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Z20 build


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#61 wayno

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Posted 27 November 2017 - 09:29 PM

High compression like that I'd set it up for 16 BTDC at idle, 30-32 total mechanical by 3200 or so rpm.  Its difficult to get that right without an accurate Sun machine that has a recently calibrated tachometer.  

Likely you'll need to weld about .040" in the shorter slot.  Maybe a hair more. 

Our race engine runs 24 at idle, 28 total.  The practice motor at 11:1 is set up as I described above.  Scalded cat!  

 

Quick calculation:

the advance weight pin travels in the slot .0143" per degree of distributor advance.  The distributor will advance half of what you see at the crank due to the doubling effect of the timing gear set.  So for 8 degrees in the distributor, = 16 mechanical at the crank multiply that figure by 8 and weld up the difference from your slot with the weight in still in it.    

So what you are saying is I basically need to fill in around 1mm to the short hole, and I do nothing to the long hole?

To me it would seem like I need to do both sides, but that is what I see in my head, I have never done anything like this before.

Is there a reason for only doing one side, does it lock it in better?


 

 


#62 nl320what

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Posted 28 November 2017 - 07:09 AM

I wanted to chime in earlier on but been busy with the kids at home.

 

In my '68 510 I had built a 81 Z20s that was a long rod motor and I used the NAPZ 3 terminal retimed dizzy directly to the I/E coils with dual SUs and was right at 11:1 comp (race gas).

 

It was fun and was about a radical as could be for a NA street/strip Z motor, only 130hp.

 

The timing thing is a game of power versus ping pong boom with the dizzy.

 

I feel with old school performance motors, they should take advantage of the use of Knock Sensors and Megasquirt EDIS atleast for spark control by using SR20 coil on plugs.

 

Its cheap and full spark control, and can use a regular electronic dizzy to a pulse modifier so you dont need a 36 -1 crank trigger.

 

68_510_Z20.jpg

 

68_510-_Z20_2.jpg


63 NL320 4x4= 5spd,Power Disc Brakes,Power Tilt Steering.80% Completed as of 7/01/2017..Mobile Mechanic Webpage: http://actfast1234.wix.com/itsmycar

I need NL320 Doors or complete L320 Doors to use, will barter value :)


#63 distributorguy

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Posted 28 November 2017 - 09:58 AM

Wayne, the other side may add 1 degree of timing above 4000 rpm, but that's a good thing.  It makes up for timing lost by the the module so its a wash.  

The whole assembly is triangulated, so you really only need one slot. None of this really matters if you don't get the springs correct.  



#64 wayno

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Posted 28 November 2017 - 01:09 PM

Well I just dismantled the only L block Matchbox I had left, it appeared to be broken as it has this plastic 3 armed piece with bearings on the end of each arm, one end was broken that held the small bearing, but that was not the real issue, I could not get the the piece of metal that slides on the shaft that has the slots in it off the shaft, I wasn't able to move it at all.

I don't have any kind of puller that will fit in that small of a place, I tried clamping on with a pair of vice grips and then using the edges of the distributor for leverage with 2 screwdrivers on each side of the vice grips, didn't work, I held the distributor upside down, put the end of the vice grips on my leg and then tapped fairly hard on the vice grips right next to the distributor without results, all I am really doing is scarring the outside of the shaft with the vice grips, I gave up and put it back together.


 

 


#65 distributorguy

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Posted 29 November 2017 - 05:26 AM

Feel free to send it to me Wayne.  I feel like I owe you one for the locker you sold me last year.  You really saved our butts!



#66 Stoffregen Motorsports

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Posted 29 November 2017 - 10:48 AM

Oh, what a nice guy.



#67 wayno

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Posted 29 November 2017 - 09:19 PM

Feel free to send it to me Wayne.  I feel like I owe you one for the locker you sold me last year.  You really saved our butts!

 

I will figure it out eventually.

I will make or buy a small puller to get that part off the shaft of that Matchbox, I have a steering wheel puller, all I will have to make is the lower piece.

The Matchbox has way more parts in there than I thought they would have, I just want the part modified before I pull the one apart on the engine that is in the truck.

 

Did you even use that locker, it didn't seem like it had the gearing you needed.


 

 


#68 distributorguy

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Posted 30 November 2017 - 05:49 AM

I used the Detroit Locker with 3.89 gears.  Truck truck acted like we were on solid pavement instead of slimy salt.  

Next year we are using a 10-bolt Chevy with 2.72 gears and a spool.  All or nothing.  The locker will go into our spares pile to bring along, or into the parts truck we're assembling to look like a Matchbox version of the 620 I was given as a gift a few weeks ago.  

 

DO NOT use a puller on the distributor.  You will damage it.  Period.  I have a system to get them apart without damage.  Its simple and effective.  I'd like to offer this to you.  I'd like more than one other person on this forum to know how big of a difference a properly recurved distributor can make.  Its the most overlooked tuning parameter, and nearly the most important.  



#69 nl320what

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Posted 30 November 2017 - 06:06 AM

On my Z20, this is how I wired up the coils. Also used my 86 Z24 carbie truck as a future reference.

 

720_Coil_Config.png


63 NL320 4x4= 5spd,Power Disc Brakes,Power Tilt Steering.80% Completed as of 7/01/2017..Mobile Mechanic Webpage: http://actfast1234.wix.com/itsmycar

I need NL320 Doors or complete L320 Doors to use, will barter value :)