I have made great progess on a number of issues regarding timing, vac. advance, and carb issues. I was going to report back on all of your recommendations, but I ran into a new problem with the Holley carb that has got me stuck again. (Holley List 3247). Here it is:

First, the carb runs quite well, in general. I have a minor problem with hot idle level which seems to be affected by hard breaking or turning. Seems to want to almost die under those circumstances. I have addressed this with careful adjustment of the fuel bowl level which has minimized this issue.

But, the main problem is with a fuel leak inside the carb. After getting the carb to fully operating temp (hot) and then shutting off, the carb interior will stay dry for about 3 hours. Then, slowly but surely, fuel will appear from nowhere on top of the throttle butterflys and slowly build up over the next few hours as the carb cools down. After a while, there is so much gas on the throttle plates that it begins to leak out of the throttle shafts onto the manifold.
I can see no fuel coming from either the venturis or the accelerator shooters.
It seems to be oozing out of the center of the carb somewhere near the gasket between the upper and lower body halves.

Needless to say, starting the car in this condition yields a semi-flooded problem which slowly disappears as the car warms up. No problems until the next complete cool down cycle.

This is very weird. I have pulled the carb and had the local carb rebuilder take the unit apart twice but he can't find anything wrong. Carb body is very solid and all components look almost new and work correctly. Fuel pump pressure is within specs and does not hold that pressure when shut off. Have any of you ever experienced anything like this before???

Thanks for any help, hints, pointers, or told-you-so's.
Mark

 

I sent mine to the "Holley Custom Shop"
It had been torn apart and tossed in a shoe box for over 20 yrs.
Got it back from Holley (like new), bolted it on, and have not thought
about it in 5 or 6 years. Its like new. But the color is not like the 60's carbs.
Its now a bit brighter, like the new Holley's (It does not bother me though)
Right around $300.00 as I recall, but I wanted everything checked out
& tested. Worked for me! I have always rebuilt my own, but this was the orig
carb, and I wanted it to be perfect.
Just another option...........
One more thing.... My old orig fuel pump used to cause strangethings to happen when starting now and then, gave me fits! I know this sounds strange, but is your fuel pump
in good shape?


[Modified by 396 RAT, 11:55 PM 3/26/2003]

 

The carb my have a warped body and seeping fuel that way. Sounds like common symptoms of the floats being set to high. Set them so that they are just below the sight holes. No fuel should run out of the sight holes at idle.

This flooding issue should be addressed soon as each time this happens you are washing your cylinders with gasoline. You get plenty of that with a carb as it is.

I sent my stock Holley to "The Carb Shop" and was extreemely pleased with the returned product. They installed some newer style boosters, milled the warped surfaces, bench flowed the carb and then they run it on a dyno. The cost was $300.00. They also could have drilled idle circuits in the rear metering block but I opted out. Some claim 4 cornering idle screws are the deal.

Mark

 

....look, if you're uncomfortable working on the holley, $300 is an excellent investment, just drop it in the mail and it will come back perfect.....

...depends on what you want to learn about your car.....this goes back to the truisms that appear here from time to time, whether it's big blocks overheating or not being able to get a holley to work correctly - these were not problems when the cars were new, so the real problem is the people who work on them and think they know what they're doing...

..who rebuilt the carb?..was it ever rebuilt?...when the carb is apart, lay a straight edge over the throttle body plate and carb base - are they flat?...machining an already flat surface is an interesting pastime...

..i don't question your observations but my guess is that the carb is leaking long before the 3 hour interval.....a couple of questions -> how do you know the running and resting fuel line pressure and what are the measurements?...if you are running a "race" carb or something equivalent, throw it away and run a pump that's rated 7 psi max or less (i think that's the magic number, check the archives)...

...even though the carb parts appear to be perfect, my guess is you have gas leaking past the o-rings on the fuel inlet valves and that is a very common problem because they can tear when first being installed due to the roughness of the bore they travel before being seated...i always coat the inlet bore with some light weight grease and that seems to fix the problem....

...i hear that whether you buy a holley carb rebuild kit or an off-brand, there is only one manufacturer so it's all the same...that's not my experience, the holley kits are of much better subjective quality...

..aren't holley's fun?

 

Mark

How are things going? Have not heard from you in awhile. I had the same problem with my 300HP Holley List # .....Idunno". Never went to the effort to actually time the events ...do you have a TMO background also??? Now if we could instrument the carb to capture and correlate the barometric pressure on the days the carb boiled over with the ambient air temp, wind velocity and direction and phase of the moon.......... Can't ya just see it? Infra red temp sensors, temperature and pressure probes, pito tubes.......those TMO guys could have a field day with this.

On my vette carb I tried everything I could think of. Lowered the floats, new floats, new seats, different brand needles and seats, insulator plates under the carb, different fuel pump.....even donverted it to a 4160 with the rear metering block. No matter what I did (and I have worked on a fair number of Holley carbs sucessfully) I just could not fix it.

