KeithinMI

1. What is the correct vacuum secondary diaphragm to replace? I tried calling Holley but they say my carburetor is "obsolete" and there's no replacement.

2. My secondary vacuum housing is missing the little ball bearing but from my reading, pre-1971 Holley carbs did not have that ball bearing. True? If I need one, where can I obtain one?

3. I bought the Holley "trick kit" (part # purchased upon recommendation of my call to Holley technical support] to rebuild my R4555 and it looks like I had all the right parts except I did not get the small little cork gasket that goes inbetween the vac secondary housing and the carburetor body. Where can I get one?

4. My car is an L48, however the PO put on the high-rise alum. manifold and Holley 4555 right after he bought the car in 1970. When I did the rebuild last weekend, I saw that the primary jets were 68's not 70's. I know the "stock" config was 70 primary, 76 secondary. Should I change the primary jets to 70's?

5. I am having an odd idle problem. Car will start and idle, higher RPMs seem to be ok, however if I let the car idle for a while (couple minutes), all of the sudden the engine will start to surge and then eventually stall. If I open the throttle all the way in time, the car will rev up and then idle again (and I usually get smoke out the exhaust when I do - smoke is black, not blue or white, so I don't suspect coolant or oil leaks, but overly rich mixture). Could this have something to do with the #68 primary jets as well?

I have tried to tune up the car using vacuum gauge. Tune one idle screw for max vacuum, then other screw for max vacuum, so I'm assuming my idle mix is with reason of being correct.

71VetteLover

I'll address your questions #4 and #5 only. Holleys are usually jetted a bit too rich and that's probably why the PO installed the leaner #68's. When an engine with a Holley idles for a long time then starts chugging black smoke it's very possible the o-ring around the primary needle seat is no longer sealing real well and gasoline is slowly overfilling the float bowl. When you remove the needle seat and find that o-ring has flat sides it's due for replacement. And it's also very possible the mixture screws are backed a bit too far out; making the mixture excessively rich and sooting the spark plugs. Normally the mixture screws need to be backed out 1-1/4 to 1-1/2 turns for the best idle quality.

MelWff

1. What is the correct vacuum secondary diaphragm to replace? I tried calling Holley but they say my carburetor is "obsolete" and there's no replacement.
Measure your old one this probably is the replacement https://www.holley.com/products/fuel...ts/parts/135-4

2. My secondary vacuum housing is missing the little ball bearing but from my reading, pre-1971 Holley carbs did not have that ball bearing. True? If I need one, where can I obtain one? Look in the passage where the ball would sit, if all you see is a hole and no slot leading up to the hole to act as an air bleed your carburetor does not use one.

3. I bought the Holley "trick kit" (part # purchased upon recommendation of my call to Holley technical support] to rebuild my R4555 and it looks like I had all the right parts except I did not get the small little cork gasket that goes inbetween the vac secondary housing and the carburetor body. Where can I get one?
This is the missing gasket try locally or Summit or Jegs https://www.holley.com/products/fuel...arts/108-67-20

4. My car is an L48, however the PO put on the high-rise alum. manifold and Holley 4555 right after he bought the car in 1970. When I did the rebuild last weekend, I saw that the primary jets were 68's not 70's. I know the "stock" config was 70 primary, 76 secondary. Should I change the primary jets to 70's?
You make no mention of what year car/compression you are running or camshaft. The 70's were used with a solid lifter, 11:1 compression engine. If you dont have that stick with the 68's.

5. I am having an odd idle problem. Car will start and idle, higher RPMs seem to be ok, however if I let the car idle for a while (couple minutes), all of the sudden the engine will start to surge and then eventually stall. If I open the throttle all the way in time, the car will rev up and then idle again (and I usually get smoke out the exhaust when I do - smoke is black, not blue or white, so I don't suspect coolant or oil leaks, but overly rich mixture). Could this have something to do with the #68 primary jets as well? The 68's will not cause that. Have you checked the float levels?
I run a 3310-1 which is very similar to your 4555. I use a tachometer to adjust the idle turning in one side by an 1/8 of a turn checking for an rpm drop and when I get the drop I turn back out 1/4 turn. Then do the other side same way and then go back to first side to make sure no change required. I also run a 900 rpm idle speed. You make no mention of what plugs you are using?

LT1driver

that price from holley for gasket is insane, i would make one before paying that price.

PAmotorman

that price is for 20 gaskets

PAmotorman

take the vacuum housing to the local auto parts and get a "O" ring to fit in the cavity

toylman

MelWff gives you excellent advice and PAmotorman's fix for #3 is what I did with success. #5 is most important since it sounds like you have the floats to high. If you loosen the float screws and turn the nut clockwise, it will drop the float. You can gauge the level with the sight screw in the side. Trying to do it with a running engine, as I've seen it recommended, is crazy.
So, Not running; If you remove the side sight screw and gas comes out, your float is to high. Lower your floats, tighten top and side screws, start car to build pressure, shut off and check fuel level. Keep lowering until level in both bowls it at the bottom of the side sight holes and not running out.
Using a vacuum gauge for idle mixture should work the best after floats are adjusted. Mine were best at about 1 1/4 turn out.