My 1971 521

[wayno]

My first question would be do you need more than 12 degrees, you know the rest of the advance is mechanical and to see it using the light you would have to rev it up and hold it there, you cannot adjust that mechanical advance unless you pull the distributor completely apart and modify it with different springs or welding on it or grinding away metal.

If 12 degrees is your goal then you are there, and that goal is determined by a lot of factors, according to the manual ignition timing on the L18 and L20b from 1974 all the way to 1980 is 12 degrees btdc unless CA engine which is 10 degrees.

[banzai510(hainz)]

Wayno Im not a expert on this but getting it to 12 is enough to keep a good idle and run but if the dist is crank all to one side its usually a no go at higher speeds and with a load.

that's why I say , once warmed up and motor should be able to go from 0 to +25 dtdc just by turing the dist with in the slots provided one its in its range.(if its a match set).  Once at a higher RPM I assume the weights and slots inside provide the rest if good

[mainer311]

24 minutes ago, wayno said:

you cannot adjust that mechanical advance unless you pull the distributor completely apart and modify it with different springs or welding on it or grinding away metal.

That only adjusts how soon and how fast the mechanical advance advances, it doesn’t change how much. To do that, you need to swap out the cam plate. 

 

More advance on these engines is better (within reason). I’m up to about 15 BTDC and it runs great with the stock advance. I also run 93 octane “just in case.”

[mainer311]

7 minutes ago, banzai510(hainz) said:

Wayno Im not a expert on this but getting it to 12 is enough to keep a good idle and run but if the dist is crank all to one side its usually a no go at higher speeds and with a load.

 

How do you figure? The dizzy doesn’t move once locked down, so how would this affect higher speeds? Are you saying it needs more than 12 at idle? I’d have to agree with you if that’s the case. 

[banzai510(hainz)]

I notice when people have the spindal off a tooth YOu can get it to run drive around if the dist is cranked to one side. but it will cut out at higher speeds. I usually find the spindal is off or something is mismatched. One can drop the oilpump and reset it or flip a timming plate/slot plate ect......

 

Even dough I have done this 100times I still once in awhile install it a tooth off as I put the spindal in even using the Nissan instruction using the spindal dimple and mark on the oil pump.

 

Just remember if he has the dist crank to one side and only goes to 12. I can get to mine to 25btdc shows how much room one has on the timming plate if installed correctly.

 

another guys car I fixed was he would cut out at High RPM. I cheak the timming all looks good then find out the guy didn't have the wire for the electric Choke wire hooked up and choke flap was still closed.

 

.

Edited November 6, 2018 by banzai510(hainz)

[Crashtd420]

Well I know dp had to move the oil spindle when he installed the pertronix,  so it's safe to say hes probably off a tooth still.....

He went from dual points , to a single points distributor with the pertronix, and now to a matchbox distributor... 

 

But what I dont get is why you say it will cut out at higher speeds if hes used up all the advance of the timing plate?

Please elaborate....

Also do you mean higher rpms or do really mean higher speeds?

 

[datzenmike]

All engines at idle crave more advance. They are artificially low for emissions purposes.  You can run more advance but this will be added to your mechanical advance and may total more than what is safe at higher revs. For example your total may be 12 + 22 or 34 total but going to 15 will total 37.  You may get pinging at part throttle and at high revs you may not hear it. 

 

 

Take a perfectly times L20B at 12 degrees and idling, and turn the distributor clockwise slightly to advance and the revs will always speed up and run better.

[Crashtd420]

Ok I get that but how does running out of the ability to adjust cause an issue?

If dp is able to get 12 degrees of advance at idle but he runs out of room to adjust why would that have a negative effect? 

Edited November 6, 2018 by Crashtd420

[datzenmike]

 It wouldn't. If you are up against the adjustment range but have 12 degrees, it's fine. 

[banzai510(hainz)]

I know what your thinking but really I don't know. I just know what seems to work..

 

maybe Im saying it wrong. when up to speed and you punch it maybe it wants more retard and it cant. till you ease of the gas and slower run it up to speed.

really his is just off with it crank to one side. that's a SIGN!!!!!!

[mainer311]

Ideally, I’d drop a 7.5 degree advance cam into my matchbox dizzy to get 15 degrees mechanical, and then time to about 16-17 degrees. That’s what I run in my R16 and it loves it.

[wayno]

6 hours ago, mainer311 said:

That only adjusts how soon and how fast the mechanical advance advances, it doesn’t change how much. To do that, you need to swap out the cam plate. 

 

More advance on these engines is better (within reason). I’m up to about 15 BTDC and it runs great with the stock advance. I also run 93 octane “just in case.”

This is why I mentioned the distributor guy in an earlier post, he is the one with the 620 Bonneville Salt Flats race truck, he does this type of stuff to make money, he told me that I could pull my matchbox distributor apart to where the plate is that has the springs, I could take that plate out and weld the short slot a 1/16th shorter, this would limit my advance on my work truck so it would quit knocking/pinging when timed according to the manual, this would do two things, limit my advance to 20 something degrees, and I could re-time my truck from 0 degrees at TDC to maybe 8/10 degrees before TDC, maybe have a little more torque and get better MPG.

