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Discussion Starter · #1 ·
Cylinder #1 is at TDC

To my untrained eye, it looks like my timing is retarded. Could this be a cause of my low engine vacuum?

109051
 

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Discussion Starter · #3 ·
I cant see the V in the gear, maybe a bit more top down.
I can see it, but I know where it is. I messed with the saturation to see if I could get more contrast. The V is almost center, but a bit to the right.

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Your cam timing is fine IF your engine is really at TDC. I say that because the crank pulleys are getting pretty old these days unless they've been replaced or rebuilt. Yes, crank pulleys can be rebuilt, if you want to order one just get ahold of me through my e-maiil or call me. Now as far as your low vacuum goes, here are a few things that can cause a low vacuum. Low compression, valves being out of adjustment, a vacuum leak, and retarded ignition timing. The last one is the most common because most people don't know how to check all the timing functions, they only know how to check the initial timing. You need an adjustable timing light to properly check the timing, here's the formula I use. A= initial timing, B= vacuum advance, C= mechanical advance, D= total timing at 3500 to 4000 rpm. What you need to check is total timing. A+B+C=D. On most z's it's going to be 42degrees. If the compression has been raised then D needs to be lowered until pinging goes away. If you get pinging then retard the timing 2 degrees at a time, then go drive it and see if it's gone. If it isn't then repeat that procedure until it is gone. Once it's gone put the timing light back on and see what your initial timing is now, and adjust the idle speed to 900 to 1000 depending on engine modifications. That is your new timing setting, log it somewhere safe. I can't begin to tell you how many cars that I've diagnosed as having a low D, compensated for it like I described, and then wait for the customer to give me some feedback. It's one of the many reasons that my customers tell me that I can always get their z's to run better than anyone else can. Z man of Washington
 

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#zmanofwashington
Not to hijack the thread but I am in the process of converting my 280zx over to a megasquirt with a 36-1 toothed crank trigger no distributor system and I would like to know how I could set the timing up for optimal performance as you have described in your post as there is no vacuum advance it's all computer controlled now with sequential spark and fuel.
Do I just set total timing advance to 42 degrees in the 3500rpm and up range and then back it off if it pings until the pingingI goes away?
I know you can do a lot with the megasquirt computer so I would like to get info on the best way to go about setting up the timing curve and what not to get max performance.
It's a slightly moded motor with a comp cam .460 lift cam 3-2-1 header the head has had the valves deshrouded and the bowls blended with a little work on casting flash and the valve guide areas and the short side radius but all was done at home DIY.
There's a custom intake home built that is similar to the lone wolf intake and a 62mm throttle body.
Any Info on setting timing with a modern computer would be great and I'm sure others can use it as well.

thanks
Berry
 

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Discussion Starter · #7 ·
Your cam timing is fine IF your engine is really at TDC. I say that because the crank pulleys are getting pretty old these days unless they've been replaced or rebuilt. Yes, crank pulleys can be rebuilt, if you want to order one just get ahold of me through my e-maiil or call me. Now as far as your low vacuum goes, here are a few things that can cause a low vacuum. Low compression, valves being out of adjustment, a vacuum leak, and retarded ignition timing. The last one is the most common because most people don't know how to check all the timing functions, they only know how to check the initial timing. You need an adjustable timing light to properly check the timing, here's the formula I use. A= initial timing, B= vacuum advance, C= mechanical advance, D= total timing at 3500 to 4000 rpm. What you need to check is total timing. A+B+C=D. On most z's it's going to be 42degrees. If the compression has been raised then D needs to be lowered until pinging goes away. If you get pinging then retard the timing 2 degrees at a time, then go drive it and see if it's gone. If it isn't then repeat that procedure until it is gone. Once it's gone put the timing light back on and see what your initial timing is now, and adjust the idle speed to 900 to 1000 depending on engine modifications. That is your new timing setting, log it somewhere safe. I can't begin to tell you how many cars that I've diagnosed as having a low D, compensated for it like I described, and then wait for the customer to give me some feedback. It's one of the many reasons that my customers tell me that I can always get their z's to run better than anyone else can. Z man of Washington
I’m willing to try it. Is there an adjustable timing light you recommend?
 
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