4 letters:
bart, cart, dart, fart, hart, mart, part, tart

5 letters:
abart, ahart, apart, blart, carte, chart, clart, daart, dartt, dmart, dpart, fahrt, gkart, haart, hardt, harte, hartt, heart, kaart, karte, kmart, kwart, lyart, mahrt, marte, narte, parte, scart, slart, smart, spart, start, svart, taart, tarte, tartt, vaart

6 letters:
assart, astart, bogart, charte, comart, copart, damart, depart, e-mart, ecarte, emhart, gocart, hobart, homart, impart, jumart, k-mart, kabart, mccart, op-art, oxcart, popart, robart, smartt, staart, tryart, tygart

7 letters:
astarte, bi-mart, bizmart, bossart, calmart, carhart, clamart, clipart, compart, dalhart, daypart, denhart, dispart, dogcart, eckardt, eckhart, elkhart, exparte, fedmart, foumart, gabhart, gayhart, gelbart, go-cart, goulart, hardart, hilgart, hughart, jiomart, lenhart, linhart, lockart, manhart, massart, mccartt, miswart, neuhart, newhart, neyhart, outpart, oxheart, p-chart, parpart, pickart, plupart, pop-art, purpart, rampart, rempart, restart, schardt, subpart, swigart, teacart, tipcart, unheart, upstart, walmart, wishart

8 letters:
alfamart, anti-art, autopart, banghart, barnhart, baumgart, bickhart, bosshart, capehart, carhartt, castpart, champart, dinehart, disheart, diskpart, dumpcart, dustcart, earnhart, eberhart, eckhardt, everhart, folk-art, forepart, foulmart, fulimart, fullmart, gabehart, gayheart, gayomart, gephardt, golfcart, goodhart, hackbart, handcart, inkheart, isambart, isenhart, jetsmart, kithcart, lanehart, leaphart, lenhardt, lienhart, linhardt, lockhart, massmart, meinhart, minecart, minehart, minimart, outsmart, outstart, overpart, pancarte, petsmart, ponycart, pushcart, re-start, redstart, reinhart, rinehart, rockmart, rothbart, shughart, tub-cart, two-part, urquhart, wal-mart, wisehart

9 letters:
applecart, arsesmart, barnhardt, baumgardt, baumhardt, betschart, billycart, bonaparte, booksmart, bornhardt, bosshardt, breitbart, brillhart, britomart, cyclekart, dagenhart, degenhart, descartes, earlimart, earnhardt, earnheart, eberhardt, engelhart, everhardt, flockhart, flowchart, four-part, goodheart, headstart, horsecart, hypermart, indiamart, instacart, interpart, jumpstart, kallapart, kickstart, lionheart, looksmart, luckhardt, luftfahrt, mediapart, meinhardt, misdepart, mollebart, moneybart, mouthpart, multipart, nosesmart, postkarte, reinhardt, rhinehart, rinehardt, set-apart, smithhart, steinhart, stuttgart, swinehart, undercart, underpart, weinhardt, wockhardt, wohlfahrt, wolfheart

10 letters:
alphasmart, benachbart, blackheart, bump-start, buonaparte, cold-start, deviantart, faintheart, familymart, glassheart, greenheart, horse-cart, jacquemart, jfreechart, jump-start, kick-heart, kick-start, leichhardt, lion-heart, middelfart, open-heart, pricesmart, push-start, rhinehardt, steelheart, steinhardt, stop-start, sweetheart, whip-smart

11 letters:
counterpart, dragonheart, false-heart, false-start, hammerheart, himmelfahrt, kwik-e-mart, openclipart, schnurrbart, speisekarte, strongheart, travelstart, white-heart

12 letters:
pseudo-heart, schweighardt, street-smart, thunderheart

13 letters:
ansichtskarte

14 letters:
bleeding-heart, heart-to-heart

16 letters:
state-of-the-art

2 letters:
ct

4 letters:
dirt, fort, girt, bert, pert, mort, sort, curt, hurt, port, burt, tort, wart, kurt

5 letters:
snort, alert, quirt, court, inert, shirt, forte, chert, torte, exert, abort, swart, sport, short, quart, spirt, overt, flirt, avert, blurt, skirt, spurt

6 letters:
invert, import, assert, exhort, unhurt, revert, resort, cavort, thwart, desert, escort, squirt, insert, divert, deport, turret, assort, extort, stuart, report, udmurt

7 letters:
convert, concert, dessert, athwart, subvert, distort, consort, pervert, purport, comport, contort, support, disport, unalert, yoghurt

8 letters:
reassert

9 letters:
transport, extravert, overexert, reconvert, worrywart

10 letters:
disconcert, animadvert