1955 ford 272

[whatdoyouwant]

Ever since I rebuilt my car in 1990. When I wind up the engine prior to shifting from first to second or from second to third, I get a backfire and really no power. Once I hit highway speed and back out of the throttle, it runs great. I have done all the tune up many times and changed the cam shaft , another new timing chain, and even ground the valves on another set of heads and installed. I read somewhere that maybe the carbon wire are not putting enough spark to the plugs, and that solid copper core are better. One other thing I was thinking was, would weak valve springs cause this kind of reaction.

any help or ideas would be great.

[1930artdeco]

Vacuum leak? Cracked dist cap?

Mike

[Oldgearz]

Maybe something with the distributor advance isn't working right. Your description sounds like it doesn't like rapid full throttle. Also check accelerator pump in carb?

[miker98038]

Just how tight are you winding it up? Do you know what valve float feels and sounds like?

[dmsfrr]

Originally Posted by whatdoyouwant

... When I wind up the engine prior to shifting from first to second or from second to third, I get a backfire and really no power. Once I hit highway speed and back out of the throttle, it runs great. ...
any help or ideas would be great.

Originally Posted by Oldgearz

Maybe something with the distributor advance isn't working right. Your description sounds like it doesn't like rapid full throttle. ...

The timing advance in '56 and earlier Y-block Loadomatic distributors is controlled only by a very low vacuum signal from a year matching original carburetor. They do not have any mechanical timing advance. Photo example below.

If the carburetor isn't original, the vacuum canister has failed or the hardware of the points mounting / advance plate is stuck... you'll get no timing advance and it won't run quite right at more than approx half throttle.
Similar internal hardware problems apply to improved '57+ distributors but a little less often.

Check that the timing advance at higher rpm's goes at least 10° beyond the initial setting at idle.
Also check the gap or dwell settings of the points are at correct specs before setting the timing.

https://www.ctci.org/gilsgarage/crac...aust-manifold/

https://www.ctci.org/vacuum-advance-mechanisms/
.

[mercman from oz]

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[whatdoyouwant]

Thanks for the responses. I have the correct dist and carb for the car. I have determined with a timing light that there is advance when opening the throttle. I have new points, condenser, dist cap and new carbon wires. I am winding it up to accelerate and no, I don't know how valve float feels. That is why I was thinking maybe I have weak springs. I have new springs coming and will try to install them without removing heads. I guess we will see.

[wellcraft17]

What carb, size of main jets, and power valve do you have? Sounds to me like you maybe running out of fuel at a higher RPM.