from tall stacks?...or why would all the cars at the strip have them?
The type-1 heads flow so bad to begin with I'd guess anything would help.
-Bob O

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Sat Apr 10, 2004 11:53 am

The Tech book is great, I learned alot from it about the way a carb works.

The TIV engine tunes alot differently, the jetting, runner length and etc are totally wacko compared to a TI. Thats why alot of TI tuners can never get a TIV totally right.

I had a 2165 engine in my old sandrail, and played with different stacks at comp hill in Glamis... The taller stacks did increase the midrange punch but seemed to shorten the powerband a bit, I needed revs so I went up a size in venturi and it broadened the power a tad, but I still went back to the short stacks a few runs later and liked it better.

bottomend · Post by **bottomend** » Sat Apr 10, 2004 12:48 pm

Great discussion!
Thanks for the tips on getting the shaft out. Are the bearing sealed? Will a bunch of little ball bearings come flying out when I remove the shaft?

After I get the shaft out do I put the carb in to a "carb bath"? I've seen a gallon bucket of this stuff for sale at FLAPS. How long do I soak it? The CB Tech book says "a short as possible". How long is that?

IMPORTANT; I've found one broken part so far. (I'm doing one carb at a time as per the CB book recommendtion) One of my pressure intake union screws is broken. It's listead as Fig. # 49 on page 82 of the CB tech book. Where can I get this part? Anybody feeling benevolent? :O

jloh · Post by **jloh** » Sat Apr 10, 2004 7:17 pm

bottomend wrote:Great discussion!
Thanks for the tips on getting the shaft out. Are the bearing sealed? Will a bunch of little ball bearings come flying out when I remove the shaft?

they are sealed, no bearings will come flying out.

After I get the shaft out do I put the carb in to a "carb bath"? I've seen a gallon bucket of this stuff for sale at FLAPS. How long do I soak it? The CB Tech book says "a short as possible". How long is that?

get the bucket. soak your big pieces first. take everything off/out! lets say 20-30 minutes depending on the tarnish. pull them out and start scrubbing! dont pake anything thing with wire etc. spray thing whole thing in and out with berrymans' carb cleaner. then dry with compressed air. paying close attention to the different circuits and venturis.

IMPORTANT; I've found one broken part so far. (I'm doing one carb at a time as per the CB book recommendtion) One of my pressure intake union screws is broken. It's listead as Fig. # 49 on page 82 of the CB tech book. Where can I get this part? Anybody feeling benevolent? :O

CB has everhting that that's still made. be careful with your float! they dont makem anymore!

samcat · Post by **samcat** » Sun Apr 11, 2004 10:00 am

And once you have cleaned and reassembled them either paint with lacquer or a color of your choice.

I went with black:

Get loads of comments about the look with the black carbs

Cya,
Sam C