Engine stalls when accelerator is pressed.
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Tuned
Joined: Feb 2016
Posts: 299
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Engine stalls when accelerator is pressed.
I feel like I am back to square one. 1979 f150 400 6.6 liter. I installed new Holley 600, new distributor, new fuel pump, new intake manifold gasket and new valve cover gaskets. Changed oil and filter. I started engine and let idle for 5 minutes no smoking engine. An hour later I restarted engine pulled forward approximately 20 feet to hose driveway off. Truck idled approximately 10 minutes, no problem. I put it in drive press accelerator and it dies. I restart and back up to original starting point, press accelerator and it dies. Restart it and let idle. This time black smoke is coming from exhaust pipes. The number 5 exhaust rocker arm was slightly loose and bolt was bottomed out when I replaced everything. Engine is not running hot. Oil pressure gauge moves to normal and then goes back to L. It is also brand new 2 months ago. Thanks for any advise.
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Tuned
Joined: Feb 2016
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Okay. I'll check that. Didn't think about being out of time since we set timing at top dead center on number 1 cylinder. I don't know where a vacuum leak would be. I did see if havery a small gas leak at the filler neck clamp.
Cargo Master
Joined: Jun 2014
Posts: 2,217
Likes: 325
From: Central Florida
On the harmonic balancer, TDC will come up twice for every full rev of the cam, once for #1 and once for its opposite in the firing order. Thus, you need to confirm that you have the correct TDC (TDC firing) when you install the distributor. Otherwise, you might be 180º off. When you're at TDC (firing) for cylinder #1, both valves will be closed and the piston will be at the top.
Once you are certain about that, set the initial advance and check to see if the rotor is pointing to the wire for #1 by peeking under the dist cap. It's easy to be off by a tooth or so on the dist gear. While you're there confirm that your spark plug wires are following the firing order in the correct (CC) direction, not cross-firing, grounding, etc.
A Q&D way to find TDC (firing) is to wad up a piece of paper large enough to cover #1 spark plug hole. Then "bump" the starter until the wad pops out. That's TDC firing. This will require a confederate or a remote starter button.
Once you are certain about that, set the initial advance and check to see if the rotor is pointing to the wire for #1 by peeking under the dist cap. It's easy to be off by a tooth or so on the dist gear. While you're there confirm that your spark plug wires are following the firing order in the correct (CC) direction, not cross-firing, grounding, etc.
A Q&D way to find TDC (firing) is to wad up a piece of paper large enough to cover #1 spark plug hole. Then "bump" the starter until the wad pops out. That's TDC firing. This will require a confederate or a remote starter button.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
Black smoke = too rich a mixture - letting un-burned hydrocabons out the exhaust. The mixture screws should be about 1- 1.5 turns out.
Check yer plugs- I'll bet they're black/sooty - and clean/replace.
How's yer accelerator pump? With the engine off and semi cool, blip the throttle - you should see two lines of fuel shooting down the carb body.
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Postmaster
Joined: Nov 2015
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From: O-O-O-Oreilly's
You mechanic set it to full manifold vacuum..which means you have full vacuum advance all the time. Waay too much initial. It can be a good thing but needs other considerations to run right. Pull the line and plug the bottom nipple. Plug the line and recheck yer timing. Should be ~ 12*BTDC.
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Tuned
Joined: Feb 2016
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Okay I'll take care of vacuum advance. The truck idled perfect for 20 minutes, then started to bogg down like it was going to die. The ran smooth for a couple of minutes then eventually died. I'll check spark plugs, but I just put them in 2 months ago. There's not 10 miles on them.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
No, vacuum advance is load related while mechanical advance is RPM related.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
Bogging down at idle, then dies.....black smoke out the exhaust, probably fouled plugs...
OP: for grins and chuckles, check the power valve. To do this, bottom out a mixture screw - go easy! If the engine still runs, the power valve is shot...if it dies, the power valve is good and some other troubleshooting is necessary.
I know you said the carb is "new" but stranger things have happened "out of the box."