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Car Forum / Mercedes-Benz Cars / August 2005advancing timing
The car in question is a 1985 380SE. Since it recommends 87 and I use 93 octane, my race car building friend tells me if I should be able to advance the timing 2 or 3 degrees without pinging, and if I do so I will get a better hole shot and sacrifice nothing at the top end. He says if I retard the timing I'll get better top end but I'll lose in the bottom end. My mechanic says the only way to get more power is to retard the timing, and that on the 380 it wouldn't do anything since the computer is handling it. Who's right? Would I benefit (I'm looking to pick up a few tenths in the 1/4) from advancing my timing? Thanks, Richard > The car in question is a 1985 380SE. Since it recommends 87 and I use > 93 octane, my race car building friend tells me if I should be able to [quoted text clipped - 11 lines] > Thanks, > Richard Leave the timing where it should be according to the factory spec. Your racing friend is right, but without recurving the distributor/advance mechanism, this isn't always a good idea, and will also mean a few degrees hotter operating temperature. You should find another mechanic by the way. Advancing the timing temporarily to gain a little bump as a test seems relatively harmless IMO. Marty I'm not worried about long term durability. This 380 engine just can't die (even after 20 years and lead feet, it still runs so smooth that even with busted motor mounts it's butter smooth). It'd be fun to try. Do I really need a timing light to do it or can I just guess and check (all I have to do is rotate the distributor, right?). richrd > I'm not worried about long term durability. This 380 engine just can't > die (even after 20 years and lead feet, it still runs so smooth that > even with busted motor mounts it's butter smooth). It'd be fun to try. > Do I really need a timing light to do it or can I just guess and check > (all I have to do is rotate the distributor, right?). > richrd You definitely want to have a proper and high quality timing light. At the very minimum you want this to be able reset the car to proper timing spec after it's been tinkered with a bit. In older american cars shade tree mechanics often would set timing without a light simply by listening and experience... This can be a tedious process and does pose certain risks to the engine. Good Luck, Marty Oh, and I don't think I'll be changing my mechanic...it was atually the shop owner for one thing, but he works on his own Benz's and used to be a Benz mechanic, and also in addition to being a good honest shop, it was the top rated Benz shop in Washington Checkbook. If you are really serious about max hp output take the car to a dynoshop and have them adjust the timing for max hp at the rear wheels. Costs a little but the results are worth it. Peter > The car in question is a 1985 380SE. Since it recommends 87 and I use > 93 octane, my race car building friend tells me if I should be able to [quoted text clipped - 11 lines] > Thanks, > Richard But see the game is getting power for free (gas consumption doesn't count), not paying for it. Richard > If you are really serious about max hp output take the car to a dynoshop and > have them adjust the timing for max hp at the rear wheels. Costs a little > but the results are worth it. Agreed. they can actually time it correctly and recurve the distributor appropriately. This can make a pretty big difference in performance. Marty How big we talking (if it helps to know, the stock settting on a 380 is 0). Richard > How big we talking (if it helps to know, the stock settting on a 380 is > 0). IMpossible to tell. If the distributor uses mechanical advance, then the springs that control it can become heat crazed over time, and not perform as they are expected to. Setting it up properly can make a noticeable difference. Marty I have tried up to 25 degrees advance in my '82 380 SL, but that requires premium gas to prevent knock. There is a significant increase in power, but I do not run with that much advance and definitely do NOT recommend it. You need a timing light and be careful, as there are a bunch of thing moving around pretty fast near where you will be working. In addition to the spring issue discussed above, cars this old usually require the vacuum lines to be replaced and often the vacuum advance diaphram leaks. Fix all of those problems before playing with timing. A really long handled hex wrench is a good idea to keep hands out of harms way. If you are not worried about long term durability, keep in mind that it is possible to trash your engine in a few seconds with too much advance. Watch your engine temperature, check your mixture, and consider low speed drivability/starting issues. > I have tried up to 25 degrees advance in my '82 380 SL, but that > requires premium gas to prevent knock. There is a significant increase [quoted text clipped - 11 lines] > advance. Watch your engine temperature, check your mixture, and > consider low speed drivability/starting issues. Yeah, what he said! Well, I was thinking more like 3 or 4 degrees (which is what the factory manuals allow for a increase in octane from 87 to 91, and I run 93), not anything close to 25. Richard |
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