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Pinging under power and drive train Q's


pwrcat4000

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I finally got the manifold(s) sealed on my L20B and the truck runs so much better. I tightened the carb too so it was probably leaking air as well.

 

So now I can hear the pinging under more than 1/2 throttle under power. it pings like I am in too high of a gear. I have adjusted timing all over the place while driving one block at a time. I started with the timing at 11 BTDC used a light and everything. I remember some one saying that is stock setting. Does not seem to matter where I put the timing.... If I advance it builds heat very quickly which makes sense to me.

Here is your chance to ruin my day

Also posted elsewhere I can not drive the truck at highway speeds >45MPH with out overheating or worse (this is my 2nd L20B, melted the head on the first one). I am guessing it is geared pretty low.  I am out of first gear before I am out of the intersection.
I am using my original 521 4 speed trans and rear end. 

I have the 620 4 speed and rear end available from my first transplant, is there an advantage in transplanting  them? geared different? will they even fit?

 

As always without this group I am lost. I would never even be able to use the truck.

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Trans won't fit; too long. Swap front half of 620 driveshaft(if it came from regular cab, short bed 620.)

 

The o ly rear gear that will do you better from a 620 was the 4.11 found on some 1979 620s.

 

 

What spark plugs are you using? Where is the cam set when at TDC? What kind of gas are you using?

 

How's the thermostat? Overheating by your gauge? Have you checked output heat with a temp gun? How's the radiator? How's the hoses? How's the water pump?

 

Is dizzy installed correctly?

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Excessive pinging can be caused by engine running too  hot. If you even suspect a heating problem replace the thermostat ASAP. Don't waste time testing it REPLACE. Gauge should read roughly in the middle of the run range. Get a $10 thermostat, don't get the $1.99 from WallMart one.

 

 

Other things that may cause the engine to run too hot...

 

Rad plugged with hard water deposits (scale) Take out and lay front down, fill with CLR over night or longer to dissolve it. Always use distilled water to refill.

Bottom rad hose soft and collapsing when revved up from pump suction. Rev it up while looking at it and see.

Timing too retarded. Re check that you are checking the timing correctly or timing light works.

Not using a rad shroud

Bugs and debris blocking air flow.

Heater by-passed by joining both heater hoses. Block both ends.

Head gasket blown or blowing.

 

 

 

The 521 and all regular standard transmission 620s used the same differential and 4th gear is 4th gear in both. No advantage changing them.

 

 

They were designed to run on regular gas and about 12 degrees of timing. 

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I run Prem Gas on my Open chamber head as they are prone to Pinging and try to lower the timming.

I also run a 160 stat and now have a 3 core radiator.  but on hot days it may ping.

I have alot of run on issues but that since I dont have a idle cut off selinoid on my car.

 

 

521 are gear low. Im in 3 rd gear just lugging thro my neihbor hood. an with a longer stroke L20 might seem different but should really haul ass IMHO.

 

 

Make sure your choke plate is open.You should be able to do 65 at least. I dont go past that much mysef. Perfect is about 45/-55mph

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Shaved head may up compression ratio to a degree. Higher octane helps reduce pinging. Too advanced timing adds to pinging. Verify running temp with temp gun or other quality device. Do this before any thing else, Oem gauge could b off.

As they say,check the stupid shit first. Otherwise you well just make things worse,ie "melted head"

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I feel like a idiot did not even consider upping the octane. I have to run premium in some of my other cars because if i don't they ping, if that does not cut it I will be back.  I will set it to 12 BTDC with the light

My worry was that some one would recommend a timing chain.

The over heat is not a problem only if i Run the engine nearly wide open to maintain highway speeds for long periods of time.
let me know if I missed something on optimizing the cooling system
I have had the radiator professionally cleaned and repaired
New Hoses

New H2O Pump
New thermostat with Bypass hole
Flushed the whole system with fresh water

 

So how difficult is it to change the ring gear in the truck? What are people using? How much money do I need to start saving up?

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These trucks have 3rd member differentials, so if you can manage to pull the rear axle shafts, you can pull the whole differential unit out from the front w/o having to remove the whole axle housing. Once the diff unit is out, you can work on it on a bench.

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You shouldn't need full throttle to maintain highway speed so something is not right. 45MPH top speed is bogus. Higher octane is masking a problem that needs fixing or you'll be paying too much for your gas.

 

Reduce your timing till it stops. Maybe your timing light is messed up and you are way too far advanced. Try another light.

 

Check your valve lash. Valves too tight will reduce power.

 

 

You don't need a different differential gear to cure this problem.

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I run the higher octane because it burns cleaner and with all the additives in todays fuel the octane level has to go down in every gallon with every additive the manufacturers put in.  So is 91 octane still 91 after all the additives?

