Well, I may not be an old timer, but I'm pretty confident they will agree with me when I say that you should definitely dial in the timing first before tuning the carb

 

I'm not an old timer really but I am certain you want to get the timing right before you mess with the carb too much, that is if it'll stay running for you.

 

ha ha jinx

 

Yeah, that's how it should be if using a timing light, but I'm going to be setting the timing with the vaccuum gauge, as I currently have no timing marks. I'm going to do the timing tape thing eventually, but I have to remove a lot of stuff in order to get to the balancer. So for the time being I'm going to check it with the vaccuum gauge. I know one affects the other (carb/vs ignition) when it comes to vaccuum, and I can't remember which one you should address first when doing it this method....

 

can you use a mirror to see the pulley bolts.. if you can get the damper mark somewhere between the 10 and 3 o clock position.. see if you can line the upper right pulley bolt 45 degrees to the right of center.. that puts the crank at TDC either #1 or #6.. both will be up at that point..

this may get you really close.. you can also with a 5/8 six pointed socket on a short extension and a breaker bar.. rock it back and forth or do it with a socket on the alternator pulley nut while you use a copper wire in the #1 or the #6 spark plug holes to find really close to TDC.. a few paint marks.. or bolt on timing pointers.. 12 o clock damper marks on an 8" damper can be handled with a mr gasket 4600.. or Mr. Gasket 4598 which can handle any of the 3 positions..

 

Ok, being as I have no personal experience with this method, I did a little checking and it would appear that with the vac gauge method, you do tune the carb first and then the timing. DISCLAIMER: this is second hand info from www.classicinlines.com/vacuum.asp

 

The Problem with setting the timing with a vacuum gauge is that you are only finding the optimum setting at idle. There is a possibility that the optimum setting at idle will grenade your engine under load.

 

Ok, being as I have no personal experience with this method, I did a little checking and it would appear that with the vac gauge method, you do tune the carb first and then the timing. DISCLAIMER: this is second hand info from www.classicinlines.com/vacuum.asp

iv used this site when i first started using a vacuum gauge and the technique worked out well then i did minor tweaking to make my application happy

 

I can probably find another source that will tell you to set timing first, by any method. Not to start an argument, but fact is whatever changes you make to the timing will change idle speed making readjusting the carb a neccessity anyway.

 

I am an old timer, been doing this since the late 60's and I will tell you that you can not set timing with a vacuum gauge. It is not even close to accurate. You need a timing light. Some carburetor adjustments are best done with a vacuum gauge or an A/F meter.
The 2 adjustments are going to affect each other. The idle has to be correct to set the timing and vice versa. I usually will set the timing first, adjust idle and idle mixture then go back and check the timing again.

 

I am an old timer, too and this is dead nuts. NEVER set timing with anything but a timing light.

 

Ok, being as I have no personal experience with this method, I did a little checking and it would appear that with the vac gauge method, you do tune the carb first and then the timing. DISCLAIMER: this is second hand info from www.classicinlines.com/vacuum.asp

That seems to be how I remember it as well, and it makes sense because with the carb you are looking for the point where adjustment no longer increases vaccuum, and not total overall vaccuum.

The Problem with setting the timing with a vacuum gauge is that you are only finding the optimum setting at idle. There is a possibility that the optimum setting at idle will grenade your engine under load.

Right...this method usually leaves you with timing that is too advanced at the top of the curve...we would use the gauge to find max vac and then back it off 2 inches. Go for a spin and listen for any detonation, back it off again if necessary.

 

I am an old timer, been doing this since the late 60's and I will tell you that you can not set timing with a vacuum gauge. It is not even close to accurate. You need a timing light. Some carburetor adjustments are best done with a vacuum gauge or an A/F meter.
The 2 adjustments are going to affect each other. The idle has to be correct to set the timing and vice versa. I usually will set the timing first, adjust idle and idle mixture then go back and check the timing again.

Right on with that X2^^ (from an older timer!) :mwink: Adjust timing for highest vacuum at idle speed then go for the A/F ratio, idle speed again, then timing again, then fine tune the A/F ratio again for highest vacuum.

 

Right on with that X2^^ (from an older timer!) :mwink: Adjust timing for highest vacuum at idle speed then go for the A/F ratio, idle speed again, then timing again, then fine tune the A/F ratio again for highest vacuum.

Did you back the timing off an inch or two after the last adjustment to the timing?

 

What should the vacuum be on say, a stock 70s 454? I think I got 15" the other day and the needle was very steady. I was surprised. I expected it to vibrate or drop or do something indicating something wasnt right - but it didnt. It stayed steady.

15 seems a bit low to me, but IDK.

 

It varies depending on a lot of varibles like camshaft profile, altitude, etc....generally normal vaccuum on a stock or mildly modified engine should be in the 14-21 inch range....lower with a more radical cam, higher altitude, etc.

 

I would suggest setting the timing aspects first, retarded timing can lower vacuum levels so yes they are related but,,,

The timing cannot be "set" with a vacuum gage. Dont go there. Get a timing light, if the balancer is too tough to get to then pay someone or get another hobby, I know you will get to it as you said

Determine TDC as has been posted on HRBB hundreds if not thousands of times. Calibrate your damper mark, piston true TDC, and the damper pointer.

This is a nifty link that can be used with vacuum gage readings it may help spot issues but that is it:
http://www.secondchancegarage.com/public/186.cfm

As mentioned you can check engine vacuum at idle and adjust carb mixture for maximum "hg with the gage, you can also look for vacuum leaks etc.

The gage can also be used when you set up your distributor vacuum advance on the bench or in the car

Hook up your vacuum gage in the car and take it out for a spin, go through the gears etc drive at cruise speed, under load, part throttle tip in, down shifting etc etc. Record the values and under what conditions and RPM. These value can be used later to set up your distributor,,,,another story.

 

agree with above - no point trying to set a carb when the timing is bad.. set the carb up close as u can (make sure it doesnt have any issues of course..)

disconnect the vac gauge and plug the hose/port it connects to (note the vac can doesnt suck air, the engine does).
Set initial timing using a light - OR adjust distributor so u dont have more than 36 degrees (approx) around 3000-3500rpm.. if you have more than that you have to use lighter springs and possibly limit the mechancal advance in your distributor..

Good luck -

 

If you have points, adjust the dwell before setting the timing.