Timing question/Distrb Advance

[DallasHannah3]

70 nova. 83' 305, 4bbl qjet. Points style Reman distributor.

This is kinda weird to me..the whole timing thing. I'm not too good at it, but i have a friend who is pretty good at getting it set.

I replaced the intake manifold and my dumbass didn't set it to TDC beforehand, so we have been fighting with it to get it right. Well, we have it running well, but I am still at a loss because we got it to operating temp.

600rpm we are at 7 degrees.
2600rpm we are at 55 degrees?

I know it should be between 28-32 (thanks 327JET) at 2500-2800rpms, but 55?! and the time before that it was at 43 at 2500rpm.

So for now we just capped the port on the carb off and left the advance off of the distributor.


What should I do?

Thanks guys!

[erik erikson]

Originally posted by DallasHannah3
70 nova. 83' 305, 4bbl qjet. Points style Reman distributor.

This is kinda weird to me..the whole timing thing. I'm not too good at it, but i have a friend who is pretty good at getting it set.

I replaced the intake manifold and my dumbass didn't set it to TDC beforehand, so we have been fighting with it to get it right. Well, we have it running well, but I am still at a loss because we got it to operating temp.

600rpm we are at 7 degrees.
2600rpm we are at 55 degrees?

I know it should be between 28-32 (thanks 327JET) at 2500-2800rpms, but 55?! and the time before that it was at 43 at 2500rpm.

So for now we just capped the port on the carb off and left the advance off of the distributor.


What should I do?

Thanks guys!

Get an H.E.I. distributor.

[R Pope]

Don't check timing with the vacuum advance connected. You want to know what the centrifugal advance is doing, the vacuum one is not doing anything at wide open, but checking it with the engine running free at part throttle lets the manifold vacuum build up and pulls the advance. That's what's giving you the excessive readings.

[C9x]

R Pope is right.

I'd like to add that since the engine is lightly loaded at the 2600 rpm level, vacuum levels at that rpm - regardless of how big the cam is - in a well sealed engine (meaning rings and valves) is probably at 18"-19".

Apparently your vacuum advance is connected to manifold vacuum (IE: tapped below the throttle blades) and you're getting full vacuum advance.
Add that to the all-in or nearly all-in mechanical advance and your result is the 55 degrees BTDC you obtained.

Doesn't hurt anything and in fact is the way to do it.

Mechanical advance is rpm related.
Vacuum advance advance is load related.
Once you roll the throttle on, the mechanical advance will advance the timing - if you're below the all-in timing rpm level - and the vacuum advance will retard the timing.

Look at vacuum advance as a vacuum retard device and it may be easier to understand.

Looking from here it looks like everything is working as it should and like R Pope says, disconnect the vacuum line when setting timing. (Plug the engine end with a golf tee or the like.)

After you've set the mechanical timing, connect the vacuum advance and see if it works like it should.
IE: advance under light throttle settings and retards when the throttle is depressed.

Be careful and stay out of the plane of the fan when doing these tests.

[C9x]

Go here for more information: http://www.route66wingsandwheels.com...opic.php?t=621



(This article was also posted on this site, but it seems to have disappeared.)

[327,JET]

It sounds like a problem with the dist. The dist. is over advancing the timing. There should be a limit pin or ridge that prevents that. Maybe it's missing or broken off . I you continue with that much advance timing , thing's could go real bad real quick. You could alway's get a conversion kit with a magnetic pickup at the very least . It's just one less thing to worry about.

[C9x]

Originally posted by 327,JET
It sounds like a problem with the dist. The dist. is over advancing the timing. There should be a limit pin or ridge that prevents that. Maybe it's missing or broken off . I you continue with that much advance timing , thing's could go real bad real quick. You could alway's get a conversion kit with a magnetic pickup at the very least . It's just one less thing to worry about.

I don't think he has a problem with the distributor.
Everything is working as it should if he shot the timing - and it appears he did - with the vacuum advance connected.

If the vacuum was shot with the vacuum advance disconnected and the mechanical advance was allowing that much advance he'd hear some serious knocking once the engine was under load and the rpm's were up a bit.

Engines like - and need - a lot of advance at light throttle settings.
Especially so at idle.
Most times, running sans vacuum advance or using ported vacuum (tapped above the throttle blades) will lead to overheating at idle and in summer traffic.

Far as I know the electronic conversion kits don't change the timing characteristics of the distributor.

[thesals]

Originally posted by C9x
Far as I know the electronic conversion kits don't change the timing characteristics of the distributor.

they sure dont, the sit just where your points would, so when your plate advances the unit still advances too...

[DallasHannah3]

Well, it doesn't matter anymore..well not for now lol. The engine ended leaking out ALL the oil and my first day back to work (since Oct due to a back injury) on a dark desolate road so i didn't have any lights to see the smoke by and the motor started knocking so i stopped and pulled over and looked under the hood and the knocking was extremely loud (coming from the back of the passanger valve cover (either cylinder 6 or 8) like a rocker arm was knocking the valve cover but it's all stock, just giving an example of the sound. Got the car towed back home, it was completely empty oil wise (oil ALL over the block/fenderwell) and ive decided to just park it and buy a crate motor when i can afford it. until then it will just some some minor body work. It still runs, but i dont wanna push it because i will probably rebuild the motor with a 400 crank and 350 pistons (is that compatible/possible) and come up with some strange displacement through boring. lol. If i use 400 crank/350 pistons, what would my displacement be?

Dallas
70 nova (dying) 83' 305 v8 & 1.76 powerglide