[David Jones]

Back to the basics. School me on the starting point for a correct "tune up".

Use the tip in method to set this. Set the APT to do this. Compression this, set the initial at this. Gap the plugs at this if you have this. Total timing should be this, but these like this. Mixture in until rpm does this then back it out. One at a time. Etc etc etc.

You've just put your new motor in your car and you think the tune is close. The oily bits are happy but the bolt on stuff needs minor tweaking.You have it to operating temp and your vacuum gauge, dial back timing light and assorted other needed tools are handy.

Where do you start?

What system do you start with and what should you do last to check and verify the state of tune?

Run me through the steps (in order) needed to end up with a good running final product.

[Schurkey]

You're asking for half-an-hour of typing.

[Cliff R]

Compression test first.

Verify no vacuum leaks anyplace.

Wires, plugs, cap, rotor, mechanical and vacuum advance operational and correct settings for what you are doing.

Verify initial and total timing, plus vacuum advance adding in the correct amount of timing and that the vacuum source used to apply it is adequate (avoid "weak" ported sources designed for EGR).

Carb idle mixture first, main jet adequate second, then fine tune APT if/as needed. ALL carb tuning should be done with the engine fully heat soaked, in ambient temperatures, using the fuel you are going to run in the engine on a steady basis.

Save the secondary metering rod tuning for the drag strip, run richer rods for street driving so it helps lower EGT's and reduce potential detonation.

Street driving can be used to tune secondary transition, but this usually changes when you get to the track with sticky tires and improved traction........Cliff

[David Jones]

Originally Posted by Schurkey

You're asking for half-an-hour of typing.

Not looking for specifics here, just what to start with and then what to proceed to next. In order.

[geeteeohguy]

Basics: Start with a good battery. Without a strong battery, your ignition system suffers. Compression test. All cyls should be within 20 psi of each other. New plugs, points, condenser. Set the dwell (points) then the timing. Then the idle speed and lastly, the idle mixture. Pretty much what Cliff said. Hot engine. If the idle speed needs re-tweaking after the mixture is set, then do it.

[67gtospud]

If all typed out well, this would be a great thread for a sticky!

[David Jones]

I think the individual steps are well known but I can't say I've ever seen the correct steps/procedure laid out in some sort of order. I know a lot of tuning on a qjet is a deal where an adjustment in one area requires a re-adjustment in another. Change the initial and the idle speed can change. Just thought it would be good to see how it [I]should[I] be approached.

If somebody wants to type more in depth that would be great.

[screamingchief]

IMO,a proper tune-up begins with an OAF change,check/change air filter & fuel filters as SOP too.

I say this as old/dirty/thin/gas fouled oil and less than perfect ring seal can affect the other areas of the tune-up later on,and a plugged up gas filter could easily make one think something is wrong somewhere else leading them to chase their needlessly tale tracking that deal down.

If using a PCV valve,same deal there,if in any doubt,R&R it.

As stated,then check for any vacuum leaks,especially around carb & intake gaskets.

Now would be a good time to check the battery & system voltages if you plan to do so.

Then a quick warm-up and a cursory compression test.

Then as stated,the ignition hard parts basics,cap/rotor/wires/plugs/etc. you can just check these if you feel compelled to be frugal,and/or just R&R (as needed).

Follow that up by checking/setting all ignition settings & timing areas including checking the vacuum advance operation if so equipped.

Then yeah,the carb stuff pretty much as stated by others already.

The actual balancing act between setting the initial timing and the carb (curb idle speed & mixture screws) is just that,a process of back & forth,so there really is no perfect way to write out the best way to do this,as it differs tuner to tuner,and car to car,so what works for one may (or may not) work for another,so this deal just is'nt that easy to say what's best IMO.

Ideally one would have access to an O2 (or maybe a 4gas set-up) to make the carb tuning chores just a bit easier.

Anyhow,yeah,it varies somewhat from time to time too,if running the valves or such,then that would get thrown in there somewhere too,so you gotta keep an open mind and approach it in a logical/sensible way.

FWIW

Bret P.

[geeteeohguy]

Working in the auto repair industry as a tune up specialist from 1980-96, I probably did several thousand tune ups. Always used the sequence laid I stated. It's also on some ASE certification tests. In the real world, I never do a compression test unless the engine condition is indicative that it needs one (rough idle, excess smoke, etc.) A practiced ear and seat of the pants can tell you a lot. If not so seasoned, you can use a vacuum gauge, which will tell you if you have a bad valve, low compression, late ign. timing, restricted exhaust, etc. etc. In the real world, points ignition/carbureted cars needed a tune up about every 12-15k miles. When HEI was introduced in the early '70's, the interval went up to about 30k miles. Today's cars go 100k miles on the original plugs with fuel injection and COP ignition. Different world.