Ok so I’ve recently built an swapped a 351 in my 90 fox it’s carbureted with ported gt40p heads msd 6lA-2 msd pro billet mechanical adv factory setting heavy silver springs f303 cam proform 750 My issue is I set the timing to 8degrees initial timing the car idles and revs great but as soon as there’s any load on the car it stumbles low rpm Is ok still not great under load any input will help I heard a lot of people say the f cam likes 12 to 14 degrees