offdensen

Tune a 1963 using a vacuum gauge

Recommended Posts

So I wanted to tune my carb and adjust timing using a vacuum gauge. I saw a few videos of people doing this on old Corvettes and mustang's so I thought I would try it since I have a vacuum gauge. 

 

I read though that I need to use manifold vacuum,  and that the 63 with stock carburetor only has ported vacuum. Is there a way to do this on a 63 or is the ported vacuum too unreliable? If I did this which vacuum source would I use? (Advance port, port behind carb to PVC, port on the manifold that leads to brake booster,ect.)

 

To note I have always just tuned it to the smoothest idle using a tachometer and using the specs in the book, but using a vacuum gauge has intrigued me.  

Share this post


Link to post
Share on other sites

I can't say how others do it, but, I have done it on other cars in the past.

 

What I did was use manifold vacuum, turn the distributor to get the highest vacuum possible, then turn it back one inch pound.

 

Like I said, I haven't done it on a Riviera, but it worked for the application I was working on.

Share this post


Link to post
Share on other sites
6 hours ago, offdensen said:

So I wanted to tune my carb and adjust timing using a vacuum gauge. I saw a few videos of people doing this on old Corvettes and mustang's so I thought I would try it since I have a vacuum gauge. 

 

I read though that I need to use manifold vacuum,  and that the 63 with stock carburetor only has ported vacuum. Is there a way to do this on a 63 or is the ported vacuum too unreliable? If I did this which vacuum source would I use? (Advance port, port behind carb to PVC, port on the manifold that leads to brake booster,ect.)

 

To note I have always just tuned it to the smoothest idle using a tachometer and using the specs in the book, but using a vacuum gauge has intrigued me.  

 

You need to use a vac source direct from the manifold, taking a vac line off the carb wont do it for you as the vac source is usually plumbed in above the throttle plate.

 

Alternative sources like the brake booster port or PCV manifold connector are fine ie any port that taps straight into the inlet manifold can be used.(make sure you have an airtight connection)

 

The benefit of vac tuning is that you get to see when the engine is running at best, as opposed to manufacturers figures, which are a good starting point but dont make allowances for todays fuels, engine wear etc. all of which can affect engine performance.

 

And as Rivman says, when you get to the highest vac reading back off an inch or so of manifold pressure before locking everything in place, this avoids potential pinging.

  • Like 2

Share this post


Link to post
Share on other sites

I vacuumed tuned my edelbrock carb.  I followed a YouTube that was made by edelbrock.  It was quite easy and I didn't really do much since it seemed well tuned for the southern California environment.  I used a vacuum port off the carb.

Share this post


Link to post
Share on other sites

17-20 is good. Very mild cam. Little leak down. Good compression.

Share this post


Link to post
Share on other sites
14 hours ago, offdensen said:

I ended with the vacuum on 19, Is this about the normal vacuum for a 401 in 1963? 

 

And how does it drive, notice any difference  ?

Share this post


Link to post
Share on other sites
19 hours ago, offdensen said:

I ended with the vacuum on 19, Is this about the normal vacuum for a 401 in 1963? 

 

OK, so tell us, using a timing light to check it, per normal tune up process (vacuum advance disconnected, at low RPM) how much initial advance did this process give you?  You can read it right off the indicator up front by the crankshaft damper.

 

For 1963 only, the factory spec is 11*BTDC.  How close to that did you end up by the vacuum method?

 

I have a lot of carbon build up in my heads, so my compression is higher than stock and it will ping at 11 degrees of advance when hot under a moderate to heavy load.  So I backed my initial advance down to 6*BTDC and it does not ping.

 

That's my main concern about setting timing at idle by vacuum, that it could be too much under a moderate load. Listen for the png and back off if you hear it.

 

 

Share this post


Link to post
Share on other sites

Tuning these cars, or at least the ones I've have a pleasure of owning, is a compilation of all of the above. When they are new the factory specs are exacting. 55 years later the advance springs in the distributor are worn, the gas burns at a different rate., for all I know I have an aftermarket camshaft installed. The carb has to be in good order. Lots of new variables. Tuning so these start easy, run well, start when hot etc is a little science , a little trial and error, a little patience and a good amount of experience dealing with these great cars.

Start off with factory specs and go from there,  use an advance timing light to see where initial/centrifugal/vacuum advance  brings you and when. If that's off there's going to be problems. Some baby their cars, others like me drive a little harder. I also have zero expectation that the 64 is going to behave like my 2014 Lincoln. When its dialed in it doesn't shudder stall hesitate and pulls forward with plenty of power. When it's dialed in it's got that "sound". Then I make my marks on the timing cover and write down specs. Steve

Share this post


Link to post
Share on other sites

You mean you fix stuff while its still attached to the car, right there under the hood.

