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Unread 04-14-2013, 11:14 PM   #1
flshovelhead
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Holley Carb is whopping my butt

My Jeep is a 1975 CJ5 with the 304 V8 and 3 speed manual transmission. I picked it up two years ago after my uncle passed away. I didn't run it much and it has been sitting in my garage for the last year and a half. When it last ran, it was very difficult/finicky to start but seemed to run ok once it had a chance to warm up (although it got around 11 MPG). The CJ was originally in the Las Vegas area, and I know my Uncle was always fighting to get it to pass their local smog check. He had it in and out of a few different shops, and had a local handyman come to the house a few times to wrench on it.

It came to me with a Holley 4412-3 carb installed. I tried last weekend to get it to start, got it to catch once or twice, but the best I could manage was a few sickly five second runs that died off when I attempted to give it gas. I took the carb off thinking it might be gummed from sitting, but it was quite clean inside.

After doing some research online I found out that the 4412's 500 CFM carb was overkill. When I pulled the spark plugs they appeared black and sooty, indicating that the carb had been running to rich. I'm not looking for huge power at wide open throttle; I'd much rather have a decent starting and reliable carb that will give me a little better mileage when running around town. As such, I picked up a Holley 7448 350 CFM carb that seems more applicable for what I want.

It looks like all the DEQ equipment has been pulled at some point, and with the aftermarket carb installed I obviously am not dealing with a stock vehicle. As you can see at some point in the vehicles life the EGR has been capped off.



I installed the Holley 7448 carb today and per Holley's instructions I turned the idle mixture screw clockwise until it bottomed out, and then backed them out one-and-a-half turns on both sides. I then hooked up the hose running from the PCV valve on the engine to the back of the carb, and ran the vacuum hose from the distributor to the "TIMED SPARK VACUUM PORT" on the side of the carburetor. Finally, I utilized the choke actuation lever to slightly open the choke plate as shown:




When I attempted to start it today, it took three 5-10 second cranks before fuel made it through the line from the mechanical fuel pump (and through an inline filter) and into the carb. On the fourth attempt the engine caught, turned over, and ran for a few seconds before dieing. I hopped out and looked under the hood and saw gas bubbling out of the carb's fuel bowl vent.

I let it sit for a few minutes, and attempted to start a second time. The second time the engine did not start, but my carb sure did spew gasoline out the fuel bowl vent at an alarming rate.

Per Holley's instructions I need to have the engine running to adjust the fuel level adjusting nut until the gasoline is just below the bottom of the fuel level sight plug in the float bowl body. Similarly, all vacuum readings are made with a running motor.

Since I can't even get the engine running, and I believe I installed/setup the carb correctly for this application I'm not sure where to go next. I don't have much experience with turning wrenches, so I spent most of the afternoon googling about Holley carbs and vacuum issues with 304's and now I'm stuck.

Your thoughts?

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Unread 04-15-2013, 12:57 AM   #2
BagusJeep
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Sounds more like an inlet valve stuck open than a float level. If it is spewing out of the tp you can be sure it is flooding the engine as well, so it will not start as it is.
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Unread 04-15-2013, 01:38 AM   #3
wrongway92407
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Take the screw out off the bowl plug off the fuel line and then try to start it. Once the fuel level drops down it should start. By not plugging the fuel line it continue to overflow and flood the engine every time you crank of the starter. Holly is an easy carb to tune the jets are easy to replace so is the power valve, metering block.
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Unread 04-15-2013, 06:58 AM   #4
Pacfanweb
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500 cfm should run great on that engine, it's FAR from overkill.

A 350 is too small, but you honestly should still not be having these issues with most any carb. Some might perform better or worse, but you should be able to get the engine to run with nearly any carb.

If you wanted the better mileage and some performance, you should have gone with a 4 barrel, 600 cfm would be perfect for a stock 304. That way, you're running on 300 cfm until you bring the rear venturis into play. And since they're vacuum secondary, the springs can be changed and make them come in pretty much whatever RPM you want.

All that aside, you might have a stuck float. You can tap lightly with a hammer on that big screw on the top of the bowl and see if your problem goes away.
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Unread 04-15-2013, 02:17 PM   #5
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Thought about this and remember one more thing: How about fuel pressure? Does it have a fuel pressure regulator? If the pressure is too high, it could force the needle valve all the seat and do the same thing as if it was stuck open.
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Unread 04-15-2013, 03:14 PM   #6
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If the needle has a viton (rubber) tip, it might have a little bit of debris stuck in it. I had this happen a few times on my old 66 Chevelle. The fuel tank had some crud in it, some of it got past my filter and stuck in the needle/seat. I pulled the whole needle seat assembly out and could actually see the rust pieces stuck to the rubber.

