Hi John,
Funny you should post this as I have just about finished by TR4A here in
Cincinnati and did a bit of struggling with the tuning also.
I have the BPNW 270 degree cam and 87mm pistons but I also have a
RevingtonTR 4into1header and mating exhaust and on of those 123 distributors
I bought from Darrell many moons ago when he went to Weber carbs. That
distributor is kind of pricey now but in my opinion, it really delivers. It
has 17 different advance curves in it. Mine is set to have about 10 degrees
at 1,000 RPM, a little over 22 degrees at 2,000 RPM and about 31 degrees at
4,500 RPM. I am running 93 octain fuel and have been carefull to listen for
pinging during long pulls up hills and such and the engine seems to be
tolerating the current timing settings.
I only have about 400 miles on the engine so far so I am not pushing it too
much but I know it pulls real strong from about 2,000RPM to as high as I
dare go now (about 4,000RPM very occasionally). I played around with the
needles too, going one step richer but the plugs fouled so I went back to
stock and just did a 400 mile tune up and the plug electrodes were tan and
the surrounding plug was black.
Tuning this thing was way different that any other type of engine I ever
fooled with I can tell you that. I found that the float levels really affect
the mixture also as you are adjusting the level of fuel at the main
jet/needle. Lots of things to think about..
Can you get someone to rev up the engine while you have a set back timing
light on it? If so, what do you see timing wise at the 1,000, 2,000 and
4500? Just curious as I think you are right in the problem being timing or
more acurately advance related..
Dave Connitt
----- Original Message -----
aFrom: "John & Pat Donnelly" <pdonnel1@san.rr.com>
To: "'Triumphs'" <Triumphs@autox.team.net>
Sent: Thursday, June 05, 2014 12:16 AM
Subject: [TR] TRactor Engine Timing
> After rebuilding my TR4A engine I've been playing around with the engine
> timing (advance/retard) to dial in the best performance. The engine has
> the
> Moss cam & 87 MM pistons, but everything else is stock. Stock HS6's, stock
> distributor with Pertronix, new gears and timing chain. The vacuum advance
> is attached.
>
> I never seem to be able to get the full range performance I would expect.
> I
> can get low end to be great but the top end suffers. Redial it and the top
> end is great but low end is sluggish.
>
> I dont think the carbs are it, as I've changed to richer needles, made it
> richer/leaner, and it didn't help. I did learn that a richer mixture seems
> to hide timing differences.
>
> And I got to thinking that the TR4A distributor has an advance limit built
> into it and was wondering if going to a more full range dizzy would give
> me
> that full range performance. Shouldn't the dizzy advance and the cam specs
> match up?
>
> Why the limited advance anyway?
>
> BTW, the weather is absolutely bitchin to be driving with top down every
> day
> here in San Diego. I'm loving it.
>
> Johnnie
>
> 67 TR4A
>
>
>
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