Green’s Dictionary of Slang

crankcase n.

also carnal crankcase

1. the scrotum.

[US]Driving Daisy Crazy n.p.: He does not know, has not yet decided; he will play it by ear, and with the advantage of a thoroughly drained crankcase to clear his head.
[US]‘Ward Fulton’ Forbidden Family Game n.p.: My crankcase was drained and I was getting the last of her juices.
[US]‘David Crane’ Naughty Lady Mechanic n.p.: Although he had recently emptied his balls all over his wife, they were full and swollen again, his carnal crankcase filled with oil.
[US]‘David Crane’ Wife in the Backseat n.p.: ‘Hummmm? Shall I make the piston pump? Shall I get the driveshaft working and drain off your crank¬case?’.
[US]Erica’s Sex Toy n.p.: And this is indeed a special occasion. The draining of his crankcase.
[US]‘Terry Moore’ ‘The WEarly Years’ 9 www.nifty.org 🌐 [T]he driver pushed the knob of his spit soaked stick shift forward, balls deep into Terry’s mouth, and discharged a mansized load of overheated spunk from his crankcase into Terry’s belly.
[US]Hustler Taboo July/Aug. 51: [H]e whips out the dental jaw spreader and props Alexis's chop¬pers wide for an easy draining of his crankcase.

2. the vulva/the virgina.

[US]‘Kenneth Harding’ Keep It in the Family n.p.: ‘Mack, she can’t wait for you. I put a quart of oil into her crankcase, so you better sponge her out or you’ll have a buttered bun to work on’.
[US]‘Maggie Kaye’ Somewhere Over the Orgy n.p.: The wicked witch of the West wanted to get Dipstick’s dipstick in her crankcase so desperately that she tried everything she could think of to make him come plow her oozing bottom-land, but Dipstick never stirred.
[US]‘Deane Christopher’ ‘Heels’ www.nifty.org 17 Nov. 🌐 What I wouldn’t give to slide that dipstick of mine up inside that tight little crankcase of hers.

3. the rectum,in the context of anal intercourse.

[US]‘William Watts’ ‘A Tragic Love’ www.nifty.org 28 May 🌐 ‘I'll lube the piston while you grease the crankcase,’ I said to him, hoping he understood.
[US]‘BigBadJon’ ‘Wifebeater Bo’ www.nifty.org 25 Apr. 🌐 My rod was going to blow in someone's crankcase before the day was over.