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I am an idiot when it comes to ignition curves etc. I have an odd situation. My 79 has an 81 engine with the 79 CIS. I also reused the 79 distributor with the vacuum retard (only, no vac advance).
Car runs excellent but power seems to be lacking a little, especially under 2000 rpm. Seems to clear up quite a bit over 2000 RPM. I checked the vac retard for leaks, and its all good. If the car idles with the retard disconnected, it idles slightly higher and a little smoother.
My question is.......is the 81 distributor better to use than the 79. Does it make a difference? Since I am using the 81 cams, I am assuming the 81 distributor may be a better match
Use the timing specs for the distributor that is installed. Check at idle and at speed. Make sure the hose for the retard can is hooked to the right port. Should have good vacuum with throttle closed.
Thanks for the information and sorry for the lack of response. I am not sure why I never got notice on this one
Glen, I need to follow your advice and time according to the distributor. In my sleepy state last night I missed that one!
IN any event, I am still trying to get this car right car seems to have a miss until around 2000 rpm and power comes alive like the flick of a switch. Today I swapped in an 83 distributor with a vacuum advance only, no vacuum retard. Car ran better but i mistakenly timed it to 31 degrees like the original distributor ( I was way too tired to be working on anything )
I also tried the 81 distributor with both advance and retard. It was better than the 79 dizzy as well.
the 79 dizzy has some play on the shaft and lacks the "notch" feeling as each stator contact turns.
I think I am going to install the 83 unit, retime to 20 and see what that feels like. I don't know if I am battling a worn distributor unit or simply that the curves of these units suit the engine better.
81 unit Original 79 unit 1983 unir
How does the vacuum advance produce the mechanical advance on the stator? Anything down there that could be dirty or dry and need cleaning for smooth action?
How does the vacuum advance produce the mechanical advance on the stator? Anything down there that could be dirty or dry and need cleaning for smooth action?
Its a good point. So little is written about distributor maintenance on our cars. I am going to double check and lube the action. All the advance and retard functions work as intended on the 3 units but the 79 dizzy is sloppy feeling. I put a dial indicator on it and confirmed that it has a ton of lateral movement. This may explain why it was so difficult timing it properly at 3000 rpm. The timing light was very jumpy.
Have either of the distributors been professionally rebuilt yet? That is SOP on the older cars I've rescued, probably good idea here too to make sure you are getting consistent behavior and proper advance.
Have either of the distributors been professionally rebuilt yet? That is SOP on the older cars I've rescued, probably good idea here too to make sure you are getting consistent behavior and proper advance.
You are absolutely correct. In my previous restorations of non 928 cars, it's the norm. Doesn't seem to be an area with a lot of info in the 928 realm. Although there doesn't appear to be anything particularly unique in the Bosch units. So I don't know the history in these three units except the say the 83 unit looks and seems to behave very fresh
Installed the 83 distributor last night, hooked up the advance and set the timing to 23 at 3000 rpm with the advance vacuum removed. Curiously enough, the timing at idle WITH the advance hooked up is around 20 BTDC. Car was easier to time [less jumpy] but the car still drives the same. Slight mis at 2000 rpm approx and below. Going to start a new thread as I basically throw away all that has been done and start all over again to get this fixed.
Do you think it could be the ignition box acting a bit funky? The large resistors under the coil also affect running.
yes. Anything is possible. I found some low compression in cylinder 1 and am looking to that as the cause for the low rpm mis but knowing my luck, I will pull the engine and fix the rings and still have the same issue
luckily I do have soared so they are easy enough to check. The resistors would be my first bet.
05-04-2017, 09:48 AM
Lets Talk 16v Distributor Differences