I mentioned welding, grinding and different springs, one can do a lot more than you think to a distributor, I had a conversation with the distributor guy about this subject, you don't have to swap the plate, you can modify the one you have with the proper knowledge.

[mainer311]

Easier just to get ahold of a plate that doesn’t have boogered up welds in the slots if you ask me, but if you want a science project, I’m not going to stop you.

Edited November 7, 2018 by mainer311

[wayno]

And it is easier to just drop the oil pump and put  the distributor drive shaft where it needs to be rather than all this talk about modifying the pedestal plate.

I said, "you cannot adjust that mechanical advance unless you pull the distributor completely apart and modify it with different springs or welding on it or grinding away metal", I just said this because that advance is still there when not modified, having the distributor clocked all the way to one side or another does not effect the total  mechanical advance, it is what it is, yes if you are at 12 degrees before TDC then the total advance combined will be more, but at some point even premium fuel will not keep it from knocking/pinging when you start advancing it even higher, and as Mike mentioned, you might not even hear it knocking/pinging till it is too late.

Edited November 7, 2018 by wayno

[banzai510(hainz)]

I have seen JB Weld or Belzona to to shorten the slots of the dist .

 

I disagree Mike on the  12deg if the dist is cranked all to one side. Its not going to work. I cant give a reason beside it being off a tooth or the 2nd version of the EI Pedastal is used and the spindal needs to be corrected to fix this. Maybe the trigger timming is really catching ther other plug wire thus when hitting the gas hard or load then it cuts out.

remember 0-25 should be perfect when turing the dist.

 

But if he figures this out soon we can see what was the fix instead of writting 5 pages on something that is really a 1/2 hour fix by dropping the oil pump if needed.

[d.p]

Why would I drop the oil pump?  

 

I am still not understanding what the possible bad outcome of having 12 BTDC at idle?  Doesn't Nissan recommend 10 BTDC at idle and 700RPMs? 

 

I could drop the pump set the tang to 11:28 and still be at 12 BTDC, then what? 

[datzenmike]

If you can set 12 degrees it's fine. However the distributor cap will be cranked over to the limit also and the rotor may almost be out from under the contact above it. When the engine revs up it will mechanically advance even farther away and the spark will have to arc the gap to fire the plug.

[banzai510(hainz)]

I guess if  YOU think its running fine then dont do anything.

To Me if the dist is cranked to one side just to make 12. then your not going to get optimum HP(drivability).

Just like having the cam sprocket off a tooth or so. It will still run but not Optimum

[mainer311]

53 minutes ago, banzai510(hainz) said:

I disagree Mike on the  12deg if the dist is cranked all to one side. Its not going to work.

 

This makes absolutely no sense.

[mainer311]

7 minutes ago, d.p said:

I could drop the pump set the tang to 11:28 and still be at 12 BTDC, then what? 

 

Exactly. Where you're at right now is perfectly fine.

[datzenmike]

4 minutes ago, datzenmike said:

If you can set 12 degrees it's fine. However the distributor cap will be cranked over to the limit also and the rotor may almost be out from under the contact above it. When the engine revs up it will mechanically advance even farther away and the spark will have to arc the gap to fire the plug.

 

It's only fine at idle. Vacuum and mechanical advance will move the rotor even farther from the plug wire....

 

6 minutes ago, datzenmike said:

If you can set 12 degrees it's fine. However the distributor cap will be cranked over to the limit also and the rotor may almost be out from under the contact above it. When the engine revs up it will mechanically advance even farther away and the spark will have to arc the gap to fire the plug.

 

[banzai510(hainz)]

all I can say is find a hill  go 40 mph and slam it into 3rd and give it all you got and see what happens. If dont cut out its good,But my experience its going not give optimum results.

I will stop now on this thread

Edited November 7, 2018 by banzai510(hainz)

[Crashtd420]

52 minutes ago, datzenmike said:

If you can set 12 degrees it's fine. However the distributor cap will be cranked over to the limit also and the rotor may almost be out from under the contact above it. When the engine revs up it will mechanically advance even farther away and the spark will have to arc the gap to fire the plug.

So after reading this quote from mike and all these pages I think I know what hainz is talking about.... 

Rotor phasing....

Here is a link....

https://www.speedwaymotors.com/tech/rotor-phasing

 

Which I think I might look at on my own truck and see if that might be a factor on my miss fire..... 

Edited November 7, 2018 by Crashtd420

[mainer311]

There's no way to adjust rotor phasing on a matchbox dizzy w/o doing some crazy alterations. The rotor is locked into position by the flat on the advance cam. You can't change this in relation to the position of the EI pickup points. Mine is adjusted almost all the way to one side, and I'm pretty sure that mine is all original. I haven't had any problems. If he's off one tooth AND adjusted all the way in one direction, I suppose it's possible to have a problem. 

 

He can test this by turning the crank to 12 BTDC, and then see where the rotor is in relation to pickup #1. 

 

If one tooth is 18 degrees, I suppose he could get closer back to center,.

Edited November 7, 2018 by mainer311

[d.p]

Yeah didn't go that far but I did check the timing again. 

 

With no advance on the light the pointer is to the right of the 2nd notch AFTER TDC.   With 12 degrees advance set on the light the pointer is right at TDC.   

 

I will move the engine to TDC and see where the rotor is pointing, at least that way I will know how far off I am.