• Registered: 2009-06-25
  • Posts: 558

Topic: Intake manifolds

I've been playing around and used some stockers and one aftermarket intake manifild made for a single barrel carb (EMPI?). The aftermarket one was almost the same as stock, except the carb throat was narrower at the top due to material thickness, and it also had a small "A" shaped wedge at the bottom to help reduce turbulence from the primary throat. It had less torque, but was smoother in general and did not wake up until 3000 RPM. However, that really did make freeway driving more fun with the extra power on top...people are really not expecting to see an old VW doing 65 and suddenly walk away like that wink
I re-installed the stocker because it had more low end torque, and I mostly drive on surface streets, 40-50mph.

I know there are several kinds of intakes out there, single barrel, two barrel, direct to head manifolds for k dogs and so forth. What have you used, how did it work out, what are your opinions?

Paul

  • Registered: 2009-06-25
  • Posts: 558

Re: Intake manifolds

Everybody running stock?

  • From: somewhere over the rainbow USA
  • Registered: 2006-07-26
  • Posts: 1,889

Re: Intake manifolds

Stock, sorry no help

burrhead

A wise man makes his own decisions, an ignorant man follows public opinion.
  • Registered: 2007-03-27
  • Posts: 2,422

Re: Intake manifolds

Yeah Altema My Neighbour just turned me on to 2 single port aluminum end casting's just for this type of playing !
Not sure what excatly there aplication is ?? Cut a stock Single port manifold ??
Possibly for High CCR Application or could be to use a 34 pict on a single port ?/ But Ive even had some one suggest a Progressive single port ???
  Can tell you this that back in the Day when single port was the only game in town ?? Pre 72 !! That the Old Coot's swore by 1835cc with the single port heads !!
  1835cc has alway's flowed head's better ??? Somethin about the 92mm bore just seem's to free them up ?? Or so Ive been told !!
                                                                       Sean

  • Registered: 2009-06-25
  • Posts: 558

Re: Intake manifolds

Ok, thanks for the input guys. I'm leaning towards dual carbs if I can find the right pieces. I think I figured out why the aftermarket manifold has less torque, but revs smoother and has more top end. Most of the time, the intake runner length and volume determines whether torque or HP is favored, with long runners generating better low end torque. I don't have time to do a full write up right now, but length affects air pulse resonance. Get it right, and the inertia of the air in the runner piles up in front of the intake valve, and when the valve re-opens, there is higher than normal pressure in the intake port of the cylinder head to push the mixtuer into the cylinder. Both of the manifolds in question have about the same internal volume. However, the primary difference is that the stocker sees the whole horizontal section as one resonant chamber, and pulls the mass of air to that side. Remember too that the air cooled four does two cylinders on one side, then the two on the the other side. The aftermarket manifold has the "A" shaped divider, and effectively cuts the intake tube length in half (more than half for cyl 3 & 4, less for cyl 1 & 2), so the resonating cavity is more equivalent to a short runner intake designed for higher rpm horsepower.

Paul

  • Registered: 2007-03-27
  • Posts: 2,422

Re: Intake manifolds

Yupp ???? LMAO
  Now lett me Blank your whole theory up !! Cause Ive had a Really Badd week and Im meaner than pack of Pitt Bull's on a Kitten !
  You got technical term's like velocity , Plenum Chambers , Even a Pulse <<< A Pulse ??? Yuppp a Pulseation !! Ask Your Doctor ??
  It's Called Flow add CFM to your List ( Cubic Feet Per Minute ) Back pressure even valve over Lapp with other Terminology Like Scavenging !
  Lott has been done on this !! Lott of shop's have sett up flow Benche's !
  Dual Carb's are not an out of the Box application !! When you decide to install them >> Lott of factor's come into play !!
  Anyone can Install a new set of K- Dog's on there stock motor and have a Presumably Ok Runnin ride ???
  But is it Right ?????? Only indicator to tell is 6 Mos. later how are the Pluggs Runnin  !! or 3 Mos.
  It really is best to Build for Dual Carb's then go that extra expense and Work and Detail and get it right !!
  But even this has it's aggravation's and Buyer beware program as to what you should Build !
  As in it never Stop's !! Once you start Buildin ??? THere's no end to it !!
  Why after 30 somethin year's I reccomend a 1776cc motor Built on a Fairly Stock modified format or Crank and Case !!
  Engine Size is Like your phallic symbol size !! Everyone has a Big Un !! Dont you wish you had a Big Un too ??
  See Im a Swede << Mean's I dont suffer from inadequate endowement syndrome !! Meaning I dont Lie about size !! Not My Rod Lenght or my engine size !!
  After 30 somethin year's I will tell you this !! If you build and carb a 1776cc motor and then gear the trans appropriately !!
  You will be Mile's and Mile's ahead of all the other's who claim 12 inches or longer or 2000 cubes or better !!
  Most of these Clown's are Lieing there Arse's off in hope's that it will somehow make there Bunny nose grow bigger !!
  Or make there car faster ??
  Truth is !!! Even a larger portion of these same Clown's who do manage to stroke a motor ??? Are strokin themselves the wrong way !!
  Doesnt matter how big the motor is !!
  But what kinda Horse Power it Putts out on the Dyno !! That and does it get Pavement everyday !!
  Dont be a Size Liar !!! Build a 100 horser that get's it every day , day after Day !! Year after Year !!
  This My Freind is the Secrett to a Long and Happy Marriage as well as a long and Happy relationship with your Ride !!
  Cause the 2 love's of your Life ??? They know the Truth !! LMAO
                                                                           Sean

