fighting the Paranoia

[Anonymous]

You may recall posts about how my exhaust runs red hot driving up the long grade to the cabing where I live. having taken an informal poll of people's opinions about
exhaust temp, I am somewhat relieved having turned over every
concievable stone to ensure some engine longevity, but I can't help
but keep thinking and digging to be certain I've ruled out everything
I can. (Just had the head rebuilt, new carb, dizzy, radiator..... running 6deg at idle, 34 deg by 3000rpm..... with a weber 32/36 jetted rich)
On a whim I thought I'd see what my advance was doing under load as
I drove up the hill this evening. When running
near 3000 RPM with a light load on the engine, the
advance is about 34 or 35 deg, but when I start up the steep
hill, the advance falls to somewhere between 12 and 20
deg..... is that normal? Generally speaking, the
advance decreases as the load increases.... with the
RPM held constant.... thanks.... (am I crazy using a timing light
while driving - my old econoline? got to love sitting right next to all those
horses)...David SoCal
PS, I wish I knew what this engine should sound like.....

 

[Mercury Mike]

Cruise to my house. I'll show you how one's supposed to sound (a 200 that is). If nothin' else, it'll be a good trip, and I live right by an In N Out. Ask Addo.

 

[Stubby]

Alot of the factory setups will retard under load. You could lock the advance and set the timing at 34 and see if it still put excessive heat in the exhaust. This might give you an idea what the engine needs, then you can tailor the dizzy to match.

If the carb is overly rich, you might try getting the mixture right first.

 

[66 Fastback]

The timing is functioning correctly with regards to decreasing the advance with increased load. However it sounds like you might not be getting much centrifugal advance contribution. If at a constant 3000 rpm, the timing is dropping from 20 to 12 with increased load then that decrease is from the vacuum advance decreasing. If what you stated is correct, it appears you only have 6 deg of centrifugal advance at 3000 rpm. Add that to the 6 deg of static, and you get the 12 deg. You may need lighter springs or heavier weights to try to get more contribution from the centrifugal advance.

Of course, I have assumed your new distributor has centrifugal advance. If you are running the Weber with a Load-a-matic distributor, the timing advance will not work properly. You need a later model distributor, post '68.

I assume your 34 deg of total advance at 3000 rpm is with the vac line connected. At 3000 rpm and low to no load you probably should be getting over 45 deg. Assuming you have a centrifugal type distributor, with the vacuum line disconnected and plugged, you should get 30 to 36 deg of advance at 3000 rpm.

So basically, it appears that the timing is retarded at 3000 rpm. 20 deg under heavy load may not be that bad as you might have some additional centrifugal advance kicking in at higher rpm's above 3000. But 12 deg at 3000 rpm is low and retarded.
Doug

 

[Anonymous]

I assume your 34 deg of total advance at 3000 rpm is with the vac line connected. At 3000 rpm and low to no load you probably should be getting over 45 deg. Assuming you have a centrifugal type distributor, with the vacuum line disconnected and plugged, you should get 30 to 36 deg of advance at 3000 rpm.

My dizzy is a DSII...... I have read quite a few opinions on the total advance discussion.... one resopnse said that 45deg was way too much (since the terminals are 60deg apart).

How easy is it to change the centrifugal advance springs etc so my advance is more constant under load?..... I'm learning a bunch here.... David SoCal

 

[66 Fastback]

one resopnse said that 45deg was way too much (since the terminals are 60deg apart).

That is incorrect. They are forgetting that the distributor only turns one time for every two revolutions of the cranksaft. The 45 deg is crankshaft degrees. That would actually be something like 22.5 deg with respect to the distributor.

I don't have any experience with the DS II distributors. But if it is similar to the older distributor, you just had to pull the distributor and everything could be taken off from the top and you did not have to disassemble the shaft. The weights on the old ones were also reversible with two different advance ratings depending on how it is installed. Many distributors of the emissions era such as HEI's were curved so that a larger contribution of the total advance came from the vacuum advance. So that may help explain why your DSII does not have an aggressive centrifugal advance curve.
Doug