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Discussion Starter · #1 ·
ok I finally swapped my Autolite 4300 out with my Holley 4150 600cfm.
So I put a new gasket on and bolted it on, hooked up the vacuum line to the distributor, but the back one that says it goes to the brake booster, I plugged it since my booster is fed from the manifold already, the one under the front of the Carb has the plug on it also.
primed the carburetor and she fired right up. But was idling way to high. I already had turned the idle screw all the way down or out so it wasn't touching. The air mixtures are 1 and half out.
I opened the choke up and that brought the idle down, but still was idling like 1200rpm.
if I put pressure on the linkage for the throttle it would drop to like 800rpms. if I let go right back to 1200rpm. on top of that the rear float plug, where the adjustment would be there is gas weeping out. then I was looking with a flashlight and found on the air mixture screw it was leaking also.
so I pulled it in the garage and shut it down. I am trying to clean my old bowls with adjustable floats to swap those out so that would solve that, but I'm not sure on the mixture screw, should I replace it or is there an O-ring in there? never had one leak. that carb was from a swap meet.
the only thing i didnt play around with was the choke, so not sure if that is why it was idling at 1200rpm even after it got up to temp. once I get the gas leaks solved then I will try the choke adjustments. so many issues with my car this year seems like I cant catch a break with it.
Really want to get it out for a nice ride.
 

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if I put pressure on the linkage for the throttle it would drop to like 800rpms. if I let go right back to 1200rpm.
That sounds like you have a vacuum leak at the throttle shaft. Start it up and spray a little starter fluid (carb cleaner would probably work too) where the shaft comes out of the throttle plate. If the idle takes a dive, you engine is sucking wind right there.
 

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Don't know. I read somewhere, probably on here, that packing a little grease around it may solve a vacuum leak there. For how long? Depends on how bad the leak is, I guess.

I don't think there is a replaceable O-ring or other seal at that location. I had my 4150 apart many times but never that particular piece.
 

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I don't think there is a replaceable O-ring or other seal at that location. I had my 4150 apart many times but never that particular piece.
I've managed to get the throttle shafts out of a couple of Holleys. I can't recall, but there are either Teflon or nylon bushings that fit between the shaft and the throttle plate. The bushings look more like small rolled up pieces of paper that fit in there. These were older Holleys I was working on and don't know if they still do that.
 

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Pull the carb and check that the throttle plates are closing fully, including the secondaries. Yes, there is a secondary idle speed screw accessible from the underside of the carb. Unless you have a really long overlap camshaft it should be adjusted so the plates are fully shut. Check the throttle shafts for play. The OEM bushings are thin strips of plastic. If there is wear present, the base can be reamed and brass sleeves installed. Lastly, check for vacuum leaks from the common sources. I like to use enough of a mix of water and dish soap to make a relatively viscous mix and spray it fairly heavily around suspect areas looking for a change in idle quality. It's non-flammable so a false indication won't be given if some gets sucked in the carburetor and doesn't harm paint or plastics like carb cleaner might.
 

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You could buy a carb rebuild kit just for the assortment of parts. I think those idle mix screws have a cork seal. You do not want fuel leaks from the float adjust screws, serious fire danger. The main thing with Holleys is to make sure the mating surface of the main body and metering plates is flat. Leaks there will cause it to run rich. Is the spring tight enough pulling the throttle shut? You may consider finding a good Holley rebuild video on youtube. Amen Woodchuck about the secondary idle screw under the bottom. Of course the choke has an idle speed cam which can be adjusted more lean.
 

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Discussion Starter · #8 ·
thanks for the replies, this is an older Holley, I got it about 12 years ago and it was used then. my buddy picked it up at Carlisle for me. I forgot to check the butterflies on the bottom plate before installing, as usual I was in a rush to try and get it fixed. the spring is new and plenty of pull on it. I watched a bunch of videos already and was leaning to what was already said but wanted some conformation. Hopefully I can get it a rebuild kit for parts and swap the bowls out this weekend and check everything else out.
I really like this forum, quick responses with great information.
 

