Timing reverse rotation engine

[KingofBeers]

I have a pair of chevy 305 in an early 80s Carver. The starboard is reverse rotation. The timing tab is in the standard location so everything is backwards. My question here is when using a digital advance timing light...can I still just dial in 8* and line up line on damper with large notch on tab no matter what direction the crank is spinning? Not a ton of info on this ive been able to find on the net.

 

[KingofBeers]

Another baffling thing on this subject was the total advance on port motor. At a 750rpm idle it had 20* of advance. I brought it back to 8*. When checking total advance it was off the charts crazy...like more than 50* at 2000rpm. I couldnt dial it back with my gun.

The motor seems to run well, just is stubborn to start when cold. Im not talking hard to turn over like you have with over advanced timing...it actually cranks pretty normally it just takes some time and a lot of dicking around pumping throttle to get it to finally fire up.

Both distributors are what i think are the factory dizzys with pertronix electronic ign conversion deals. Ive read and have had 1 person tell me these are garbage. Planning on putting HEIs in these but still need to time that reverse rotation bucket of bolts.

 

[rivermobster]

I have a pair of chevy 305 in an early 80s Carver. The starboard is reverse rotation. The timing tab is in the standard location so everything is backwards. My question here is when using a digital advance timing light...can I still just dial in 8* and line up line on damper with large notch on tab no matter what direction the crank is spinning? Not a ton of info on this ive been able to find on the net.

Move the distributer. Does the rpm increase? If so, you are advancing the timing. Watch what the timing marks do with the light, and you'll know which way to go.

 

[rivermobster]

Another baffling thing on this subject was the total advance on port motor. At a 750rpm idle it had 20* of advance. I brought it back to 8*. When checking total advance it was off the charts crazy...like more than 50* at 2000rpm. I couldnt dial it back with my gun.

The motor seems to run well, just is stubborn to start when cold. Im not talking hard to turn over like you have with over advanced timing...it actually cranks pretty normally it just takes some time and a lot of dicking around pumping throttle to get it to finally fire up.

Both distributors are what i think are the factory dizzys with pertronix electronic ign conversion deals. Ive read and have had 1 person tell me these are garbage. Planning on putting HEIs in these but still need to time that reverse rotation bucket of bolts.

From what you are saying, it Sounds like the balencer has slipped. You'll have to verify TDC and then check the timing marks to be sure.

I'll take a Pertronix ignition over most any HEI any day of the week!

Normal Performance timing is 35 degrees total with 15 at idle. 20 degrees of mechanical advance, no vacuum. But you must verify TDC first.

 

[KingofBeers]

Move

Move the distributer. Does the rpm increase? If so, you are advancing the timing. Watch what the timing marks do with the light, and you'll know which way to go.

I get that. Lets say there is 10* advance at idle. Will 10* advance dialed into a timing light zero the mark on both reverse and standard rotation engine? Assuming the damper hasnt slipped like you mentioned.

 

[rivermobster]

Since I've never timed one before, I honestly do not know the answer.

Shouldn't be hard to figure out though with the engine running and a timing light in your hand, by moving the distributor around.

Verify the marks line up at TDC FIRST!

 

[n2otoofast4u]

Car motor boat problems.

 

[KingofBeers]

Car motor boat problems.

Its even worse....backwards carmotor boat problems

 

[obnoxious001]

The timing light has no idea what direction the engine is turning, it just knows when the spark plug fires. That being said, of course the advance dial will work properly for the reverse rotation engine.

 

[DaveH]

I have a pair of chevy 305 in an early 80s Carver. The starboard is reverse rotation. The timing tab is in the standard location so everything is backwards. My question here is when using a digital advance timing light...can I still just dial in 8* and line up line on damper with large notch on tab no matter what direction the crank is spinning? Not a ton of info on this ive been able to find on the net.

yes IF the timing pointer/mark is at true TDC.

 

[mattyc]

TDC is TDC no matter which way the engine is rotating. Lets say you want to set base timing at 10deg btdc, on the reverse rotation engine, you would be using the atdc scale.