Opener David Thomas struck 70 from 103 balls, while Clapham smashed a brilliant 138 from just 87 deliveries, including eight sixes and 13 fours.
The hosts racked up 243-3 from their 36 overs, the match having been reduced due to rain delays, with Valley using nine different bowlers.
Daniel Taylor (34) and John Flinton (36) battled hard but Valley fell well short on 133 all out, Perrie Bunton, Robbie Kerr and Scott Wilson bagging two wickets apiece.
Leaders Scarborough RUFC romped to a 154-run home win against Malton & Old Malton 4ths, maintaining the hosts' unbeaten start to the campaign.
Scarborough RUFC head coach Simon Smith (51) and rugby team skipper Matty Jones (49) shared a second-wicket partnership of 94, while Mark Kelly (34) and Simon Norris (28) also chipped in as the hosts posted 208-7 from their 35 overs.
Jones capped a superb day with 3-9 from his 10 overs, Phil Fletcher snapping up 3-6 from four overs as Malton crumbled to 54 all out.
Great Habton 2nds continued their fine start to life in the league with a nine-wicket success at previously unbeaten Flamborough.
The quality of batsmen Dan Walker (90no) and Jack Stockdale (75no) proved far too much for Boro, the second-wicket pair sharing an unbeaten stand of 170 to ease Habton past the home side's 172-7 from 40 overs.
Josh Garbutt's 86 had been the leading light of Flamborough's innings, fellow opener Andy Dixon chipping in with 33.
Walker scooped 4-20 and Harvey Wood 3-28, and then the former smashed nine fours and fours sixes in alliance with Stockdale to sweep aside a Boro side who are also hunting promotion.
The Stokoe family took centre stage as Ravenscar 2nds claimed a 60-run win against Wykeham 3rds at Snainton despite only having 10 players.
Skipper Jonny Stokoe (28 from 74 deliveries) and opener Les Hall (25 from 75 balls) shared what turned out to be a crucial half-century stand as Ravenscar posted 103-8 from their 40 overs, Robin Shepherdson bagging 3-10 from seven overs for Wykeham, who must have been confident of wrapping up the win at this stage.
The visitors had other ideas as Luke (2-18 in eight overs) and Daisy Stokoe (3-3 in seven overs) followed their father's batting effort with superb bowling, John Nelson also taking 2-4 as Wykeham slumped to 43 all out
Pickering 4ths, who have been struggling to raise a side so far this season, eased to an eight-wicket win against promotion-chasers Sherburn 2nds.
Matthew Bowes was the star man for the hosts, bagging five wickets as the nine-man villagers were dismissed for 61, Dan Bean top-scoring with 29 at number six after the top five batsmen fell for ducks.
Veteran John Kinghorn's 46 not out sealed a simple win for the Ryedale Sports Club-based outfit.
Thornton Dale 2nds conceded their home game against Cayton 3rds.
Division Three leaders Nawton Grange 2nds had to dig deep to earn a 21-run win at Ravenscar.
The home side looked to be in charge at the interval, as spinner Freddie Barker's superb spell of 5-16 pegged Grange back to 112-9, skipper Darren Smith hitting 35 and Byron Marshall 22.
Ravenscar looked to be in control at 71-4, but fine bowling from Smith (3-21) and Sam Degazon (2-7) sent the 10-man hosts crashing to 91 all out, losing their final five wickets for 20 runs.
Mulgrave 2nds remain second after a comfortable 106-run win at Malton & Old Malton 3rds.
The visitors racked up 207-8 from 45 overs thanks to solid batting from Chris Spenceley (59), Simon Kipling (37), Kory Boushall (36no) and Luke Jackson (34).
Josh Mann took 3-27 and Steve Chapman 3-48 for Malton.
Ben Duell's excellent 5-21 then helped the visitors dismiss Malton for 101, Alistair Blacklee carrying his bat for 41 not out while his teammates struggled to show any form.
Muston won by five wickets in their clash at fellow strugglers Ganton 2nds.
The home skipper Dan Reardon carried his bat for 54 not out as Ganton posted 139-9, Alex Smith adding 27, while Scott Orange took 4-49.
Former Filey and Hunmanby batsman Andrew Burrell then showed his class, as his 62 steered Muston to victory.
Folkton & Flixton 3rds claimed a 44-run home win against Filey 2nds, who are still searching for their first victory of the campaign.
The hosts were all out for 229 thanks to 52 from Harry Edwards and 45 from George Stephenson, allied to 32 by Jack Stephenson, and Filey made a good effort of their run-chase before being dismissed for 185 from 40.1 overs, Freddie Gunning taking three wickets for the home side.
Grosmont claimed maximum points as their opponents Heslerton 2nds conceded.