  • Registered: 2009-06-25
  • Posts: 558

Re: Intake manifolds

Nah, CFM flow on a work bench is not the same as running the intake on an engine.
Why? CFM flow will help you with problems like surface turbulence, port matching, and so on.
In the real world, the intake valve opens, sucks air and fuel from the carb through the plenum and intake runner.
Then what happens? The valve shuts.
What happens to the air moving towards the valve? It tries to keep moving and compresses against the intake valve.

We all know air can be compressed. Now, there is some theory that the air bounces back when the valve shuts, and the accoustic reflection travels backwards through the intake runner in the "resonant chamber" space, and comes back again just in time to help shove the air sitting at the intake valve into the cylinder. Me? I think that it has more to do with the column of air compressing, and not having time to decompress before the valve opens again due to the inertia of the air column in the runner, but it might be a combination of both, depending on runner length. So then whether it is due to a reflected accoustical pulse, or the primary induction pulse, it is still a case of matching the resonance frequency and rpm to optimize your torque and horsepower bands.

Put THAT on your spider bite and let it fizzle for a while! LOL

Here is one link to a write-up on one of the therories, but I didn't learn anything new there. Resonance is one of the basics for accoustical physics, and THAT I've got down. You don't get trained by Barry Gordy's master engineer and not know about waves!
http://www.team-integra.net/sections/ar … icleID=466

Oh, and here's a simple sketch showing linear flow and resonance.

http://i235.photobucket.com/albums/ee288/altema/Misc%20tech%20photos/ACintakecomposite.jpg


Paul

  • From: somewhere over the rainbow USA
  • Registered: 2006-07-26
  • Posts: 1,889

Re: Intake manifolds

Why can't you just drive the dang Ghia and enjoy it rather than trying to reinvent it?
If you are bored I have lots of projects that I need done  wink

burrhead

A wise man makes his own decisions, an ignorant man follows public opinion.
  • Registered: 2009-06-25
  • Posts: 558

Re: Intake manifolds

burrhead wrote:

Why can't you just drive the dang Ghia and enjoy it rather than trying to reinvent it?
If you are bored I have lots of projects that I need done  wink

It's just the way I am! Not trying to reinvent it, but nothing wrong with minor improvements wink
Seriously though, I don't do anything unless it's reversible. I'm not going for any records with the Ghia though.

By the way, they said my other car could not be improved. Now it's the fastest production vehicle of it's type, officially in the 1/4 mile, unofficially in top speed. It all started with my first car; a $200 clunker that I made into a serious contender in the 1983 Grand Nationals and a regular winner at Detroit and Milan Dragway. The local Milan newspapers published the story on my current car.

Paul

  • From: somewhere over the rainbow USA
  • Registered: 2006-07-26
  • Posts: 1,889

Re: Intake manifolds

Altema wrote:

It's just the way I am! Seriously.

The local Milan newspapers published the story on my current car.Paul

I would not have guessed this in a million years,  LOL wink

So if you are going to toot your own horn, how about some info on this media covered car? Anthony says we need some positive news to lift our spirits. I was a crew chief but never had an article written about me sad                   The important guy gets left out, LOL

burrhead

A wise man makes his own decisions, an ignorant man follows public opinion.
  • From: Portage, Indiana
  • Registered: 2004-03-27
  • Posts: 454

Re: Intake manifolds

Well. I gotta say, I rarely agree with sean, but in this case I mostly do, re: his above post. 1776 with duals, properly built, is a fantastic motor. You can easily get better than stock gas mileage, and at least stock if not better longevity. I have played around with most types of  duals on stock and larger motors, and I have to say if you are willing to learn how to tune and interpret your motor, it's a much better setup than the puny factory carb. Contrary to popular opinion (which mine usually isn't btw smile duals are just as reliable, you just have to take the time to learn them and the linkage and jetting and whatnot. Post with some specifics of what you are thinking of doing. For what it's worth, I feel that the dellorto is the best carb ever adapted to the VW motor, not only in quality but also ease of tuning, maintenance, and parts availability. Dual 36s on a 1600 with no other mods is a BIG improvement in overall power and driveability.

