86 351W: cold engine driveability problems
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86 351W: cold engine driveability problems
ok, this is in my 1978 f100 with a swapped in 1986 351W HO motor swapped in. The engine runs great, starts right up, has a good fast idle. This is the 1st start of the day when the engine is cold. The problem is when I come up to a stop sign and let my foot off the gas, the engine will die if I don't keep one foot on the brake and one on the gas. I have to drive the truck like this for about 20 minutes before it will run without giving it gas. I can step up the idle speed and it will run, but then when it warms up, it is idling way to fast. The choke is working properly, I have let the engine run without the air filter housing and watched it open up. the temps aren't cold here, it is in the 50's and 60's in the mornings. Also I noticed it takes forever for the temperature gauge to move. Yestersday was the 1st time I took the truck on the highway since I got the engine swap finished, and the gauge barely moved, and was no where the C for cold, and not in the normal range. woud this be the thermostat?...thanks, Ben
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86 351W: cold engine driveability problems
Thermostat will help. Do you have the warm air tube from the shroud over the exhaust manifold to the air cleaner snorkle in place and working? That will help too. You could also try setting the choke a little richer. It might be opening a little soon.
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86 351W: cold engine driveability problems
Did you rebuild the carb when you rebuilt the engine? If not it could be somthing with the carb.... Maybe Idle mixture? Bust out your vacuum advance from your tool bench and hook it up and re-adjust your A/F mixture. To do this start the truck up, let her run untill she runs on her own, and then adjust the screws evenly, IN first and if the vacuum is lower then screw them OUT untill you get the highest possible reading. Also have you checked your timing or maybe vacuum advance to see if it is working properly latley?
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86 351W: cold engine driveability problems
thanks for the ideas guys. I can't hook up the hose from the exhaust to the air cleaner because I am using the exhaust manifolds from the 302 that was in the truck to start with. The carb was rebuilt by a reputable builder on his bench, not on the engine. Now, silly question time: Where are the idle mixture screws? this is the stock 4 barrel carb on the 351w HO. When I put the carb back on the truck, I noticed 2 screws by the base of the carb on the 2 barrel side. Is this them? and how do I adjust them? I can't hardly see them with the carb on the truck!! thanks again for the advice, Ben
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From: Seattle/Tacoma Washington U.S.A.
86 351W: cold engine driveability problems
umm.... Well somone else help me out here... I am only farmiliar with the EDL 4 bbl carb...and the motorcraft 2bbl.... The 2 screws should be near the botom of the carb...Its hard to explain.... To set your Air / Fuel mixture you have to ither have an electronic A/F ratio tester to hook up to your exhaust or (what I use) a vacuum guage. Hook the guage up to full manifold vacuum (vacuum tree on your intake) and write down the reading, mine read at the very beguining of NORMAL.. in the green area (vacuum guages will vary.. color and marks) but I believe it was 15hg in vacuum, and I slowly started screwing both of the screws inwards, 1/2 turn each at a time, untill I seen the guage start to read higher and higher, I slowed down the turning to 1/4 turn at a time, untill my engine started to stumble and backed them out a tad bit. and after that I was reading 22hg... Edelbrock carbs are set very ritch at first.... Keep that in mind of you ever put one on. Hope this helps.
P.S. Has anyone ever used the A/F guages that tap into your exhaust and you can mount in your cab so you can see what your mixture always is? Because I thought they were just for racing untill I seen a towtruck guy had one mounted on his dash...?
P.S. Has anyone ever used the A/F guages that tap into your exhaust and you can mount in your cab so you can see what your mixture always is? Because I thought they were just for racing untill I seen a towtruck guy had one mounted on his dash...?
Last edited by Racerdave; May 7, 2003 at 01:59 AM.
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From: Oak Harbor, OH
86 351W: cold engine driveability problems
you have a holley 4bbl those two little screws are the adjusters, and you will probably need a special tool to turn them. I would take it to the guy who rebuilt the carb and have him adjust it.
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From: Oak Harbor, OH
86 351W: cold engine driveability problems
that Motorcraft 4bbl isn't a conventional 4bbl, its the 4 bbl VV (variable venturi) anyone remember those old POS? It was prolly in a car, or a medium duty truck, the 370s had them in the early 80s as did a few cars in the late 70s and early 80s.
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From: Still under the hood in O
86 351W: cold engine driveability problems
Racerdave - The A/F guage needs a wide band O2 sensor installed in the exhaust.
No problem on EFI but on a carb motor you need to have a bung welded in.
cjben - Does it smoke at all?
No problem on EFI but on a carb motor you need to have a bung welded in.
cjben - Does it smoke at all?
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From: Midwest
86 351W: cold engine driveability problems
I have looked to see if it is smoking, but can't see any smoke...the exhaust does smell like it is burning rich, and burns my eyes if I run it in the garage to long...thanks, Ben