Reverse Rotation Crankshaft Question

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dodgetkboy78

dodgetkboy78

EDELBROCK HEADS SUCK!
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SOMEONE has to know.........

Besides the grooves on the seal journal, is there a difference between a standard rotation crank and a reverse rotation crank?

:read2:

CHrysler marine is very vague, but say you need a directional crank.........
 
It's a gear to gear drive right? I thought so myself.
The cam turns backwards.

As far as I know (Which aint much about them) everything else is the same minus the big gears under the timeing chain cover and the way they grind the camshaft.
 
I think I got this one all screwed up!
 
Hu what?

Chevy's that turn backards are gear to gear, I'm not sure if Mopars are, considering this is the only Mopar reverse rotation motor I have ever seen aprt.

The 360 I built, has a ghose oiling problem, and kills rod bearings, due to a hole in the casting, the machine shop didn't catch.

Now I am building a 318, and just paranoid.
 
I'm quite sure the only difference are the grooves on the seal surface, like you had stated.
 
Reverse rotation should require a different camshaft. Cam lobes are not necessarily symmetrical. Reverse rotation on a normal cam puts the lift on the close side and vice versa. The same amount of lift is still available, the rev rotation motor would be bass ackwards in terms of how it gets there.

You'll also need a reverse spin starter.
 
just don't get it mixed up and accidentally put it in your car instead of the boat... WHOOPS!
 
GM used the gear to gear cam drive. This way you can use a standard rotation cam. The crank runs "backwards" while the cam runs the "normal" direction. If the cam runs "normal" direction then the oil pump will not require a special drive gear to rotate the correct direction. Can't run an oil pump backwards. If you can find a gear to gear cam drive any motor can be reverse rotation without really changing anything else internally.

Running a motor backwards is an old short circle track trick until someone caught on. On a reverse rotation motor the engine torque tries to twist the body toward the left and not the right like a standard rotation motor.


Chuck
 
i think op was asking about crank differences only......

cams are different, yes, i have a scott brown custom for my reverse rotation 318.....but the question that nobody could ever answer me when i rebuilt mine, was if the pistons go in backwards since the major and minor thrust surfaces are opposite of conventional rotation engines.
in my case, my aftermarket pistons have zero wristpin offset, it didn't matter, but it was/still is a question i always ask the marine guys and they can't give me a straight answer (i think i know the answer though).....
 
Yes, an offset piston HAS to go backwards, because the piston is pushing on the rod on the opposite side of the crank now....

Get this..


Mopar small blocks have had rods with offset in the past, what would happen if you had then in a RR motor??

I need a new cam, where is yours from?
 
i ordered mine thru scott brown....my brother deals with him and has his contact info......comp wouldn't/couldn't grind me a reverse rotation cam.......
 
I've read that piston pin offset was only used to keep the pistons quiet when cold and putting them in backwards gave the rods a slightly better angle twards the crank on the power stroke. Never heard of the offset rods except for stuff that wasn't drilled right, I guess it would put more meat on the rod where its needed.
 
dodgetkboy78 said:
SOMEONE has to know.........

Besides the grooves on the seal journal, is there a difference between a standard rotation crank and a reverse rotation crank?

:read2:

CHrysler marine is very vague, but say you need a directional crank.........
Click to expand...
Yes this is an ancient thread, but if you still have that 360 reverse rotation crank, I need one. BTW, there is more to a reverse rotation crank than the opposite direction oil sling grooves. The oil holes from the main journals to the rod journals are drilled at the opposite angle as well as the chamfering of the holes. Turning the crank a few thousandths to eliminate the sling grooves does solve the constant oil leak at the rear main seal. However the crank rotation will limit the amount of oil that gets to the rod bearings; and will starve the rod journals at high rpm.

So with that, if you have already learned this and you still have that crank sitting in your garage because you thought something was wrong with the journal RMS run out, I'm an interested buyer.
 
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