302 cutting out under acceleration

winter1973 · May 19, 2019

my 1968 mustang 302 hesitates when accelerating

rbohm · May 19, 2019

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

winter1973 · May 20, 2019

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 · May 20, 2019

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 · May 20, 2019

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

winter1973 · May 21, 2019

Realmongo said:
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 · May 21, 2019

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

winter1973 · May 21, 2019

under light acceleration it runs fine

winter1973 · May 21, 2019

rbohm said:
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 · May 21, 2019

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 · May 21, 2019

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 · May 21, 2019

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

rbohm · May 22, 2019

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 · May 23, 2019

rbohm said:
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 · May 23, 2019

JmP6889928 said:
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 · May 23, 2019

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 · May 23, 2019

winter1973 said:
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;

Holley Accelerator Pump Discharge Nozzles

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2Blue2 · May 27, 2019

JmP6889928 said:
it has to be electrical.

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

rgsauger · Jun 1, 2019

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

302 cutting out under acceleration

winter1973

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rbohm

winter1973

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Realmongo

I prefer to be called "Evil Genius"

JmP6889928

You might slide out if you are going too fast.

winter1973

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winter1973

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winter1973

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winter1973

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JmP6889928

You might slide out if you are going too fast.

winter1973

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JmP6889928

You might slide out if you are going too fast.

rbohm

winter1973

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winter1973

New Member

JmP6889928

You might slide out if you are going too fast.

rbohm

Holley Accelerator Pump Discharge Nozzles

2Blue2

will be trying this sex one when I can find it

rgsauger

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302 cutting out under acceleration

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You might slide out if you are going too fast.

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will be trying this sex one when I can find it

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