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Author Topic: Single Carb Options..  (Read 3671 times)
plasticblack
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« on: November 27, 2011, 20:06:16 pm »

I'm exploring what single carb options I have for my current project.

  I'd like to know what historically was used back in the 70's perhaps?

     Engine will be no bigger than 1641 with only basic mods.

       Pics etc, most welcome.. 
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Rennsurfer
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« Reply #1 on: November 27, 2011, 20:54:06 pm »

Holley progressive two-barrel or Zenith. Those were the two most popular ones that I remember. Use a higher profile air cleaner, though. Don't make the mistake that I did with a low profile K&N. Not enough fuel stand-off. But then, I was a teenager and didn't know better yet.

My first engine (1,641cc) with the aforementioned Holley. Had small high ratio rocker arms, dual port heads, and an S&S header with a single quiet pack muffler.

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Zach Gomulka
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« Reply #2 on: November 27, 2011, 22:11:05 pm »

Zenith 32 ndix all the way. I loved that carb on my 1600.
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TexasTom
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« Reply #3 on: November 27, 2011, 22:50:08 pm »

48 IDA.

 Wink
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plasticblack
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« Reply #4 on: November 28, 2011, 18:59:11 pm »

I don't think there are any 48 ida's in my future sadly, but I like the Zenith idea.

  Anyone have any Holley Bugspray experience/info please..  Cool
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Dave Rosique
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« Reply #5 on: November 28, 2011, 19:37:05 pm »

I don't think there are any 48 ida's in my future sadly, but I like the Zenith idea.

  Anyone have any Holley Bugspray experience/info please..  Cool

Bugspray will have a huge flat spot just off idle... they run good wide open throttle but that's about it.

Go with a Zenith, you'll be happy.

 
 

 
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Torben Alstrup
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« Reply #6 on: November 28, 2011, 19:54:03 pm »

Never had the pleasure of trying a centermount Zenith, so canīt comment on that.

For me the progressive Holley/Weber 32/36 sold by many (Redline has the best linkage set up) was almost always good on mild engines. It took a little while to figure the jetting out, but when that was solved they ran/run smooth right from idle, - with one exception. That is if you hit the WOT button in the "the wrong rpm spot so to speak. Then it will stumble for 2/10 of a second and then come back strong.
Other than that i have been working with modified 34 Solex PITC 3 carbs for the last 3-4 years, and am actually able to pull very good power with stock look. (Up to 90 hp is relatively easy) Above 90 it get complicated.

T
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TexasTom
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« Reply #7 on: November 28, 2011, 19:57:03 pm »

Cool Torben!
What kind of mods do you make to the 34s?
TxT
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speedwell
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« Reply #8 on: November 28, 2011, 20:07:31 pm »

 Wink
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Torben Alstrup
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« Reply #9 on: November 29, 2011, 02:04:24 am »

Cool Torben!
What kind of mods do you make to the 34s?
TxT

In the beginning we had the housing bored out to accept a 38 mm butterfly, and inncreased the venturisize according to what the engine liked. Anything from 28 to 33 mm (W.O venturi actually)
Lateron  we found that on this side of 90 hp there is not much need of enlarging the carb, if the rest of the engine is built right, because the limitation is in the end castings. I have also tried to have a set of end casings made with 2 mm larger I.D. and also 1" longer isolated runners. Then shortened the center section accordingly. - At least on the 1914 I used as a test animal the performance increased from 87 hp @ 4400 to 96 hp @ 4600, and pulled clean to 5300. BUT the peak torque decreased from 165 Nm @ 3300 to 156 Nm @ 3500. The owner said that he felt that the engine was more nippy and didīnt mind the loss of the torque over the extra power. I actually have a small video of the car pulling clean from 30 to 140 km/h in third (about 130 km/h IRL) and its not exactly slow. That is from 1200 rpm to 5400 rpm real time.

The trick is airspeed, and it needs to be almost supersonic. But once you get that right you can pull over120 hp through a modified 34 mm Solex. Itīs been done already with a 2275 to take care of the vacum  Grin
When I get the time and extra money for it, I would like to try and see what a 2275 with the larger end pieces will yield. Theoreticly we should be able to hit 130 hp. @ 4400 rpm. and 210 Nm. @ 3000 rpm. But thatīs for the future, unless somebody walks up and drops a serius deposit  Roll Eyes Grin
T
« Last Edit: November 29, 2011, 02:11:43 am by Torben Alstrup » Logged
hotrodsurplus
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« Reply #10 on: November 30, 2011, 00:51:37 am »

I say Bug Spray or Zenith.

A 200cfm Bug Spray on a ram manifold (isolated tube) would work beautifully on that size of engine...if you spend time with it. Any carburetor will have a flat spot if not tuned properly.

You WILL have to ream the idle circuit as those carburetors don't have conveniently interchangeable idle jets as we know them on Webers and Zeniths. You also may have to open up the air bleeds to get the main circuit to come in earlier. You CAN tune out the flat spot and it's not that hard. You can also get parts and jets for it at any corn-rocket speed shop.

Go with a Zenith, you'll be happy.

I totally agree with that but you'll still have to sort out the jetting (which is way easier as that carb still has support in this industry). Use an isolated-tube (ram) manifold on that displacement engine.

Either way, devise a way to get warm air to the air intake if you live in a cool climate. Those carbs are both prone to freeze when used as singles and manifold heat usually isn't sufficient. Also flycut the step from the head and try to reduce your cylinder deck to at least .055". That'll get CR up to 8.2 or so--fine for mid-grade gas. It'll make more power and will be easier to tune with the higher CR. I say run a stock cam. Ratio rockers on ported heads would make that little engine flat-out fly. 

And both setups would be super-duper '70s. Most cars in magazines from that era had those carbs, not Webers.
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Zach Gomulka
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« Reply #11 on: November 30, 2011, 02:54:51 am »

My engine, bone stock, ran 20.3's. I installed the Zenith (PO10 on isolated runners), and a header with glasspack, and I was running 19.6's. I did nothing but adjust the idle mixture, and it ran as smooth as the stock carb. I loved it! Later I got greedy and installed larger venturies, and "super tuned" it, but I never got it back on the track in that configuration. It probably was running a tenth or two quicker.
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kingsburgphil
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« Reply #12 on: November 30, 2011, 06:41:25 am »

X2 all the previous posts.  Wink

IMO try these guys, they absolutely hammered the single Zenith as a winning combination.

http://fatperformance.com/home/

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