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I feel like a idiot did not even consider upping the octane. I have to run premium in some of my other cars because if i don't they ping, if that does not cut it I will be back.  I will set it to 12 BTDC with the light

 

My worry was that some one would recommend a timing chain.

 

The over heat is not a problem only if i Run the engine nearly wide open to maintain highway speeds for long periods of time.

let me know if I missed something on optimizing the cooling system

I have had the radiator professionally cleaned and repaired

New Hoses

New H2O Pump

New thermostat with Bypass hole

Flushed the whole system with fresh water

 

So how difficult is it to change the ring gear in the truck? What are people using? How much money do I need to start saving up?

 

So I had/have the same issue, originally I had the cam timed wrong and it was easy to time it so it didn't knock/ping that much, only when hot did it knock/ping slightly when going up a slight incline, if I floored it or let off it quit knocking/pinging.

I re-timed the cam on all my L blocks, on my 520 I run non-ethanol premium so not much changed, but the work truck I burn regular, I have a reason to burn regular(lets leave it at that), originally I had the work truck set at 6/7 degrees BTDC and it ran fine, but when I re-timed the cam it knocked/pinged like crazy, I kept retarding it a degree at a time till it quit knocking/pinging for the most part, it only knocks/pings when it starts getting warm(around 5/8ths over on the temp gauge) going up slight incline, I ended up at 0 degrees BTDC before it was over, it is the only place it will run without knocking/pinging, to fix it properly I will have to re-curve the distributor so it doesn't advance so much, then I will be able to time it properly, until then I am at 0 degrees BTDC, I have plenty of power as the engine is an LZ23, but the truck weighs 3900lbs and I haul a trailer full of pressure washing equipment, I am pushing 6000lbs plus most the time, so when climbing a slight incline my foot is into the pedal around half way, maybe a little more when raining or bucking a head wind, I was floored most the time(slight incline) when I had an L20b in it.

 

Changing the rear gears is easy in an H190, first you need to find a 3.90 gearset/pumpkin from a Datsun 720, there are lots of them out there, should be able to get one for under $150.00/$200.00 plus shipping if you don't have one in your area, then you drain the fluid out of the rear axle, then remove the brake lines from the backing plate, disconnect the e-brake cable in the middle(521), remove the driveline from the axle(do not pull it out, just push it to the side, remove the 4 nuts on each side holding the backing plates on, then slide the axles out around 4 inches, remove the 10 nuts holding the rear pumpkin in and then drop it out, clean everything up and put the new to you 390 gearset in and fill it up with gear oil, you are then good to go.

Gearsets/pumpkins should have less than an 1/8 play in the pinion flange, any more play and I don't use them if I can help it and I have never sold one with more, my H190 LSD has more but it is an LSD so I live with it as it doesn't knock or make noise.

 

I had 437 gears in my 1971 Datsun 521 work truck for years, it ran just under 4000rpms at around 70mph as I recall, I got used to it, my L20b lasted 15 years that way, I now have 4.625 gears in it since making it a dump truck, I like it better with them gears as my truck weighs a lot now since making it a dump bed(3900lbs), I used to just turn the radio up louder to drowned out the engine noise, now I cannot hear the radio because I need a better muffler, another thing I will eventually get around to.

 

I run non-ethanol premium in every gas engine I own except the work truck and they are timed properly/normally, all the L blocks have peanut heads on them, I believe they are all around 8.9 to 1 compression ratio, the LZ23 was the best upgrade I have ever made to my work truck, I hardly ever have to floor it anymore.

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Octane is a measure of how sensitive gas is to self ignition. Higher octane rating is harder to get to burn by itself from the heat of compression. High octane gas is not more explosive nor does it contain more energy but you can safely extract more power from it by having a more efficient compression ratio because detonation is controlled. 

 

 

If it over heats, by 'over heats' I mean the temperature gauge reads high in the run range,  above 45 MPH there is something seriously out of whack. So where it the needle when it runs this hot????

 

And again.... an over heated engine will ping like crazy. It's basically trying to become a diesel. I'm comfortable when I see the needle about 1/2 way up in the NORMAL or RUN range on the gauge. Perhaps a needle width above 1/2. When it gets to 3/4 the electric fans come on.

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Full throttle to maintain highway speeds sounds like you are running way lean richen up the mixture at the carb and see if this helps with throttle position, temperature, and pinging at highway speeds.  Severe lean top end will cause all the symptoms you are describing.

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To eliminate possible causes, i would do a compression check on the engine.   Then warm the engine up, and check manifold vacuum.

Another possibility, was this originally an EGR engine?  Or are you using a distributor off an EGR engine?

 

Make sure the timing pointer is correct.  Is indicated TDC actually TDC? 

 

With a correct timing pointer, try to see how fast the mechanical advance comes in on the distributor.

 

I would also check and clean the distributor advance mechanism, make sure it moves freely, and some mechanical advance it not being held advanced as the engine slows down, but then goes back to normal at idle.

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