Logo

318 reverse rotation

johnnyred

New member
Can anyone tell me what makes

Can anyone tell me what makes a 318 a standard rotation and what makes it a reverse rotation. I have a 24 Lyman with a 318 velvet drive and the prop says Right Hand. I also checked with Doc Lyman and he said it is right hand. I am putting in a rebuilt and I want to make sure I buy the right motor. A Mechanic told me that standard rotation is left hand and right hand is reverse rotation. So I am a little unclear.
 
Do a search on this discussion

Do a search on this discussion for engine rotation. There is a great deal of previously posted info here.
 
"Look at the front pulley of t

"Look at the front pulley of the motor (looking aft). If it's turning clockwise, that's a 'standard rotation' engine. If not...

How are they different internally? Was that your question? The pistons are installed the other way around to reduce piston slap (the pins in pistons are offset); the cam is reverse ground, with the distributor gears cut to turn the distributor and oil pump the other (ie: normal) direction). Also, in some cases, crank seals are different to prevent oil loss.

Jeff"
 
"Many thanks, I will take a lo

"Many thanks, I will take a look at the front pulley to see if it turns clockwise or counter clockwise. Appreciate that fast response.

Cheers,
John"
 
"Johnnyred,A reverse rotation

"Johnnyred,A reverse rotation motor means opposite automotive rotation.The starter is different rotation,The camshaft is different,distributor drive shaft is different.The pistons should be installed the same way according to the chrysler service manual(when they go up and down they don't know which way the crank is going).The port engine on a twin screw would be automotive rotation.A single screw would be reverse rotation unless you have a left hand prop(Pretty rare on a single)."
 
"Must stick nose in here:

&


"Must stick nose in here:

"The pistons should be installed the same way according to the chrysler service manual(when they go up and down they don't know which way the crank is going)."

Where have you read this? I'm curious to see how this can be since the reason for piston offset is to keep the skirt of the piston from smacking the wall as the rod goes past over-center. Since the rod moves over-center in the opposite direction in a reverse rotating motor, then not putting the pistons in the opposite way would cause severe piston knock.

Jeff"
 
"one thing that has not been m

"one thing that has not been mentioned here is that chrysler marine engines have serations on the back of the crank so a Lm318bwr would have serations going one way and a Lm318bwl would go the other way. in otherwords the crankshaft is different according to the rotation. pistons are put in backwards on reverse 318,340,360,426 and 440. the cam,starter,oilpump drive gear,and crank must be addressed. the neoprene aftermarket seal rarely holds on a 440 so a rope seal must be stuffed and cut at a precise angle to seal. remember also that a bidirectional front seal should be used 3619687 which fits all chrysler marine engines that are v/8 thanks keith"
 
Back
Top