2.4 Timing without Vacuum Retard

[bliebler]

For years I set my 73S idle timing at 5 deg ATDC. Last week, after warm up, I removed the vacuum and pluged it. The timing bumped up to 5 deg BTDC and as expected, idle went up...I then checked at 6000rpm and got a tad shy of 35deg.(call it 34 3/4) . At 4500/4700rpm I'm getting 33 deg and around 5700 it stops advancing at the 34 3/4 deg,remains there even at 6200rpm. My manual states to set timing 32 to 38 deg at 6000. That seems like a wide range. My questions are: Should I bump up to near 38deg?( I live in SW Fla. so heat is an issue). Will I gain anything or perhaps enter a danger zone if doing so? Also, why the wide range of 32 to 38deg?

[edmayo]

What manual are you using? Factory shop manual says says 30 degrees at 6,000. With the 5 degree initial advance that's 35 total. Nothing about 38 degrees. I have two 72 S's, I've always set between 32-35 degrees.

[bliebler]

The 73 OWNER'S MANUAL p. 61 states "Timing should be between 32-38 BTDC".

[edmayo]

Now you've got me curious, I'm going to look in my owner's manual! I just wanted to make sure you weren't using a Bentley or some other aftermarket one.

[RSTarga]

I think you have it backwards, Thats 5 degrees retarded (atdc). Anyway I think you should set it at max advance , whatever the book says, with vac hose disconnected. I wouldn't worry too much about the idle timing.

[bliebler]

The Owner's Manual clearly states, "between 32-38 BTDC with the vacuum line connected. The only reference to ATDC is idle timing which is 5degATDC which I assume is for emmissions. I used to think that the vacuum retard helped starting because the piston is on the way down, however, now that I set it without the vacuum the car starts better.

[edmayo]

David I was referring to the 5 degree advance you get with the vacuum disconnected as the initial advance I mentioned. The 5 degree retard at idle helped to enable legal hydrocarbon settings back when these were new cars. When I set mine I do it with vacuum on, check for the 5 degree retard (actually I cheat and use 2 1/2 retard) then disconnect vac to check that I get the 10 degree advance (from 5 retard to 5 advance) then with vac off go to 6,000 and see that I'm getting 32 -35 degree advance. Forgot to look in my owners manual today, I'll do it tomorrow.

[RSTarga]

OK Ed, Now we are on the same page. It's just that he is leaving the vac hose on when he does his high speed setting. Although, and correct me, once the throttles are open is he really getting any vacuum to make a difference? To me the important number is total advance, if that is set right idle setting should be about right if his dizzy is in good shape.

[bliebler]

no, I'm not using the vacuum retard anymore. I removed it, pluged it, then set at 6000. What I said was ,prior to the vacuum removal, I set idle at 5degATDC. When I removed vacuum line & pluged it the idle bumped up 10 deg to 5 deg BTDC. Then, with the vacuum eliminated, checked at 6000 and it was pretty close to 35 deg.

[edmayo]

The Owner's Manual clearly states, "between 32-38 BTDC with the vacuum line connected. The only reference to ATDC is idle timing which is 5degATDC which I assume is for emmissions. I used to think that the vacuum retard helped starting because the piston is on the way down, however, now that I set it without the vacuum the car starts better.

You are dead nuts right! Right there in the owners manual, and it is also in the spec book. The shop manual doesn't indicate as high as 38, but it is basically showing the half speed distributor graph so it isn't as obvious. I know I've seen that spec, but the 38 just didn't stick in my mind. I suppose because the pulley is only marked to 35. Because there is a little timing flutter at 6,000 they must have figured on giving you a little tolerance with the timing light! None the less I do always keep to the 35 number. Thanks for bringing that up, and forcing me to refresh my memory. (It certainly needs refreshing!)