Marine Chevy 350 Vortec Reverse Rotation - Explained

Hello everyone, this was a requested video from a viewer and had asked to describe and document the reverse rotation motor.

Details:
This is a 2007 Marine Power 5.7 Vortec. It does indeed have a roller cam/lifters. This motor is supposed to be good for 315 horsepower and is fed by a Holley 4150 4 barrel carb that has vacuum secondaries and electric choke at 600 CFM.

I have come across the unique application where this motor also in fact has a timing chain, and the cam spins CW with the CW crankshaft. This added a challenge to the distributor requiring a reverse cut helical gear to maintain CW rotation of the distributor. The tricky part is the reverse cut helical gears excerpt a downward force on the distributor shaft that has to be compensated by additional bearings.

[yunoguy]

Back in the day before companies started making GM HEI distributors for other brands of engines we modified one to fit in a small block Ford by making a sleeve to adapt it and a custom shaft with a Ford gear. In my first attempt it died after a few weeks and upon inspection I found that due to Ford having counter clockwise rotation and the direction of thrust being downward it had eaten into the pickup coil. If you're ever in a bind and need to use the ccw gear on a regular distributor it will work for a while and won't ruin your motor but eventually it will eat into the pickup and shut off

[ewell]

Great vid!! Best explanation of reverse rotation i've seen. Do you know how many discussions ended in arguments over this topic .Geez o Pete!! I have a 34 uniflite (1974) with crusader 454 with right hand engine. Thought about replacing with SBC . I pondered finding a standard marine sbc and do a conversion, but I have never been able to figure out exactly how. Maybe I can look you up, I'm tied up at Gwynn's Island in Mathews. Thanks for a great vid !!!

[guyprimo]

The oil journals are 180° off also the opposite rotation if the On crankshaft end towards the oil pump the crankshaft has been knurled to push the oil forward not so many people know that one just figure a little food for thought 🤔

[rhare]

I have rebuilt many marine engines and have never seen a reverse rotation engine like you described all of the mercruiser crusader marine conversions use gear drive cam to change the cam direction allowing the use of standard dist and oil pump, of course starter, water pumps are configured different one other internal change that not many builders know is that the pistons are pressed on the rods backwards the notch will face the rear this is cause the piston pin is offset if this is not done you can end up with cracked pistons

[guyprimo]

I forgot the opposite rotation engine usually has a gear instead of a timing chain

[TWillWin]

Just out of curiosity. You’d think they could make an oil pump that can run in reverse quite easily ? Also why not make the counter rotation happen in the transmission ?

[minx]

10:45 Chevrolet RHR uses a timing gear set instead of a chain . This makes the camshaft standard rotation reverse firing order. No need to use a modified distributor

[andrewarmstrong]

Backwards? A person with auto experience drives a marine parts counter clerk crazy. The engine spins opposite rotation to the other engine.

[mikejohn]

You wrote that your reverse rotation is CW. I’m assuming your looking at the motor from the flywheel? It should be CCW from the front. I’m asking because I have one of the same unicorn motors I’m dealing with.

[guyprimo]

They have also bi-directional water pumps this is just stuff for your viewers that's all so don't use automotive water pump because you're going to end up with the wrong one on one of your engines

[mrsamsung]

Sounds like a lot of work to have it ass backwards for no reason at all