Defending champion Fuzzy Zoeller shares fourth place at 1-under-par 69. He is joined there by Allen Doyle, Larry Nelson, Doug Tewell, Vicente Fernandez, John Harris and Morris Hatalsky.
Wadkins struggled out of the gate. He bogeyed the short par-4 second as well as the par-4 third.
'I felt pretty good,' said Wadkins, who held the 54-hole lead at this event last year. 'I just had to kind of slow down and say, 'Wait a minute. You still have 15 holes to go. Let's see if we can get something started.''
He came right back to birdie the lengthy par-4 fourth and followed that up with a birdie at the par-3 fifth.
Wadkins steadied his play with five consecutive pars. He again notched back-to-back birdies from the 11th at Aronimink Golf Club.
The 51-year-old stumbled with a bogey at the par-4 15th, the longest par-4 on the course. He closed out in style though with a 12-foot birdie putt at the par-4 18th.
'The wind blew harder than it did in the morning, but it was also a little warmer and the ball might have been flying a bit better,' Wadkins said. 'So, I think it all equals out.'
The long-hitting Jacobs was in one of the first groups off the first tee and took advantage of the calm conditions. He birdied the second, but dropped a shot at the fourth. Jacobs then came back to birdie the par-4 sixth.
He then ran off nine straight pars before birdieing the par-5 16th for a share of the lead.
San Filippo, the reigning Senior PGA Club Professional champion, had six birdies and four bogeys during an up-and-down round that started on the back nine. He bogeyed his first, which was the par-4 10th. That hole played as the most difficult all day.
He came back to record two straight birdies from the 11th, but dropped another shot with a bogey at the par-4 13th. He made the turn in fashion with back-to-back birdies from the 17th.
On the front side, San Filippo birdied the par-4 first, but dropped a shot at the next. He responded with a birdie at the third, but stumbled to a bogey at the fourth after his second shot went over the green. He parred the final five holes to end at minus-2.
'I'm not an experienced hand, but I've been playing well of late,' said San Filippo, a tour rookie. 'I certainly was hoping that I could come and play like I know I can play.'