Got it to pass smog, the work begins now... 1986 Nissan 720 project

[bottomwatcher]

Swap ain't cheap or easy. If you have smog laws probably next to impossible. 

[A guy named Rick]

3 minutes ago, bottomwatcher said:

Swap ain't cheap or easy. If you have smog laws probably next to impossible. 

nah, it can be bar'd and ref'd in California. I'm looking into it. As far as Cali's swap goes, it has to be offered in the vehicle and newer. seeing how the hardbody had the ka24e, and the hardbody is basically the successor of the 720, it should be no problem. A V-6 swap could be done too, but too much hassle.

[Charlie69]

Here in Phoenix I run the 15w40 year around.  When I have a newly rebuilt engine with a new cam I run 30w for the first 500 miles and then change to the 15w40 with a new oil filter.  On a fresh engine my first 2 oil changes are 500 miles apart after that I change oil and filter every 2000 miles.

[A guy named Rick]

Well idk what went wrong, but it sounds like a slight knock at idle, only after warming up. Doesn't happen cold. What can cause that, where it's after it warms up? You don't hear it so bad when revving the engine. It's different than a valve tick noise. Happening towards the back, I'm thinking cylinder 3 or 4. 

[datzenmike]

Well IF a rod knock it's excess bearing play that the oil cannot cushion. It never gets better and can only get worse. This can be sudden if pounded on or can go for years if driven lightly and kept full of oil but in the end the bearing is pounded as thin as a razor blade, slips off the rod and rotates till the oil hole is blocked, it over heats quickly and welds to the crankshaft and stops the engine. At highway speeds it can't stop so the rod snaps and rod walks through the side of the block.

 

Gotten to early you may just need a new bearing.

 

 

[Charlie69]

Sounds like the oil change undid what the previous owner might have done to hide the rod knocking noise.

[A guy named Rick]

3 hours ago, Charlie69 said:

Sounds like the oil change undid what the previous owner might have done to hide the rod knocking noise.

 

Nah I've changed oil in this truck several times. Owned since 2012, sat the last 7 years and finally did something with it.

 

4 hours ago, datzenmike said:

Well IF a rod knock it's excess bearing play that the oil cannot cushion. It never gets better and can only get worse. This can be sudden if pounded on or can go for years if driven lightly and kept full of oil but in the end the bearing is pounded as thin as a razor blade, slips off the rod and rotates till the oil hole is blocked, it over heats quickly and welds to the crankshaft and stops the engine. At highway speeds it can't stop so the rod snaps and rod walks through the side of the block.

 

Gotten to early you may just need a new bearing.

 

 

 

I went driving earlier. Honestly tonight it ran better. The rattling/knocking noise is only really at idle, you don't hear it after stepping on the gas. It isn't anything clutch related, checked that. I think it may be safe to say not rod, but who knows. It clatters at idle like a faint sound of a diesel is about the best comparison I can come up with. 

 

This weekend I'm going to pull plugs anyways, I want to run a compression check again, and might take it to a mechanic friend and have him listen.

[datzenmike]

Valve clearance noise would not change with RPM, just speed up and slow down.

Timing chain noise might be louder at idle but you think it's to the rear of the engine.

 

Rod noise is usually louder under load when the firing cylinder slams the rod downward onto the crankshaft. Often much quieter when you let off, even silent depending how bad it is. Not a high pitched tap but a sledge hammer on something very solid but muffled through the block.

 

I was out late 30 miles from home one night in my '64 Dodge going up a long hill. Before I got to the top there was a loud knocking sound over the radio music. I limped all the way home at very light throttle. Next day drove it down town to the garage. One crankshaft (probably reconditioned) one rod replaced that had turned blue from the heat and one oversize rod bearing. Super slant six with 318 2 bbl and dual exhaust.

 

[A guy named Rick]

On 8/28/2021 at 6:27 AM, datzenmike said:

Valve clearance noise would not change with RPM, just speed up and slow down.

Timing chain noise might be louder at idle but you think it's to the rear of the engine.

 

Rod noise is usually louder under load when the firing cylinder slams the rod downward onto the crankshaft. Often much quieter when you let off, even silent depending how bad it is. Not a high pitched tap but a sledge hammer on something very solid but muffled through the block.

 

I was out late 30 miles from home one night in my '64 Dodge going up a long hill. Before I got to the top there was a loud knocking sound over the radio music. I limped all the way home at very light throttle. Next day drove it down town to the garage. One crankshaft (probably reconditioned) one rod replaced that had turned blue from the heat and one oversize rod bearing. Super slant six with 318 2 bbl and dual exhaust.

 

 

So it really sounds like it's only at idle, after it's warmed up. It's got me confused. 225 Slant six, those are good engines. They can last 2 or 300,000 miles. 

[datzenmike]

Hows your oil pressure? It would be lowest at idle.

 

 

[Charlie69]

The Z24 in my 86  has over 450,000 miles on it and I dirve it daily like I stole it.  Nissan builds good engines.

[A guy named Rick]

10 hours ago, datzenmike said:

Hows your oil pressure? It would be lowest at idle.

 

 

 

Circling back to that, haven't tested it but would be a good idea. A mechanic my parents have gone to for about 20 years advised oil pumps generally don't wear out often, and said try checking the pickup screen first. When telling him about the plier and vise grip trick, he says yeah you can do it that way but best thing would be do the timing chain and tensioner also, so may as well pull the timing cover. Dude, I'm not trying to do all that right now. My timing chain is tight and in fairly good shape. Is there a test gauge I can install for oil pressure without having to go as far as getting an actual oil pressure gauge? 

