Rebuild, replace or swap moms 510 carb/engine?

Engine, Transmission and related drivetrain.
510wagon
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Rebuild, replace or swap moms 510 carb/engine?

Post by 510wagon » 07 Apr 2019 10:36

I took over the pleasure of fixing up my moms 72 510. I have done quite a few thing to it, but next is the engine. I rebuilt ten years ago, stock L16. What’s key here is it has a automatic transmission, My mom likes it. It runs like shit, always had problems with the carb. Had it rebuilt twice a while ago and still isn’t reliable... for being 47 years old. Sometimes/rarely it drives great for 30-45 minutes. Most of the time it runs sluggish when it’s cold then runs okay for like two minutes, then it runs horrible after that. Once i press on the accelerator it wants to bog down. If I hold it in the exact right position it runs like crap but accelerates very slowly. Takes about 30 seconds to go from 0-15 mph.
In conclusion, i’m at the point where I want to either buy a new carb, swap engine to the L18 or L20b, KA24, or even a sr20det (sr is probably unlikely since it’s for my mom and most expensive). Like I mentioned before it needs to be automatic.... i know lol what the heck.
If anyone can help with suggestions or anything that would be greatly appreciated. I did get a quote for ka24 swap at around $3,500-$4,000. I just want it to be able to drive 40 miles on the freeway (to the beach) with no worries. Also the 3 speed auto trans it has right now keeps the rpms up high. I don’t know if they have a 4 speed auto out there. Thanks for any help!
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bertvorgon
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by bertvorgon » 07 Apr 2019 11:14

Given that timing, ignition, valve adjust are all good, as is compression, the simplest and best upgrade would be a Weber 32/36 carb. An adapter lets it fit the intake manifold, the carb is virtually a plug and play, and it is a known swap. There are jet recommendations that would get you up and running right away.

http://www.redlineweber.com/carb-kits/auto/nissan/

https://www.pegasusautoracing.com/produ ... oduct=1580

NOTE: I also see a vacuum line missing from the bottom of the intake manifold!!!!! That should go to the distributor, that is a BIG problem.

You are NOT getting proper ignition advance, which will make the engine crazy lazy.

That float level is low also, should be up to the line on the glass, that delays circuit start up.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

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1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer

510wagon
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by 510wagon » 07 Apr 2019 11:26

Thank you I will read up on those two links! Also that vacuum line plugs into my air filter housing. I had to remove it in order to remove the air filter housing to get these pics. I will take a picture once I get home today. Also the bowl is empty because I havent started the engine in two or three weeks. It usually evaporates for me in about a week and a half, I don’t know if this is normal, maybe it’s a clue to something wrong if it’s not normal? Thanks for noticing and thanks for your help!

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bertvorgon
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by bertvorgon » 07 Apr 2019 11:45

Ok, yah, there should be a vacuum line to the bottom of the carb from the distributor, I was thinking of my setup. STOCK has not been my world for a long time.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

Keith Law
1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer

datzenmike
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by datzenmike » 07 Apr 2019 13:18

Everything you describe sounds fixable with some checking and adjustments, hardly a candidate for replacement...... yet.
As mentioned set valve lash HOT. Set timing. Then....

The slotted screw near the carb base next to the vacuum advance pipe is the idle mixture adjustment. The idle speed screw is just out of sight behind that spring. Set the idle as low as you can (in neutral and thoroughly warmed engine, naturally) and then slowly turn the mix screw in or out whichever improves the idle. Try 1/4 turns and wait a few seconds for any improvement or worsening of the idle. When you have the idle as improved as you can get, turn the idle speed back down and repeat the mixture adjustment looking for the fastest smoothest idle you can, turn down the speed and repeat. This may take 7 or 8 tries but when the idle cannot be improved and the speed is around 700 or so you're done. Have someone hold the brakes on and place in DRIVE while you adjust the idle speed back up to 650-700. A good strong idle with high manifold vacuum is essential when driving an automatic.


Image

The ported vacuum advance hose to the distributor connects to that elbow on the carb base at bottom of this picture.



Image

The fuel level looks a little low in this picture, judging by the float. It should be up at the white fill line. If fuel level is wrong it will affect the running and why Nissan put a line there. Otherwise it wouldn't matter. Have you replaced the fuel filter in the last 2-5 years??? If driven every day it should be changed every 2 years.


Image

If the engine is cold, step on the gas once and then look at this choke plate. It should snap fully closed and when started the idle speed should increase. After a 10 min warm up it should be fully open and the idle drop to normal. If not working right it will make it difficult to take off when engine is cold.

