Help engine stumbles and almost stalls on sudden acceleration
Le Mans Master
Joined: May 2007
Posts: 5,007
Likes: 1,114
From: North tonawanda NY
So I had a thread like this going about a year ago for the same symptoms on my 355 after I swapped the 180 /64 cc iron eagles with 190 /64cc aluminum heads. In my case Turns out I had a few issues. One was the adjustable vacuum canister not playing nice with the vacuum loss just off idle which I resolved with a new adjustable canister that had a working baseline that worked with my vacuum level and rerouting my pcv valve plumbing by running the pcv valve hose from the valve to the intake manifold vs the base of the air cleaner (This also corrected a crankcase pressure issue I had which caused my fuel pump seal to fail and spray oil everywhere).
The other issues I had were fuel delivery. I had to jet up to fatter jets due to the heads but I also had to replace my squirter cam and squirter nozzles with larger sized versions as my engine was starving for fuel just off idle. I also was flooding my engine with too much fuel at the same time with my idle circuit which was causing the engine to smoke I have a holley quickfuel 680 carb though so a bit different setup
One of the things I was told to check was the intake manifold gaskets sealing since a leak between the intake and galley under the manifold could cause the issue I was having but in my case it was not the issue.
The other issues I had were fuel delivery. I had to jet up to fatter jets due to the heads but I also had to replace my squirter cam and squirter nozzles with larger sized versions as my engine was starving for fuel just off idle. I also was flooding my engine with too much fuel at the same time with my idle circuit which was causing the engine to smoke I have a holley quickfuel 680 carb though so a bit different setup
One of the things I was told to check was the intake manifold gaskets sealing since a leak between the intake and galley under the manifold could cause the issue I was having but in my case it was not the issue.
Last edited by augiedoggy; Jan 9, 2024 at 02:56 PM.
Melting Slicks
Joined: Apr 2021
Posts: 2,616
Likes: 2,074
From: Minnesota
If you’re going to be tearing into the carb again I would double check the accelerator pump. You said in an earlier post you checked that it returns to its original location after pressing on it, but a defective pump can move against the spring underneath without actually moving on the rod. Even a new pump can fail after a very short time if it’s not the ethanol resistant kind.
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
