345 stalls when coming to a stop

C

Cudamank

Member
Trouble with the 345 v8 in our 62 c110.

345 v8, 4bbl intake, 4150 600 cfm 4bbl. T98 4spd.

Just added the intake off a 392 and the carb was rebuilt with Holley rebuilt kit.

Truck starts right up and idles at 700 rpm. Once warmed up runs well with no issues, unless you come up to a stop. As you pull up to the stop, foot off the gas, the idle drops and dies. If you feather the gas pedal, it will come up to idle. Thought maybe the floats where to high, checked, they are adjusted to just below the sight glass holes.

Any ideas? Plan on devoting this weekend to get it fixed.
 
Did you check the fuel levels while running?
I would try and lower the levels 1/2 turn on each bowl. Start on the secondary or rear one first. See if it improves.
Also could be the brake booster if you have power brakes.
 
Need more info. It sounds like you're saying it's bogging down with too much fuel, not leaning out, correct? Does it do it every time you stop or intermittently?
 
rmscout said:
need more info. It sounds like you're saying it's bogging down with too much fuel, not leaning out, correct? Does it do it every time you stop or intermittently?
Click to expand...

He did not say lean or Rich and probably doesn't know for sure hence the request for help.. He has tasks to do so we might ultimately determine a potential root cause. The doe I suggested for him will hint at the changes the doe needs to zero in on the problem.
 
I thought it might be flooding, so I lowered the floats. I went that way since it runs and drives okay, even under throttle, I didnt feel any hesitation or lean misfires.

Working on it tonight. Will start by checking floats while running. Will report back.
 
With running, front float is set for just below site hole, rear a little lower. With vacuum gauge hooked up, and a good timing light/with rpm, started with timing. 26 all in at by 1500 vacuum disconnected from distributor. . lowered idle to 800 rpm . (should have checked timing again . engine vacuum not stable between 13-15 in . with engine warmed up, choke plate open 1/4 in idle hunts a little . if you push the choke plate closed, idle picks up and smooths out .
so I have a vacuum leak somewhere ? the carb only has the one vacuum port on the front metering block . the intake has 2 at the back . the large one connected to the valley pan, the small one blocked with a plug . the choke is a heat riser type, put no pipe hooked to it . I capped it off just to insure no vacuum leak .

smoke test ? suggestions ?

suggestion
 
I agree with fdchappie now that we have seen the result of your testing. Definitely lean.

Per the recommendations, back the idle screws out after you warm the engine up. Adjust for best idle. Have a few passes from the right to the left. Have the idle speed at about 600 while adjusting.

A couple of questions for you.

Is this 4150 new? Used and rebuilt?

Is the throttle response smooth off of idle while accelerating off idle?

Do you have a brake booster. I don't know what was offered on your year of IH.

Could you post a couple of clear well focused pictures of your engine that show the hose routing including the pcv system.
 
Once the kids are at school ill adjust the idle screws.

The 4150 was rebuilt using Holley trick kit 37-485.

Throttle response is smooth, no hesitation, or rough spots.

No power brakes, good old drum brakes with single brake/clutch master.

Will take some photos. Being a 62 there are only 2 vacuum hoses.
 
Reporting back after finally getting back to the truck. Ended up turning the screws 3/4 turn out. Adjust idle speed after warm up, now idles at 800 rpm. Probably a little high still. No more stalling at comming up to a stop. Take off is smooth with no hesitation, both from a complete stop or from say 25mph.

Thank you for the help!
 
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