How to set timing on 81 sc?
03-28-2006, 06:27 PM
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How to set timing on 81 sc?
Guys here I am again asking for help. I am very new to this machine and set up the timing light on #1 pulled the vaccuum hoses at dist. and plugged them. Then I happily pointed the light looking for 5 deg. at 900-950 rpm. What I cannot understand is where are the timing marks! On my 928's they are right on the crank pulley and the pointer is highly visable. All I see on this 81 sc 3.0 is a few holes on the pulley and a notch in the alternator housing. Someone enlighten me please.
Major thanks!
Kevin
Major thanks!
Kevin
03-28-2006, 07:05 PM
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The TDC and 5 degree mark should be in plain sight on the crank pulley - easily visible with the timing light. Are you sure your inductive pickup is on cyl #1 wire?
Pete
Pete
03-28-2006, 09:08 PM
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Pete, looking into the engine bay from rear, I have the pick-up on the wire closest to me on the left (drivers side) bank. At the rear of the engine there are 2 pulleys, a small one and larger one to the inside of the smaller one. I don't see a pointer or the marks. I assume the larger one is the harmonic balancer, but wouldn't there be a pointer on the housing near it? I guess what I am asking is assuming I have the pick-up on #1 where should I find the timing marks and the pointer to set them by? Pete. I must sound like such a greenhorn here, but this car as incredible as it may be,is totally different from my 928's!
Thank you Pete, Kevin
Thank you Pete, Kevin
03-30-2006, 11:37 AM
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Kevin,
There is no harmonic balancer on a 911 engine, just pulleys. It sounds like you have the double pulley for an A/C belt on the outside. There is a timing mark notch cut into the lower center of the fan housing. The inner pulley has full length (both sides) notches cut in it at 120 degree intervals. The timing mark is cut on one side only (inner) in front of the notch for TDC #1 (Z1). If you are setting the timing on a 911SC, do yourself a favor and disconnect and plug the inner vacuum retard line (blue or gray braided). The vacuum retard is strickly for the curb idle HC test and leaving it disconnected makes for better cold start running and lowers the engine temperature at idle when hot. The factory setting is 5 BTDC @ 900 rpm, both lines disconnected, but I prefer to use 7-10 BTDC with premium fuel. You have to reset the idle, which is controlled by the large screw on the throttle body, when adjusting the timing. You can easily reach in there and turn it by hand once you know where it is. If you have an SC with lambda, you should learn how to hook up a dwell meter to the test port. You can check the mixture and the default settings of the frequency valve. This CIS system works very well once you learn how to adjust it like a carburetor. It is not like a digital EFI system with fixed controls.
Paul
There is no harmonic balancer on a 911 engine, just pulleys. It sounds like you have the double pulley for an A/C belt on the outside. There is a timing mark notch cut into the lower center of the fan housing. The inner pulley has full length (both sides) notches cut in it at 120 degree intervals. The timing mark is cut on one side only (inner) in front of the notch for TDC #1 (Z1). If you are setting the timing on a 911SC, do yourself a favor and disconnect and plug the inner vacuum retard line (blue or gray braided). The vacuum retard is strickly for the curb idle HC test and leaving it disconnected makes for better cold start running and lowers the engine temperature at idle when hot. The factory setting is 5 BTDC @ 900 rpm, both lines disconnected, but I prefer to use 7-10 BTDC with premium fuel. You have to reset the idle, which is controlled by the large screw on the throttle body, when adjusting the timing. You can easily reach in there and turn it by hand once you know where it is. If you have an SC with lambda, you should learn how to hook up a dwell meter to the test port. You can check the mixture and the default settings of the frequency valve. This CIS system works very well once you learn how to adjust it like a carburetor. It is not like a digital EFI system with fixed controls.
Paul
03-30-2006, 02:11 PM
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Paul
I have tried to hook up my dwell meter to the test port a number of times. There was a post here a number of months ago and explained in detail how and which of the three prongs to connect to. I could never get my meter to move. Any clues??
