Glenn,
I'm not sure if your '76 is like my '77, but mine had a vacuum retard (not
advance) unit on it for emissions purposes. It made the car too sluggish at
low RPMs, so I kept the vacuum unit plugged with the idle setting at 10-12
deg BTDC. I have since replaced the distributor and Lucas ignition with a
Mallory Unilite distributor set at 6-8 deg BTDC (I now have 9:1 compression
ILO the original 7.5:1). Total advance is limited to 30-32 degrees. You
don't want to exceed 32-34 degrees or engine damage can result. I hope this
helps.
Michael Altomare
'77 Spitfire 1500
MTAltomare@Prodigy.net
-----Original Message-----
From: Glenn Trunnell <trunnell@mindspring.com>
To: spitfires@autox.team.net <spitfires@autox.team.net>
Date: Wednesday, February 17, 1999 10:10 PM
Subject: need distributor help
>Hi everybody,
>
>My big debut at autocrossing is coming up on Feb. 28 and I'm trying to get
>my Spit tuned up so that I at least won't be embarassed by poor mechanical
>performance. The drivers performance is another matter! Any way I'm a
>little confused about the vacuum advance on my distributor. I have a '76
>distributor with what appears to be a vacuum advance unit ( the vacuum
>canister has the input on the front like every advance unit that I have
>ever seen), it originally had the Lucas constant energy ignition (a
>magnetic pickup and a seperate module mounted on the firewall shelf) which
>has since been replaced with the Crane optical system. So here's the
>questions:
>
>1) At idle with the vacuum connected I get about 12-14 degrees of advance,
>so if I have the timing set at 10 deg BTDC and I pull the vacuum line off
>the timing instantly retards to about 2-4 deg ATDC. If I give the car some
>gas the timing retards even more to about 10 deg ATDC and then as I hold it
>steady at about 2000 RPM in moves back towartd 10 deg BTDC. This seems to
>indicate to me that my springs are too strong or the weights are stuck and
>are not allowing the timing to advance. Is this correct?
>
>2) If I disconnect the vacuum line and plug it and then set the timing so
>that it reads 10 deg BTDC with no vacuum advance installed the distributor
>advances to about 30 deg. BTDC and stops there regardless of any further
>advance in rpm. This seems like the mechanical advance is working to
>advance the timing as engine speed increases? Driving the car like this
>gives much quicker acceleration, but... the engine seems very noisy, like a
>lot of valve noise, no miss but almost like a volkswagen diesel or
>something, the car has had a recent valve job and has the 7.5:1 pistons
>and I'm running 93 octane is this detonation that I am hearing? Is the
>timing being overadvanced and causing this?
>
>3) Finally as an experiment... my car has the flame traps that have been
>discussed recently. One vacuum line runs from the bottom of the carb
>through the trap and to the distributor, another runs from the top of the
>carb through the trap to the egr valve. I thought that I had perhaps gotten
>these lines switched so I interchanged them. The results were that the
>vacuum advance and the mechanical advance now seem to give a cumulative
>effect and provide about 45 deg BTDC of advance, but there seems to be so
>much vacuum to the EGR that it is on all the time even at idle which causes
>the car to miss very badly. So this is probably incorrect any thoughts on
>this?
>
>4) Do I perhaps have the incorrect distributor? Was an advance unit used
>on US spec cars and should it be plumbed differently to make it function
>correctly?
>
>I appreciate any help that anyone can give me on this, I'm sorry it's so
>long but maybe this will answer a lot of questions other people have as
>well. I'll be racing as number 44 in H stock on the 28th, kind of cheesy I
>know but hey someones got to carry the banner!
>
>Glenn Trunnell
>'76 Spitfire
>
>
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