Looking to correct a few things with the 521

[anthonydavis521]

My name Is Anthony I have a 1971 521 Datsun pick up with an L16 everything is pretty much stock except the carb it came with a 32/36 DGEV Weber carb. I tried rebuilding the carb but I had a lot of issues with the choke so I just saved up and bought a new Weber I installed the Weber and it fired right up I have been learning about tuning and attempting to get it to that sweet spot. I noticed it pops a bit if you hit the high rpms just right. I assume it’s running rich just cause the popping happens often. I also believe the timing is off, when I shut the motor down it still fires a bit here and there yesterday I drove it into town where I work and I went somewhere on my lunch turned off the truck and she fired 8 times so I turn the key back over and it fired up I shut it down and it completely shut down like it should have. I am still new to working on the truck and am just trying to soak up as much knowledge as I can that being said any advice is very much appreciated I can take photos, videos and try to provide better info. 
thanks in advance

[datzenmike]

 

 

 I would start with a check of the points gap. Set to 0.020"-0.022" Then check or set the ignition timing. Off hand I don't know what the L16 ignition timing on a '71 is but find out and set it. 

 

Next set the valve lash. 0.008" intake and 0.010" exhaust on a cold engine or preferably, 0.010" intake and 0.012" exhaust on a hot engine. An overly tight valve can cause the high RPM 'popping' you mention.

 

Carburetor set up

 

http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm

 

http://www.redlineweber.com/html/Tech/34_ICT_tunning.htm

 

 

 

Run on or dieseling is the firing of the engine even without the ignition spark. Just like a diesel it's the heat of compression that sets off the gasoline.

 

Some causes

An overly hot engine.

 

Too high a compression (not likely the cause here on a stock L16)

Too low an octane gas (not likely the cause here on a stock L16)

 

Idle set too high.

 

Too rich idle mixture. The '71 had manual choke but if the Weber has an electric and it isn't connected properly it may not shut off all the way.

 

Wrong spark plug heat range. Always use NGK plugs B6ES I think but check for the '71. NGK are what the factory put in them. Other makes may not match the heat range properly. The heat range determines how well the plugs self clean themselves. Too hot and they are just like a glow plug in a diesel.

 

 

[anthonydavis521]

1 hour ago, datzenmike said:

 

 

 I would start with a check of the points gap. Set to 0.020"-0.022" Then check or set the ignition timing. Off hand I don't know what the L16 ignition timing on a '71 is but find out and set it. 

 

Next set the valve lash. 0.008" intake and 0.010" exhaust on a cold engine or preferably, 0.010" intake and 0.012" exhaust on a hot engine. An overly tight valve can cause the high RPM 'popping' you mention.

 

Carburetor set up

 

http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm

 

http://www.redlineweber.com/html/Tech/34_ICT_tunning.htm

 

 

 

Run on or dieseling is the firing of the engine even without the ignition spark. Just like a diesel it's the heat of compression that sets off the gasoline.

 

Some causes

An overly hot engine.

 

Too high a compression (not likely the cause here on a stock L16)

Too low an octane gas (not likely the cause here on a stock L16)

 

Idle set too high.

 

Too rich idle mixture. The '71 had manual choke but if the Weber has an electric and it isn't connected properly it may not shut off all the way.

 

Wrong spark plug heat range. Always use NGK plugs B6ES I think but check for the '71. NGK are what the factory put in them. Other makes may not match the heat range properly. The heat range determines how well the plugs self clean themselves. Too hot and they are just like a glow plug in a diesel.

 

 

I will set the points and get my timing corrected I do think the motor gets hot sometimes but I have been talking to few people I know they said it’s normal cause it’s old but I did turn my idle up I’ll make these adjustments and report back 

[datzenmike]

The gauge normally should read just a needle width above 1/2 on a Datsun and being old is irrelevant. Cars today run much hotter.

 

 

Does your new Weber have a electric idle cut solenoid. Most new ones do.

[mklotz70]

I'll add that when tuning a weber, it's a bit backwards of a stock carb.  The goal is to get the butterfly as close to closed as possible and still run.  If it's open more than it should be, it will uncover the vacuum advance port and advance the timing...NOT good.  When you set your timing, make sure you disconnect the vacuum advance tube from the dizzy just in case there's a vacuum signal.  If there's any suction at that tube, the carb isn't tuned right.  I'm pretty sure the instructions say to turn the idle down until it chugs like a tractor, then adjust the idle air mix.  If the rpm's go up, turn the idle down(closing the butterfly more) until it chugs again.  tweak the air mix again. If idle goes up, repeat.  The goal is to get the rpm as low as possible until the air mix doesn't make it go up anymore.....now it's okay to turn the idle up a bit until it hit 700rpms. 

