Author Topic: Carburetors...  (Read 7678 times)

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Offline lsrjunkie

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Carburetors...
« on: March 02, 2015, 01:55:18 PM »
Just fishing around for input. Things are progressing nicely on my project, and I'm trying to decide what I will be running for a carb. I am leaning toward a Holley style mechanical four barrel, such as a Mighty Demon, Quick Fuel, or a Pro Form. What have you guys run and what do you like the best?
Maybe there is no Heaven. Or maybe this is all pure gibberish. The product of a demented hill billy who has found a way to live out where the winds blow. To sleep late, have fun, drink whiskey, and drive fast on empty streets with nothing in mind except falling in love or getting arrested.    H.S. Thompson

Offline Harold Bettes

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Re: Carburetors...
« Reply #1 on: March 02, 2015, 08:06:08 PM »
Please consider that all carburetors are merely organized leaks and as such, it is up to the individual using them to make sure the things work correctly. The result is not brand loyal nor type dependent. The higher the density altitude, the more importance is the circuit that controls droplet size. :roll:

Everybody that has a set of screwdrivers and a numbers drill set (including miniatures) does not a carburetor tuner make.  8-) :-( :evil:

If you can get on a dyno over there in Grand Junction, you might be surprised how close to Bonneville conditions you might get during the tuning process.

Regards,
HB2 :-)
If it was easy, everybody would be doing it.

As iron sharpens iron, one man sharpens another.

Offline Leadfoot

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Re: Carburetors...
« Reply #2 on: March 03, 2015, 08:56:57 AM »
Holley Dominator works for me.

Offline kiwi belly tank

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Re: Carburetors...
« Reply #3 on: March 03, 2015, 11:17:13 AM »
The fact you are asking for input on carbs tells me you are not a carb guy & like Harrold just said, they are only as good as the tuner. I have no idea of what you're building but if you can run a self learning TBI, do it.
  Sid.
 

Offline fordboy628

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Re: Carburetors...
« Reply #4 on: March 03, 2015, 11:41:42 AM »
What is it going on?
Science, NOT Magic . . . .

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Offline Milwaukee Midget

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Re: Carburetors...
« Reply #5 on: March 03, 2015, 12:29:55 PM »
I'm only somewhat familiar with the Holley offerings, but what I would be looking for is the choice that gave me the quickest and easiest route to rejetting and adjustment. 

We were fortunate, in that we used a Weber, and Mark had a boatload of jets and emulsion tubes at his disposal.  During dyno work, we were able to rejet and test in less than 5 minutes between pulls.  It's my understanding that turnaround on a Holley is somewhat s l o w e r than that.

At that point, anticipate what you're likely to see at Bonneville and limit the number of choices.  I want to say we saw adjusted air densities from 6000 to 7200 feet on any given day. 

I expect Harold is right - you should be able to get a pretty close dial in at 4500 feet.   
"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  :roll:

Offline lsrjunkie

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Re: Carburetors...
« Reply #6 on: March 03, 2015, 01:41:27 PM »
Sid, my carb experience has been limited to mostly daily driver applications and a few warmed over hot rods. I'd love to run any type of EFI, but my understanding is that class rules won't allow it. My biggest concern will be ease of tuning, hence my leaning towards the Holley type of carb. In my experience any adjustments on that style of carb aren't terribly tough with the carb installed. FYI, I plan on running XO/GCC.

Fordboy, I am building a 320" GMC six cylinder. Stock cylinder head with some port work, and a plenum type intake.

There's a couple of pictures, http://www.landracing.com/forum/index.php/topic,12252.330.html towards the bottom of the page.

MM, I agree 100% Tuning the carb in the shop or on the dyno is one thing, but I want the same ease of tuning on the salt.
« Last Edit: March 03, 2015, 03:04:51 PM by lsrjunkie »
Maybe there is no Heaven. Or maybe this is all pure gibberish. The product of a demented hill billy who has found a way to live out where the winds blow. To sleep late, have fun, drink whiskey, and drive fast on empty streets with nothing in mind except falling in love or getting arrested.    H.S. Thompson

Offline fordboy628

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Re: Carburetors...
« Reply #7 on: March 03, 2015, 02:58:19 PM »

Fordboy, I am building a 320" GMC six cylinder. Stock cylinder head with some port work, and a plenum type intake.

