What's "air gap"?

[TZmtrsprt]

I always see "air gap" mentioned when changing and adjusting clutches. What is it and how do you adjust and measure it when you have a one piece Lakewood bell housing? I have a 68 Camaro small block with a stock Muncie M21. I'm getting ready to pull the motor and trans and want to blueprint/align the bellhousing while it's out. Can you adjust the air gap at the same time? How do you get a feeler gauge to measure it in the Lakewood housing? It's probably simple but.... Any advice is appreciated. thanks, TZ

[chicane67]

The importance of measuring the distance between the clutch disc and the flywheel in order to fine tune the amount of release necessary for peak performance. This distance is called the air gap and by manipulating the amount of clutch release (or air gap) we (you) can lengthen or shorten the time it takes to engage the clutch, therefore effectively increasing or decreasing reaction time.

To adjust the air gap it is necessary to fine tune the amount of pedal throw, as this controls how far the clutch cable will pull the clutch fork. Often, the best way to do this is by building a pedal stop that will limit the throw of the clutch pedal. With such a device you can adjust your air gap and tune reaction time without going inside the bellhousing. Building a clutch stop for your ride also has an added benefit. By limiting the clutch throw you will not over engage the pressure plate, which is known to cause premature clutch failure. In just a few hours you could built a super-strong adjustable clutch pedal stop for next to nothing.

[TZmtrsprt]

Thanks for the response chicane, But from what I've seen and read they call air gap as "measuring the air gap between the clutch disc and pressure plate or flywheel with the clutch pedal fully depressed against a stop". For a Borg and Beck style clutch like I have it should be @ .040 to .060". My bellhousing has a small hole on the bottom which might let me stick a feeler gauge thru but have you ever heard of or checked that fine of an adjustment? I've put about 1000 miles on it and haven't had any problems but I want to do it right. I'm just wondering how critical "air gap" is and who else pays attention to it. Thanks again, TZ

[chicane67]

Have I checked that fine of an adjustment....

Yes. It can make the difference between your clutch lasting just a year or lasting three years. It can be critical, but it depends on what you expect to get out of your parts.

[Jagarang]

The little bit of daylight seen through a very tight pair of jeans....OH..sorry..not what you meant!

[CarlC]

The little bit of daylight seen through a very tight pair of jeans....OH..sorry..not what you meant!

Nope, that's "Factory Air"