My 66 L72 motor has just been rebuilt and I was installing a new idler belt on it today. The belt doesn't seem to be tight, it's not loose enough to come off the pulley but it doesn't seem to be as tight as it should. Can anyone tell me how tight this belt should be, if it isn't tight enough, what could be causing the problem, this belt is from paragon and is supposed to be an exact reproduction. I know I have both correct pulleys as I have checked and double checked this, any ideas.
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Re: 66 Big Block Idler Belt Questions
correct belt and pullys : if thats so then installing the idler fan belt is a bear. usually have to install the belt and h20 pump simultaneously. good luck, mike -
Re: 66 Big Block Idler Belt Questions
I have the same problem on my '67 427. The old belt is slightly shorter than the Paragon replacement. That coupled with a potentially smaller belt cross section 1/64 or so, allows the belt to ride deeper in the pulley which results in a loose fit. The old one was not tight either but did fit better. With no take-up idler this is the best you'll get these days. This belt does little anyway as the water pump/fan are primarily driven by the main belt. The paragon replacement has the correct dimensions +/-.Comment
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Re: 66 Big Block Idler Belt Questions
I have the same motor ,I have quanta replacement belts (cut wrapped style)and when installing I had to loop it onto the bottom pulley and then into the water pump pulley and then pull it up with slight fource to slide it over the water pump,Again this was a struggel to slide it up and onto the water pump.Comment
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Re: 66 Big Block Idler Belt Questions
How does this belt fit? Is it tight? I have around a 1.5 inch play in mine. Is this normal?Comment
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Re: 66 Big Block Idler Belt Questions
NO mine fits like a glove.doesnt squeal.
With a inch and a half of play that means you would be able to just slide it on on off.
Whos belts are they?How do you know you have the correct belt?
What pulleys are you running.I can go out and see what numbers are on my belts.or post a picture of how it fitsComment
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Re: 66 Big Block Idler Belt
Jim, While you may have a belt that is not accurate in lenght there is another possibility. If the engine mains have been alingbored it will bring the C/L of the crank closer to the water pump. I believe there is a shorter belt made for this case but I'm not sure who sells it.Comment
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Re: 66 Big Block Idler Belt
Mark, that must be the problem, I know the mains were alignebored. Do you know if this shorter belt has the correct p/n and is of the correct style? If not I will just get a shorter one from paragon, they are made from the original molds.Comment
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Re: 66 Big Block Idler Belt
Jim - align boring will affect the crankshaft to camshaft distances no more that a thousanth of an inch or two, it will not cause and perceptable difference in the water pump to crankshaft distance that would ever be noticed in a belt length. I would check your pulleys first, if you are certain you have the right belt. You should have a 480 water pump pulley, this pulley is a wide groove 2 sheave unit with an OD of 7 1/8". The crankshaft pulley should probably be the 108 cast iron 2 groove unit, which is still available from GM last I checked....CraigComment
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Re: 66 Big Block Idler Belt
agree with craig: in order to effect idler belt fit, the machine shop would have to raise the centerline of the crank a half inch or so and align boring that much from the block would make it useless. mikeComment
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Re: 66 Big Block Idler Belt
Jim, Sorry for the confusion. I agree with Mike and Craig that alignboring will in no way account for the excessive play you have. Incorrect pulleys and/or belt are most likely the culprit. However, I did some research this AM and found that Long Island Corvette is the vendor who sells a W/P belt this is listed as "shorter". How much shorter LIC will have to answer but I suspect it is for use in an engine that has been reworked. Good luck.Comment
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Re: 66 Big Block Idler Belt
Mark, I have checked the pulleys again and both are correct. The only thing I changed since the motor was rebuilt was the 480 pulley. I have two of these and used the newer one, but I have compared both and don't see any difference. Do you know how tight this belt should be, its not loose enough to come off the pulley but it sure doesn't seem tight enough to do anything. I was told by someone to check the belt tension by pressing in on the belt and see how much it moves, when I did this, the belt moved around 1.5 inches. Is this too much?Comment
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Re: 66 Big Block Idler Belt
Jim, The 1.5 deflection is definately too much. I get about 0.5 inch deflection on mine and I would consider this to be on the loose end. If the pulleys are correct then it must be the belt. Paragon lists the length of the GM belt as 34.40. I believe an auto parts store can check your belt length and that may point you in the right direction. Have to go now and get ready for the road tour to the Convention which just happens to pass throught Mike McCagh's farm. Can't wait! Good luck.Comment
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Re: 66 Big Block Idler Belt Questions
Hi Jim,
I have a 67 big block and when installing the Belts from Quanta had the same issue (Too Loose), I phoned Quanta and they informed me there was two different sizes for my motor and subsequently supplied the correct one.
MylesComment
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