The message to which you are about to reply is shown first. GO TO REPLY FORM



 VIEW    REPLY TO THIS MESSAGE    PRINT   SAVE 

b20b dizzy - vacuum RETARD ???? 140-160 1970

posted by  Phil S. on  Fri Jan 24 07:27 CST 2003
Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
last visit: Fri Oct 24 13:18 CST 2014
[RELATED]

Rhys,

I'm sure you're correct about what the manual says, but that doesn't mean the manual makes sense other than for smog purposes. Typically, the centrifugal mechanism provides about 17 degrees advance, and the vacuum 7 degrees of retard. Let's examine how that works with the vacuum hooked directly to the manifold.

Version 1 - basic timing set to 10 BTDC with vacuum disconnected:
At idle (full vacuum) = 3 BTDC
1/4 throttle, low RPM = ~7 BTDC
1/4 throttle, high RPM = ~23 BTDC
WOT, high RPM (no vacuum) = 27 BTDC

All that is too little advance, regardless of the particulars of your motor, carburetion, fuel type, etc. You'll get boggy performance and poor economy.

Version 2 - basic timing set to 10 BTDC with vacuum connected:
At idle (full vacuum) = 10 BTDC
1/4 throttle, low RPM = ~14 BTDC
1/4 throttle, high RPM = ~30 BTDC
WOT, high RPM (no vacuum) = 34 BTDC

That's still very conservative timing for a street motor, IMHO...





USERNAME
Use "claim to be" below if you don't want to log in.
PASSWORD
I don't have an account. Sign me up.
CLAIM TO BE
Use only if you don't want to login (post anonymously).
ENTER CAPTCHA CODE
This is required for posting anonymously.
OPTIONS notify by email
Available only to user accounts.
SUBJECT
MODEL/YEAR
MESSAGE

DICTIONARY
LABEL(S) +
IMAGE URL *
[IMAGE LIBRARY (UPLOAD/SELECT)]

* = Field is optional.

+ = Enter space delimited labels for this post. An example entry: 240 muffler


©Jarrod Stenberg 1997-2022. All material except where indicated.


All participants agree to these terms.

Brickboard.com is not affiliated with nor sponsored by AB Volvo, Volvo Car Corporation, Volvo Cars of North America, Inc. or Ford Motor Company. Brickboard.com is a Volvo owner/enthusiast site, similar to a club, and does not intend to pose as an official Volvo site. The official Volvo site can be found here.