KB 2.4 pulley questions, Whipple guys cmon in too!

[JA$ON]

Searched a bit a couldnt find the info I'm looking for. Dana gave me a good reply on Modfords, I just wanted to see whatcha local guys have to say about it.

I will more than likely have a 2.4 going on the car shortly. My dilema is that I was to run it @ 17-18 PSI on the street-pump gas (hopefully will delay the inevitable), and kill mode will be 23-25 PSI on a race tune and race gas (110 octane).

I have a 10 lb lower available to use and would like to use it on kill mode to reduce belt slippage. I was thinking a 10lb lower and a 3.75" or 3.5" upper for the track.

But then the dilema for the street is with a 10 lb lower and 4" upper (largest I have seen) is 21 PSI, which is too much for pump. I have no problem swapping lowers for track days, but then the alternator problem arises.

What size, if any, would be appropriate for the alternator to let me use a 10lb lower and a 6lb lower (street)??

I dont necessarily have to use the 10 lb lower, but want as little belt slippage as possible @ ~24 PSI.

How much slippage could there be with say, a 6 lb lower and a 3" upper for 25 PSI? I do have a RR manual tensioner, BTW, and an aux idler. So that would be for the track, and then a 6lb lower and 4" upper for 17 PSI street?

Or, if there is a better pulley solution that would fulfill both PSI ranges, please let me know

Thanks
Jason

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[rdsnake]

im in the same boat as you...it hurts my head to think about it!

 

[03RedCobra]

I've got the 2.4L K/B, with a 6# Lower.

I use a 3.75" upper on street duty (~17#)

I use a 3.50" upper for track duty (~21#)

I have on a 3.70" diameter Alternator pulley. Now, with that size, I have had problems with 2 Alternators, but then again, they were PA-Alternators, so, I think no matter what size pulley I had on there, there was still probably going to be a problem anyhow. I switched back to a stock alternator with the 3.70" pulley, and have had no problems for about 1000-miles.

With the 10# lower, I'm not sure what diameter alternator pulley you would need, but probably somewhere in the neighborhood of close to 4". There is a chart on ModularFords.com that has been posted several times, and it gives recommendations on pulley sizes for alternators, and I believe they do use a 10# pulley as one of the examples.

I hope with that 91-Octane gas you have to use, that you are not running too much timing ?? I have 17-degrees of timing on my street tune, with 93-Octane.