 

Also....too high an rpm will cause the mechanical advance to activate in the dizzy.  The vac adv is only used as the butterfly is just starting to open up. If you stomp on the gas pedal, you bypass the carbs ability to send a vac signal and the dizzy won't advance until the rpms go up and the mech adv kicks in.  Basically, if the port is above the butterfly at idle, there no suction above the butterfly, so no vac signal.  As you open the butterfly, all of the suction(vacuum) that the engine is currently making...18ish Hg?....is now available at that port so the dizzy's vacuum advance should start to advance the timing.

 

The timing is between 7 and 10 deg.  You can download the factory manuals in several places online.....or here....

http://www.bluehandsinc.com/manuals.html

 

The goal with the timing adv is to have enough that it runs smoothly at idle.....NOT to have it run the fastest.  Once the total adv is up around 25deg...maybe 30deg, I think....been years since I've tuned a truck, the engine will be too advanced and the plug will be firing too early. Basically, if your timing is advanced too much at idle, when you get to the higher rpms where the mechanical advance has fully kicked in, you could have too much advance.  Gas burns pretty slow which is the point of the timing advance.  As the pistons start moving faster, the gas has to get ignited sooner so that it can be at full burn at the right time to push the piston down with the most possible force.  

 

I could probably add more, but hopefully, some of this will help.......either you or someone else reading this. :)

 

 

[datzenmike]

Well put Mike.

 

On the '70-'72 L16 distributors, advance starts 11.5 -13 degrees or X 2 = 23 degrees at the distributor. Total advance (mechanical and initial) is about 32 degrees on any L series.  If you subtract this leaves 10 degrees of initial advance set with timing light. So this totally agrees with your numbers.

[anthonydavis521]

9 hours ago, datzenmike said:

The gauge normally should read just a needle width above 1/2 on a Datsun and being old is irrelevant. Cars today run much hotter.

 

 

Does your new Weber have a electric idle cut solenoid. Most new ones do.

I don’t think that it does it mentions it in the direction but says it will vary on the type of kit but I’ll verify a few things get back here

[Stoffregen Motorsports]

Here's what the idle cut solenoid looks like.

 

[datzenmike]

Only the L16 in the 620 had an idle cut as well as L18 and L20B the 521 didn't have one so it should shut off without dieseling. An idle cut will solve it but does not get rid of the underlying cause. Wrong plugs or wrong heat range, idle speed set too high, running too rich an idle mixture......   

[Stoffregen Motorsports]

The underlying cause on a Weber is often throttle blades that are open too far. But, it is a very very common problem with DGV Webers, hence the introduction of the cutoff valve on later models.

 

 

[mainer311]

I hated my DGV. Almost all Webers (DCOE’s included) have an issue where the progression holes aren’t in the right spot. That’s the issue with setting up the Weber with the butterfly almost closed. It’s too far away from that first progression hole. What ends up happening is that you have a lean “dead spot” right as the butterfly is cracked open because the first progression hole is too far back and there is an inrush of air before the fuel can keep up. Some people drill an extra progression hole closer to the butterfly, and/or you can partially tune it out by messing with the accelerator pump.

 

[mklotz70]

The best running engine I've had was with a Hitachi.....way more torque and response off the line.  The problem is the hole for the throttle shaft gets worn out and creates an air leak.  ZTherapy would fix SU's by machining a pocket for a sealed bearing.....no leaks ever again.  I've thought about doing that for webers and hitachi's, but I've never gotten around to seeing if it's feasible. 

[Crashtd420]

7 hours ago, mklotz70 said:

The best running engine I've had was with a Hitachi.....way more torque and response off the line.  The problem is the hole for the throttle shaft gets worn out and creates an air leak.  ZTherapy would fix SU's by machining a pocket for a sealed bearing.....no leaks ever again.  I've thought about doing that for webers and hitachi's, but I've never gotten around to seeing if it's feasible. 

They do sell a bearing fix for the weber downdrafts.... I believe there is no machining necessary....

 

 

 

[mklotz70]

That's awesome!  I don't see a site address or part number.  Typed the product name into google......

 

https://www.pegasusautoracing.com/productdetails.asp?RecID=5949

 

two of them are on order. Thanks!!! :)

 

[Crashtd420]

2 hours ago, mklotz70 said:

That's awesome!  I don't see a site address or part number.  Typed the product name into google......

 

https://www.pegasusautoracing.com/productdetails.asp?RecID=5949

 

two of them are on order. Thanks!!! :)

 

Sorry i guess I should have posted a link but yes comes up easy with a search.... Glad that helped, i wasnt aware you had a need.