 

How quaint.

Dist1.jpg.cc256fdb13d9b9521b278b284a604145.jpg

Share this post


Link to post
Share on other sites

Kinda LOL...I mean if its broke fix it once. There'll be plenty of times when a car tells me it needs immediate attention, I just try to get it so it don't say it so much.  I don't use a screwdriver for a pry bar unless I have to either LOL There's method to everybodys madness

Share this post


Link to post
Share on other sites

The car runs alright for the most part but pings at high rpms. Something that I recently noticed. It isn't running stock ignition though as I no longer have points. The way I tuned it before was with a timing light that has a tachometer on it. 

The way I did it this way was adjusting the timing to find the smoothest idle, not the fastest. Smooth was what I was looking for. I then adjusted the carburetor for the smoothest and fastest idle. 

Because of the pinging I figured I would try it with a vacuum gauge. It isn't pinging anymore after I drove it today so i consider it a success. 

I also ended around 5 degree initial. I would use the shop book mostly as a reference to for procedure for parts of getting ready to adjust timing. I acknowledge that stock timing specs go out the window when the ignition system is no longer stock. 

 

When I set timing using my tachometer method, I did end up around 10 initial timing. 

Edited by offdensen (see edit history)

Share this post


Link to post
Share on other sites
On 10/14/2018 at 3:42 AM, offdensen said:

I ended with the vacuum on 19, Is this about the normal vacuum for a 401 in 1963? 

 

Can you let me know where you tapped into for the vacuum source ( any chance of a photo)

 

My ‘63 is set by the book with a dwell and tachometer and one particular hill gives me grief with pinging. 

Am running 95 and 98 Octane but still pings when overtaking with near WOT.

Might bring it down to 8-9 degrees BTDC .

 

be interested in how you did it and the readings you ended up with.

Rodney ????

Share this post


Link to post
Share on other sites

THE ONLY TIME YOU USE VACUUM TO SET INITIAL IGNITION TIMING IS WHEN YOU DON'T HAVE A TIMING LIGHT.

With that being said it ONLY gives you a basis & you fine tune, advance or retard, as nec. to get the performance, mileage or pinging to where you feel most comfortable.

 

Rodney,

 

I thought the bushings I sent mostly solved your problem???

 

  • Like 1

Share this post


Link to post
Share on other sites
5 minutes ago, telriv said:

THE ONLY TIME YOU USE VACUUM TO SET INITIAL IGNITION TIMING IS WHEN YOU DON'T HAVE A TIMING LIGHT.

With that being said it ONLY gives you a basis & you fine tune, advance or retard, as nec. to get the performance, mileage or pinging to where you feel most comfortable.

 

Rodney,

 

I thought the bushings I sent mostly solved your problem???

 

 

The whole point of using the vac guage is to fine tune,  get the basic settings with the timing light then use the vac guage to adjust timing and mixtures to obtain the highest vac reading, then back timing off to lower your highest vac reading an inch or two. Follow up with a road test and listen for pinging, if you encounter pinging back off timing in small increments until it stops.

 

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, rodneybeauchamp said:

 

Can you let me know where you tapped into for the vacuum source ( any chance of a photo)

 

My ‘63 is set by the book with a dwell and tachometer and one particular hill gives me grief with pinging. 

Am running 95 and 98 Octane but still pings when overtaking with near WOT.

Might bring it down to 8-9 degrees BTDC .

 

be interested in how you did it and the readings you ended up with.

Rodney ????

I will take a picture tomorrow when it isn't pitch black out for you. I unscrewed the hose clamp that connected the brake booster to the intake manifold and stuck the vacuum gauge in there. To my knowledge that appears to be the only source where a vacuum port goes into the manifold as all the other vacuum ports on the 63 originate from the carburetor. 

 

The procedure I used just followed with what Rivman said (first response). Just turned the distributor a bit in both directions to see what would happen. When I got vacuum to its highest point I retarded the distributor a little and tightened the distributor. 

 

As far as I can tell this is the best way aside from using a tachometer to set timing when the ignition isn't stock anymore. I no longer have a points system. I still used a timing light to check and make sure that I didnt end up with some ridiculously high timing though. The car doesnt ping anymore and it starts as soon as I turn the key so it seems fine

Edited by offdensen (see edit history)

Share this post


Link to post
Share on other sites
8 hours ago, rodneybeauchamp said:

 

Can you let me know where you tapped into for the vacuum source ( any chance of a photo)

 

My ‘63 is set by the book with a dwell and tachometer and one particular hill gives me grief with pinging. 

