Thread: UR Pulleys Belt Size?

It's been about 8 years since I changed the belts in my car. I have the two pulley set on my B13. Anyone remember what the belt size or # is?

If you don't find out somehow, take some string and measure around the pulleys. Go to the local Pep Boys and ask for a belt the length of what you measured with the string. Make sure the string follows the usual OEM belt path though. Also if you give them lengths in terms of inches I'm pretty sure they can give you the appropriate belt.

http://unorthodoxracing.com/install/Ultra_SS/04100170_.pdf

I just swapped in a 2 pulley set. A couple of tips:

1. Set your timing before you swap in the smaller crank pulley. Two reasons: 1) Many of the UR pulley's timing marks are way off; and 2) because of the smaller pulley diameter, the timing pointer will be so far away from it that when you move your head a coulp inches to site the timing marks you will experience several degrees of error. Basically, after you install the smaller pulley you will never be sure what your base timing is. You might want to even physically mark 15* and 19* on your distributor mounting bracket for future reference -- in case you want to retard your timing in the future for emissions testing or to install a modded ECU or something.

2. Don't forget to have a front crank seal handy in case you have an oil leak.

Now, on your question about belt size, I found an issue with this guidance from the UR instructions:

Alternator without Air Conditioning - Use Gates K040310 (31 5/8” or 805MM), alternate belt size use K040315 (32.25” or 820MM).

I bought the larger belt (820mm) because I thought it would be easier to get over the pulleys and I could tighten it up with the adjustor. But I found that it was too long and could not be properly adjusted. Go for the shorter belt in this instance (w/o AC only).

Good luck with your install.

Bill

billc,

Thank you very much for the very informative post

I was thinking that was the case with th Pulleys, but now I know for sure

Thanks for all the info guys.

Look everybody, installing a UR crank pulley to ex track more HP from your Sr20 is not a good idea, sure you can get a extra 8-12 HP, but you are internaly putting your engine out of balance, out of its harmonics, and could wind up causing it to grenade.

I'm not trying to argue with anybody, just words to the wiser!


But do what you must do....lol



BTW: Hell the part isn't even manufactured right, the timing marks aren't even right on it, that ought to red flag it right there, its a bad part, don't fvck with it.

well i have yet to "grenade" a motor with ur pulleys. been running them on my former n current sr20 no problemos. and yeah, go for the shorter belt because once it starts to stretch overtime you will want the smaller one to be able to tighten it. otherwise you will find that turning the wheels at a dead stop or anyothertimes it floats because its not making contact.

i havent found any conclusive evidence that these pullies will blow your motor. there are ALOT of people who are running these on their 350z,g35's and others. all with no problems

there are alot of sentra/sr20 guys and 240 guys that run these pullies with no problems what so ever, robchaos is one that ran it for over 130k miles no problems and is running them on his current naturally aspired motor.

i think you are even less likly to blow anything up if your motor is fully internaled with aftermakret parts and fully balanced.

im not arguing with anyone but i avent seen any kinda solid 100% evidence that suggest these do harm. and even if you do have someone woh tries to place oil or bearing related problems on a pulley, there isnt 100% way to tell if it was a pully or if it was mechanical failure on other mechanical parts ie: bearing install,bearings age,oil related problems, oil pick ups,oil pump,ect....its just to hard to narrow all auses down to one single thing.

Well, to be realistic, you are talking maybe gaining 3 WHP from the 2 pulley set.

And the issue of harmonics and balance has been discussed many times over the years -- even going back to the SE-R Mailing List, the grandfather of The Dash. The general consensus among many very knowledgable SR20 people is that there is little risk associated with installing the pulleys on a DE.

One benefit that has not come up in this thread is that the pulleys slow down the DE water pump which is a good thing because it keeps it from cavitating (basically stopping to pump water because of the physics of the design) at high RPMs. This can cause over heating, especially on a road racing course when you spend long stretches of time at high RPMs.