Calling for help from the datsun tuning gods.

[scooter]

Good evening gentleman.

 

Im wondering if anyone has a picture of an advance plate thats been modded to allow for only 20 degrees of advance or so.

 

Im running dual 45's on a 2.3' with a isky z-196 cam. Its happy with 12-15 degrees at idle, and about 35 total. But with the stock matchbox dist i cant get a happy medium.. At 35 total, it doesnt have enough at idle, and if i get where its happy at idle, it has wayy too much on top 40+. The vacuum advance is not hooked up.

 

I was thinking of jb welding up my advance slots, but i wanna see what other people have done.

 

I was also tempted to just lock it up, but thats not the greatest solution for the on road driving it does too.

I do have a start/retard box on it, so i can pull timing out if i do lock it up. But some kind of mechanical advance would be better.

 

 

Cheers.

[MicroMachinery]

Each tooth on the distributor drive is equal to 18 degrees(20 teeth total) if my memory serves me correctly... perhaps it's the other way around. If you want 20 degrees advance, just drop your oil pump and move it one tooth.

[datzenmike]

First, run with vacuum advance. It adds needed advance at part throttle and improves your mileage and part throttle performance. Disconnect to set the initial static advance. Vacuum advance at idle will increase so the static timing can be decreased which will lower the high rpm total advance. I'm guessing your carbs don't have a vacuum advance port?

 

 

 

What about stiffer advance springs that won't allow so much high rpm advance?

Or lighter centrifugal counter-weights?

[banzai510(hainz)]

there is a write up soemwhere of a guy JB welding the slots and recutting them out to what he needed.

[Stoffregen Motorsports]

Weld the slots and then file them to get the perfect tune. If you TIG the slots with a soft rod like silicon bronze, it will be easier to file, but won't last as long in the car.

 

You want a dead stop on the mechanical advance. Putting stiffer springs in to act as the stop is asking for trouble. Besides, you want that timing to come in early, and stiff springs won't allow that.

 

To get the timing in early, instead of buying the kit with all the different springs, I remove one of the springs and use only one. You can fine tune the tension and/or preload on the spring by bending the tang that the spring attaches to.

 

I don't think JB weld would hold up. Have you ever looked at the wear on the slots and pins before? They certainly take a beating. JB weld would be totally temporary.

 

Good luck

[Stoffregen Motorsports]

Each tooth on the distributor drive is equal to 18 degrees(20 teeth total) if my memory serves me correctly... perhaps it's the other way around. If you want 20 degrees advance, just drop your oil pump and move it one tooth.

I don't think this is what the OP is referring to. He's talking about advance inside the distributor.

[MicroMachinery]

Ah.

[EricJB]

What RPM are you trying to idle at? I have ran a 2.3 with the same cam, and 48 dcoes, 1 3/4 merged with a megaphone, with a stock point dizzy/pertronix (no can), and a Mallory DP/pertronix, and mine always idled chunky at 950 to 1000 RPM. plumbing a vac can to an isolated runner intake might be a pain, (if you chose to try manifold vacuum) and the carbs dont have ports.

 

I played with several different combo's on my V8 Zcar. No can, can to ported vacuum, can to manifold. I also messed with advance springs and limiting the vac can travel. With no can at idle, 36 total, 12 idle, it would get hot sitting still really fast. What worked best for me was setting the initial/mechanical at 36 total at 3k with one light spring, one stiff. Then limiting the can to 12 degrees and plumbing it to the manifold vacuum, giving me 24 at idle, 48 at cruise, 36 wot.

 

The car runs cool in traffic (or the staging lanes) has crazy good throttle response, good idle. Just mess around with different combo's till you find one that works. You might find that just locking the plate down solid and using your start retard gadgetry to be the ticket. 

[scooter]

I can tig up the slots with silicon bronze, thats no problem, id like to get a measurement from one allready done, so i dont have to take mine apart 60 000 times. Im aiming for about 20 degrees of mechanical advance, so i can set it at 15 at idle and 35 all in. Not gonna run vacuum advance.

 

 

 

 

Ericjb, it wont idle down to 1000 if i set 35 degrees total, it backs down to 5 or so then starts running like shit and egt spikes.. This is what happens when i go below 1500 or so.

