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Ancient History

2K views 15 replies 13 participants last post by  farna 
#1 ·
This one is for all or most of the old timers (or anybody really): Any of you guys ever time an engine with a vacuum guage, advancing the timing until you got the highest vacuum reading? I was wondering if anybody has any opinions on it. and how good/bad it ran after the timing was set this way?
 
#6 ·
302/Z28 said:
Back in the day we used to "power time" an engine. Once it is up to operating temperature raise the rpm to about 3000 and hold it there. Advance the distributor until the engine starts to misfire, then retard just a hair.

Vince
I remember doing this and I'm not that old. I remember watching older guys time their engines by ear, and actually learned something here and there from them that has helped me along the way.
 
#7 ·
302/Z28 said:
Back in the day we used to "power time" an engine. Once it is up to operating temperature raise the rpm to about 3000 and hold it there. Advance the distributor until the engine starts to misfire, then retard just a hair.

Vince
I bet a dyno would show that this teqnique isn't far off from optimum if the advance is all in by 3K.
 
#8 ·
Everybody knows that under light load an engine needs more timing, like with a vacuum advance can kicking in.

So if you time an engine with the vacuum line off, revved to 3000 or more, all you get is a lot of timing in a zero load condition that will usually give you detonation when you drive the car (load), and especially when the vac can kicks in another 13-24 degrees under a light load actual driving condition.

So, ya, I have seen it done for years, but with a marginal fuel octane condition, it NEVER works. That is, you are going to have to adjust it again to stop the detonation.
 
#10 ·
Like Ian, I set timing "by ear". Advance until it rattles, then back off 2-4 degrees, which is also done "by ear". I used to take a light and see what I had for future reference, but stopped doing that as well. If it pings later I just drop it another degree. This can happen not only with different gas, but under differing conditions such as altitude and temps. I used to change timing 2-3 times a year, but now I'm using EFI and don't need to.
 
#11 ·
wow, young people like me can learn A LOT from this thread. :thumbup: they don't even teach my best friend how to recurve distributors in college for mechanics anymore; everything is all computer computer computer :(


UGH! I hate complicated stuff.
 
#15 ·
ChevelleSS_LS6 said:
wow, young people like me can learn A LOT from this thread. :thumbup: they don't even teach my best friend how to recurve distributors in college for mechanics anymore; everything is all computer computer computer :(


UGH! I hate complicated stuff.
The majority of what I read on here is how to absolutely NOT dial in timing. I'd not base my learning of engines on this thread.
 
#16 ·
Once you get into a specific EFI system you soon realize it really isn't complicated at all. Not as much "zen art" into it as tuning a carburetor and recurving distributors, that's for sure! Never mind that you can't change much on the factory EFI systems... you can "tweak" them once you figure out what they're doing. Crankshaft sensors can be moved a little, and a resistance or voltage changed here and there to make a big difference. Or go all out an get a programmable system and connect the laptop -- easy fuel and timing curve changes! But those systems cost $1000+ depending on how far you want to go. But try www.megasquirt.com (or search for Megasquirt) and www.sdsefi.com. The SDS system is one of the best DIY installer products out there.
 
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