Got a question about Holley Carbs...Can anybody help??

[Silverback]

I knew as soon as I seen the title of this thread that Jack would be all over it. My advice is listen to the man.

My guess is it's the fuel pressure, or something that was related to the original high pressure.

Back it down to 4.5 to 5.0 psi. That is plenty. Then turn on the pump and using a flash light, look down the throttle bores. If you see gas, you have a leak somewhere, or it could be that gas is leaking past the needle and seat.

I have one more idea, but I will save it if you do not resolve it with the input you have received to date.

 

[kennygene]

I backed the pressure down to 4.5 psi and it seamed to help but very little. I removed the carb and tore it down. Everything was still nice and clean and the floats were perfect. The needle valves and seat were working correctly as well. No problems observed so I put everything back together. I have been working late this evening (daughter is in bed), so I didn't start it. Matter of fact, I went upstairs and watched Bullrun and then went back down.
Now, I am going to admit my stupidity and how the KISS method should always be used. I CHECKED THE PCV VALVE AND IT WAS STUCK WIDE OPEN!!!! MAKE FUN OF ME OR WHATEVER, I DESERVE IT!!!
I dug through my parts bin and put on a new PCV valve. I'll drive the car to work tomorrow and report back in. I know this will (should) solve the rich situation. Then, I'll just have to tune everything else back in.
I feel like such a jackass!!!!!!!!!

Anyway, I have size 60 jets in the secondary side and size 62 in the primary. How does that sound for 800ft above sea level and a 5.2 engine single plane M1 intake and 3000lb car?
The power valves are both the same. They read either 6 or 9-can't tell for sure.
Like I said, I'll report back tomorrow with any improvement. I can't pull out my hair, don't have any. hehehehe!!!

 

[FSTJACK]

I backed the pressure down to 4.5 psi and it seamed to help but very little. I removed the carb and tore it down. Everything was still nice and clean and the floats were perfect. The needle valves and seat were working correctly as well. No problems observed so I put everything back together. I have been working late this evening (daughter is in bed), so I didn't start it. Matter of fact, I went upstairs and watched Bullrun and then went back down.
Now, I am going to admit my stupidity and how the KISS method should always be used. I CHECKED THE PCV VALVE AND IT WAS STUCK WIDE OPEN!!!! MAKE FUN OF ME OR WHATEVER, I DESERVE IT!!!
I dug through my parts bin and put on a new PCV valve. I'll drive the car to work tomorrow and report back in. I know this will (should) solve the rich situation. Then, I'll just have to tune everything else back in.
I feel like such a jackass!!!!!!!!

Anyway, I have size 60 jets in the secondary side and size 62 in the primary. How does that sound for 800ft above sea level and a 5.2 engine single plane M1 intake and 3000lb car?
The power valves are both the same. They read either 6 or 9-can't tell for sure.
Like I said, I'll report back tomorrow with any improvement. I can't pull out my hair, don't have any. hehehehe!!!

Sounds like the jets are reversed........Usually the smaller jet goes in the primary.

What size is the motor and what is the compression ratio?

 

[FerrariTruck]

Sounds like the jets are reversed........Usually the smaller jet goes in the primary.

What size is the motor and what is the compression ratio?

its a 318...But with that size carb I hope he's running at least some good ported heads and at least 9:5:1 compression.. If not he's running too much carb esp on a 318

 

[WOT]

Too much carb can be made to work, it just ends up being kinda touchy. And, it's usually hard to get rid of the bog when you stand on it from idle. You end up having to put the big cc accelerator pump on it and the fast squirters. But it can be made to work. On super high revving 302 Chevys, 750 double pumpers work great. As long as you were running a stick shift, it works just fine. His 650 double pumper will be just fine.

I'm still not sure why a stuck open PCV valve would make it run rich. Maybe a stuck shut PCV valve.

 

[Silverback]

One more thing to look at.