 

Off its current idle of 1500 or so, the car is a monster! This slot shortening trick should solve my issues and make my idle less erratic.

 

 

Eric, what size throats do you have in your 48's? I have 45's with 40 mill throats and i still have zero bog, and still pulls real hard at where i shift it.

 

I feel in the future im gonna end up selling these and getting 50 or 55's

[Stoffregen Motorsports]

I don't have a pic of the distributor cam for you, but I can say that you don't have to put much of a weld in there.

 

45's ought to be good enough for the street unless you've got a pretty insane port job, big valves, a long runner intake, and a killer exhaust (good header and 2.5" exhaust).

[scooter]

Well.. It is ported out like crazy, has 45 and 36mm valves, ported cannon intake and a 2.5 inch exhaust. I do have one of those top end performance shorty headers on it though. Eventually its getting a nissan comp ceramic header. It needs bigger primaries.

 

Thats good to know about just a little bit of weld in there. I have somewhat of a jig tool to measure the advance on the bench thought up in my mind. if it works ill post it along with a how to.

 

Cheers.

[Stoffregen Motorsports]

You coukld make a small degree wheel and tape it to the top of the dist cam, make a wire pointer for it and set it that way. Or you could buy a small plastic or aluminum degree wheel for motorcycles.

 

...or you could just try a bit of weld, clean it with a small round file, install it and check with your timing light. The numbers don't lie.

[EricJB]

 I do have one of those top end performance shorty headers on it though. Eventually its getting a nissan comp ceramic header. It needs bigger primaries.

 

 

 

I started out with one of those POS shorty headers. No one makes a decent header for a 521, so I ordered a v8 header kit and hack and slashed this together. That was after building the merged collector and sourcing a flange. It was a fun project and made a HUGE difference. 1 3/4 primaries.

 

Dont remember what chokes are in the 48 dcoe's. I will have to look.

 

 

 

[datzenmike]

My hatred of headers stems from one I bought in the 70s for my 521. Used on the L20B swap I did also. There was zero improvement proving the stock manifold is plenty good enough. Now a modified engine? ... probably something there.

[EricJB]

I still have my shorty. My conscience wont let me sell it. Worthless.

[Stoffregen Motorsports]

My hatred of headers stems from one I bought in the 70s for my 521. Used on the L20B swap I did also. There was zero improvement proving the stock manifold is plenty good enough. Now a modified engine? ... probably something there.

Mike, that was like 50 years ago...

[Stoffregen Motorsports]

I still have my shorty. My conscience wont let me sell it. Worthless.

Attachment is the source of all pain.

 

- Confucius

[EricJB]

Attachment is the source of all pain.

 

- Confucius

 

You're right. First six pack of Henrys gets it.

[datzenmike]

Mike, that was like 50 years ago...

 

The trucks are still 45 years old and haven't changed. They don't fit, need to be modified, they rust, run hotter under hood temps, difficult to seal the gasket at the head, leak, noisy, flange bolts constantly come loose and lucky to get 5 years use out of them. Had to remove torsion bar and loosen engine mount to get on, took three tries to get it to hold water... flange thickness isn't the same as the intake and won't clamp properly. A Sat. morning job took all weekend. Back then were $80 or $90 bucks and on a stock L20B did nothing. This is '78 money that could have been put to way better use.

[Stoffregen Motorsports]

Agreed. They never fit right and the gaskets usually blow out over time.

 

• Modern cam and exhaust technology have proven the need for good headers.
• You can get them to fit if you're willing to take the time.
• The newer header flanges tend to be thicker and flex less.
• You could make some step washers for the flange studs.
• Modern V-band clamps eliminate the 3-bolt clamps of the past for better sealing and more ground clearance.
• Once it's fit, coated and installed, you should not have to remove it for a long time.
• A larger exhaust will help expell all the hot gasses for actually cooler under the hood temps.
• You can make an OEM style header gasket out of a cut up Z-Car gasket (cut out the pieces and fit them to the L4) that won't blow out...ever.

 

There, I addressed all of your 1978 concerns.

[EricJB]

IMO, the "fits everything and nothing" header available for our cars and trucks has primaries that are too short, and too small in diameter to offer any performance gains. It isn't tuned, and the collector is poo.

If I was forced to use one, I would cut the collector off and make it a tri Y.