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Mustang Technical Discussion > Pre 1973 > car runs differently/better when warm > Community Forums > Mustang Forum Australia - Mustang Tech

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seany-boy
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Hiya, well finally found this site - yeah I know you can't help some people but finally made it Very Happy

The 351C has a bit flat spot when cold or dies on initial acceleration - not sure which is best description- and needs some choke to run well and overcome this when cold. Also prefers a fair bit of choke on starting. when warmed up no choke needed and no flat spot- car runs great once up to temperature generally. The idle revs also seem to pick up when car is at normal temp.
It has a 750 DP so possibly a bit over carb'd but seems to like the juice.

Is this normal or something i need to look at as it has been a while since I had a carburetored car?

sean


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gbx78
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Welcome!!! .. great guys in here!! and very helpful! and the ladies woooahhh hot hot hot .. oh wait thats a different site Razz ..

im not one to give advice on mechanicals .. however along time ago i used to have a 351C with a 750DP that did the same thing.. my mechanic at the time said to put a 1 inch spacer between the carby and the manifold .. it fixed up that flatspot pretty good.

thought id mention it.. some of the experienced guys no doubt will be able to help and may advise differently . Very Happy


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Shaunp
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It's lean when cold.


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IGALOP
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Yep, agree with Shaunp, cold idle attention needed.


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seany-boy
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thanks guys. I was thinking about the idleness of it. Does this simply mean I need to readjust the idle mixture or is there something else to put some attention towards?
Would the idle mixture screws make more difference when cold?


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hybrid
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Check your float heights too.


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seany-boy
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done , at least as per instructions Smile


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ponyride
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Joined: Aug 15, 2010
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Location: Perth, W.A.

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seany-boy wrote
Hiya, well finally found this site - yeah I know you can't help some people but finally made it Very Happy

The 351C has a bit flat spot when cold or dies on initial acceleration - not sure which is best description- and needs some choke to run well and overcome this when cold. Also prefers a fair bit of choke on starting. when warmed up no choke needed and no flat spot- car runs great once up to temperature generally. The idle revs also seem to pick up when car is at normal temp.
It has a 750 DP so possibly a bit over carb'd but seems to like the juice.

Is this normal or something i need to look at as it has been a while since I had a carburetored car?

sean


I'll bow to more knowledgable people on the mechanics of it but that all sounds perfectly normal to me. That's why carby engines have chokes, they don't run smoothly or have good acceleration without help from choking (richer) until they'vey've warmed up.

I'd be cautious about changing any settings if it runs OK with some choke and is fine when it's warm.

My 2C.


Rick.

Old things amuse all minds.

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BOSS289
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You will usually have the car carrying on a bit when it's cold due to the incorrect heat which helps to ignite the fuel within the combustion chamber.

Once the engine has reached its operating temperature (around 180-185 farenheit) the fuel mixture is then condensed better with the in coming air.

Also, obviously re-setting idle mixture and engine vacuum (power valve) will help to eliminate some of the slight stumbling when cold as well.


Cheers,

BOSS289


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donoauto
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Usually they run ok cold if you nurse them. It's a great way of the engine telling you " Don't thrash me yet, I'm too cold!".
That's why i went EFI, i'll teach it a lesson!! Make me headbutt the steering wheel when you're cold!


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gbx78
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BOSS289 wrote
You will usually have the car carrying on a bit when it's cold due to the incorrect heat which helps to ignite the fuel within the combustion chamber.

Once the engine has reached its operating temperature (around 180-185 farenheit) the fuel mixture is then condensed better with the in coming air.

Also, obviously re-setting idle mixture and engine vacuum (power valve) will help to eliminate some of the slight stumbling when cold as well.


Cheers,

BOSS289


Ahhhh now that was well explaind thanks!!


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mert
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Once the engine has reached its operating temperature (around 180-185 farenheit) the fuel mixture is then condensed better with the in coming air.


Minor observation... the fuel would not "condense" better at a higher temp, it vaporizes... and the operating temp of the engine will marginally affect the mixing of the air fuel mix in the carb, if hot intake air was better no one would bother with cool air induction systems to the carb... cool air is denser and that means more power when combustion hits...

Conversely, one of the explanations for poorer performance on start up is the theory that as the carb and intake are cooler, some of the fuel does condense on the walls, and as temps are lower in the carb/intake prior to entering the cylinder fuel vaporization is reduced. = apparently "leaner" mix than when warm = poorer detonation. As the engine warms up vaporization increases, smaller drops = larger surface area of fuel droplets = "richer" mix when warm (as the engine see it, the carb is still doing the same thing..) ... and runs better...


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Ausjacko
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but how did the egg get in the bottle?


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jas24zzk
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Ausjacko wrote
but how did the egg get in the bottle?



JUST LIKE THIS



Jason Pigdon
Pigdon Automotive Services
Historic Smash Specialists
3/1 Burgess Road, Bayswater Nth, Vic.
(03) 9761-4801

PS: Forgive me for I was jilted by peterp

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ponyride
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Location: Perth, W.A.

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jas24zzk wrote
Ausjacko wrote
but how did the egg get in the bottle?



JUST LIKE THIS


"
Now there's a blast from the past. "Why is it so?"


Rick.

Old things amuse all minds.

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