[E-Type] Maximum distributor advance

what is the maximun distibutor advance you would want to see on a
4.2 with tri carbs, standard ignition, high test, US 92 octane, 9:1
comp, .020 overbore with .010 off the head, no porting standard
jets and usual SS exhaust. Help, don’t won’t to fry one of these.
Peter–
bwanatiro
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In reply to a message from bwanatiro sent Mon 26 Jan 2009:

Peter,

the standard 10 degrees BTDC should work just fine. The possible
issue would come from the .010 head shaving, that will raise the
compression ratio by an amount I don’t know – Ray Livingston has a
spreadsheet that may provide an answer.

My car is a 3.8 with all the same specs except less off the head,
and it does not ping under any circumstances on California 91
octane premium. The 4.2 is a lor less prone to pinging than the
3.8, another indication that you should be fine.

Pinging will be affected too by mixture, so get that right. If you
are close and the car still pings, you won’t do any damage unless
you are pulling flat out up a steep hill in 100 degree weather.
Even then you will get only a mild ping at about 2600 RPM as you
accelerate.

High speed ping can be very damaging, but with your setup it’s just
not going to happen unless you are doing speed work at Bonneville
in the summer. Frying the engine is pretty darn hard to do with
these engines. I have even driven mine 3 miles or so with no water
in the block – very carefully – after a freeze plug blew out, no
damage at all (though this was a big risk). There is no tenderness
in a well sorted XK engine.

Jerry–
The original message included these comments:

what is the maximun distibutor advance you would want to see on a
4.2 with tri carbs, standard ignition, high test, US 92 octane, 9:1
comp, .020 overbore with .010 off the head, no porting standard
jets and usual SS exhaust. Help, don’t won’t to fry one of these.


Jerry Mouton '64 FHC 889791 ‘MIK Jaguar’
Palo Alto, California, United States
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In reply to a message from bwanatiro sent Mon 26 Jan 2009:

Take a plug lead off and put it somewhere it won’t ground
out. (Or tape it.) Start the engine and run it up to 3,000.
Advance the distributor until you get pinking. Retard
slightly. Lock distributor and reconnect lead.–
1969 4.2 Series 2 E Type
Brentwood Bay, B.C., Canada
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In reply to a message from bwanatiro sent Mon 26 Jan 2009:

Peter,

Keep it 36 degrees BTDC or less total advance with the
vacuum advance disconnected. Check this by blanking off the
vacuum advance and gradually take the rpm up to a point to
where it stops advancing (3-4000rpm), and you will find your
total advance. If it is 34-36 your in good shape.

Regards

-Don–
Petrarch
Los Gatos/CA, United States
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In reply to a message from IanCameron sent Mon 26 Jan 2009:

Ian

very curious about your method, what is the rational for removing
one spark plug lead, and is this with the vacuum advance connected
or blocked off. Thanks Peter.–
The original message included these comments:

Advance the distributor until you get pinking. Retard


bwanatiro
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