Stage 5 Twin Disc Installation Guide

1. These instructions apply to all Collins multi-disc racing clutches from 4-1/2'' up to 7-1/4'' disc diameter. Before proceeding, ensure that you have selected, and received the correct clutch for your application. 

2. Any components that may affect clutch performance must be in good condition and suitable for the use for which they are intended. IE: Bell housing, flywheel, clutch release system, pilot bearing, etc. 

3. Check the pilot bushing in the crankshaft. It should have a hole of proper size with no evidence of metal chips, out of roundness, cracking or splitting. A McLeod spline-a-lign clutch alignment shaft can be used for checking the proper size of the pilot bushing. It has a properly sized pilot on the end. Simply insert it into your pilot bushing and check for excess play.

4. The transmission input shaft must be accurately aligned to the engine crankshaft. The bellhousing performs with this critical alignment function. Check your bell housing to insure that the transmission register hole is concentric within 0.006'' (0.15mm) total indicated run-out to the engine crankshaft. The back of the engine block has to be parallel to the transmission mounting surface of the bellhousing within 0.002'' (0.05mm) or less. Performing this step avoids excessive spline wear on the clutch hubs and input shaft. It also helps prevent cracked clutch discs, hard shifting and other problems.

5. Ensure the input shaft and clutch disc splines are clean and dry. Do not lubricate. Check the new clutch disc(s) splines for proper engagement on your input shaft. They must fit easily on the input shaft spline and not bind, overhand or bottom out. Take the opportunity now to look at the input shaft spline closely to insure that it is not worn, pitted, corroded or twisted. 

6. Install the clutch bolts that came with your clutch from the backside of the flywheel. (Some flywheels do not require this.) Check the crank flywheel mounting surface for corrosion, pitting, scratches or imbedded debris. The flywheel must be able to sit absolutely flat on the crank mounting surface, with no evidence of rocking. Install the flywheel. Torque the flywheel mounting bolts according to the engine or crank manufacturer's instructions. We recommend using Loctite or a similar anaerobic thread locking compound. DO NOT USE STAR WASHERS!

7. Check to see that the clutch disc nearest to the flywheel is not in interference with the flywheel bolts or crankshaft. 

8. Degrease the metallic clutch discs, floater plate(s), pressure plate and the flywheel prior to installation. Keep organic facing clean and dry, taking special care to avoid oil or grease contamination.

9. Ensure that the clutch is assembled correctly. If your discs are labeled showing clutch disc orientation, Install the clutch discs according to the labels. Please refer to the drawing below for proper hub assembly or to the instructions that came with your clutch.

10. Center up and align the clutch disc splines. Locate the clutch over the flywheel register. Clutches are designed to locate on a flywheel register that is 0.100'' (2.54mm) tall. Flywheel clutch register diameters are as follows:
4 1/2'' Clutches:  4.6255'' / 4.6265''  (117.488mm / 117.513mm)
5 1/2'' Clutches:  5.6160'' / 5.6170''  (142.646mm / 142.672mm)
7 1/4'' Clutches:  7.3555'' / 7.3570''  (186.830mm / 186.868mm) 

11. Insert a clutch disc alignment tool into the clutch. Install the washers, and self locking nuts that came with your clutch. Tighten the clutch retaining bolts evenly, checking to see that the clutch cover has seated correctly. Final clutch retaining bolt torque is as follows:
4 1/2'' Clutches:   10-12 lb./ft.
5 1/2'' Clutches:   18 lb./ft. max.
7 1/4'' Clutches:   18 lb./ft. max.

12. The clutch release bearing must incorporate a radiused contact face, not a flat face. 
Minimum contact diameter = 1.65'' (42mm)   - recommended size, most clutches
Standard contact diameter=  1.75'' (44.5mm) - suitable for most clutches
Maximum contact diameter=  2.00'' (51mm) - only suitable for use with 7 1/4'' clutches

13. The clutch release bearing contact position will gradually move toward the transmission throughout the normal life of the clutch. To allow for this the clutch release bearing system MUST be able to accommodate an initial clearance of at least 0.125'' (3.17mm) between clutch bearing and point of contact on the clutch diaphragm spring PLUS at least the maximum allowable travel to release the clutch. Clutch release travel, as measured at the release bearing, is as follows:
4 1/2'' Clutches:  0.16'' (4.0mm)
5 1/2'' Clutches:  0.19'' (4.8mm)
7 1/4'' Clutches:  0.30'' (7.6mm)

14. The clutch release bearing system MUST be set-up with operating clearance between the clutch release bearing and the diaphragm spring fingers. It may be necessary to disable any clutch cable auto adjust system and convert to full manual adjustment. 

15. The clutch pedal MUST be fitted with a positive pedal stop. It should be adjusted to allow sufficient travel to prevent clutch drag, and yet not exceed the maximum allowable stroke for the clutch installed. Ensure the clutch actuation system is set to operate within its normal range. 

Failure to closely follow steps 12 thru 15 could results in serious damage to, or premature failure of your clutch. 

16. Inspect your clutch at frequent intervals. This interval will vary depending upon use. Replace the clutch disc(s) when they are worn to the minimum thickness. This avoids clutch slippage which leads to excess heat that can permanently damage your clutch. Clutch disc wear limits are as follows:

At the end of the racing season, your clutch should have a thorough service and inspection.