305 chevy reverse rotation

Reverse rotation Chevy uses a gearset in lieu of timing chain just as you mentioned. What this means is that the camshaft, distributor and oil pump all rotate as would a conventional rotating (LH) engine.

So, the crank rotates reverse. Means reverse main seals and I believe you are supposed to install the pistons 180 degrees rotated. I.e. the dot facing the rear of the engine. Can someone confirm this, please.

The firing order will be the conventional (LH) order with the #1 and #8 spark plug wires swapped position.

Captan 1
On this engine the only thing that turns reverse is the crank the cam, oil pump & distributor all turn LH. (normal)
I think the pistons are installed kattywampous
because of the side load put on them during the power stroke( if the piston pin is off set)
I,ve built auto engines before but this one is a little different.I've got a 4 bolt block & a nice set of 041 heads.The plan is to have the machine work done and put it together myself. Does anyone have a favorite cam. ( 0 - 5500 rpm) I'll call comp cams & see what they say.        - Thanks -     

62 Wood
      I haven't taken my engine apart so I'm
     not positive the crank & cam are gear
     to gear.I'd like to build an engine
     so I can swap them out. That's way I
     need the info before I send the stuff
     off to be machined.
      My boat is a 77 Ski-Tique and more fun
     than ''Just''about anything!
     Antique fiberglass is the way to go !!!

I have to respond to this as I have done quite a bit of research on "marine camshafts". First of all, you can't just throw in a "standard rotation" camshaft and a gear drive to turn it in the opposite direction as the crank and expect the engine to run backwards. The firing order will be wrong. For example: a small block chevy motor "standard rotation" has a firing order of 1-8-4-3-6-5-7-2. Now if you spin it backwards (CCW looking at the pulley end) the same crankshaft will need a firing order of
1-2-7-5-6-3-4-8 regardless of how you polish the thing for the bearings to last. But the automotive camshaft will still have a firing order of 1-8-4-3-6-5-7-2. So the valve phasing will be way off. Another thing about marine camshafts is that they are commonly ground with a wider lobe separation to give less valve overlap (time when intake and exhaust valves are both open). This reduces the likelihood of water getting sucked into the exhaust valve should it ever get past the riser in the manifold. The marine camshafts that come stock in most of our ski boats do have slightly higher lifts and longer duration than a stock automotive cam, however they have a less aggressive lift rate than a "performance" camshaft to increase longevity of the valvetrain.

79
Those gear drives are automotive type. When the crank and cam gears mate(no idler), its the crank ,not the cam that runs backwards.
The starter has to either be a reverse rotation unit, or mounted "backwards" on the flywheel.

As for the cam, when I ordered mine, Im pretty sure they had a listing for LH and RH rotation motors.

I know this is an older thread but it might confuse somebody on the difference between standard and reverse rotation. Each motor builder did it differently, GM, Ford and Chrysler all had their way of reverse rotating an engine. I had a friend who had a machine shop rebuild his Mercruiser reverse 305 out of a correct craft last year. He complained that he could not stop it from backfiring no matter what he did. He also had a Holley carb, power valve each time it backfired. I told him to bring it to my shop we would pull the engine and tear it down. We pulled the motor and began tearing the engine down. I was pulling out the camshaft and there was the problem. Stamped on the gear end of the cam was 1505, as in Sealed Power CS1505, a mild automotive cam for a standard rotation automotive engine. He ordered a correct cam and we installed it and the motor fired instantly on the test stand we let it run for 30 minutes with no problems. As far as I know, Melling is the only one still manufacturing these cams as a reverse rotation engine has become a lost art as the transmission is gearing is what changes prop direction on new boats.

Some of the parts in these engines may be interchangeable as to fit but WILL NOT function and can create problems.
CRANKSHAFT - Some of the reverse rotation cranks have the oil holes drilled symmetrically opposite. Check this closely.
CAMSHAFT - In the above combinations, none of the cams are interchangeable. The lobe timing and/or the distributor drive gear angle are different.
DISTRIBUTOR/OIL PUMP - In all of the applications we know of both the
distributor and oil pump turn the same direction regardless of the crank rotation. This is done by making the angle of the drive gear on the cam and its mating gear opposite when the cam turns the opposite direction. This makes the thrust of the gears in the opposite direction. For example, the SE Chevy thrust is up and is taken by the base of the distributor housing and the drive gear. If the cam rotation and
gear angle are changed, the thrust is down and there are no provisions for this in a stock distributor. A ball bearing distributor or magneto is required.
When working on Marine Engines be sure you know what the components intended usage is and do not vary from it.
This is a reverse rotation GM engine timing gear.

The above is for GM only as Ford and Chrysler both did things there way.

That Gear set is a great idea, Takes away all the worry about the correct camshaft and opens the door to using any of the hundreds of performance GM cams available.
It would be nice if Ford offered one for the 351W.