The MSD Programmable Timing Computer has several features in common with the pre-programmed PN 8980 Timing Computer. Both are adjustable for 4, 6 and 8-cylinder operation and both models have a High Speed Retard function. The difference between the two models is that the PN 8981 Programmable Timing Computer has an adjustable timing curve whereas the PN 8980 is fixed. The Programmable Computer allows you to adjust the start point, rate and total amount of the advance curve to fit your application. The PN 8981 must be used with an MSD Ignition Control and is supplied with a 2°, 3° and 4° module. Page 105 lists a full selection of retard modules and selectors. 8981$244.99 Don't see what you want? .......... Need help? Or, IF THERE IS NO ORDER BUTTON AVAILABLE on the part you want to buy, please call us TOLL FREE at 1-888-6 GO FAST(1-888-646-3278) Monday - Friday 8AM - 4:30PM Pacific Time and talk to one of our experienced Sales Agents. Some parts may not be legal for sale or use in California and other states on any polution controlled motor vehicles. Check your local laws for use. Copyright © GoFastParts.com all rights reserved. No part of this site may be reproduced without prior written consent.