302 cutting out under acceleration

[winter1973]

my 1968 mustang 302 hesitates when accelerating

 

[rbohm]

there are a myriad of things that can be the problem here, what have you checked into thus far?

 

[winter1973]

I built the engine & it has all new parts in it . I bought all my parts to throught Summit racing, & after getting it together & having the problem. I started replacing parts to try to resolve the hesitation problems,when I accelerate the car when Iam driving it. When iI have it in the garage & run the engine performs great, its only under a load when it acts up. I have replaced spark plugs ,spark plug wires,coil, distrubutor,carburetor,fuel filter,fuel pump,& it hasn't resolves the problem,& I have have the distributor advanced to 36 max advance seams to run best there.

 

[Realmongo]

When you say it hesitates, is it when under a heavy acceleration (such as when you floor it), or is it when under a light acceleration when gently speeding up from say 35 to 40 MPH?

 

[JmP6889928]

Sounds like the distributor could be off a tooth if it runs best at max advance.

 

[winter1973]

When you say it hesitates, is it when under a heavy acceleration (such as when you floor it), or is it when under a light acceleration when gently speeding up from say 35 to 40 MPH?

under heavy acceleration

 

[winter1973]

Its under heavy acceleration. when diving the car with out jumping on it ,it runs ok

 

[winter1973]

under light acceleration it runs fine

 

[winter1973]

there are a myriad of things that can be the problem here, what have you checked into thus far?

running the car under light acceleration it runs fine ,its only under heavy acceleration when it acts up.

 

[JmP6889928]

If you know the distributor is in on the right tooth, the from there-What carburetor? Have you checked float levels and accelerator pump to make sure it squirts as it should? Also, does it have a mechanical fuel pump or electric? You might check fuel pressure.

 

[winter1973]

I have a msd dirtributor# 8352 & I have a quick fuel hr-series carburetors hr-450,the float levels are half way up,primary power valve is 6.5hg,it has a mechanical fuel pump holley&fuel pressure is 5.5 to 6.5

 

[JmP6889928]

Maybe valve lash too tight? I'm running out of ideas...LOL

 

[rbohm]

start by getting the accelerator pump shot right, i think that is where you issue will be. you probably need a larger pump squirter to get a bit more fuel into the system to prevent the hesitation.

 

[winter1973]

start by getting the accelerator pump shot right, i think that is where you issue will be. you probably need a larger pump squirter to get a bit more fuel into the system to prevent the hesitation.

thank you for all the information . I will try a larger accelerator pump.

 

[winter1973]

Maybe valve lash too tight? I'm running out of ideas...LOL

thank you for all the ideas. I will try reajusting the valves.

 

[JmP6889928]

Thinking about this.....if there are no mechanical issues with the engine (correctly assembled), timing is correct, fuel system is performing correctly, and valve lash is correct, it has to be electrical.

I would try grounding the distributor directly to the battery and see if that might be the issue. I had a 1975 Ford Torino that had some issues similar to this after a rebuild of the 351 and I grounded the distributor and it all went away. Perhaps the distributor is not picking up a solid ground on the engine block.

 

[rbohm]

thank you for all the information . I will try a larger accelerator pump.

no no, not a larger accelerator pump, a larger accelerator pump shooter, aka discharge nozzle;

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[2Blue2]

it has to be electrical.

Start with all grounds.
Also a defective coil will behave as you described.

 

[rgsauger]

Ignition problems show up under load. Ditto's on checking the coil, grounds, etc.