Finally I found the answer...a new carb. The original one made such a nice clunk hitting the bottom of my trash can........About $250 or so for a new carb from Summit. Bolted it on and forgot about carb troubles. People say that todays junk gas perculates at lower temps that the gas of old and that lowering the floats will fix the problem you have had. Well I am here to say that lowering the floats did NOT fixt the problem and that the new carb. (with factory float settings) worked perfectly out of the box.

I think a top notch rebuilder like Holley or Jerry Luck might have saved the carb, obviously whatever was wrong was a problem that was deeper down than I could address. If you are hell bent on keeping the original carb think about Jerry Luck...he did my 3x2 carbs for my other Toy Car and the work is terriffic. I had him do those because they came with a 3x2 system that looked like it had been in a junk yard for 15 years.

On the 4BBL carb ......truth to tell I had just plain had it with the darn thing. Too much down time for the car, too many headaches and sinus issues from breathing the gas fumes. Final straw was the day it crapped out on the road and I had to wait FOREVER till the gas it puked into the engine evaporated. I was also forever in fear that the thing would eventually mess up and burn the car down...worse it might have burned my house down. I have a basement garage (shop actually) where my collector cars are kept, the daily driver cars are in another attached garage. Anyway llast thing I wanted was a basement fire.

 

When I got my car a little over a year ago, one of the Bubba's standing around when I first took it to the shop, said that it was running too rich, and that I needed a new carb.

I was determined to keep the car as original as I could, so I sent it off and got it restored. Got it back, and it still ran rich, and after it finally fouled out the plugs, and washed down the cylinders, they put it a new kit in it here, and it did a little better for a while, then it was determined that it needed rebuilding again, then later, it developed a pin hole leak in the gas line connection that could not be fixed. At that point, quit messing around and got a new Holley and it ran great.

Bubba was right, and I had to back up to him to admit it. If I had listened to him to begin with, I would have been dollars and a lot of fun driving ahead.

Mechanically, I am challenged, and can't help you a bit, but the new carb sure changed my outlook, and frustration factor.

 

i picked up a spare carb at a swap meet for $15.
i've used parts from it 3 times. it is very handy to have a spare so you can study it :yesnod:

 

now see, this is why i get along so well with theOman...i go through his trash and sell his junque to unsuspecting ebayr's :thumbs:

 

the metering bodies and or the main body are warped and allowing fuel to by pass because of a bad seal between them :chevy


[Modified by clem zahrobsky, 12:17 PM 3/27/2003]

 

Right again Clem! I should have added that warpage usually causes symptoms like those outlined above and those experienced by my carb. Jerry Luck and I discussed that phenomina when he got my 3x2 carbs to work on. I had no idea what condition they were in and therefore want "all the bases" covered in terms of assuring that I got a perfect set of carbs. Jerry advised that he machines all mating surfaces on the carbs to assure that this kind of spill over / perculation does not happen.

In the case of my 4bbl carb it was long gone before the 3x2 project started, I had spent enough $$$$$$$ on that ^&**^%^%$# carb. already and would not have spent another dime, even for Jerry's QUALITY work plus I don't much worry about correct numbers anyway.

 

Thanks for all of the suggestions.

I had the carb rebuilt by a local carb shop....I have not done any of the work on it. Maybe I should have sent it to Holley. Anyway, they tell me they don't see a warp on any of the mating surfaces. They flow test the unit every time and it tests good. My fuel pump is at 5-6 psi and does not have pressure after the motor is shut off.

As for the leak, I have actually set up a test where I observe the carb every 15 minutes for 6 hours (ya, isn't that fun?). So I know that the leak starts in the 3 to 4 hour time slot.

I was hoping to be able to keep this carb in the car, as it is the correct carb. However, I am beginning to lose hope and recognize that a new Holley would be a fairly easy thing to do. I am going to give the carb shop guys one more chance. Will let you know what happens.

Oman...yes, I started with T&M as a systems engineer.

Regards,
Mark

 

...i hear 'ya...let me know when you throw out your existing carb and what day is trash day in your neighborhood :thumbs:

..in all seriousness, do NOT assume your current carb has no value if you buy a new carb..you never know

btw, can you describe your fuel line - does it include any 3/8" flexible gas line upstream from the pump?


[Modified by Kid_Again, 7:49 AM 3/28/2003]

 

Mark.. In my experience with Holley carbs, and its true that thru the 35 years that i've been running and rebuilding these, doesnt mean that I know what im doing with them...It does allow me the knowedge to know when someone has their head where the sun doesnt often shine.. hence the remark
I recently read..

.."...depends on what you want to learn about your car.....this goes back to the truisms that appear here from time to time, whether it's big blocks overheating or not being able to get a holley to work correctly - these were not problems when the cars were new, so the real problem is the people who work on them and think they know what they're doing...