Ernie 81 SC
I have tried to hook up my dwell meter to the test port a number of times. There was a post here a number of months ago and explained in detail how and which of the three prongs to connect to. I could never get my meter to move. Any clues??
Ernie 81 SC
03-30-2006, 03:38 PM
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Kevin: The notch is your "pointer." The left rear cylinder is definitely #1. The marks on the pulley are sometimes hard to see, so rotate the engine by hand until you have your TDC and 5 degree marks in sight (with distrib cap off the rotor should be pointing inboard toward the large strap that holds the alternator housing - there will also be a small groove visible at that position after you remove the black dust cover inside the distributor). Use a chisel to make the marks slightly bigger (LIGHT TAPS ONLY until you feel how much damage you're doing!), or a dab of paint might help. Some of the double pulley (A/C) cars had marks that were pretty hard to see, I guess the mechanic that's been doing your car's valve adjustments all these years has great eyesight! I know others advocate slight changes to the timing, I always use the 5 degree spec, done by disconnecting both vacuum hoses, slowing the idle to 950 using the idle speed screw, and then checking/setting the timing. After you're done reconnect the hoses, raise your idle (do this whole thing on a warm engine) to 900 rpm and button it up. Always use Premium fuel, Chevron if you have it in your area, and have fun!
Pete
Pete
03-30-2006, 07:12 PM
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Ernie,
You need to connect the dwell meter wire that normally goes to the coil to the test connector green/ white wire. Often the prong is corroded, clean it up first. Most dwell meters need 12v power, you can use one of the fuse blocks under the left hand cover and a good ground. Start with a fully warmed up engine or the dwell meter will read the default setting. There is very little printed information about the final lambda version of CIS and most of it is incorrect. The needle should be swinging back and forth around 40-55 on the 4 cylinder scale, more than once a second. If you get a fixed reading , start troubleshooting the sensor, it may be bad. You need to understand that you are really only adjusting the open loop mixture. The system will compensate for a rich or lean mixture in closed loop and the amount of compensation is indirectly telling you what the mixture is........For best performance you want the needle fluctuating between 35-45 dwell, this will give you the enrichment you need to run the timing advance the engine wants. Porsche tuned the US SC engine for the spec'd 87 CLC fuel, the ROW engines had more ignition timing and more power. A hemi head engine with domed pistons continues to make more power out beyond 40 BTDC, if you have the octane. The US SC engine runs best with a few extra degrees of timing, a slightly rich open loop setting and no vacuum retard. The engine is really close to the knock limit on the spec regular fuel in hot weather.
Paul
You need to connect the dwell meter wire that normally goes to the coil to the test connector green/ white wire. Often the prong is corroded, clean it up first. Most dwell meters need 12v power, you can use one of the fuse blocks under the left hand cover and a good ground. Start with a fully warmed up engine or the dwell meter will read the default setting. There is very little printed information about the final lambda version of CIS and most of it is incorrect. The needle should be swinging back and forth around 40-55 on the 4 cylinder scale, more than once a second. If you get a fixed reading , start troubleshooting the sensor, it may be bad. You need to understand that you are really only adjusting the open loop mixture. The system will compensate for a rich or lean mixture in closed loop and the amount of compensation is indirectly telling you what the mixture is........For best performance you want the needle fluctuating between 35-45 dwell, this will give you the enrichment you need to run the timing advance the engine wants. Porsche tuned the US SC engine for the spec'd 87 CLC fuel, the ROW engines had more ignition timing and more power. A hemi head engine with domed pistons continues to make more power out beyond 40 BTDC, if you have the octane. The US SC engine runs best with a few extra degrees of timing, a slightly rich open loop setting and no vacuum retard. The engine is really close to the knock limit on the spec regular fuel in hot weather.
Paul
