Belt Sizes - OEM, aftermarket and decipher

[centralcoaster33]

Hello, I need some help with belt sizes please. I have a 1995 240sx with a KA24DE engine. I have a three part question related to three belts. AC, Water pump with fan with PS, and Alternator.

What are the stock belt sizes and part numbers please?


What do the part numbers mean please? I think it shows a rib count, length, maybe width or thickness, whatever is known for sure.

Lastly, I have been saving an Unorthodox Racing SS Aluminum underdrive crank pulley. I'd like to install it. I have misplaced the little peice of paper that came with it telling me some belt sizes or perhaps it was part numbers for Dayco... What belt sizes and part numbers do I need for my pulley please?

Thank you.

[asoomal]

Ditch that pulley, it'll do more harm than good.

Stock sizes according to Contitech

PK030395 PS Multirib Belt
PK040305 ALT Multirib Belt
PK040355 AC Multirib Belt

[centralcoaster33]

Hmmm, I'm thinking about ditching it. Is it because of the seal? Is it because there's no harmonic damping or what? Harmonic has to do with crank twisting, but flywheels don't have rubber insulation for balancing. I don't understand and haven't read anything scientific about it. However, I have read a lot, but all I've found is just heresay and comment. Do you know of any real comparison data for a crank pulley with and without a damper?


Thank you very much for the spoon fed belt sizes.

It appears that the first digits in a belt number are for the ribs and the second set of numbers are for the length. Like the PS is 3 rib and the Alt and AC are 4 rib. I haven't found any correlation to the width (beyond rib count) or thickness of the belts. Perhaps the letters define that.

[krash]

Moved to 240sx Tech

[compactfean]

You're better off using the stock crank pulley because it dampens vibration at higher rpm. Think of hitting 2 pieces of pipe together. Itll vibrate so bad itll hurt you're hands. Than do the same thing holding those pipes with some rubber insulation, nor only will it prevent the vibration from your hands but it will absorb most of the vibration eliminating damage to your ”hands” (bearings) the ”pk03” refers to ribs, the ”0395” is how long the belt is in mm I believe. Of the rest of your pulleys are Unorthodox pulleys go to there website and download the installation instructions for your pulley set. It will have the recommended belt sizes for the under drive pulleys.

[centralcoaster33]

Hey guys, thank you for the information and opinions. I appreciate them.

I did try to get on with the manufacturers website but it's been down for a couple weeks now. I'm not sure when, if ever, they will have it up again. I won't put my email address in their temp webpage for security reasons.

I read up again on general engine harmonics. Sadly, I find no specific data for our engines, where the resonate frequency lies in RPM's, deflection angle measurements, etc. So I can't make an educated decision based on personal usage (where I drive and where I wish I drove in certain RPM situations). So, I found out about the risk... it's only crankshaft failure. No Biggy right? I did not find any other risks other than a potential variance in timing at some point that is unknown to me (I'm sure the engineers at Nissan a few decades ago know it). Anyway, I searched for broken, cracked and failed crankshafts in KA24DE's. I only found one and as it turned out, it was not his crankshaft but some extension to make an Xtreme (or some X brand) flywheel work with his ka-t setup I think. So, no one, with any of the solid aluminum CP's has bothered to report or admit to toasting their engine or breaking a crank. I'm willing to be the first.

I'm not sure why I never thought of this but... while getting some random belts from the parts store, I mentioned I was going to return some of them after floating them over the pulleys to check their sizes. He said, 'why don't you tie a peice of string around them for measurement?' Freaking Brilliant! I'm not sure why I didn't think of this. Anyway, at home I asked the fiance if we had string and she thought of yarn only. That stuff is stretchy but made me think of present wrapping ribbon. So, I'm gonna take some ribbon to the pulles at minimum and maximum tensioner posistions. Then I'll know the min. and max. belt lengths to use. I will try to follow through with posting my measurements for others to find in the future since UO support is down.

[compactfean]

Can't you just call them? The ribbon idea is a pretty goods idea. As far as when your crankshaft gets harmonically ” active” is past like 7k rpms. (at least that's when sr's do) check out Mazworx manufacturing, they had a written article about it.

[centralcoaster33]

Follow up: I chickened out. I put the stock pulley back. I'll accept my gains from removing the AC and the clutch fan. I also did not measure with a ribbon due to laziness. Thanks for your help though. Feel free to email me if you'd like to buy my pulley for maybe 100 bucks. U.R. Alluminum SS underdrive pulley. Timing marks are real (unlike ebay item) and seal portion has stainless steel collar.

[compactfean]

Its all good man. I'm putting a new motor in my 200sx and the front main seal was leaking because of the ua pulley so I went back to stock.