Contrary to popular belief, Holley carbs have been used on MANY applications, and your problem is typical on more than yours.. That being said,,, when my Holleys would percolate, it was up thru the main vent tubes, and as the term says,, they appeared to act just like a coffee pot perculating
from the heat in the bowls.. And it allways showed its face directly after engine shut down,, If yours is doing its thing after 3 or 4 hrs.. I doubt that heat is the primary cause.. It may be the symptom aiding the problem in your case.

Now for the help part you asked for... I have had alot of excellent troubleshooting help when I called and talked to a Holley factory Tech..
They have seen and delt with every possible symptom and are glad to answer your questions.. It may take them a couple days to get you an answer, sometimes they go to their engineers for an answer and E-mail you the results.. The information you have discribed should be all they need to know to help you out.. Best of Luck..

:smash: :banghead:

 

Using the wrong metering plate gaskets can cause leaks like you discribe. Mel

 

I have seen this problem due to a slight leak in the power valve diaphragm or a loose power valve.
If the diaphragm is slightly ruptured, fuel will run onto the main body of the carb onto the throttle plates after shut down time. As the rupture in the diaphragm gets larger, a rich condition will become evident when the choke is on and at idle.
It only takes a slight backfire from your engine to injure the diaphragm.

Steve

 

Your leak sounds like it is caused by a warped main body.

I've never repaired a Holley that didn't have warped main body gasket surfaces. You can't detect these small dips and rises with a straight edge. You can see them if you run a large flat file over the surface though.

Most mechanics don't resurface the main body because they don't know how or don't want to go to the trouble. New gaskets sometimes seal the irregular surfaces. In fact, Holley doesn't even machine these surfaces when the carbs are new. They just assemble them with the main bodies "as-cast".

I do not think much of the Holley Custom Shop rebuilds. They do not normally resurface the main body. They never hot test the finished carb. They flow test it with mineral spirits (or something other than gasoline) and never run it on an actual engine with fuel pressure on the inlet. As a result, many of their rebuilds leak at the pressed in plugs. Yes, I know some people are happy with their work. I think these individuals were lucky. Some carburetors could probably just be cleaned and re-gasketed and run great. Those carbs would run right no matter who rebuilt them, including J. Fred Muggs or the Holley Custom Shop.

 

Its good to here different opinions, its the 1st I have heard where someone
was not happy with a Holley Custom shop rebuild. I have only used them once. I have rebuilt several myself, but this carb was torn down to its smallest element, rolling around in a shoe box. I was not even sure I had all the parts. What was wrong with the work they performed for you? Just curious?

 

I tried them twice about seven and four years ago. Both times the pressed-in plugs in the bowls leaked immediately on initial fire up.

One carb had poor adjustment sensitivity on the passenger side idle mixture screw when it went to them and when it came back. It was caused by a warped main body. On teardown I found that neither carb had the main body surfaced by Holley. On the positive side, I found that both carburetors were very pretty and had shiny hardware when I got them back.

Holley will tell you right up front that they don't engine test their work or even fill carbs with gasoline. They use an air flow machine with a non-explosive "substitute liquid" for cold testing. I think the results of such testing are very limited.

I don't expect a large number of people to understand the necessity of surfacing the main body. There have been far too many magazine articles in Super Chevy and Car Craft that encourage people to just re-gasket their Holleys and put in larger jets when they don't run right. These articles imply that Aunt Bea could make her Camaro run 10 second e.t.'s if she would just buy used Triple Whumper Holley at a swap meet and "rebuild" it. That doesn't match my life experience, but maybe I'm just unlucky. Right, Clem?


[Modified by jerrybramlett, 11:27 AM 3/29/2003]

 

yep,jerry there is more to rebuilding a carb that just throwing in a kit. i have been doing this for almost 45 years and i still run into problems that take a while to solve. it is nice to have a engine to run the carb after rebuilding but since i do not have that i just stick to doing carbs close to home in case there is a problem. i do pressure test the fuel inlet system to make sure that there are no leaks and i show the customer that so after they get dirt in the needles and seats while installing the carb they know it was not something i did. i have a booklet put out by holley 30+ years ago titled "a guide to carburator and manifold modifications" and on the first page they tell you to check for warpage on the bodies. i even have a special jig to straighten the metering bodies because you can not machine them. i guess they do not follow their own advice. :D:chevy


[Modified by clem zahrobsky, 12:38 PM 3/29/2003]

 

I thought I was alone with my Holley (list 3370). Mark my carb is doing the samething as yours. About 3-4 hours after I shut it off gas is coming from the same place as yours. I've really thought I knew my way around a Holley carb till I came across this problem. I have checked every part of my carb with a straight edge just as I do with every carb I rebuild be it a Holley or Q-Jet. Yesterday I called Holley's tech line and they weren't much help. This carb has been rebuilt lots of time because yearsago the car would sit for a year at a time and the gaskets would shrink and leak. Well now I know I,m not crazy. If you happen to find out whats going on let me know.
Thanks Dave :flag