Slant six 225 Stumble

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Slantsix64

Slantsix64

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Having this issue suddenly happened while driving my slant six 225. . when i give it a quick rev it stumbles and will almost die. i can still drive the car but have to grandma the motor until it pick ups speed. the first quick rev i give it will stumble but if i keep doing it will be fine after the first stumble. So say i do three quick revs the first one will stumble and the other two after it will be fine. what i have tried and eliminated our the followings

1. Rebuilt my carb checked the acc plunger it was fine still swaped it for a new one. after all that it still did the same thing so i swaped over another carb that was a good runner and it did the same thing so i dont think its my carb. i use a 2280 holley and a carter bbd the gas was clean have a new tank and cleaned out my lines.

2. i checked for vaccum leaks i put my hand over the top of the carb and the motor died right away which means i dont have a leak or else it would still be running

3.i swapped my dizzy for a new one checked the cap and rotor they are brand new with no signs of wear almost, also swapped my ecu box and coil. but the problem is still there.

The timing chain i installed on the motor was new but i'am thinking that is my next place to look. background on the motor its been rebuilt and has good comp my set up is a 225 slant six with a a833 4 speed thanks in advance all advice is welcome and hope i did not confuse the **** out of you.lol
 
was the cam degreed in properly?
 
IMO this is an accelerator pump problem.
It could be pump-timing but I think the well was dry or low, or the pump is not conforming to the housing or the check system is faulty. And yes it could be low fuel level,too.As well, it could be the linkage, or it's adjustment.This can easily be checked with the engine off. Pop the filter house off, and get eyes on the pump nozzle(s). Then, ever so slowly, begin to open the butterflys, and at a steady pace, run them to WOT . Fuel must come out of the nozzle immediately, and it must be a steady stream with no lazy dribbles, and should last all, or most, of the way to WOT..
It be the power-valve system as well.Probably one of these is not working right.

I suppose it could be a weak coil as well,(but you said you changed that) or late timing.The factory timing is very lazy. Most guys say they are running 10* or more base timing.
The statement that it just "started suddenly while driving" is a bit perplexing tho.Unless you just got a load of bad gas.Or you just set the valves, or you just installed new plugs.
And it does it with two different carbs.... It sure sounds like a lean issue.Maybe you got gas with too much ethanol?
Plug gaps too wide for the coil have been known to cause a stumble, but it doesn't go away after a second or third stab.
A too-tight valve lash can cause this as well.But it will be worse when warm, and get better with rpm, being worst at idle.
BTW
Putting your hand over the carb will not find a vacuum leak, cuz you just starved the engine for calibrated fuel. In order for the engine to continue to run with your hand over the airhorn, with an assumed vacuum leak; that leak would have to have it's own fuel supply, cuz you just dried up the regular channel.The engine is pretty sensitive that way; I mean getting the right amount of fuel with the right amount of air.
 
Last edited:
wanted to update the thread
i found the issue and fixed it i ended up re-adjusting my valves a little looser and wow what a difference it made really woke up my motor. thanks for every ones advice!!
 
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