Automatics don't rev much different than manuals. Ears can easily be deceived. The L16 is a revver and needs to, to get the job done.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

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Byron510
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by Byron510 » 07 Apr 2019 17:13

Mike has some awesome advice above - do follow it - BUT FIRST .... rule out all ignition issues before adjusting the carb. As the old adage goes, 95% of all carb issues - are in the ignition! And it’s very true.

I also agree that it’s way too soon to write off the existing motor. Unless there is significant signs of wear or some major mechanical issue, for the use of the car you are way better off staying with the stock engine. The L motors are very strong, and run quite well. The motor earned the good name of reliability for the 510’s. The only reason people have gone to newer motors now is output and building hot rods, and it doesn’t sound like this is what you mom wants. These cars can start in a flash, purr like a kitten and go pleanty fast enough to get the job done.

Firstly, make sure the plugs are good, clean and gapped correctly for your ignition system - likely stick points, correct? Check you manual, it memory- as bad as it is - says somewhere around 0.032”

Points are capped correctly- somewhere around 0.019” - again this is memory, confirm with a manual.

Cap and rotor have clean contacts, and the rotor sits and locks firmly on the top of the distributor shaft.
Don’t laugh, many of the recent aftermarket rotors don’t fit well, and flop and wobble around. Something to check.
Speaking of distributor shaft - is there a pile of sideways play in it? This throws you point gap all to heck if this is the case.

Plug wires have been checked for too high resistance? Nothing worse than the spark not even getting to the plugs.

And lastly timing - as Bert noted before Mike, Incorrect timing throws all performance out the window.

With the ignition done, move onto Mikes carb advise- it’s very well written and extremely good advise.

Byron
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because the opposite never works.

datzenmike
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by datzenmike » 07 Apr 2019 18:47

Ha ha ha and 95% of ignition problems are.... carb related. We're saying if the carb is suspect never dismiss the electrical and visa-versa. You need spark and gas delivered at the right time and the right amount. It's one or the other... can even be both.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by RMS » 07 Apr 2019 23:15

Image
I just had a problem on my 72 goon were the boot on the throttle pump fell apart and plugged up some jets. yours looks suspect. pull and clean the idle jet and .... or just buy a weber
Image

Image
I dont think the vacuum port went strait to the air cleaner.... didn't it worked with the evap system and went to the lower port on that little block bolted to the drivers side strut tower then the top line went to the air cleaner?
Image
is that a ac pump I see poking out ? if so most of the pollution control would have been deleted. evap system should be checked or just block off that vaccume port on the manifold.
two_68_510s wrote:I guess our donkeys are quicker then your sled dogs!

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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by datzenmike » 08 Apr 2019 05:58

Re vacuum line on side of intake....

You're thinking of the flow guide valve. There is a vent line from the fuel tank and a sealed gas cap. The vent line sends fumes to the crankcase for storage when engine is off and tank pressure rises. When engine is started the stored fumes in the engine are drawn out by suction from the PCV valve through the block vent. The third hose goes to the air filter and allows filtered air back into the tank as the fuel level drops and a vacuum is formed in the tank. There is no hose to the intake other than through the PCV valve.

That vacuum connection to the intake is most likely for the ATC (auto temp control) in the air filter snorkel. The AIS is a vacuum powered gate that is regulated by a temperature sensor in the air filter. It mixes cold outside air with air warmed by the exhaust manifold under a sheet metal shield. The sensor regulates the air into the carburetor at around 100F. Strict control of the intake air allows the engine to operate normally under a wide range of external weather conditions and improves performance during warm up. When the throttle is fully open under heavy load the intake vacuum drops and the ATC relaxes to it's normally closed position and warmed air is closed off and only cooler outside air is let in to provide maximum power. With warmed air during near freezing high humidity weather, carburetor icing is totally eliminated.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by 510wagon » 08 Apr 2019 06:51

That vacuum connection to the intake is most likely for the ATC (auto temp control) in the air filter snorkel. The AIS is a vacuum powered gate that is regulated by a temperature sensor in the air filter. It mixes cold outside air with air warmed by the exhaust manifold under a sheet metal shield. The sensor regulates the air into the carburetor at around 100F.


This is exactly what that vacuum line is for.

