Datsun Roadster Forum-311s.org

Check cam timing
pull the VC and plugs ...check turning torque of crank or estimate ...turn crank over finding the exact spot where #1 exh valve comes up and intake goes down both even - the middle of that
That should be TDC ...or if it can be done with a rod thru the plug hole and lite / boroscope takes 2 techs
...if it's 30_ 40 degrees off then likely it stripped a cam gear tooth ...from being started and had a dry cam bearing / spun / gaulded it explains the rotor off and low compression.

Thank you all for your help & patience - please let me know if we’ve missed something!

Ok, we worked on it for a while today, and here’s the info:

Pulled distributor, found gear was parallel to block, therefore 90 degrees off. Wow!
Removed gear, reset at “12:15/6:15” position, reassembled.
Couldn’t get spark at breaker point, lobe on dizzy shaft was too early.
Removed dizzy, rotated gear back one tooth ccw (11:45/5:45 position), reassembled, lots of backfiring & after-ignition.
Checked valves, realized we were off 180 degrees.
Reset with valves at correct position, set points to just sparking.
Now it cranks, but still no firing!

So it will backfire or after-fire, but we can’t get it to fire in the cylinders?

How can I tell smog from non-smog dizzy?

Also, the rotor has about 45 degrees of play when I wiggle it, but there’s no play in the gear to the oil pump when the dizzy is out - is this correct?

Play in the rotor is your mechanical advance. The good news is that it is not gummed up or locked up and moves freely. You should be able to twist it, release and it will spring back to its original position. If it moves freely and does not spring back, then something may be broken, a spring or a post. Bad news is if it’s 45° in motion you probably have a smog curve on it.

The distributor cam is down under the advance plate, that is where either 7.5 or 17.5 is stamped. That tells you if you have an early (7.5) or late dizzy. The timing is different for each. If all the smog stuff has been removed from a later year car, then chances are they upgraded the dizzy too. So you don’t want to dismantle the dizzy, it has little ball bearings on the advance plate, unless you have to in order to check which distributor you have. There are 2 little springs in there too on the cam and I have had one break before, but that is usually bad running, and you haven’t got it started yet
Here is a pic of the dizzy innards. Ignore the number stamped on the cam, I have the wonderful EI dizzy upgrade. Note the broken spring.
viewtopic.php?f=3&t=30590&p=280730&hili ... ng#p280730

Linda

I'm thinking your initial timing is still off, especially if you have a smog dizzy. As noted, if you have that much rotor movement it suggests it's got a lot of advance built into it. It's literally a slot(s) and the length of the slot determines how far the rotor can move... about 16-20 degrees with a non smog, 36 degrees with a smog. The end result is the same amount of max timing advance, but if you time a smog dizzy to non smog initial (16 degrees instead of 0) you'll be in the 50s or more advance while it's running! Bad!

With the engine mechanically set at 0 on the crank (far left mark on the crank pully is 0) and the distributor unsecured so it can rotate a long distance, you should be able to switch on the key, rotate the dizzy until you see the points open and if the gears are right you should be able to lock the dizzy down. There is an additional adjustment bolt on the dizzy that holds the flat bolt plate to the dizzy, 8mm size, that will allow you a bit more adjustment if you're close, but if done correctly you shouldn't need it. Some are off though, so check it if your close.

Like I said, this will get you close, but some minor dizzy movement while cranking will help find that spot where it will fire. Once it's running and you can get a timing light on it and make it perfect.

To confirm TDC on #1, just look at your valves. As you rotate the engine forward from what you believe is TDC, the next event or movement of the valve train that should happen for that cylinder is the exhaust valve should begin to open. That will take some movement because it just fired the plug and the piston will start down on its power stroke before coming back up and exhausting out the exhaust valve as it opens. If the next event is that the intake valve is opening you're 180 degrees out.

Hi WalterBuddy, just sent you a PM.

Hi all,

Just want to say thank you so much to those of you that are answering & following our saga - you’re the best!
Ok, here’s the results of today’s work:

- Checked under breaker plate, it’s a 17.5! Also, mechanical advance is ~35 degrees, seems good?
- We set the crank pulley to 0 for smog, then pulled the dizzy, pulled the gear and turned it clockwise one tooth so it’s now at 12:15/6:15.
- Screwed the mixture controls in all the way (clockwise looking from bottom), was about 2.5 turns per; screwed then back out to 2.5
- Set dizzy pointer to center, plate bolt to center

Then, we cranked it - still no start in any position we tried! JUST TO MAKE SURE: turning the dizzy ccw retards timing, correct? It seems to spin fastest when dizzy is all the way cw- (advanced?) Should we be trying very small movements of the distributor ~1-2 degrees at a time?

FWIW:
- Spark plugs all fire when tested for spark near block
- Spark plugs were slightly gassy-wet when pulled - don’t know what flooded would look like, but not dry
- Carb “cylinders” both fall freely when lifted
- Float bowls have fuel

ps You’ve all restored my 17- and 18-yr-old boys’ faith in the power of the internet for good - thanks again!

Yes small increments to change the timing should work. Sounds like everything else is in line so it’s just a matter of hitting the sweet spot on timing. I have often slowly rotated the distributor (timing) while cranking to get it to fire. Slow and steady within the range of travel. Just be aware that you could get a backfire that way which can scare the crap out of you, or you can get it to fire which can make you very happy! Stay clear of the carbs and exhaust.

As soon as you can, maybe after you get it firing, I would do the upgrade to change out the cam to an early one, 7.5. The car will run cooler and it is a standard upgrade that is recommmended. Or you can be on the lookout for a used early distributor to scavenge the part. Or you can upgrade to the EI distributor that is very popular. Then the 123 distributor is for the hypertuners
Here is a link on the smog distributor:
viewtopic.php?p=288636#p288636

Linda

Ok, good work. Now, have a spare set of plugs available... you'll need them someday anyway, so have them on hand now so you can avoid dealing with a flooded engine. Do me a favor: Put the engine at 0 on the crank, remove the dizzy cap, confirm the rotor is pointing at plug wire/post #1, remove the valve cover and continue to rotate the engine forward while watching your push rods operate. The next thing that should happen is the push rod for the exhaust valve should come up and actuate the exhaust valve. If it starts to open the intake valve next then you're 180 degrees out and firing the plug on the exhaust stroke and not the compression stroke. The next valve train event after firing the plug MUST be the exhaust valve opening. I know I've harped on this but the key and slot that the distributor gear goes into is offset and allows you to be 180 degrees off. Also, plug #1 is the front cylinder. Confirm firing order 1, 3, 4, 2 and make sure you have them in the right order in the direction the dizzy rotates. It easy to get these mixed up... I ran my first engine to 80mph with crossed plug wires. It even idled (poorly) that way while snarfing out the carbs (Solex).

If it has adequate spark and the right amount of fuel it will run unless there's no compression. Very careful and sparing use of starting fluid may help determine if you are getting enough fuel, but be aware that it is a solvent and will wash the oil off the cylinder walls if a lot is used, leaving it unprotected... just a short (1/2 a second), light spray will work.

My R16 has 165 - 175 lbs of compression ...normal
You may want to pick up a magic wand ....mines on the blink . Or
I'd start looking for the 80 more psi 1st ,around
like a leak down test , or the one I noted ...very likely your pulling eng & trans for that and or new eng

Question : Would the cold compression readings be correct if one or more of : distributor installation, timing, valve adjustment were possibly incorrect?
Linda

Compression readings would not be affected by distributor installation or timing - unless you are talking CAM timing. The valve adjustments would have to be pretty far off to significantly affect the CR.