Having Holley problems and looking for some ideas.
Car ran great last year, took it to the track and it kept getting better. Had a 750 vacum advance. At the track late in the year it back fired and stalled and broke the plastic choke mechanism. We tied a string around the choke went out there and ran a best 12.6. Soon after I repaced the choke mech with a new metal piece. On the last run down the highway before putting it away for the season it bogged down real bad under hard acceleration (second gear). Did'nt think much of it. Went to the track this year with new engine and same car. Car comes off the line like mad, but when I got to third gear, it starts sputtering real bad lasting a couple second before it clears up. Thinking I messed something up putting the choke mech on.
Since the old man has an extra 750 double pumper laying around I figured I woud'nt worry, I would just switch. Put the DP on today, sounds good but when I turn the car off it floods the secondaries with fuel. Seems to be coming from the bottom idle passage. Floats are fine.
Any ideas what is wrong with these two carbs? And which one would be the best candidate too fix first.
Thanks in advance

 

Unless you have steep gears and a stall I would go with the vacuum carb.
Sounds to me like when you backfired it blew the power valve? Also see what your manifold vacuum is in gear then go 2 size numbers under that with the valve. If the car is getting a reading of 7 at idle then get a 4.5 powre valve ETC. I run a 2.5 or 3.5 no matter what anyway.
Anyway get a spring kit and keep going lighter until it bogs then go back 1.

 

Chuck the Holleys. For street only, get an Edelbrock...for street and strip, or strip only, get a Demon.

 

I am stuck with what I have. We have these two 750s. Another couple 650s. Have a couple quads. I will check the 750 vacum for power valve, any idea what is ailing the 750 dp?

 

If you can't get a Holley to work , then you don't need to be working on cars.
I have never had any problems I couldn't fix very easy on a Holley with a power valve, jet or gasket change.
Holleys are made to fit from a 350 to a 454 out of the box, you have to make it work with your combonation just like cams, gears, tires and ETC.

 

I'm sure you already considered this, but the gaskets shrink when they dry out.... so when you re-use a Holley that has been side-lined for a while, you have to replace all of the gaskets. Even the new style gaskets need replacing. Otherwise, you get internal leaks.

I also install Power Valve protectors in any Holley I rebuild if it doesn't already have it installed.

 

 

Tim and Les,
I can't help but being a little put off by your responses. I asked for some help because I was under a deadline for a race and was having difficulty getting the car to run right. Thought perhaps I could get some input that might help steer me in the right direction. I am new to this forum and have had some positive input from others for some specific questions, but perhaps I am looking to the wrong people for help and will take and future issues elsewhere.

By the way we ran 12.3 on street tires, so perhaps we are doing fine by ourselves.

 

ARCH,
I can understand why you would react that way to the comments made- no ill will whatsoever was intended on my part. I didn't have time to sit down & clarify anything at the time. Tim's response was to Roughrider's advice to "Chuck the Holleys"- I was agreeing with Tim that there's no need to do that because Holleys are really easy to rebuild and tune once you have even a basic understanding of them. There are a number of good books out there about caring for & modding Holleys- I have an old one written by Dave Emanuel that's still very helpful to me.

I'd get a quality rebuild kit & rebuild the 750 DP after cleaning it thoroughly. If it was laying around very long the gaskets may have gone bad & the needle & seat could be sticky from varnish deposits.

I hope that helps and, by the way, your 12.3 is a very respectable ET.

 

Have you checked and/or adjusted the secondary float level on the 750 DP? It sounds like it's too high.

 

Not trying to hijack thread, thought this question fits in. Les, I am a novice mechanic, but have enough of the basics down to have been able to rebuild a rolling chassis. I will be buying a 383 stroker from GMPP, and will need to provide many of my own parts to complete the engine. I have never rebuilt a carb of any type before, but would really like to get a core and try to do one to use on my stroker. BS aside, is it realistic to think I could do a rebuild with no experience if I had a book as you mentioned, or am I better off just buying new. Its not the money saved I am after, it is the understanding of the carb to help keep my car running great, that I seek. I know if I drop $400.00 on a new carb, I will be reluctant to modifying or working on it for fear of messing it up. If you think it is doable, please reference book title and author, to get me going.

Thanks,
Willem

 

Think the older Holleys...pre 1990...a backfire can harm the power valve...and can leak...the later ones..Holley installed better power valves..

Great ET on street tires,btw..

Rich

 

Willem,
It's very do-able if you're good at making sense of diagrams. If you're not confident after looking at them, have a friend who has experience help you the 1st time. As many rebuilds as I've done over the years, I still only work on one end of the carb at a time. This just about eliminates confusion about what goes where when you re-assemble. If you have to completely disassemble the carb all at once for cleaning purposes, lay the parts out in order just like an exploded diagram to make reassembly a snap.

Take your time and replace the little gaskets as you go, such as those that go on the bolts that hold the float bowls in place. There are different metering block gaskets in the rebuild kits, so make sure you match up new to old & have the correct side facing outwards.

Bear in mind that older metering blocks can be warped from overtorquing, so if you don't have new ones you'll want to check to make sure the surfaces are square before putting them back on.

Count the number of threads showing at the top of the needle & seat so that you can duplicate that with the new ones you put in- this will get your float level right in the ballpark until you can adjust it via the sight holes.

There are a few other small tips that come to mind but it will all be covered in a good book. Dave Emanuel has been considered to be one of the top Holley experts, so a recent edition of his book would serve you well. Mine is titled "Volume One- Carburetion: Holley Carburetors" but I've had it forever so I'm sure there are updated versions of it.

Good luck & feel free to hit me up if you have any questions.