283 -"backward" pistons?

Was the motor you are rebuilding a reverse rotation engine to start with? And did the crank and pistons come from a reverse rotation engine as well? If the crankshaft was a counter rotating one and in good condition, there's no need to have it ground. The reason for grinding a crank in the reverse direction is to get the journal surfaces correct so you don't wipe out a bearing. So if it came from a clockwise rotating engine it will need to be ground CCW. On your pistons, I would check with the manufacturer about installation. I believe most pistons produced today do not use any offset on the wrist pin. But check with them to be sure. You are going to need a reverse rotation camshaft (must have). I know of 3 companies that supply reverse marine camshafts. They are: Clevite, Federal Mogul and Compet*tion Cams. Comp Cams has a library on cores and will grind any specs you want into a cam, however they cost the most as well. The only other thing that I know of that you will need is a drive gear for your distributor for reverse direction. This is also a must have. The oil pump and distributor from a CW rotation engine will work as long as you change the drive gear. All other pieces of the engine,... bearings, cam drive chain etc. will be the same. You will need to unbolt and change the indexing of the velvet drive pump if it came from a CW rotating engine. You will need to do this before bolting it to the engine obviously. That's all I can think of. Anyone else want to chime in?

One thing to keep in mind is piston to bore clearance. Others on this board have learned this the same way I did....the hard way.

Marine engines need a looser piston fit than automotive engines. This is due to the larger temperature swings a marine engine sees due to running cool lake water through the block and piston temperatures being higher due to the higher load factor of a marine engine.

The pistons I used in my 351W called for .0015" minimum clearance in an auto application. My machine shop hadn't done any marine work and didn't know the difference (nor did I) and set the clearance to 0.002-.0025". The engine ran great for 25 hours and then scuffed 2 cylinders.

I had the block rehoned with .0035" to .0045" clearance and the engine ran great for the 50hrs I put on it this season.

If the wrist pin is offset then it will effect the piston travel within the cylinder depending upon which side the offset is. For instance if the wrist pin is centered then it makes no difference and the distance between the centerlines of rotation are the same if it is mounted up or down all you need to keep in mind is valve clearance if the piston dome is notched, (high compression type set-up). Now if you have an offset wrist pin depending upon which side the offset is on, the top of the piston will be slightly higher or lower when compared to a centered wrist pined piston. This happens because you have change the centerline distances between the crank and the wrist pin (centerlines of rotation). Now this can be compensated for by changing the connecting rod length. But you have to look at several other things as well, piston skirt clearance, valve clearance, head clearance, and a list of others. So if the engine is designed and spec'd with a specific offset and rod length you need to use it unless you know what your doing and compenstate for everything, otherwise it's going to take a couple of engine rotations during break-in before it comes apart, sooooo don't stand too close and get hit by the rod as it flys through the block and on the ground.

Thanks for the input so far!
Can anyone tell me ,since my crank is standard and doesnt need to be turned,is it ok just to have it polished backwards? Im using the 283 crank from the original truck motor.

I'm not sure if polishing alone would be enough. But you could get .010" oversized bearings and turn the crank down then have the block line honed???? Also Tim brings up a great point because it effects the crank seals as well. So you may have to get a new crank as well.

62 wood wrote: BTW has anyone ever figured out WHY they ever started running motors backwards? It would seem so much easier to just use LH props? It would sure make things easier.

The experts here have answered that before- the idea was to have to have the rotation of the prop counteract the weight of the driver (rather than exaggerate it). In the newer CC's with the 1.23:1 tranny, the rotation is switched in the transmission- the engine is standard rotation.

David F,
It makes sense in twin engine installations.

TRBenj and David,
Ive heard the torque/driver offset before and it kinda makes sense, however the ironic thing in this case is ,this motor is actaully going in one of my "other" boats (ok I have to admit it, I have something other than just my 64 C C American Skier..but still an inboard! :0 ) Its a wooden 1962 Higgins that happens to have left-side controls..meaning the engine could have run right to offset the driver...go figure.

dont forget that you CAN use a standard rotation engine and switch the direction of the tranny pump.

Nate,
The reverse rotation Im talking about is the crank-spin direction.
This boat has the flywheel facing back ,like the 76 nautique I used to have was. The Chris Crafts were always famous for small block Chevy flywheel-forward set-ups. In fact I have one of those motor/trans set ups in the barn. I just couldnt bring myself to using it. I never liked seeing that big -ugly flywheel when you open the engine cover. (plus if you were to start putting some HP into those set-ups,all you had "holding" your tranny was the harmonic balancer key way.)

In fact my 64 Correct Craft american Skier has an inline ford motor- that happens to be a flywheel forward set-up. Its the first Correct Craft Ive seen with that style motor/trans. The flywheel on it is pretty small, making it a little less noticable tho.
So many options....