Engine Hesitation?

[ThatOneBlue67]

Well, the 350 has been in my truck for a week now. It runs pretty good except for a hesitation. If I smoothly accelerate, it generally does ok.

If I romp on it a little harder, it tends to misfireas if a spark plug isn't connected I suppose. The engine quiets down and fights for gas and if I don't handle the situation right, it can actually stall completely. This happens especially early morning, when it's cold outside.

The intake manifold is stock, I haven't even touched it, and I don't hear any vacuum leaks.

The Holley Street Avenger on top of it is on correctly and tightly.

I've been informed that Holleys tend to be too lean for a 350 and the jets need replacing. Does anyone agree with this? Also, the distributor is fine, fuel filters are new, carb adjustments are correct, and I have not had any previous fuel travelling problems with the 6cyl that was in there.

[ThatOneBlue67]

I started her up to go to work today and thought I heard a whistle, as if there amy be a vacuum leak. I'm thinking of replacing the intake gaskets in the near future. If not this, anythign else?

Again, things that I know are OK:

-Distributor
-Spark plugs and wires
-Carburetor bolted on and hooked up correctly (for the most part)
-Choke is always at wide open throttle.

*I read somewhere that the secondary vacuum spring may be too weak or to stiff for my application. Anyone else?

[Psycho71]

Call the holley tech line. They are great and will give you all the little tricks for that carb. I put the SA 670 on my 350, and after a few calls & tuning sessions, mine works great. I'll bet that with the new engine, the tuning parameters changed. If I remember correctly, I was talking to Ricky. But that was a few months ago.


Jay

[al's71gmc]

Mine had the same type of hesitation. A mechanic told me the carb was warped and it had a serious vac leak. He offered to put a rebuilt qjet in it for only $680! I opted not to do it. After putting in a recently rebuilt carb, the same thing happened. I had to set the timing all the way to about 25 BTDC. I think the PO put the distributer in wrong. I think he had it at TDC on the exhaust stroke instead of compression/fire. I haven't had a chance to check it yet, but it runs great when set waaaay advanced.

[ThatOneBlue67]

I guess I'll call the Holely tech line. It staleld on me again today twice. I sure hope it's just me and it isn't getting worse

[8696steve]

You say the distributor is ok but what is the timing set at, and are you sure you got the correct base gasket on the carb?

[GREASEMONKEY72]

does it still due it even after the engine is fully warmed up???? cause mine used to do it and still kinda does, but its nice and smooth once its fully warmed just food for thought hope you get it fixed

-steven

[jhow66]

Did you install the Holley on a Q-jet manifold?

[glock35ipsc]

I was wondering that too.....square flange carb on a spread bore manifold? Get a can of carb cleaner and start checking for vacuum leaks.

[kbs71]

I had this exact same thing happen to me a couple of years ago. I had just put a Holly on a Q-jet manifold. if you look at both sides of the carb at the manifold you'll see the manifold "disappears" under the carb. There is a gigantic hole there under the carb and will cause the thing to hesitate real bad at idle when cold. It will appear to get better as the engine heats up. You need to either get a manifoldadaptot to adapt the Q-jet manifld to a spread bore or you can look for a isolation plate for the spread bore. Put gaskets on both sides and it will stop the leak. this way isn't really the right way but it will work.