Underdrive pulley diameters ?

David Neibert

SCCoA Admin
I'm trying to determine what rpm my alternator is spinning at 1000 rpm engine idle, and need to know the diameter of the March or ASP underdrive crank pulley (accessory belt portion) and the alternator pulley to figure that out.

Thanks, David
 
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David, I still have an SCI underdrive crank pulley that I never installed because it was slightly heavier than the ASP pulley. When you come over to help my put my car back together, we can look for it.
 
David, I still have an SCI underdrive crank pulley that I never installed because it was slightly heavier than the ASP pulley. When you come over to help my put my car back together, we can look for it.

Kurt,

The crank pulley diameter is the one I need most, and the ASP brand looks to be the same as the March pulleys I'm using. Not sure what diameter the SCI pulleys are, so I don't know if that will work. I don't have a set a calipers or I'd crawl under the car and measure it myself.

David

PS: I've got plans for Friday and Saturday is my Annivesary, so if you want to get your car back together this week, we need to do it by Thursday.
 
I'm trying to determine what rpm my alternator is spinning at 1000 rpm engine idle, and need to know the diameter of the March or ASP underdrive crank pulley (accessory belt portion) and the alternator pulley to figure that out.

Thanks, David

The SCP underdrive pulley i have is 6.127" across the outside part of the pulley.I could not measure inside where the belt runs -calipers not long enough.
 
Kurt,

The crank pulley diameter is the one I need most, and the ASP brand looks to be the same as the March pulleys I'm using. Not sure what diameter the SCI pulleys are, so I don't know if that will work. I don't have a set a calipers or I'd crawl under the car and measure it myself.

Why don't you just PM Ryan Harris?
 
David,

On my March pulleys I get a crank diameter of 6.872" and the alt is 2.910"

Stan

Stan,

The 6.872 dimension sounds like the supercharger drive portion. I need the acessory drive portion of the pulley, which sould be very close to 6.000 diameter. Can assume those dimensions are to the top of the ribs ?

David
 
Stan,

The 6.872 dimension sounds like the supercharger drive portion. I need the acessory drive portion of the pulley, which sould be very close to 6.000 diameter. Can assume those dimensions are to the top of the ribs ?

David

I have a underdrive crank pulley I could check tonight.
Do you want top of ribs or groove measurement?
 
Stan,

The 6.872" dimension sounds like the supercharger drive portion. I need the acessory drive portion of the pulley, which sould be very close to 6.000 diameter. Can assume those dimensions are to the top of the ribs ?

David

That 6.872" is from the 7 groove portion of the crank pulley. The 8 groove portion is smaller. Yes, that dimension is to the top of the ribs.

Stan
 
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That 6.872" is from the 7 groove portion of the crank pulley. The 8 groove portion is smaller. Yes, that dimension is to the top of the ribs.

Stan

Stan,

The 7 groove portion is for the jackshaft pulley, I need the OD of the 8 groove portion measured at the top of the ribs.

Thanks, David
 
Stan,

The 7 groove portion is for the jackshaft pulley, I need the OD of the 8 groove portion measured at the top of the ribs.

Thanks, David

My bad. :( My pulleys are setting on a shelf and I thought the 8 groove portion was for the blower like it is on the jack shaft pulley to the SC.

I can get the other measurement for you after work but after some digging I guess my pulleys are made by ASP not March if it makes a diff. I only bought them about 16 years ago....

Stan
 
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