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Discussion Starter · #11 ·
Ok, last weekend I swapped bowls from my old old 4150 600 and put on my newer 4150.
leaked from the float adjustments and from the accelerator pump.
now I admit I was in a rush to get this fixed and wasnt paying to much attention, my bad.
after a few times taking it on and off, checking and swapping more parts. still the same outcome.
I opened up my original carburetor an Autolite 4300 and replaced the accelerator pump and gasket.
put that on and bingo no more leaks and she starts up every time now.
it still hesitates when I get on it and sputters, but took her for a ride around the neighborhood.
as far as I can tell I will need to send it out to get cleaned and rebuilt. as far as I know it was never rebuilt.
the old accelerator pump was so dry and cracked that was why she wouldnt start without a squirt of fuel.

Now back to the Holley.
I had my old old one sitting in some pine-sol and water for a few days at work.
it actually cleaned it up pretty nice. had to use a brush but after a hot water rinse and dip looks good.
so Friday night while having a beer I started to put it back together and found a few things I missed.
1st the float adjustments both were missing the bottom gaskets :oops:
2nd for haha's I took the accelerator pump cover and magic markered it and put it on my sharping stone, it was definitely not flat. after a few passes no more black marker left.
so I learned another lesson slowdown and look at what Im doing
I might try and swap it out again and see if I fixed the leaks and see how it runs.
If not I will buy a new 4160
 

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so I learned another lesson slowdown and look at what Im doing
That can be said for anything.

Holleys get a bad rep because people let them sit for years and then get upset when they leak. Like anything, they need periodic maintenance. I can almost guarantee you'll have greater success with the Holley than an Autolite 4300.
 

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First follow woodchuck’s post.
If you still have issues then try lowering the floats and additional 4-5 flats of the adjusting nut beyond (lower than) the factory setting.
 

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Discussion Starter · #14 ·
Yeah, I read Autolites need adjustments, I didnt notice anything wrong the first 10 years owning it, then I started having starting issues and hesitation stuff. I plan to get a new Holley and rebuild the Autolite just to have as a backup.

The floats I had adjusted and only a little fuel would weep out when I pushed on the fender.
I think Hemikiller nailed it, both of my Holleys sat for many years, the older one I actually took it off my old 78 mustang right before they took it for parts that was around 1999. I think it still had fuel in it, because the floats were stuck to the bowl.
The newer one was from a swap meet and I have no idea how old it is, the inside looks new and it has all newer blue gaskets on it.
 

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AutoLites are engineered to be more reliable and require less maintenance than any other type of carburetor that I’ve encountered.

just in the area of gasket placement alone , the AutoLite design is light years ahead of Holley.

Z
 

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AutoLites are engineered to be more reliable and require less maintenance than any other type of carburetor that I’ve encountered.

just in the area of gasket placement alone , the AutoLite design is light years ahead of Holley.

Z
I doubt you're referring to a 4300....
 
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Just consider that your sharpening stone is probably not flat either if it has had use. May be better off with surface plate and fine sand paper. Amazon used to have them in the $30 range. More expensive now.

Ahhh,,, grizzly... 9" x 12" x 2" Granite Surface Plate, No Ledge at Grizzly.com

I'm not saying that you need/should take off a bunch of material. That could cause other issues. gotta be careful. But they do warp and get tweaked from over tightening.

(I've heard of some people using a piece of glass instead of a surface plate)
 

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As soon as you save up your dollars,I think a new holley will solve your problems. lol
 
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Discussion Starter · #20 ·
well I bought a new Holley 600 carburetor and slapped it on.
primed it and stared it up, it started and revved to 2500+rpm shut it off instantly.
checked for fuel leaks, then checked the curb idle was all the out just barely touching,
air mixtures were 1.5 turns out. Started it again same thing.
Loosened up the choke, disconnected the power.
Turned the choke clockwise to the last line. started again same thing revved to 2500rpms.
Turned it past the line about an inch started and it was barely running.
Brought it back a little and again revving around 2500rpms shut it instantly.
the fast idle screw is such a PITA to get to I think I will pull the carb off and see if it is causing the issue. so freaking aggravating. if I was back in my 20's one of those carburetors would of got the sledgehammer. my patience is better 30 years later but not much.;)
what do you think, could it be the fast idle causing this?
also it has a spread bore plate on it can I use the open gasket that came with the Holley or do I need the spread bore gasket? I have 2 sets of each.
 
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