How to get the most out of my '72 2 bbl 350 with 115000 miles on it.

First off let me explain that I am not experienced in any type of motor building and this forum has become my Facebook replacement. I have replaced parts when needed, the most difficult for me being a timing chain and gear set. I'm an average, at best, backyard mechanic and I know how to use a wrench and hammer (sledge if it calls for it). So my knowledge is lacking and I'm not ashamed to admit it. I google everything. I have been reading as much on this site as I can since I got my 72 Buick Skylark Custom and I need help getting started. This is going to be a long winded post if you haven't figured that out yet. I purchased the car in July and it had sat in a barn for about 20 years previously. The car seems to run fine, would like more power. I am currently running everything stock. I purchased a dwell meter to set the points, and I got a timing light to check the timing and possibly play with it a little bit. I set the dwell at 30* and hooked the timing light up. I disconnected and plugged the hose for the vacuum advance. The timing mark shows up at about 7* at 800 RPM (idle). Basically I would like to get the most out of this engine with out tearing it down for now. I've read the power timing post and am wondering it's the same for 350 motors. I left the hose plugged and held the motor at 2500 rpm in neutral and it showed 0 at 22* advance on the timing light. Without adjusting anything and connecting the hose to the vacuum advance and holding at 2500 rpm the timing light showed 0 at 33*. I'm not sure I'm doing this right or if I should be checking it at the initial 7* which is where it is at idle. Also I am wondering if in order to not crack open the engine to get more take off and "ahhh" is all that is necessary is a stall converter, 3.08 gears and a factory 4 bbl intake and carb? Like I mentioned in the beginning, I know how to break stuff not make it better. Thanks for taking the time to read this. Any help is greatly appreciated.

 

Yes the power timing will work for you. Do it without vacuum advance connected. You will want a recurve kit for distributer. I would suggest a points conversation. A 2000 stall and 3.08 or 3.23 gears would give Alittle more performance. A good dual exhaust with H or X pipe would be good too. A 4 barrel doesn't really gain much at this level . but if you do that you will need a 4 barrel accelerator cable or you won't get full opening of secondarys. Mark at Quadrajet power can get you similar performace from the 2 barrel . stick to the factory quadrjet for 4 barrel.I would consider pulling heads and shaving them .050-.070. Then if you choose to change cam it will show great improvement. At that point the TA 212 is a decent choice but the Crower level 2 or 3 is better.

 

Thanks Alec. Can I use the points system with the recurve kit? Heaven forbid we get and EMP at some time and I couldn't drive the Buick because the electronic ignition got fried ou:. Thanks for the advice. That's kind of where I'm thinking of going with this until I can find another motor to play with.

 

Larry's thread explains it well. Yes you can use your distributer. They do have a kit to convert the original distibuter to electronic and can convert back at any time. But ons step at a time.

 

Ok I've read the document and that is the distributor that I have. I have a digital timing light and there is no knob. It does have a tack built in. Should I be at 0 when I start? When I plug the line and let the car warm up I'm sitting right around 7*. I set the timing light at 22* advance because that's what I was seeing yesterday. The car was in neutral and I held at at right around 2500 RPM and the mark is at 0. Should I start out at 8* at 800 RPM and be at 0* when full advance? After 2500 RPM the mark starts to go back down again.

 

Thanks Larry forgive me for asking so many questions. If I understand you correctly, it doesn't matter where I am at with my initial timing (aside from the fact that the car needs to run smoothly), I want to shoot for a total of 32*. So what I have now is 22* total timing at 2500 RPM. I should have set the light to 32* and saw if it showed up, but I will do that tomorrow. I think I know what I'm shooting for now though with the stock distributor: 32* at 3000 RPM and this is at the 0* mark on the tab. Is that correct? Thanks again.

 

Some lighter springs on the weight under rotor will give more timing at higher rpm . you can have it come in aroubt 2800 for 32 degrees. That will bring up your initial timing also.

 

If you are a novice mechanic and you purchased a car that has been sitting for 20 years, the first thing I would work on is the brakes. I would replace everything that touches brake fluid, master cylinder, wheel cylinders, calipers, brake lines, everything, then worry about squeezing more HP from the engine. Sorry to throw a wrench in the works but I've wrecked 2 cars that were sitting for years due to frozen wheel cylinders.

Get rid of the points, put a curve in and connect the vacuum advance directly to manifold vacuum, not ported vacuum. That's the easiest way to increase performance and fuel mileage.

 

Ok thanks Alec and Larry. I will play around a bit more tomorrow with the stock setup and if that doesn't get me there I will get a spring kit to get me there. I can't express how grateful I am to both of you for your advice.

 

Thanks for the concern philbquick. I am not a novice at brakes by any means. That was the first thing I did with the car when I got it. The lines looked ok when I trailered it home, but blew as soon as I got it off the trailer. I replaced the lines, proportioning valve and master cylinder but I didn't replace the calipers or wheel cylinders as they seem to be working properly. I replaced the pads and rotors in the front and checked out the rear drums and shoes. I do need new tires because the ones on it have nice tread but are dry rotted so I don't take it up the road very far anyway. Right now I'm looking for stuff I can do without having to drive it much until I get the tires replaced.

 

Use ported vacuum for the advance. Manifold vacuum can create a stumble off idle.

 

Please correct me if I'm wrong, fellas, but I thought 34-35 degrees total advance was what was required on a Buick mill. (Total being mechanical plus initial).

