Super Six, Slant Six Timing

[smitty040]

Just finished the motor swap on my '67 Dart. Swapped in a slant six from a '69 Dart.

Currently I have the carter two barrel super six set up. Distributor is stock with points.

When I got the motor it was two teeth out of time. Getting ready to work on the timing and wanted to know best practices. Trying to get the best gas mileage with a 904 and still have some jump.

Where should I be looking at as initial degrees at idle and onward from there?

Should I be disconnecting vacuum advance during the whole process or part?

I also have a spare tach laying around should I be using that as well to get as accurate as possible.

I know ultimately HEI is the way to go and it's in the works this winter. Until then I just want a fun realiable motor to get me through the summer.
Im really good at the nuts and bolts part and eager to learn the more technical aspects.

Thanks!

 

[kesteb]

I would do basic tune up and set the initial to the factory settings. When you do the HEI upgrade, use a F-body distributor with a 9R governor and sit it 12* BTDC.

 

[jbc426]

I had Doug Dutra build a Super 6 Slant for me with his smaller cam. The motor ran very well. It wasn't until I gave the motor significantly more initial advance and reduced the total advance to keep it at 32 total, that the motor cam to life.

It loved the timing set at 22 initial and 32 total. I hooked the vacuum advance to manifold vacuum and reduced the throw enough to keep it out of gas knock range on the freeway at light throttle (around 40 total, if memory serves). As you know, the vacuum advance goes away when you open the throttle, which subsequently reduces the incidence of detonation under heavy load.

With the timing set like this, the car would burn the tire with ease.

 

[smitty040]

Everything is stock in my motor. I am assuming from other posts I've read to start at 5^ BTDC and work form there with the vac advance disconnected and plugged at the carb. Ideally end up between 7^ and 8^ BTDC. I've got a piston stop tool to find true top dead center just in case the balancer has shifted. Going to check the governor and vac advance to determine where I should fall at cruising speeds. I've seen 48^ advanced?

Just wanted to check this information to make sure it's right.

 

[AJ/FormS]

Heres what you do. Disconnect the Vcan for a long time. Reach down and crank some advance into it;forget the light for a sec. Just keep advancing it until the idle speed stops rising. If you run out of room on the advance slot fix it, reduce the idle back to the beginning,and continue with the advancment. As long as the idle rpm is increasing, the engine is telling you, she's liking it. Keep backing off the curb idle screw and adjusting the mixture screws as may be required.Now put a light on it, measure it, and write the number down.
Next, crank the rpm up to 2000 rpm or a little more maybe as much as 2200. Reset the mixture screws for smoothest fast-idle. Now retard that dizzy. If the motor speeds up, keep retarding it, until plateaus.If it slows down, return the carb to base idle speed and reset the timing to the former amount.Leave the mixture screws where they are, unless it idles rough, you can move them a bit. This will be your new official idle timing for the fuel that is in the carb.
Now there are two more things to do. #1, is power timing, and #2 is the Vcan.
But first take it for a spin. You will be testing for spark-knock/detonation/pinging/rattling, whatever term you are familiar with. You will be testing for it, in 2nd gear, and from idle to 2000 rpm, with various throttle settings.Anytime you hear detonation,grab an rpm reading and back off the throttle. Write it down and include an approximate throttle setting, like WOT, 3/4, 1/2, or 1/4 throttle.Work your way up slowly. Take your time. Take a week or more.If you never hear it, move up to 3000 and repeat. And if you still never hear it, move up to 3500, and repeat, and once more to 4000. Stop there.At 3000 you only need to test 3/4 and Full throttle. At 4000,you only need to concern yourself with full throttle. But if you ever hear the dreaded rattle, back off the throttle immediately.
Now keep in mind, you have to be able to hear it. If your hearing is bad or your muffler is screaming, or you don't know what detonation sounds like,... All bets are off.
Ok now, back to the garage. Get the lite on it. Rev it up to 2000 and verify the previous setting, whatever it was, is still valid. Then move thru 2500,3000,3500, and 4000, recording the timing numbers as you go.If it maxs out over 36* you will have to mod the dizzy. If you never had any detonation, and you are sure about that, you can let her max at 38*.
But chances are you had all kinds of detonation after 2500 and over 1/2 throttle. So we can get into that in another post. Do not hook the Vcan back up until the power-timing is fixed.
When I Super-Sixed my slanty she liked a lot of timing.
Report back whenever you think you are ready to proceed, or need any other help.

