1952-59 Ford motor stutters while under load

I've been banging my head on the wall, now It needs spackle. I have a 1990 rebuilt 5.0 with a rebuilt 4 bbl carter carburetor (thanks Jeff ) and a gm style hei distributor. I have the car timed at 10 btdc and the car stutters when under a load. I've changed the timing to 6 btdc and have the same thing but only worse. The car runs great when idling. I've played with the air fuel mixture screws and does not seem to help. I'm not sure what to do next, was wondering if it could be the distributor. Also the motor came out of a mustang which uses platinum spark plugs, I left the ones the machine shop installed which are not platinum. Any suggestions would be a great big help.

 

These Ford HEI's seem to like about 12 degrees timing,I would go back to the original spark plugs it called for.

 

What brand is the HEI ? most of the cheaper ones need the advance curve set up to suit your engine . Throw away the timing light and use a vacuum gauge to set your timing , much better result every time .

 

Check it doesnt have a vacuum leak around intake manifold (i usually squirt wd40 around perimeter. If the engine changes when you do you have an issue. Just because it idles fine doesnt mean you dont have a leak. Also check or byp*** the pvc valve. Check which port is suplying vacuum to the advance pot on the distrubutor if it has one. Above the ****erflys give a very different result from below the ****erflys.
If you suspect carb can you swap for a known one?

 

Your Carb has two ports for distributor vacuum looking at the front of the Carb the large center port is PCV vacuum the left one is if you have an emissions equipped car the fitting to the right is where you should have the distributor vacuum hooked up to.The HEI you have has a 24 degree mechanical advance with vacuum hooked up and timed at 12 degrees you should get 36-38 total which seems to be the SBF's "sweet spot".

 

You say the motor stutters under load. A common cause of this is a broken/cracked distributor cap. Spark plugs leads cross arcing. Easy way to check is watch the engine running whilst in a garage with the lights off.
Sounds stupid but it will show up arcing problems.
Also check that you haven't got leads crossed.

 

Thanks everyone for the info. I will recheck everything this weekend and see if I can figure out what her issue is. I will let you guys know what I find.

 

After 1985 the firing order changed in the 302/aka 5.0 here is a handy chart,it is common to get this mixed up: http://www.aa1car.com/library/ford_firing_orders.jpg

 

I had that problem once. I closed up the spark plug gap by .005 and it ran like a different motor.

 

Also, you should be around 12-14° initial timing to start with.

 

i had the same issue with my 302. it turns out that the hei was not the way to go. I got one of the 60 buck electric dizzy from ebay and a coil and it totally changed the way my car runs. so much smoother and seems like more power. i did lose the pop out of the exhaust when i changed it but i dont mind.