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1978 Cadillac SDV (Commodore Blue Met.)
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Discussion Starter #1
While swapping the stock single plane intake manifold on my 78SDV 425 with the stock 500 manifold it was discovered that my AC system is inoperable n needs to have the compressor replaced n system recharged. I plan on fixing this but not for awhile. In the meantime i have begun removing the AC system n all its components. My question is, with the compressor removed i now need a smaller belt to replace the existing one which now doesnt have the pulley on the compressor to go around. Does anyone happen to kno what size belt that would be? Or the proper way i would measure to figure out the size needed? The new one will be going around the power steering pulley n the pulley down below. Anyone who can share any knowledge of experience with this would be greatly appreciated! Thx alot n have a good week everyone!
 

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The first hit simply searching, "how measure engine v belt"

 

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1978 Cadillac SDV (Commodore Blue Met.)
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Discussion Starter #3
The first hit simply searching, "how measure engine v belt"

Thanks FTSS, thats on me bein lazy, ive began to skip the google search from time to time lately due to it leading to a migraine n producing no useable info so often, i appreciate ur help tho, thx
 

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I had immediately imagined using a rope, just wanted to know what the most "accurate" dia. should be to match to the pully typical groove profile. Voila! 1/4"! They even make emergency repair cuttable rope kits.

My default for intel is ALWAYS search first and cherry-pick attractive hits, then follow-up online where it leads, or maybe an intelligent-sounding specific request on here. The trick is learning to think like a search machine - no nuisance articles, pronouns, conjunctions, punctuation etc. etc. Just highest-to-lowest prioritized (and fewest possible) keywords. I find Duck Duck Go best smartest hits / least distracting other glop. Eezy Peezy
 

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1978 Cadillac SDV (Commodore Blue Met.)
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Discussion Starter #5
I had immediately imagined using a rope, just wanted to know what the most "accurate" dia. should be to match to the pully typical groove profile. Voila! 1/4"! They even make emergency repair cuttable rope kits.

My default for intel is ALWAYS search first and cherry-pick attractive hits, then follow-up online where it leads, or maybe an intelligent-sounding specific request on here. The trick is learning to think like a search machine - no nuisance articles, pronouns, conjunctions, punctuation etc. etc. Just highest-to-lowest prioritized (and fewest possible) keywords. I find Duck Duck Go best smartest hits / least distracting other glop. Eezy Peezy
Yeah ur absolutely right lol, theres a thread i found on here covering just what i was lookin for, im still getting used to the forum, this is my first one, so now im home from work n starting to work on car n im noticing that i have a steel fuel line that seems like itll be in the way if i try to run a shorter belt from the ps pulley to crank pulley, ive come across some ac compressor delete pulleys when searching for parts, what r ur thoughts on those? On the other thread on here they talk about also just replacing the fuel line with a steel braided one so u can position it out of the way and then go ahead n use the shorter belt. Would one of these fixes be better than the other? I kinda feel like the delete pulley is soundin better, i wouldnt want the steel braided line to somehow wiggle loose n come into contact with the spinning belt, plus wouldnt have to bother with a fuel line if i went that route. I was really hopin to get this done this evening tho but i dont think the parts store will have either of the things i need to do so.....shoot!
 

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"diRtyD'ville78, "
1. ......i have a steel fuel line that seems like itll be in the way if i try to run a shorter belt from the ps pulley to crank pulley,
2. ive come across some ac compressor delete pulleys when searching for parts,
A. what r ur thoughts on those?

3. they talk about also just replacing the fuel line with a steel braided one so u can position it out of the way and then go ahead n use the shorter belt.
B. Would one of these fixes be better than the other?

4. I was really hopin to get this done this evening tho but i dont think the parts store will have either of the things i need to do so.....shoot!

A = No.
B = No.
4. It's been 7 days, so have you completed a temp workaround? If not, you could have easily gotten all the AC work done by now. All too often a "temporary solution" winds up the "lasting state", and the car could spend the rest of its (and your) life with it with no AC. Just fix the car the right way the first time. Sorry, but you asked. Good luck.
 

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1978 Cadillac SDV (Commodore Blue Met.)
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Discussion Starter #7
"FTSS"
Sorry for not posting any updates on this issue, ive told myself i would be better about this, as ive found it disappointing when so many threads ive searched on here relating to common interests, problems, etc. that i have dealt with that are full of good useful info but then abruptly end without any explanation of whether or not their work was a success or failure. Now that i have began to post on here i see how easy it is to do. So anyways, thanks for the interest. I got the job done without much trouble the following day after my last post. I didnt wanna bother with the ac delete pulley as i woulda had to wait atleast another day for the part to arrive since the auto parts store doesnt have them in stock. Which was fine cuz i never fancied that route much to begin with. After getting everything torn apart n the first belt outta the way i could see that there was no way i wasnt gonna have to move the fuel line. So i did just that, chopped it off, routed it under n around the distributor, threw the new shorter (48") belt on, said screw it this radiator is old n will break soon enough im sure so picked a new one up n while i had the easy access to it i switched that out too! Installed my double hump crossmember last night n havin my duals installed today or tomorrow. Really been gettin after it lately n im pretty stoked on how well things have been turnin out! Best of luck to all u out there doin work on u caddies as well!
 

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Thanks for the follow up. I hate it when there is no follow up to whether it was fixed or not.

To answer the original question: How do you measure for a belt? This is my technique.

First I make sure the alternator or power steering pump (or wherever you use to tighten the belt) is centered within its range of movement. I use a 12 gauge piece of stranded electrical wire. Its stiff enough that you can pre-bend it to get around the bottom pulley and still be able to grab it from the top. Then mark it where it overlaps on the top pulley with a sharpie, take it off and measure it. Then buy a belt that size, the next size smaller, and the next size bigger. I find that the one size bigger is usually correct, as we measure the bottom of the trough of the pulley, but the belt seldom touches that and rides higher in the pulley groove supported by the v in the sides of the belt. I then take the other two belts that don't fit back and exchange them for another belt of the size that actually fits and I keep that extra one in the trunk.
 

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1978 Cadillac SDV (Commodore Blue Met.)
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Discussion Starter #9
Yeah that sounds like a good method. As for buying a few sizes of belts at once, this is something i learned lol, first trip to store i bought what i had thought, at the time, was the correct belt but got home n couple min later realized it was too big, it fit was almost tight enough when i had the power steering pulley pivoted all the way out, either way i wouldnt have wanted it like that, what really sucked was when i had gone to the parts store i had just beat closing time, so even tho it didnt take more than just a few mins for me to realize i needed a diff belt as well as only living 2 or 3 min away from store, i was gonna have to wait another day to finish the job n that was a bummer, when i returned to store i was sure to grab a few sizes n the 48" was the one that worked just right for me, id like to go back n redo the fuel line i had to cut out n reroute, i just ran a piece of rubber fuel line from end to end n tightened w/ hose clamps, my first choice would be to bend some new hard line like was originally there, but im not sure how difficult that would be for me so im thinkin what ill probly do is just end up replacing the rubber line w/ a braided steel one, basically the same fix i did but more aesthetically pleasing....we'll see
 
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