The spring recurve kit should give you about 20, and as mentioned before, you want to use the lightest springs to get full mechanical advance in by about 3000.

Now, if you want great off idle acceleration, lower idle temps, and better mileage, you want an adjustable vacuum can, and you want to use FULL MANIFOLD VACUUM.

Limit it to about 11 degrees, so at "off idle" with the throttle plate cracked, you get about 11 degrees.

This will make starts much easier, as you get vacuum advance during cranking. Once the throttle is cracked, full manifold vacuum and ported act exactly the same...and both go to 0 at WOT.

So, at WOT, you get 34-35 degrees. Off idle/part throttle, you get about 45-46, which is about perfect.

You can then drive test it with light acceleration up slight hills, and see if you get any detonation. If you do, dial down the advance.

I don't care what anybody tells you, search for it yourself: Ported vs. full manifold vacuum was a change by Detroit only to meet air emissions requirements. Remember, the emissions readings were taken at idle...

The idea was, once you remove vacuum advance, and engine runs hotter, burning more HCs. It's as simple as that.

Once the throttle plate is cracked, full manifold and true ported vacuum act EXACTLY THE SAME.

Try it out yourself...but don't do it if you don't have an adjustable vacuum can, as you can get too much vacuum advance at part throttle, which can lead to detonation.

Oh yeah, look at the vacuum diagrams of most of the cars prior to 1968... They were all full manifold vacuum.

When I converted, it reduced my idle temps about 10-15 degrees, and made starts a one-bump event. No more hot-start woes, either, as it starts on one bump when the water temp is 195 (where my thermostat is at).

To figure out your settings, I would put the light springs on, and note the rpm where it stops advancing. That is your target point, and note the number of degrees the mechanical advance moves.

Subtract the mechanical /spring weight advance from 35, and the remainder should be your initial timing setting.

This is with a regular timing light... So, say mechanical moves 20. Subtract from 34-35, and you get an initial optimum setting of 14-15 degrees BTDC. Then hook full manifold vacuum up, set adjustable can at minimum setting, and start doing some tests to see how much it moves at part throttle... Like at 2500. Make sure it's limited to about 11 degrees, and you should be good to go.

Doesn't matter if you have a dial back timing light or original, figure it out to get 34-35 total advance.

Get it to the rpm where the mechanical doesn't move any more. Figure out how much it advances (yours, currently, is 16 a but I'd wager that it will advance more if you rev it higher...). Once you figure that out, go back to idle, and adjust the initial to 34-35 minus that mechanical advance number.

 

68-69 distributers are designed for more mechanical advance due to using manifold vacuum on the advance. it actually looses vacuum on heavy accelloration and timing is reduced hence the need for more mechanical advance.

 

Both ported and manifold vacuum go to zero on heavy acceleration (or WOT). No difference between the two... Now, there is a different kind of ported vacuum that starts at 0 at idle, and increases all the way through WOT, but this is not the common "ported" vacuum. It actually pulls vacuum from above the main ventures, so is really a vacuum created by airflow through the carb, and not vacuum created by the pistons.

You may be correct in that the '68-'69 had more mechanical advance, which equates to a lower initial advance setting as well...and this was compensated for by full manifold vacuum on starting...

Regardless, ported vacuum was a cheap man's fix from the big 3 to "get around" emissions tests by increasing IDLE temps by eliminating vacuum advance.

Again, looking at where ported vacuum comes from on the carb (above the throttle plate' which is closed at idle) compared to full manifold vacuum (below the throttle plate), you'll see that once the throttle plate is cracked, the vacuum is the same.

Don't take my word for it...there are literally hundreds of threads on dozens of muscle car tech sites that cover this, with far more science and data than I could ever hope to provide here...

 

Most people misunderstand how ignition advance works and why. What many are saying and doing is eliminating any useful advance and it amounts to spark retard for starting purposes. If you set it up with vacuum advance at idle and all mechanical advance in by 2000 RPM and your torque converter stall is 2000 or higher then you have NO advance during actual acceleration 2000 thru redline. In that case why not just lock the distributor at 36 degrees initial and be done messing with it?
As RPM increases you need to advance the timing to compensate for the time it takes to light the fire at the optimal moment.
Now if you have a low compression, undercammed lazy engine, such as stock you can get away with lots more timing advance at idle because you don't have enough compression to preignite. In this case the added timing will improve idle quality at expense of smooth/flat acceleration thru the RPM range. This trick was used by many people on mid 70's cars to perk them up a little.
Check your timing with manifold vacuum and watch what happens when you crack the throttle open like your leaving a stop light. The timing dips causing as bog as the vacuum drops off.
Tinker with it both ways and see what works best for your combination. Seat of the pants will probably feel better with timing all in early. Dyno or drag strip times will show differently.

 

Agree the total number is most important. Nobody with any performance mods sets their initial timing to stock spec or at least shouldn't. My 72 dist was advancing about 18 and initial was about 16 with my old combo. The new combo wants more initial so I limited the mechanical back to about 14 and now have initial around 20. Will fine tune at the track where actual improvements can be documented.
I can't stress enough that testing with either dyno or track time is the only sure way to know if the changes made are actual improvements or just your brain telling you it should be better because you did some work. Also many times people make changes and think its better because their initial settings were incorrect. I think that is what is happening with the SP3. Nobody has provided any actual numbers to show an improvement other than the SS racer who admits the engine it was installed on was not really the best suited for the manifold.
Again if seat of the pants is good enough for you and your happy then thats great.