Bill,
You don't say much about your motor's particulars ie; cam profile, piston
size, carburetors, manifolding, etc.. but I wonder how your ignition timing can
be correct with a possibly incorrect distributor..
The DM2 distributor (TR3-early TR4) has different mechanical and vacuum
advance specs than a 25D distributor (late TR4-all TR4A's).
And an MGB distributor is for a different motor altogether!
What specs do you want for your TR3A, stock TR3A specs, or late TR4/4A specs?
I believe you can make your MGB 40897 distributor into a late TR4/ TR4A 40795
distributor because the MGB distributor weights and advance arm (10 degrees)
are the same BUT the weight 'springs' need to be changed to 40795 specs -
available new at Moss for $8.00/pair.
The late TR4/4A vacuum units (2-6-3) are hard to find - the only critical
difference inside these many identical looking vacuum units is 'the spring'.
If
you can find a used or leaking 2-6-3 unit they can be rebuilt (just ask
Randall!).
Then you'd have the latest official S-T factory spec'd distributor for TRs
(TR4-A).
I recommend changing the punched numbers on housings too to reflect changes
to your distributor. The shaft bushings on MGB distributors seem to be a more
robust iron or mild steel bush VS the bronze bushing used in the TR units -
maybe MGBs are higher revving? Longer lasting? The iron bushing seems better to
me.
If you want to see what Holden recommends and see a rebuilt vacuum unit (note
thicker edging) go here --> www.holden.co.uk/hvc-home.htm
ps; I wouldn't push your brand new motor too hard with 'timing doubts'.
Regards,
Carl
'63 TR4 since '74
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Last December I started a string about a Lucas 25D distributor vacuum
advance markings. I got some good advice, but am still not sure what I have. I
went to the JCNA website and read their stuff, but still didn't find what I
was looking for.
I have a 25D Lucas distributor. The side markings say 40897, which should
mean that it was for an MGB, I think. It also says 564 on the side, which
should mean that it was made in May of 64. The Vacuum advance on this
distributor says 5-13-10.
Someone said that I should have a vacuum advance that says 2-6-3.
The DM2 distributor that was on the car when I bought it has a dead
vacuum advance that's labeled 4-11-7.
I have a spare vacuum advance that I got off of Ebay (NOS) that the guy
said was for a TR3 and it's marked 4-8-5.
Can someone tell me what the mechanical advance inside the distributor is
supposed to read? Is it the same for a TR3 as it is for an MGB?
Does anyone have the right distributor for a TR3 or 4 that has the
correct vacuum advance and mechanical advance that they would part with? I
would be happy with just the vacuum advance part.
Are these distributors around? I was thinking about trying Triumphs Only
or some other place.
Does the vacuum advance really make that much difference?
Any other good websites out there about Lucas vacuum advances?
My TR3 runs like a banshee, but only gets about 20 mpg. Newly rebuilt
engine, with carbs and timing set right. It didn't get good mileage before the
rebuild either. Something tells me that at least some of my problems are in
the distributor.
Bill Brewer
1960 TR3A
1974 Mini Cooper
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