[datzenmike]

The pump is fine but the main and rod bearings bleed oil. As the mileage goes up and the clearances increase so does the bleeding. At idle the pump can't keep up and why idle oil pressures are lower than running. I put KA oil pumps on all my L and Z series engines. They move more oil so the pressure rises sooner at lower RPMs. 

 

KA24E and KA24DE in the D21 truck have longer rotors

[A guy named Rick]

On 8/31/2021 at 1:20 PM, datzenmike said:

The pump is fine but the main and rod bearings bleed oil. As the mileage goes up and the clearances increase so does the bleeding. At idle the pump can't keep up and why idle oil pressures are lower than running. I put KA oil pumps on all my L and Z series engines. They move more oil so the pressure rises sooner at lower RPMs. 

 

KA24E and KA24DE in the D21 truck have longer rotors

 

 

Alright. Good to know.

 

Well, update on my truck.i haven't done anything really to it laely, but been driving it a bit and the last tank was mostly highway, a little town driving, and I got 22.3 mpg, having the weber on it. I know I need to dial it in more. I'm also concerned the engine may be consuming a little oil. I need to keep an eye on that.

 

I have done 2 dump runs. First one wasn't as much weightasi had thought it had. The second was today @ 780lbs. It was squatting a couple inches. I'm concerned about going to the max of 1100. I have a lot of dirt to get rid of, and a full bed would be more than that. 

 

Here's a pic of exhaust pipe after unloading. Loaded. It was sitting on the ground. So, gives an idea how much clearance I gained. It's kinda zoomed in so maybe won't give that good of an idea. I should have measure the difference. i will next time. I'm just concerned if the springs are weak. 

 

[NC85ST]

I used to regularly carry over 1000lbs on my ‘85, of course, I added an extra spring on mine. Sometimes over 1500lbs one day a week.

[A guy named Rick]

2 hours ago, NC85ST said:

I used to regularly carry over 1000lbs on my ‘85, of course, I added an extra spring on mine. Sometimes over 1500lbs one day a week.

 

How low would it sit? My front is lower than the rear. It had a good rake going on. With the weight in the rear, I was even. Maybe a little lower in the rear. I'll take a pic next time. 

[datzenmike]

That pipe has been replaced so it shouldn't be that close to the ground. These trucks will carry a fantastic amount of weight. The risk is that it will sag and LOOK like it's carrying a fantastic amount of weight to the police. You won't hurt the truck but you WILL have an increased stopping distance than you are used to and handling goes out the window. I would load till level and make 2 or even 3 loads.

[A guy named Rick]

7 minutes ago, datzenmike said:

That pipe has been replaced so it shouldn't be that close to the ground. These trucks will carry a fantastic amount of weight. The risk is that it will sag and LOOK like it's carrying a fantastic amount of weight to the police. You won't hurt the truck but you WILL have an increased stopping distance than you are used to and handling goes out the window. I would load till level and make 2 or even 3 loads.

 

Hey Mike, sorry I was backed up to a curb which makes it look lower haha. No, the pipe wasn't replaced. It has, however, been cut off before and then rewelded on (Don't ask). I think because it was dirt and spread out may have an effect of sagging more idk. I could try putting more towards the front of the bed next time. I'm going to try about 1000lbs next. Picking up speed, you can tell there was extra weight. Not too bad at all though. 

[NC85ST]

It was resting on the bump stops. You do have to watch your stopping distance. Never had a problem with enough power. These trucks are built to haul. I used it to deliver a local classified ads paper. I had a topper on it, cab high, and I would fill the bed to the roof. When we would have big papers, I would have to fill the passenger seat and behind the seats of the KC as well. Thankfully the further I got in my route the less weight I would have.

[A guy named Rick]

On 9/7/2021 at 2:27 PM, NC85ST said:

It was resting on the bump stops. You do have to watch your stopping distance. Never had a problem with enough power. These trucks are built to haul. I used it to deliver a local classified ads paper. I had a topper on it, cab high, and I would fill the bed to the roof. When we would have big papers, I would have to fill the passenger seat and behind the seats of the KC as well. Thankfully the further I got in my route the less weight I would have.

sounds like you really were putting the truck to work.

So this is interesting: I discovered last night i had the 3 hard vacuum lines crossed. i basically was running around with no vacuum advance. honestly, after connecting it back properly, i am getting more low end power, my idle improved ( i must have been drawing a little extra air making it lean out) but i am losing up top a little. Now i need to go back through making sure the Weber is set up properly since i think i may possibly be drawing a tiny bit of vacuum advance at idle, also check timing again.

[captain720]

When they run with no advance the base timing tends to get set wrong to compensate

[A guy named Rick]

19 minutes ago, captain720 said:

When they run with no advance the base timing tends to get set wrong to compensate

Yeah, which can affect idle speed, which also affects base mixture setting too. Oh well, still need to get an AFR gauge to really dial in the carburetor. I also want to a compression test again since last time i was stupid and didn't hold the throttle open 😳

[datzenmike]

Never seen the throttle open/closed made much difference. Maybe extra turn or two till gauge maxes out.

[A guy named Rick]

2 hours ago, datzenmike said:

Never seen the throttle open/closed made much difference. Maybe extra turn or two till gauge maxes out.

True, i was thinking that too.

Edited September 9, 2021 by A guy named Rick

[captain720]

6 hours ago, datzenmike said:

Never seen the throttle open/closed made much difference. Maybe extra turn or two till gauge maxes out.

This is also my experience