There's a couple of pictures, http://www.landracing.com/forum/index.php/topic,12252.330.html towards the bottom of the page.


There are more knowledgeable carburetor guys on the board, than I am.    Especially for modified Holley stuff.    But having said that, some advice:

A)    If you are going to dyno test, weld small 1/8th NPT bungs in the top of your intake runners.    Being able to record vacuum during "pulls, (even 1 tap at a time) may prove "insightful".     BTW, do not presume 3 separate vacuum gauges will read identically, if you go that route.    Pay to have any you use, calibrated.

2)    Choose your carb size based on measured flow of the carb, Vs theoretical engine air capacity * x % Volumetric efficiency, in the rpm range you intend to use.   This will give you a low/high number to select a carb.    You will need someone experienced with your engine to suggest a probable V/E %.   Or, you will need to flow the whole inlet tract, and then run a computer simulation based on the flow/displacement/geometry.

d)    If you don't know how to do the above, BUY & READ "Performance Automotive Engine Math" by J Baechtel.    Also BUY & READ "Engine Airflow" by Harold Bettes.

HB2 or Dynoroom may be able to recommend a carb size from their experience.    But be prepared to do the math on your own anyway.     That way you learn something.
 :cheers:
Fordboy
Science, NOT Magic . . . .

I used to be a people person.  But people changed that relationship.

"There is nothing permanent except change."    Heraclitus

"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."     Albert Einstein

Offline lsrjunkie

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Re: Carburetors...
« Reply #8 on: March 03, 2015, 03:58:21 PM »
Fordboy, As always you have the information inquiring minds want to know. Thank you very much! You're recommended reading has been purchased and is en route. Here's to hoping I can learn a little about this whole going fast business.  :cheers:
Maybe there is no Heaven. Or maybe this is all pure gibberish. The product of a demented hill billy who has found a way to live out where the winds blow. To sleep late, have fun, drink whiskey, and drive fast on empty streets with nothing in mind except falling in love or getting arrested.    H.S. Thompson

Offline 1leg

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Re: Carburetors...
« Reply #9 on: March 03, 2015, 08:36:15 PM »
Stick with the traditional Holley in the race models. The proform and quickfuel are made in china and seem to have out of the box performance issues. Would be a good idea to check out the offering of some carburetor shops that work on NHRA stock and super stock car carbs they also hot rod the holley carbs.
Jerry
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Offline wobblywalrus

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Re: Carburetors...
« Reply #10 on: March 03, 2015, 10:19:17 PM »
Vizard wrote a book on tuning Holley carbs.  It is in print.  I saw a new one on the book shelf a few days ago at Barnes and Noble here in Oregon.   

Offline lsrjunkie

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Re: Carburetors...
« Reply #11 on: March 04, 2015, 09:33:51 AM »
Thanks 1leg, That's good information to know.

WW, I'll keep an eye out for that book. I'm all about learning something new. Thanks for the tip.
Maybe there is no Heaven. Or maybe this is all pure gibberish. The product of a demented hill billy who has found a way to live out where the winds blow. To sleep late, have fun, drink whiskey, and drive fast on empty streets with nothing in mind except falling in love or getting arrested.    H.S. Thompson

Offline WOODY@DDLLC

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Offline Leadfoot

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Re: Carburetors...
« Reply #13 on: March 04, 2015, 10:50:23 AM »
Call Patrick at Pro Systems Carburetors.

Offline Stan Back

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Re: Carburetors...
« Reply #14 on: March 04, 2015, 12:43:05 PM »
Well, hope I don't step on my . . . , whatever here.  I believe you can run a self-adjusting throttle body f.i. in XO/CC.  You're not running Classic, as there are no Classic Comp Coupes.  You're not running Vintage -- as you've stated.  Maybe DW will confirm this for you (us).
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