[mklotz70]

I just assume I'll have a need. lol  :)

 

[anthonydavis521]

So I got the motor running how I wanted it, I have been running it as my daily for the last couple of months. On Tuesday I was driving up I-5 doing about 75 I heard a knocking I let off to pull over and check it out before I could it went boom! Have not had time to pull it apart and verify but I had it towed to the shop my pops runs and I turned it back over to hear chunks of metal clunking around. That being said I am almost positive she’s toast. I want to rebuild the motor or swap an sr20det or Ka24de or maybe even K24 swap it. Any advice as far as what would be  most cost effective or even the most fun? I have been reading several threads on the ka24de and seen a thread about swapping the Honda K24 which seems like some work but would be pretty sweet any thoughts on this?

[datzenmike]

The L series is almost impossible to 'blow up' as long as you keep full of water (don't over heat) and full of oil. 

 

Cost effective? Rebuild the L series engine or get another L20B and rebuild it. Perfect fit no mods meeded.

 

Most fun? probably an engine/transmission swap but a lot of money and work to get there which tempers the 'fun' part. If you have never done one maybe re-think it a bit more.

 

 

[Stoffregen Motorsports]

Best bang for the buck is a KA24E swap. They are dirt simple and easy to source. Buy a whole donor Hardbody truck for $1000 and have all the parts you need. If your dad runs a shop, it's likely either he or someone there will know how to make all the connections one the motor is installed.

 

Old engines leak and can have blow-by at the rings, and keeping oil in them is important. My wife's commuter has over 400k miles on it and it's starting to use oil, so I check it once a week just to be safe.

[anthonydavis521]

19 minutes ago, datzenmike said:

The L series is almost impossible to 'blow up' as long as you keep full of water (don't over heat) and full of oil. 

 

Cost effective? Rebuild the L series engine or get another L20B and rebuild it. Perfect fit no mods meeded.

 

Most fun? probably an engine/transmission swap but a lot of money and work to get there which tempers the 'fun' part. If you have never done one maybe re-think it a bit more.

 

 

Yea I have been running it hard we have been talking about it and we think the piston snapped or something along the lines Of that. I am gonna start to tear into it this week and I will have better info on what my dumbass did. I have heard the L20B would be ideal in the aspect as far as cost effective and “easiest” but I want a challenge and It’ll take some time  but I’m patient fersure I am leaning towards the KA24DE or K24 which ever motor I can get my hands on. I have looked ever since that night and just been reading about other’s projects and I feel it will be worth it in the end. I just refuse to let this truck become a junker it’s my favorite car I have and I want my kid to be able to have it in the years to come. I am willing to put the work into it I have a place I can leave it so it stays in the same condition until the project can be completely finished.

[anthonydavis521]

15 minutes ago, Stoffregen Motorsports said:

Best bang for the buck is a KA24E swap. They are dirt simple and easy to source. Buy a whole donor Hardbody truck for $1000 and have all the parts you need. If your dad runs a shop, it's likely either he or someone there will know how to make all the connections one the motor is installed.

 

Old engines leak and can have blow-by at the rings, and keeping oil in them is important. My wife's commuter has over 400k miles on it and it's starting to use oil, so I check it once a week just to be safe.

Yea it’s been using oil fersure I have added oil a handful of times since driving it I think I will rebuild the L16 regardless of if I am using the motor or not just to have as a back up so it stays on the road

[NC85ST]

Just remember, if you want more power, you need to be able to stop it as well. Drum brakes do ok, as long as you keep them adjusted properly.

[anthonydavis521]

9 minutes ago, NC85ST said:

Just remember, if you want more power, you need to be able to stop it as well. Drum brakes do ok, as long as you keep them adjusted properly.

I think I’m gonna do the conversion to disc just because the price is not terrible. I appreciate the advice because it would suck  to have all that power and a terrible braking system 

[anthonydavis521]

Looking to know if anyone knows where I can get a rebuild kit for the L16 or even an L20 

[datzenmike]

You may have to source the items individually. Most auto supply houses will have or can get them although you may have to go to several. On line is another option.

 

A bare bones hone and ring job would be oil pan, head and valve cover gasket, manifold gasket, standard cast iron rings, main and rod bearings. Probably a good job the replace the valve seals while the head is off. Depending on cylinder wear this is not going to run like new and if there is damage not even feasible.

 

Optional....

New timing chain kit includes, chain guides, tensioner and cam/crank sprocket with gasket.

Have the head rebuilt with new guides and seats, but this will cost more than all the parts mentioned above.

 

Absolute best results would be to overbore and replace with oversize pistons and rings. Here you can use chrome or moly rings for longer life. Again much more expensive but you have basically a brand new engine.