Adjusting OD down from 25% to 15%

[pablon2]

I am trying to figure out the best configuration for 15% OD with the pulleys and belts I have. Pulleys I have are stock Crank and JS pulleys, 10% 10-rib JS, 10% aluminum crank pulley, and 5% 10-rib SC pulley. Belts include the stock set as well as the belts needed to run an MP 25% OD setup.

Option 1: I figured I could run the 10% OD JS since it allows me to run a 10 rib on the SC, a 5% OD on the SC and then the stock crank pulley (heavy metal though). I don't recall if the pulley on the MP 10% JS that routes to the crank is stock size? I believe it is in that the 10% OD factor for that JS should come from the pulley section that goes to the SC, right? If this is true then I should be able to run a stock length belt from my stock crank pulley to the MP 10% JS, correct? I have all the belts I would need to run this combo. This seems to be the best route for ease of assembly given the belts I have, but may sacrifice performance with the metal stock crank pulley.


Option 2: Run the 10% crank pulley (I like it b/c it is aluminum), stock JS and 5% SC pulley. Doing this would mean I am running an 8rib belt from the stock JS to the 10 ribbed SC pulley, not sure how I feel about doing this in the event the belt travels onto the extra ribs and becomes misaligned. I would conceivably need two new belts....one to run from the 10% crank to stock JS and then one from stock JS to 5% SC pulley. Not sure what the sizes would be.

Any other ideas you guys have or opinions on options #1 and #2?

 

[90blkbrd]

I am trying to figure out the best configuration for 15% OD with the pulleys and belts I have. Pulleys I have are stock Crank and JS pulleys, 10% 10-rib JS, 10% aluminum crank pulley, and 5% 10-rib SC pulley. Belts include the stock set as well as the belts needed to run an MP 25% OD setup.

Option 1: I figured I could run the 10% OD JS since it allows me to run a 10 rib on the SC, a 5% OD on the SC and then the stock crank pulley (heavy metal though). I don't recall if the pulley on the MP 10% JS that routes to the crank is stock size? I believe it is in that the 10% OD factor for that JS should come from the pulley section that goes to the SC, right? If this is true then I should be able to run a stock length belt from my stock crank pulley to the MP 10% JS, correct? I have all the belts I would need to run this combo. This seems to be the best route for ease of assembly given the belts I have, but may sacrifice performance with the metal stock crank pulley.


Option 2: Run the 10% crank pulley (I like it b/c it is aluminum), stock JS and 5% SC pulley. Doing this would mean I am running an 8rib belt from the stock JS to the 10 ribbed SC pulley, not sure how I feel about doing this in the event the belt travels onto the extra ribs and becomes misaligned. I would conceivably need two new belts....one to run from the 10% crank to stock JS and then one from stock JS to 5% SC pulley. Not sure what the sizes would be.

Any other ideas you guys have or opinions on options #1 and #2?

I can tell you mixing 8 and 10 rib pullies is not an issue. At the moment I'm running 6 and 10 rib pullies.

Option 3. If you are permanently going to 15%. I recommend under drive pullies and the 15% MP 10 rib setup for the JS and SC pullies. This is what I was running and I think this is the very best combination for 15%.

 

[pablon2]

I can tell you mixing 8 and 10 rib pullies is not an issue. At the moment I'm running 6 and 10 rib pullies.

Option 3. If you are permanently going to 15%. I recommend under drive pullies and the 15% MP 10 rib setup for the JS and SC pullies. This is what I was running and I think this is the very best combination for 15%.

I won't put UD pullies on as I don't care to slow down my alternator and water pump. In just 5,000 miles the alternator is already showing signs of being overworked due to my electrical add ons. I think I need a 200amp 3g. But damn....$300

 

[90blkbrd]

I won't put UD pullies on as I don't care to slow down my alternator and water pump. In just 5,000 miles the alternator is already showing signs of being overworked due to my electrical add ons. I think I need a 200amp 3g. But damn....$300

What did you do, install a microwave?

In those 5000 miles how often was the car driven? What I am getting at is, is it being overworked because it sat for a week, month since that last time it was driven and it is just charging a drained battery. If my car has sat for more than a week or 2 and I know I am driving it the next day, I try to remember to throw the trickle charger on it the night before. I am planning on getting a battery tender for it.

I've had under drives on both of my SC's and never had any issues. You could check with Ryan A. Harris and see if he still has a stock diameter crank pulley laying around.

 

[pablon2]

What did you do, install a microwave?

In those 5000 miles how often was the car driven? What I am getting at is, is it being overworked because it sat for a week, month since that last time it was driven and it is just charging a drained battery. If my car has sat for more than a week or 2 and I know I am driving it the next day, I try to remember to throw the trickle charger on it the night before. I am planning on getting a battery tender for it.

I've had under drives on both of my SC's and never had any issues. You could check with Ryan A. Harris and see if he still has a stock diameter crank pulley laying around.

I have a stock crank pulley. I usually put the battery tender on the car when not driving it for more than a few days. Unless there is a draw the battery should not be down after sitting for two weeks. It has sat for five months and I checked it and it read 12.6v. Might be just the surface voltage, I don't know for sure.

 

[91BLOWNBIRD]

I am dealing with the same issue and I spoke with Charles about it and he said stock crank and 10%JS and 5%SC to keep the 10 rib to insure no belt slippage (more important than lighter pulleys or underdrives).

 

[90blkbrd]

I have a stock crank pulley. I usually put the battery tender on the car when not driving it for more than a few days. Unless there is a draw the battery should not be down after sitting for two weeks. It has sat for five months and I checked it and it read 12.6v. Might be just the surface voltage, I don't know for sure.

The reason I mentioned Ryan is because he used to make aluminum stock diameter crank pullies.

I am dealing with the same issue and I spoke with Charles about it and he said stock crank and 10%JS and 5%SC to keep the 10 rib to insure no belt slippage (more important than lighter pulleys or underdrives).

I disagree. I don't think anyone should have belt slippage at 15% on a MPx when using the stronger tensioner springs and a good belt. The weight savings between a aluminum crank pulley and stock pulley are substantial.

I've been running 15% OD on a 8 rib belt for 2 years now and I've never found any signs of belt slippage.