Am running 95 and 98 Octane but still pings when overtaking with near WOT.

Might bring it down to 8-9 degrees BTDC .

 

be interested in how you did it and the readings you ended up with.

Rodney ????

 

Rodney-

I had the same problem.  I went back to 6*BTDC.  He says he ended up at 5*BTDC.

 

So I suggest you go back to 8 or 9 and see how it does.  You may need to go even lower.

 

Don't ping the engine.  It will really tear it up.

 

 

Share this post


Link to post
Share on other sites
7 hours ago, telriv said:

THE ONLY TIME YOU USE VACUUM TO SET INITIAL IGNITION TIMING IS WHEN YOU DON'T HAVE A TIMING LIGHT.

 

I will agree with that one. When I first got into the car hobby there were a lot of great depression survivors who liked to brag about how they could do something with nothing, tools included. Those fables and urban legends are hard to die. I started reading mechanic books about the same time I started listening to their stories, didn't take long before I started listening for entertainment.

 

Now, if you are real serious about pinging, what you do is draw file the tops of the pistons just a little at a time until you get it dialed in. Start with the pistons at the rear because water circulation can be a little low back there and the bores will run hotter.

  • Haha 1

Share this post


Link to post
Share on other sites

In the picture in the middle where the hose clamp is. That's what I disconnected and hooked my gauge into. The metal line goes straight to the intake manifold so I chose that one. 

20181015_130236.jpg

  • Haha 1

Share this post


Link to post
Share on other sites
1 hour ago, offdensen said:

In the picture in the middle where the hose clamp is. That's what I disconnected and hooked my gauge into. The metal line goes straight to the intake manifold so I chose that one. 

20181015_130236.jpg

FYI - This direct line is only on the manifold for a 63.  It supplies vacuum for the power brakes.  On a 64/65, vacuum comes from a T on the back of the carburetor.  On the 66 manifold, there is a direct port in the intake manifold.

Share this post


Link to post
Share on other sites
16 hours ago, telriv said:

THE ONLY TIME YOU USE VACUUM TO SET INITIAL IGNITION TIMING IS WHEN YOU DON'T HAVE A TIMING LIGHT.

With that being said it ONLY gives you a basis & you fine tune, advance or retard, as nec. to get the performance, mileage or pinging to where you feel most comfortable.

 

I disagree.

 

Under perfect conditions, yes, a timing light is the way to go, however, if the situation will not allow for it, you have to do what you have to do. I had the tools and knowledge needed to do the job, but doing it by the book with the correct tools would not accomplish the task.

 

The situation I had was a customer had an ‘80s Chevy P/U, the engine had been “worked” on over the years. I can’t remember which, but, the engine, block and heads, were assembled from ’69 and ’79 parts. I tried using the ’69 settings, no good, then I tried using the ’79 specs, still no good. I ended up setting the timing using the vacuum gauge I mentioned in post #2, and that got it running great. I believe I got 21-inch pounds of vacuum on that engine, then backed it off to 20-inch pounds.

 

The original post was asking how to accomplish the task, not whether it was right or wrong, and that was what I responded to.

  • Haha 1

Share this post


Link to post
Share on other sites
21 minutes ago, RivNut said:

FYI - This direct line is only on the manifold for a 63.  It supplies vacuum for the power brakes.  On a 64/65, vacuum comes from a T on the back of the carburetor.  On the 66 manifold, there is a direct port in the intake manifold.

 

That’s good, since he was asking about a ’63, NOT a ’64 or ’65 or ’66, looks to me like he used the correct port.

Share this post


Link to post
Share on other sites
2 minutes ago, Rivman said:

 

That’s good, since he was asking about a ’63, NOT a ’64 or ’65 or ’66, looks to me like he used the correct port.

Just didn't want any 64/65 owners asking where to find this line.

Share this post


Link to post
Share on other sites
10 hours ago, offdensen said:

In the picture in the middle where the hose clamp is. That's what I disconnected and hooked my gauge into. The metal line goes straight to the intake manifold so I chose that one. 

20181015_130236.jpg

 

Thank you for the photo, that really helps. And that’s where I was thinking it would fit.

 

FWIIW using the vacuum gauge will be a good step to check what settings have been made.

 

As mentioned I use a dwell meter with tacho, so can get the rpm to 400 when setting to specs.

 

And as Tom mentioned, it is wise to check if the vacuum advance has the two rubber bushings intact as these will affect how quickly the vacuum unit works and also the amount of travel ( that’s my understanding of it anyway)

 

Will keep you posted on what I find,

cheers

Rodney ??????

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now