 

[the wall]

simple and easy what jbc 426 wrote simple and accurate aj/forumS lot of detail and also on point

 

[nm9stheham]

Now there are two more things to do. #1, is power timing, and #2 is the Vcan.
But first take it for a spin. You will be testing for spark-knock/detonation/pinging/rattling, whatever term you are familiar with. You will be testing for it, in 2nd gear, and from idle to 2000 rpm, with various throttle settings.Anytime you hear detonation,grab an rpm reading and back off the throttle. Write it down and include an approximate throttle setting, like WOT, 3/4, 1/2, or 1/4 throttle.Work your way up slowly. Take your time. Take a week or more.If you never hear it, move up to 3000 and repeat. And if you still never hear it, move up to 3500, and repeat, and once more to 4000. Stop there.At 3000 you only need to test 3/4 and Full throttle. At 4000,you only need to concern yourself with full throttle. But if you ever hear the dreaded rattle, back off the throttle immediately.

The hard part is telling the difference between mild spark knock or pinging, and detonation. Pinging is OK and many engines in the 70's suffered from it but kept going fine as the manufacturers leaned carbs to meet emissions; it is light sounding and high pitched, similar to a marble rattling in a tea cup. I had a '76 Dart Lite that pinged all the time with moderate to large throttle openings if I had it in too high a gear and at low RPM's; in 4th gear OD up a mountain at 50 mph, it was guaranteed to ping... a lot. I sold the car with over a quarter of a million miles on the engine, going strong.

Detonation is a much heavier sound, like a big hammer striking aluminum, and sometimes the engine can seem like it is jerking around.

BTW, an HEI ignition (yes, redundant!) will act like some level of advance, as it gives a much better start to the spark and the burn process in the cylinders.

 

[smitty040]

That's a lot of info to digest. Hopefully when we get some good weather in Ohio soon I can run it through its paces.

 

[AJ/FormS]

Keep in mind that on a slanty, a poor tune versus an on-the-money tune, is not a whole kick in the butt. You might find 10hp or 15ft lbs.
The #1 quickest, most noticeable, kick in the pants/smile on your face mod you can do, is to change the rear end. Most slantys come choked with 2.76 type gears. A swap to the go-to 3.55s will up the giddy-up to;3.55/2.76 = plus 28.6%.To get that on motor only would require something like 225 x 1.285 = 289 cubes.To make that in the motor only would require an increase of about 40 horsepower. To get plus 40 hp from a slanty is not easy, and most definitely, not cheap!
The #2 quickest way,is to find a tranny with the wide gear ratios; 2.74/1.54. And
The #3 quickest way, is to combine the two.

For instance; if you currently have a 2.76 and a 2.45low-904, then your starter gear is 2.76 x 2.45 = 6.76 with a TC of 1600, this is downright snail slow.
But swapping to 3.23s and the 2.74low, gets you a starter gear of 3.23 x 2.74 = 8.85. And this would be 8.85/6.76 = plus 31% increase in take off torque, while increasing the hiway revs just; 3.23/2.76 = plus 17%; or from about 2400 @ 65 to about 2850 with 25" tires.
Now go back and re-read that part about plus 31%. Plus 31% is HUGE!! This will make your lowly 225(3.7l) take off like it was a 295! Thats nearly 5 liters!If your head can't get this, you have just got to try it!
And the part I didn't mention is that the 2.74 tranny usually has aTC with a bit higher stall. And sometimes a loc-up, too.You will need a tach and/or a rev-limiter

If your car happens to be one of those with 2.45 gears, and you do the swap,wear a diaper on your first trip out!