11 degrees at 1500 rpm would be correct for a North American 1973 18V672 or
673 with a 41491 distributor. The figures should be dependant upon the
distributor you are using, which should be matched to the engine you have.
Have you got some free play in the accellerator cable at idle? With the
screws all the way out are you getting audible suck on both carbs or only
one? If one then it could be a poorly seated throttle disc on that carb.
If both then it could be cables or linkages.
When tuning twin SUs you should set both mixture and idle speed with the
throttle and choke shaft clamps (four clamps) loosened.
Dieselling when turning off from an idle speed of 1100 rpm when hot is to be
expected.
PaulH.
MG Cars Webring MG Site of the Month - September '99
http://freespace.virgin.net/paul.hunt1/
(or if that URL doesn't work try )
(http://194.168.54.52/paul.hunt1)
-----Original Message-----
From: Tyson Sherman <mts3@ra.msstate.edu>
To: MG Mailing List <mgs@autox.team.net>
Date: 18 September 1999 19:05
Subject: SU Tuning Questions
>My SUs are on and the car is running. I have some
>tuning questions. I understand that the carbs are
>the thing to do last, and that valve clearances
>and timing are supposed to be set first.
>
>I set the timing to 12 deg BTDC @ 1500 rpms
>dynamically. I was going by a 73-74 spec. Does
>that sound right? With the idle screws all the
>way out, I can only get it as low as about
>1100rpms. Also, when I mash the gas, the idle
>speed doesn't always go back. The throttle shafts
>on these carbs have no wiggle. When I lift the
>piston pins at idle, the speed drops for a few
>seconds then picks back up.
>
>I have listened w/a piece of tubing for whistles
>indicating air leaks, and about the only place I
>can find is at the air cleaners.
>
>What else do I need to do to get the idle low
>enough? BTW, the car dieselled a lot when I shut
>it off. It had been idling a while and the temp
>guage was getting right past the N.
>
>--
>Tyson Sherman
>mts3@ra.msstate.edu
>ICQ# 10494960
>http://www.tecinfo.com/~tsherman
>
>
>
|