I pulled and rebuilt my 4150 Holley because of a low speed drivability issue. I've rebuilt carbs before and never had an issue, until now. Now it's a bitch to start and it idles high after revving and idles down by itself in increments until it dies. Everything is adjusted as it was before the rebuild. No choke. The vacuum advance and mechanical advance are operating properly. Any ideas guys? What have I missed?

 

Mr 4 -

Sounds like either a vacuum leak or fuel starvation.
Check the vac at idle and make sure you see fuel squirting after the engine dies.

Archer

 

I Agree....

 

Thanks boys. I'm digging back in tomorrow morning, I'll report back my findings

 

Definatly not a vacuum leak and definatly not lean, just the opposite. Four corner idle screws in all the way, float levels lowered, and power valve intact and it is still pig rich. Like smoking out the entire neighborhood rich. And none of this extra fuel is coming from the accelerator pump squirters or boosters. I'm stumped. Out of frustration I pulled the power brake booster hose off to create a manual vacuum leak and the RPMs jumped from 750 to 1750 and the exhaust smelled way cleaner. Any ideas guys?

 

All the Air Bleeds still accounted for?

 

metering blocks could be warped ? Check everything with a straight edge.

 

Float valve(s) not closing ? I had this happen to me many times, especially with dirt in the fuel. A good way to at least temporarily resolve it is as follows. When the engine does that, remove the fuel line and either block it with your iinger or reroute it to a bottle. Let the engine use up all the fuel in the bowl and die. You may see the idle improving as the fuel level drops. When the engine dies, the float valve is completely open. When you restore the fuel line, the debris holding the valve open is flown clear of the valve.


Easy test to do, it may fix your problem. If not, you lost nothing. I have a shut off valve in one of my 440s on the fuel line, I had it installed to do this easily, back when the fuel was suspected dirty.

 

Air bleeds are clear, present, and operational Bob. I swapped the needle and seat valves part way through this mess with no difference Demitri. Archer, this is an interesting thought. They were almost certainly straight when I began (the original issue turned out to be loose baseplate to main body screws) but I may have warped them during reassembly. I will do a full autopsy when my new Holley HP arrives. I ran out of patience messing with the old one when my girl gave her blessing on me just replacing it

 

You did get it from BIGS PERFORMANCE ? Rite!!!!!???????

 

Amazon. $513 W/ shipping!

 

Well... Too late to Dog you now..lol
Let us know how it works....

 

You know I will!