Bought a re-issue (brand new) 4555 from thepartsladi. It became clogged with whatever was in my gastank, no filter from the tank to the carb. I put an inline filter in, bought a 4150hp, swapped carbs and pulled the 4555 apart tonight to rebuild it. (Never rebuilt a carb before, and I needed to drive it back from my parents house before it snows in the mountains, that's why I bought the 4150hp)

Both metering blocks are garbage in my opinion. One is cracked through and had to be leaking fuel on my intake when I was using it, the other one is peeling and flaking, whatever coating is on it is coming off everywhere. I sent emails to both thepartsladi and holley tonight and I'm waiting to hear if they will do anything to correct this, seems like for almost $700 it should have been a lot better carb.

Anyway, I need to replace the metering blocks, and I'm a little confused. The metering blocks I have now look identical except there are no idle screws on the secondary block. Is this how it is supposed to be? I was looking at metering blocks on summit from quick fuel and proform, they look like machined and anodized aluminum, which in my estimation means that they are about 1000x better than what I have now (cast mystery metal with unknown finish that appears to flake off in the presence of gasoline). The 4555 is a 4150 carb right? So, if I order metering blocks for a 4150 series that should do it eh? Am I missing anything? Should I do anything else to it while I have it apart, should I just leave it off, back over it..?


Just out of curiosity, the crap that clogged it looked like a white crystal/powder substance and was too big to get through the sintered brass filters, it must have built up from much finer particles over time. It was all over the primary metering block, any idea what it is?

 

Sounds like you biggest issue is the crack you found in one of the metering blocks, that may be a warranty claim from Holley, Second issue is the white powder, water obviously attacked the anodizing/aluminum on the metering blocks, this will certainly cause the flaking/corrosion you found, the only one way for water to get in your fuel bowls is from your gas tank?

If I were you, I'd drop your tank, either have it professionally cleaned or replace it. If you don't, you will have the same issue with any carb you use. Water in fuel systems is nothing but destructive and can cause many problems, as you have found out. A fuel filter would have helped but not stopped the corrosion the water caused. Replace the fuel sock in your fuel tank sender unit before you button the tank back up.

If Holley see's the white powdery corrosion, even on the cracked metering block, they probably will not warranty any part of the carb.

I would also suggest replacing the fuel pump since its been pumping water as well, could be some corrosion in there too and could come back to haunt you after a lot od work making it right.

The 4555 did not have 4 corner idle mixture capabilities, just in the primary metering block or 2 fronts, left and right.

You will probably have the same issue with the carb you just installed if the water sits long enough in the bowls,

I'd pull it off and take the bowls off and check, try saving the fuel from the bowls and pouring it into a clear glass, you'll probably be able to see water in the fuel through the glass!

Good luck,

Gibby

 

Most 4150's do not have front and rear power valves, but the 4555 did. If you order a set of metering blocks for any 4150 the rear won't have a provision for a power valve. Either get the correct metering blocks for the 4555, or you could probably use a primary side metering block in the rear and screw in the idle mixture screws all the way (guessing here-hope somebody more knowledgable can help).