[dv657172]

Just finished rebuilding my Holley 750 DP (0-4779-6), 1st time for one of these and only 2nd ever so definitely a rookie.

Put it back on car which fired a few times when started but wouldnt run and fuel puked out of both vent tubes. What did I do wrong? Float bowl settings? Whats a good initial setting for these.

I know you adjust them after the car is running to where they trickle out the hole but need to get it to run first.

[Scott65]

Either float adjustment, or if you had the floats separated from the bowls, the orientation may be incorrect. A good book comes in handy when you're first getting started.

[dv657172]

Thanks for the reply. Guess I will take a look at float bowls again.

I thought I had a good book...guess we arent all experts are 1st time....

[dv657172]

All Holley stuff from their Renew Kit (37-485)

New Holley N&S
New gaskets (plastic ones currently from the kit, maybe should be using paper-type also in kit instead?)

Adjusting nut and screw are the ones previously on the carb

Didnt replace the floats but they looked good imo

[Scott65]

Absolutely. Take your time, you'll get it. Another thing, if you have jet extensions, or vent "whistles" added, extra caution is required. Sometimes it's helpful to fit the bowl to the metering block, and give it a shake to make sure the float is free, then stab the whole thing to the main body.

[dv657172]

Scott

Thanks so much!. It does have the whistles added so I will definitely give that a try as I thought I put it all together correctly.

[dv657172]

All checked, no gasket debris and nuts look flat although havent done any honing on them yet as you suggested (good suggestion)

[Tom Vaught]

Have posted in the past about the white whistles being too long for performance work from Holley.

I trim the whistles the distance of the factory window on top of the whistle and make a new window in that shortened whistle. Works much better for performance work.

Also your #4779-6 should be the first year of the 4 corner idle adjustable metering blocks. Where do you have the screws set for the rear metering block??

Tom V.

[dv657172]

Tom

I turned the idle mixture screws all the way in and then backed them out 1.5 turns for both the primaries and secondaries. Planning on adjusting them once I get float bowls at the correct level.

Will have to go and find some of your past postings on the whistles and take a look.

DV

[Kenth]

For center hung floats Holley recommends setting the floats in center of bowl as an initial setting with bowl bottoms up.

[dv657172]

Update

Issue was the plastic gaskets. Used the paper ones with float bowls set at a 0.45 gap when turned upside down and started right up no leaks at N&S screws and fuel level just about perfect. Thanks for all the help on that issue.

DV

[Tom Vaught]

Originally Posted by dv657172

Tom

I turned the idle mixture screws all the way in and then backed them out 1.5 turns for both the primaries and secondaries. Planning on adjusting them once I get float bowls at the correct level.

Will have to go and find some of your past postings on the whistles and take a look.

DV

The 4 corner idle carbs vs the 2 corner cars you would think would be the same on the idle circuit and mixture screws.
THEY ARE NOT.

Prior to the 4 corner idle carbs, the 2 corner idle carbs used an IDLE FUEL FEED RESTRICTION ORIFICE at the lower part of the metering block. The Idle mixture was drawing from liquid fuel for the calibration.

When Holley came out with the 4 corner stuff, they moved to a high position Idle FUEL Feed Restriction up near the vent whistle on the metering blocks. Now the idle mixture was influenced by the high position in the circuit. The idle speed is erratic at times depending on weather conditions. Most carbs really need the idle circuit changed BACK TO the lower restriction position. Erratic idle depending on the weather is the main issue.

Jeff (Shaker455) could return the carb to the previous IFR location easily.

One of the first Mods Holley did to a carb that was working fine with the previous idle circuit but they HAD to change stuff, (just like Edelbrock with their 4 circuit carbs) today.

Tom V.

[dv657172]

Thanks for info. Using the plastic gaskets for the N&S definitely wasnt the right idea, lesson learned lol. They were same size as paper ones and I thought they would hold up better. Not the case. Not sure what they are in the kit for.

fyi, the float bowl screw gaskets in the kit (#37-485) are a hard looking plastic so hopefully those will hold up well over time

The accelerator pumps that came in the Holley rebuild kit look the same as the picture you posted so I hope they hold up well too. Definitely dont like the idea of one leaking over top the intake

DV

[dv657172]

Agree, definitely will give the paper gaskets a try. Never expected something this easy to be so time consuming. It keeps it interesting. lol

Thanks and will let you know how it goes!

[dv657172]

Thanks Kenth - very helpful

[dv657172]

So I set the floats lower with carb off the car and it started right up with no fuel puking out the vent tubes when I put it back on but.......

I have a fuel leak around the secondary needle & seat adjustment nut & screw. I am using new plastic gaskets which came in the kit and the sealing surfaces all look fine. The primary needle & seat does not appear to have a leak around it.

With the car now running my guage at the end of the fuel line is showing a PSI of 8 lbs which I know is high. Is that likely the issue or is it a needle and seat issue which is brand new.

[Scott65]

Check the condition of the o-ring on the needle and seat assembly. I used either Vaseline or Dow Corning o ring grease on them to help them slide without cutting/tearing. That's if the gaskets for the screw/adjustment nut aren't obviously torn.

[dv657172]

Tom V

I have sent you about 3 private messages on car details but they dont seem to be going through

Here is picture of transfer slot on primary side as carb currently sits and runs with PCV fitting unplugged.

Secondary side is completely above the throttle plate

Is it optimal to try and get it to run with PCV plugged or just tune it as is (i.e. unplugged) which is has been since it first ran? Whats optimal

[dv657172]

I originallly put a little oil on the o-ring but will inspect it again. The gaskets are plastic so they shouldnt be the issue.

Will reverse assemblies tomorrow if they look ok and see if issue moves to primary side or stays on secondary side.

[Tom Vaught]

Good Luck and post up when you get to the 4 corner idle settings.

Tom V.