Engine assembly question

[John Fitzpatrick]

I recently read an article on engine building that stated you should be able to turn the crank over with two fingers with all eight pistons installed. It didn't state whether that was with a breakover bar on the balancer bolt or directly pulling on one of the counterweights, but it got me wondering, how much torque should it take to rotate the crankshaft on a newly assembled engine--plugs out?

 

[Bill D]

With heads and plugs installed, it will take more than two fingers to rotate the engine

 

[John_1949]

Not so sure about ford motors, but Chevy small block it should be about 35 foot pounds via a torque wrench and no more then 5 foot pound per cylinder as you are putting the engine together.

 

[Jac Mac]

Around 4 ft lbs per liter for the Block assy (eg: 302ci/5000cc = 20 ft lb ) for race engine, some higher tension ring packs etc on normal motors up to 8 ft lb per liter. The Bore/Stroke is factor in this also older rope rear seal etc add more still.

Bare crank only with all mains torqued- around 1ft lb ( you should be able to twist it by hand on the crank snout/damper area quite freely with no real resistance - No rear seal fitted ). A length of cord wrapped around the front pulley with a known weight for the pulley dia will give you a torque figure in this scenario.

Once the valve train is installed all bets are off due to spring rates etc, It pays to pre install valve train one step at a time in radical setups to check for interference etc. Some stroker applications MUST have the cam timed before turning the assy over in order to prevent the crank/rod assy from contacting the lobes- if a timing chain ever breaks on one of those babies there is a lot of mech mayhem in a short time frame.

 

[John Fitzpatrick]

Thanks guys.