Ancient History
 

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?

I think you would wind up with the timing way overadvanced.

Using vacuum gauge for setting idle mixture would be good though.

It does work good timing with a vac gauge I know a lot of people that do it, you have to use ported vac tho, not manifold vac.

the only vacuum tuners are concerned with these days is BOOST...PSHHHHHHHHHHHHHHH!

i like to set my valves to a vacuum guage. ive also set the timing and idle to vacuum also. never let me down.

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.

I bet a dyno would show that this teqnique isn't far off from optimum if the advance is all in by 3K.

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.

I used to 'power time' by advancing until it rattled uphill or 1 gear too high. 20 years on I do the same but retard 3 - 4 degrees from this as fuel quality is no longer consistent. I also run much less compression these days.

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.

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.

In the early 80s a co worker (the Bear) and I used to bet on how close to factory dwell angle we could get setting points by eye. Mostly within 1-2 degrees, I got bang on about a 1/2 dozen times. (M/Benz with the dissy up front) Just practise, nothing more.

That is definately NOT a statement a real mechanically-minded person would make. Making sense of complicated systems is what hot-rodding is all about!

Cleanup on aisle 5.

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.