Hi,
I was going to reply earlier to this thread, but I wanted to make sure that
my cam was installed correctly before I started sharing my experience, but
since it's come up so often I'm going to jump in anyway. My car is a '76
with all the emissions installed, I currently have my timing set at 10 deg
btdc, with no vacuum advance installed. I found that the vacuum advance
will indeed overadvance the spark at idle and the engine runs much more
roughly. If I set the timing at 2 degrees atdc or even 10 deg btdc with
the advance installed the car is incredibly sluggish and has a top speed of
about 72 mph. I understand the idea behind vacuum advance is to increase
economy while your'e cruising at part throttle, but the Spitfire is geared
so low that I don't think it is going to come into play very often. Heres
some hard facts from the shop manual though:
There are 4 distributors listed for the Spit
Triumph part no. RKC0638 TKC1224 TKC2755 TKC3289
Lucas part no. 41449 41593 41646 41697
CEI replacement no. 41804 41805 41807
The Lucas EID distributors with the electronics on the side of the
distributor were replaced with the CEI units (with the seperate black
boxes) when they failed or were phased out.
Advance curves are as follows (degrees of crankshaft advance, distributor
advance will be 1/2 of the crank advance and the distributor RPM will also
be half the crank)
Centrifugal advance
RKC 0638
RPM (crankshaft) Advance
600 none
1100 2 to 6
1400 6 to 10
2000 8 to 12
3200 12 to 16
TKC 1224
850 none
1200 0 to 7
1600 8 to 12
2600 11 to 15
3200 12 to 16
5000 12 to 16
TKC 2755
800 none
1500 5.0 to 8.6
1700 6.0 to 10.0
3000 10.4 to 14.0
3500 12.0 to 16.0
TKC 3289
800 none
1200 0 to 10
1500 6 to 14
2200 12 to 16
3500 16 to 20
Vacuum Advance (inches of mercury vacuum)
RKC 0639
2.0 none
3.0 0 - 1
6.5 1 - 6
8.5 5 - 9
11.0 9 - 13
18.0 10 - 14
Vacuum Retard
TKC 1224
1.0 none
15.0 10 - 14
20.0 10 - 14
Vacuum Retard
TKC 2755
3 none
5 1.5 - 3.0
7 3.0 - 6.0
11 6.0 - 12.0
15 6.0 - 12.0
Vacuum Advance
TKC 3289
3.5 none
5.0 0 - 5
7.0 5.0 - 13.0
9.0 14.0 - 20.0
10.0 16.0 - 24.0
Also if you have a CA Spit the numbers are:
Lucas EID# 41656 41698
Lucas CEI# 41804 41808
My '76 apparently came from the factory with the CEI style of ignition and
has the TKC 3289 distributor and I have checked it against these values and
found it to be accurate.
Good luck,
Glenn
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