I didn’t get a chance yesterday to work on the car but I will today. Thanks for everything everyone

510wagon
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by 510wagon » 08 Apr 2019 19:41

I did some work with the short amount of time I had today. The distributor didn’t look too bad. I’ll replace the points at the very least. No slop or wiggle of the shaft. One of the points is wearing kind of strangely, they are at .026 and .028”. Rotor has wear and will be replaced. Cap doesn’t look too bad. Plugs are between .030 and .035”. Cylinder #3 has oil which I didn’t suspect since I installed oversized pistons (I forget how much but had the cylinders bored) and had the head machined flat. Multimeter has a blown fuse so I couldn’t measure resistance in spark plug wires but I assume they aren’t too bad.
The vacuum advance strangley didn’t advance with my manual vacuum applied. But it did advance when I was running it and came off of idle. See pictures. My repair manual says 4 slots after tdc and it’s set to about 3 1/2 slots. Supposed to be at 700 rpm but I don’t have a tachometer so that might be alright? Idk. I’m pretty sure the white slot is tdc.

Byron510 wrote:
07 Apr 2019 17:13
Mike has some awesome advice above - do follow it - BUT FIRST .... rule out all ignition issues before adjusting the carb. As the old adage goes, 95% of all carb issues - are in the ignition! And it’s very true.

I also agree that it’s way too soon to write off the existing motor. Unless there is significant signs of wear or some major mechanical issue, for the use of the car you are way better off staying with the stock engine. The L motors are very strong, and run quite well. The motor earned the good name of reliability for the 510’s. The only reason people have gone to newer motors now is output and building hot rods, and it doesn’t sound like this is what you mom wants. These cars can start in a flash, purr like a kitten and go pleanty fast enough to get the job done.

Firstly, make sure the plugs are good, clean and gapped correctly for your ignition system - likely stick points, correct? Check you manual, it memory- as bad as it is - says somewhere around 0.032”

Points are capped correctly- somewhere around 0.019” - again this is memory, confirm with a manual.

Cap and rotor have clean contacts, and the rotor sits and locks firmly on the top of the distributor shaft.
Don’t laugh, many of the recent aftermarket rotors don’t fit well, and flop and wobble around. Something to check.
Speaking of distributor shaft - is there a pile of sideways play in it? This throws you point gap all to heck if this is the case.

Plug wires have been checked for too high resistance? Nothing worse than the spark not even getting to the plugs.

And lastly timing - as Bert noted before Mike, Incorrect timing throws all performance out the window.

With the ignition done, move onto Mikes carb advise- it’s very well written and extremely good advise.

Byron
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510wagon
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by 510wagon » 08 Apr 2019 19:44

I have more pics and comments I’ll post in a short bit
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datzenmike
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by datzenmike » 08 Apr 2019 19:57

Image

These are totaled. Looks like the contact came off and welded to the other contact. The other set could be filed down but if replacing one might as well do both.


The plugs look very good except Champion??? Nissans only use NGK. Running another brand will only be 'close' to the correct type and heat range. Get NGK.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

510wagon
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by 510wagon » 08 Apr 2019 20:40

Yeah they don’t look good. I will replace them no doubt about that.
And here are clear pics to clear up what that vacuum line was for, you were absolutely correct. Hose goes up to the air filter housing to a temp controlled valve that sucks in warmer air around the exhaust manifold. I did take off the ducting to the exhaust because it was cumbersome taking the intake on and off. Also I don’t drive it on cold days. I’m in Los Angeles so we get like 6 cold days a year ha.
And here are a couple better pictures of the carb, one with fuel in the bowl.
Other than the points I don’t think it looks too bad. Not bad enough to cause spuratic bogging which was my original complaint?
datzenmike wrote:
08 Apr 2019 19:57
Image

These are totaled. Looks like the contact came off and welded to the other contact. The other set could be filed down but if replacing one might as well do both.


The plugs look very good except Champion??? Nissans only use NGK. Running another brand will only be 'close' to the correct type and heat range. Get NGK.
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510wagon
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Re: Rebuild, replace or swap moms 510 carb/engine?

Post by 510wagon » 08 Apr 2019 21:05

Here is a better angle of that point. Doesn’t look too bad at this point of view. Will still replace them.
Also I wasn’t aware of the importance of the plug brand. Thank you I will get the correct ones tomorrow. I must have just went into AutoZone and got the cheapest ones. This was almost 10 years ago when I was in college probably, that’s when I did all the work on the car. It was my daily for like two years.
datzenmike wrote:
08 Apr 2019 19:57
Image

These are totaled. Looks like the contact came off and welded to the other contact. The other set could be filed down but if replacing one might as well do both.


The plugs look very good except Champion??? Nissans only use NGK. Running another brand will only be 'close' to the correct type and heat range. Get NGK.

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