Another time, I had a composite float that had absorbed fuel and ended up sinking.. causing the engine to flood. If you've got a brass float, it's probably okay, but if it's a composite (plastic) float, it may be something to look at.
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Unread 04-15-2013, 04:56 PM   #7
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ONe problem I constantly had on my Scout with a Holly 7448 was the power valve was always blowing. Any sort of intake sneeze would rupture its diaphram, and lead to gas dripping into the intake. This would lead to the odd problem that it would not start while hot because the gas had empied the bowl into the intake, flooding the engine.

Later 7448s were redesigned with a pressure relief valve to prevent damage to the valve... and I think most rebuild kits come with a retrofit... but what a pain in the butt...
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Unread 04-15-2013, 07:57 PM   #8
Ivehad4
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On my holley 2300 the instructions say to rough in the float level 1st. You have to remove the fuel bowl to do this. At the same time make sure the float valve is moving freely. I would take float valve out and clean the port. Then when its back together and running you fine level the float - but engine must be hot.
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Unread 04-15-2013, 09:18 PM   #9
flshovelhead
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Quote:
Originally Posted by wrongway92407 View Post
Take the screw out off the bowl plug off the fuel line and then try to start it. Once the fuel level drops down it should start. By not plugging the fuel line it continue to overflow and flood the engine every time you crank of the starter.
I pulled the fuel inlet line to the carb and routed the fuel line to a clear glass jug. My wife turned the ignition on and the engine started right up and ran for 10 or so seconds until it consumed all the fuel in the bowl. It seemed like the engine was idling high, but I did have the choke applied.


Quote:
Originally Posted by Pacfanweb View Post
All that aside, you might have a stuck float. You can tap lightly with a hammer on that big screw on the top of the bowl and see if your problem goes away.

...

How about fuel pressure? Does it have a fuel pressure regulator? If the pressure is too high, it could force the needle valve all the seat and do the same thing as if it was stuck open.
I pulled the float level fuel valve assembly and verified that it was clean/free of sediment (I didn't see anything) and that the needle slid up and down inside the body. While I had the fuel valve assembly out I sprayed it down with carb cleaner and then blasted it with the air compressor.

I'll say this: the fuel pump was really pushing the fuel fast. Perhaps it's pumping out too many PSI??? How do you adjust the fuel delivery rate coming from the mechanical fuel pump?



So, I learned that there's a good chance I can get the carb to correctly, I just need to solve if it's a fuel PSI delivery problem or an issue with the float bowl (which MAY have been solved by cleaning the float bowl fuel valve assembly).

However, this is what the gas that pumped into the glass jug looked like:



The gas tank is currently just about empty. If I fill the tank it should help dilute the overall mixture, but won't do anything for whatever sediment is inside the tank. Assuming I get more gas in the tank, will I cause damage running this now mildly diluted gasoline mixture while I attempt to solve the carb issue?
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Unread 04-15-2013, 09:39 PM   #10
Ivehad4
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The return line from the fuel filter handles excess fuel delivered by the pump. Since fuel delivery varies based on engine speed your mechanical pump is designed to deliver the maximum demand and the return line handles excess at lower speeds. If there is any adjustment to the fuel pump, I'm unaware of it.
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Unread 04-15-2013, 09:52 PM   #11
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If the gas in the fuel tank is over 6 months old I would suspect the fuel is not what it should be. If its been over a year I would drain the tank, and put fresh fuel in. Running exceptable out of the glass jar is partial treatment.

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Unread 04-15-2013, 10:16 PM   #12
sean112280
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I had problems with a Holley carb as well. My fix was a switch to an edelbrock and my SBC is running great now and it's easy to tune the carb now
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Unread 04-16-2013, 06:11 AM   #13
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Quote:
Originally Posted by sean112280
I had problems with a Holley carb as well. My fix was a switch to an edelbrock and my SBC is running great now and it's easy to tune the carb now
I got a wonderful Holley 650 manual secondary carb because a friend just got a 67 vette and wouldn't listen to my brother.

The friends carb guy said the Holley's are junk and cause engine fires. So I got the 650 for free and he put the AFB clone on the 327 and had his carb guy set up the AFB. After Dean gave up on the guy my brother set it up for him. Performance kit with jets and needles. (That other carb guy didn't know about) and dean wished he didn't give me the 650 double pumper. (Which is working great on the 396 in the Chevelle after it was converted to 4 corner idle)
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Unread 04-16-2013, 06:33 AM   #14
Matt1981CJ7
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Quote:
Originally Posted by hp_lovecraft View Post
ONe problem I constantly had on my Scout with a Holly 7448 was the power valve was always blowing.
From my reading on various carbs, Holleys are notorious for blowing power valves. That's their one fault that all the Rochester guys like to point to.

Fishhead, are you running a bypass fuel filter?

Matt
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Unread 04-16-2013, 07:34 AM   #15
flshovelhead
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Quote:
Originally Posted by Matt1981CJ7 View Post
From my reading on various carbs, Holleys are notorious for blowing power valves. That's their one fault that all the Rochester guys like to point to.

Fishhead, are you running a bypass fuel filter?

Matt
There is an inline fuel filter in between the fuel pump and the inlet to the carb.

What is a bypass filter?
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