If it has those funky solid phenolic floats, they over time start to absorb gas and no longer float and provide the pressure required to seat the needle. And sometimes the brass floats will develop a hole and leak.

It's all the chemicals they now add to the gas to provide us with clean air.

 

[kennygene]

The engine is a 318 magnum I built from a 95 Ram Truck. It has roller comp cam with .480 lift 264/270 duration. Compression is 9.5:1 running stock magnum cylinder heads (outflow 340 X heads). Intake is Mopar M1 single plane.
The jets are where they were and the metering plates cannot be reversed. The front metering plate has the air adjustments. I probably need to change jets but need to learn a little first.
The car was absolutely different this am. The idle has been approx. 800 and was 400 this am even after I got to work. I don't know how it even idled that low. I turned up the idle and set the air after I got it to work. It sounds a lot better but there is more to do. It really sound to me now like the timing is very retarded. I'll check it this evening and do some more tweeking.
I'll update this thread as I progress. One wrench at a time for sure!

 

[kennygene]

Brought it home today, turned up the timing a little and reset the air bleeds and walla, it is running great!!! I looked into the Holley jet selection and really, mine are pretty small.
Jack, can you give me a baseline for my combo?

 

[WOT]

It is important to remember that idle fuel screws (or idle air screws)** only work if the throttle is closed enough to be running on the idle circuit. If you have the timing severely retarded and the idle turned up, you are likely operating in the transition circuit and/or the main metering circuit.

The way to tune the idle circuit is to set the timing to the proper setting, and then set the idle speed with the throttle stop screw. Next, with a vacuum guage connected, turn the idle mixture screws either way until the vacuum maxes out on the handheld guage. If the idle goes up or down, you will need to reset the idle to the proper setting (800 rpm or 850 or whatever), and then tweak the screws again to get the max vacuum reading. It is common for the optimal idle mixture screw setting to be slightly different on either side.

After doing this, if there is no lean hesitation when you first tip-in off of idle, then you have them set perfectly. If it stumbles a bit, then you need to richen it up just a tad so as to maintain driveability.

If you find that fully closing or fully opening these screws has little affect on the idle quality, then you have the throttle blade open too much, and the carb is running on the transition and main circuits. The fix is to drill a small hole in each of the primary butterflies so more air passes through the carb and then reduce the idle with the throttle-stop screw. This will position the butterflys so that the idle circuit mixtures screws will come into play like they should. The idle mixture screws will not have any affect at part throttle or full throttle.

**Depending on the carb, it will either have idle fuel-mixture screws or idle air-bleed screws. The fuel-mixture screws will have a small straight blade slot in them. The air-bleed screws will have a plastic philips cap over them. The both accomplish the same thing: they control the idle mixture. But they do it in kind of the opposite manner. Closing the fuel-mixture screws will lean out the idle circuit, while closing the air-bleed type mixture screws will richen the idle circuit (by reducing the air flow to the idle circuit emulsification tubes).

 

[kennygene]

Thanks for the info. I have it idling at 700rpms and the timing is now perfect. I have absolutely no hesitation off idle and the car is running super smooth at cruise speed. I'm really starting to love this thing!!!
I'm not sure if it would outrun my Viper truck yet but it is sure close.

 

[kennygene]

OK, so the Holley drove me bonkers, I bought a used Carter AFB 625cfm off an efriend. Here we go again, the Carter runs great at WOT and surges at cruise. Looks like I'll have to calibrate this carb to work. It feels lean which is confusing to me as it should be rich with 625cfm? Why is this happening???

 

[kennygene]

I took the Carter back off after the surging drove me bonkers. I put the Holley back on and fixed a few issues. All I have to say is Holley all the way!!!
I retuned the Holley and timed the distributor again and WOW!!! This car runs the way it should. There is absolutely no surging at low-mid and top end is awesome.
I got a question though, why did the Carter make so much induction sound and the Holley make very little? All 4 barrels are working correctly but the Holley is much quieter. Can anybody answer this? Is it because the Holley is a spread bore?