I'm also curious about this "other" car you have. Do tell.

  • Registered: 2007-03-27
  • Posts: 2,422

Re: Intake manifolds

Well Now My only claim to Fame is that my Pic was in 4 Wheel Drive Magg back in the Mid 80's !!
  My Lowwer half was stickin out from under the Truck while both My Bosses' Stood over the top of Me !! LMAO
  Hey least I made the front cover ?????
  Im hurt that you rarely agree with Me !!
  Dellorto's ???? Dont even make um anymore ???
  Webbers basically same animal !!
  Im gonna wait to make a comment on your Experimental Manifold , It's Been year's since Ive done anything regarding Flow and Resonation !
I usually leave that to the Guy's who are doin it !!
But as to My Spyder Bite ?? It's Healing !! 3 Week's !!
Just imagine how quick I was out of My pant's when an Ant crawled up my Legg !!
  Absolutely want nothin more to do with insect's in my Pant's !! Definately done with that Bussiness !!
  But thank's for your Miss Placed Concern !! If I was there I would throw Insect's down the back of your Shirt while I watch you work !!
  Im gonna try to get thing's Movin again today !!
  Thinkin Im gonna sell my Baja !! Use the Money to build the 58 streeter !!
  A Base Car No Frill's No B.S. OLd School Car !! Strictly Utilitarian !
  Im tired of Waxin Chrome Rimm's , and Washin Motor's and Vaccuming Dirt out etc .
  Tired of Stressin where I park it ! Tired of commin out the store's just to find some Blank of the Earth has Ripped all My Plugg wire's out !!
  Gonna save all the $$ for what's under the Deck Lidd wich I intend to paint, an unassumeing flat black !!
  Absolutely No Bling Bling !! Just all Bussiness !!
  Thinkin a Double Engine sett up !! Runn the 1776cc for everyday then start a Stroker on the same formatt !!
  Stiffin the Fork's/ pann for 200 H.P. Runn a Painted OEM style rimm only wider than OEM Dropp Spindles with Disc Brakes !!
  Smoke Grey !! and Flat Black !! Tinted window's !! Plain wrapper !!
  Tired of Raven's Crappin on my Chrome !! Tired of having to cover my Carb's when the Sand Blow's or it Rain's ?? Too Much up Keep !!
  Im gonna get on that soon as I get My Napp !! Im gonna start on It !! LMAO
                                       Sean

  • Registered: 2009-06-25
  • Posts: 558

Re: Intake manifolds

  • Registered: 2009-06-25
  • Posts: 558

Re: Intake manifolds

JordanK wrote:

1776 with duals, properly built, is a fantastic motor.

Yes the 1776 is a good one, and I also think the 2110 is nice. I actually think mine IS a 1776, but I'll have to pull a head and measure the bore and stroke to confirm. Just seems to pull too hard on the freeway to be a 1600. I don't want to pull the heads for that reason alone. Matter of fact, I don't wanna pull the heads for any reason! I bought the car from the previous owner's daughter, so I should probably ask her if she has any paperwork. He aparrently went through several engines before getting this one according to her. One of the drawbacks to any carb tuning on the VW is having to wait to check the plugs for the correct AF mixture. Also with the 34 carb you have to drain the fuel bowl. With my old cars I could pull a plug to check, adjust the carb, and go right back to driving. The Rochester carbs could be rejetted without draining, but the Holley carbs I'd just pull off because you had to remove the fuel line and bowl anyway.

Paul

  • From: Portage, Indiana
  • Registered: 2004-03-27
  • Posts: 454

Re: Intake manifolds

Altema wrote:

Also with the 34 carb you have to drain the fuel bowl. With my old cars I could pull a plug to check, adjust the carb, and go right back to driving. The Rochester carbs could be rejetted without draining, but the Holley carbs I'd just pull off because you had to remove the fuel line and bowl anyway.

Paul

Hence my preference for the dells, if you're going dual. Jets on top, easy to swap. Although I do recommend an electrician's screwdriver if you don't choose to use the taller idle jet stacks...the stock ones are flush with the top of the carb and kind of a pain to remove. Webers are basically the same, quality is spotty in my opinion. As sean said, dells aren't made anymore, but there are plenty available, either from italy or other european countries as stock on fiats and whatnot, or on samba.