Timing and Preignition, Engine Heating

[Leewolf]

All of the smog equipment has been removed from my 450SEL engine in my 79 450SLC. In order to get it to run the timing had to be advanced considerably. It runs very well , BUT, the faster I go the hotter it gets. If I hold it at 70 to 80 MPH it will get up to about 112 to 115C. I haven't taken it any faster for this reason.
QUESTION: at what point in timing advance does preignition become a potential problem, ie 10degrees, 20degrees, 25degrees or ???. Is the engine timing and the high engine tempurature related. My timing is advanced 26 degrees.
Thanks for any help on this question.
Lee
79 450 SL (sold)
79 450 SLC
88 Lincoln Town Car (its a jewel)

[Kestas]

A couple of thoughts come to mind. One is that the egr system reduces peak flame temperature. If this was removed, you may be seeing higher engine temperatures.

On your timing, remember that what you're setting is base ignition timing. Are you checking it with the vacuum to distributor removed and plugged? The actual timing changes when vacuum is reconnected to the distributor. Also, the running timing changes with engine speed and load (vacuum). You may not have the proper distributor curve. Lighter springs for agvance weights may be needed.

Preignition is only a problem if you hear knocking. Timing advance of 26° seems rather high. I would start at 12° BTDC and move the idle up to see how it runs. Setting timing for max idle is not the way to go.

Though I've disconnected smog equipment before, I personally don't like making changes to a car unless I know exactly what I'm doing. Too many things are dependant on each other.

[psfred]

I'd just put the "smog" stuff back on, you aren't going to get it to run properly without it. Your problem is that the timing is mechanical with extra control provided by the vacuum switchover and diaphram that you have disconnected (I think -- certainly true of the 73). With this off, you aren't getting the advance you are supposed to, and have it set far too high at speed.

What rpm are you setting the timing? If you have limited mechanical advance inside the distributor, you are going to have to choose between high rpm or low rpm operation -- 26 degrees is about right for 2500 rpm up, but it won't run properly at low rpm, and if you have 26 degrees at low rpm, you are surely much too fast at high rpm.

I don't know when spark knock starts, but for sure you WILL NOT hear detonation at high speed. At least you won't immediately burn holes in the pistons, but running hot is an indication that you have overadvanced timing.

As far as I know, you have, for "smog" equipment on this car, some timing control via a swithover valve and maybe air injection and a catalytic converter. Only the 1980 models had electronic mixture control. I don't know if you have EGR or not, but if you do, I'd leave it on, too, to prevent too hot a combustion temp -- after all, it was designed to have the EGR, it wasn't just stuck on willy-nilly.

Why did you remove the emissions control stuff? If you want more horsepower or better milage, you won't get it -- the "problem" is in the cam, not the emissions control equipment, which in any case is very minimal. The 116/107 chassis is a gas hog, and suffers from low performance compared to the 280 SE/L 4.5, and the only difference is the head and cam -- the K-Jetronic fuel injection gives more hp and less fuel consumption.

Peter

[Leewolf]

Thanks to Kestas and psfred for your replys. I need to clarify regarding the "smog" equipment removed. The "cats" were completly rusted through, would have had to be replaced. The "smog" pump was removed primarily to get the belts to line up for the items removed from the other engine, ie AC and power pump. I had to take the main pully from the other engine, it did not have a "smog" pump. These were the items removed. As for the EGR, I cannot find anything corresponding to this item on this or the old engine. I definatly will go back to the timing and start over, at this juncture we were just trying to get it running then fine tune it. I sincerly appreciate your comments. Believe me when I say I love this part of the country to live in (south central missouri, ozarks) but it has its drawbacks when trying to work on this kind of a vehicle with the closest dealers/garages from 120 to 200+ miles away.

[psfred]

Lee:

All you did was remove the air pump and cat -- the only other emissions control here is the vacuum retard on the distributor.

Here is what I would do: 1) veryify that the vac diaghram holds vacuum -- you can just put a bit of hose on it and suck on it or you can get a MitiVac or similar pump. If it doesn't, I'd get a new one, hard to get it to run properly. Also, make sure the vac servo moves the breaker plate -- if it is stuck, it won't do anything and cause you the problems you have. I don't know what it would take to fix, but since the 116 was such a rustbucket, I don't think a used distributor would be all that hard to find.

2) Test the retard switchover valve -- I don't know where it is on the 450 SEL, I'd have to check. It's on the firewall on the 280 SE, it is connected to the manifold and to the distribtuor.

3) Verify that you have vacuum at idle to the diaphram.

If all is in order, set timing to about 5 degrees BTDC with the vac line plugged and see what happens. If this doesn't work, check the distributor for mechanical advance -- the timing should change with rpm. If not, you have a distributor problem (mechanical).

If the vac system is toast, plug the line to the manifold and use the post listed above to set the timing.

You may also want to make sure you plugged the air pump lines properly -- otherwise you will have an exhaust leak if the check valve fails!

Good luck, there is no reason it shouldn't run.

Peter

If the diaph