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Old 12-23-2008, 12:14 PM
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Autolite 4100 Rebuild - Help!

So I'm gathering all the required parts for my latest project, an Autolite 4100 rebuild. The carb that I purchased (C5AF-F) was sitting atop a shelf and has been gathering dust and debris for God only knows how many years.

To start, I got organized on a clean surface and then I completely disassembled it and she's been soaking in lacquer thinner for about a week now. I naturally didn't put the carb in with gaskets, only the metallic parts. I clean out all the passages with carb cleaner on a daily basis, just to sure that they are free from deposits. Now 7 days after this routine, I'm ready to get started putting Humpty Dumpty back together again.............Just hopping that I won't be needing all the King's horses and all the King's men in the process

I've ordered the Carburetor Doctor's SK4100B super kit with floats and electric choke as a starting point. Eventually, I'll be calling Pony Carbs for nitrophyl floats........but I'm not at that stage yet.

In my online search for parts, I discovered that Walker Products makes a ton of parts for these old carbs(http://www.walkerproducts.com/downlo...ord4barrel.pdf), including jets ranging from 0.035" to 0.072" (http://www.walkerproducts.com/downlo...teringjets.pdf). My power valve enrichment assembly will need to be replaced, but I can't determine which one is correct for my intended application?

(2.5" HG)
(3.5" HG)
(4.5" HG)
(5.5" HG)
(6.5" HG)
(7.5" HG)
(8.5" HG)
(9.5" HG)
(10.5" HG)

My intent for the engine will comprise of a 1976 ford 302-2v and a C4 trans, with +3cc pistons, an Edelbrock Performer RPM Top End Kit, Lunati Voodoo series 61003LK cam and lifters (not sure if it's too much cam for the street+carb?), full length Hooker headers, Pypes x-pipe, Magnaflow side exit mufflers.
I appreciate any and all help+input,

Chris

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Last edited by sixty9santa; 12-25-2008 at 11:51 AM.
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Old 12-23-2008, 03:05 PM
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Stock engines can have high vacuum readings (10-18 inches at idle) and the Holley power valves with higher readings like 6.5 to 10.5 will work correctly. Long duration non-stock camshafts and other performance related parts can cause a problem, because engine manifold vacuum may be lowered with these performance parts and the power valve, if incorrect, will always be open, even at part throttle, leading to an overly rich air/fuel mixture. The solution is to choose the correct power valve and to do that you need a vacuum gauge. On a manual transmission vehicle, hook up the vacuum gauge and take the reading with the engine at idle. Then use a power valve that is rated 1-2 inches below that amount. For example, a motor that shows 7" of vacuum at idle should use a 6.5 or 5.5 rated power valve. If you have an automatic transmission, take the vacuum reading at idle in "Drive" (with the emergency brake on and the wheels blocked) and chose the power valve 1-2 inches below that figure. You can get a little more detailed information by driving the car with a vacuum gauge hooked up with a longer hose so you can read it while driving. Drive the car at medium loads and while cruising and note the various vacuum readings. Then chose the appropriate power valve rating.

Holley makes performance style "standard" flow or a "high" flow power valve which has a large opening. "Single stage" power valves are available in 1" increment sizes from 2.5" thru 10.5". There are "two stage" power valves available that are more for "economy" minded users rather than "performance" enthusiasts.
Source- MORTEC
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Old 12-24-2008, 01:25 PM
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4100s are great carbs, simple and reliable....just a little short on the cfm. As Gary's post suggests, you really need to put any( preferably one with the highest #) power valve in to get it running. Then you can take some readings and make a final evaluation. Because of the lower cfm( read; higher vacuum signal) you may be able to run the stock one.
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Old 12-25-2008, 11:48 AM
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Much thanks gentlemen,
Very informative and I learned something new and important today!
Anyone have any recommendations as to what brand gauge to get, I'd like to get something reliable and accurate?
Much thanks and Marry Christmas to all,


Chris
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Old 12-26-2008, 01:45 AM
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You should be able to pick-up a reliable gauge (no CHI-COM) for under twenty bucks. KD would be a good name.
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Old 12-26-2008, 01:51 AM
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http://www.harborfreight.com/cpi/cta...emnumber=39522

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http://www.harborfreight.com/cpi/cta...emnumber=93547
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Old 02-03-2013, 09:32 AM
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some will say that an autolite 4100 series fall a bit short on the cfm.But i have used the smaller of the two on a 351 cleveland that had a small aftermarket cam and intake with no trouble at all,it was not starving for fuel or air at.In fact i had initially used a Holley 650 and it was running a bit rich and i couldnt lean it out as much as i needed.It was on a dyno.The only other carb i had was an autolite 4100,So i stuck it on the cleveland the results were immediate! after a few runs and some adjustments i picked up 6 horsepower and a bit more torque..while those certainly not huge horsepower gains it does show that less can be more.I also picked up 3mpg and cleaner burning plugs.the only troubles that began to show was when the motor was wound up to 5,800-6,500rpm then it did begin to starve but only a bit..and who runs a daily driver at 6,000rpm everyday anyways?
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