What's the correct length for the main alternator belt for a '68, 327/350 w/o air conditioning or power steering? I had ordered one from a very reputable vendor, made by a GM-licensed manufacturer, and it measured 54 3/8" but was too long for the application. The belt that was on the car measured 52 1/2". Curious if anyone's run into this problem. While the engine is original to the car, I wonder if the alternator pulley is not correct? Its diameter is 2 5/8". Should the Rochester Q-Jet carburetor have an idle vent cover?
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Re: '68 Engine Questions
Joel------
I'm away from home right now, so I can't confirm the belt length. I have found, though, that from time-to-time, th "official" GM belt length doesn't fit right. I've never figured out why this is. The reproduction source for GM belts is probably providing the belt part number (and, therefore, length) that is the "official" part. Your alternator pulley sounds right. As I recall, it should be a stamped steel-type pulley.
ORIGINAL Rochester Q-Jets used for the 1968 model year did have a stamped steel cover for the idle vent. However, some later SERVICE carbs do not use an idle vent system like original carbs. So, for these carbs there is no idle vent cover nor is there the traditional idle vent.In Appreciation of John Hinckley -
Re: '68 Engine Questions
This is the kind of information that can be found in the AMA/MVMA specs that are available complementary to vintage Corvette owners from GM.
Also note that service replacement belts were often consolodated without adequate engineering review. In some cases 3/8" belts were replaced by 7/16" or vice versa without adjusting length to take into account depth in the pulley groove for different than OE belt width, or a slightly longer belt was substituted that was common to other applications.
Most of the aftermarket keyed off the GM service replacements, so the errors are throughout the industry.
In most cases you can use the AMA spec information to buy an EXACT duplicate or one that is very close.
Case in point is my Cosworth Vega. The service replacement belt was longer than OE, and proper adjustment could only be obtained by moving the alternator to the extreme of the slotted adjustment bracket and this caused the belt to infringe on the lower radiator hose, damaging it.
This was before the AMA specs were available, so I bought a new hose and took the original belt to a parts store where they had a tool to measure belt length, and I got an EXACT Dayco replacement, which was a standard belt in their catalog. GM never changed the improper belt number in their parts catalog, and it's still there, today, but the supply of lower radiator hoses was exhausted long ago.
DukeComment
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Re: '68 Engine Questions
Joel I do not believe you have the original alternator pulley. I have an original owner 68 327/350 built in FEB 1968. No power or air conditioning and my original alternator pulley is solid metal.
Weighs about 1 1/2 pounds. (weight obtained from scale used for personal weighing and the metal fan was not included).
Diameter is 3 1/2 inches
Depth of belt groove is about 3/4 inch
Top of belt wear area in groove is about 5/16 inch below the top of pulley.
Pulley groove is much thicker, about 1/4 inch, at the top of the back side of pulley towards the alternator. The front is thinner, about 1/8 inch, at the top of the pulley.
Pretty much a heavy duty piece compared to the stamped steel versions.Comment
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