Getting dual SU setup to run

[rundwark]

I'm converting my 510 from the single downdraft stock Hitachi to a dual 38mm SU setup using a second-hand K-14 intake manifold.

 

Thanks to a bunch of posts that I found here, I think I have most of the plumbing sorted out (everything starts looking simple when you pull the air gallery and air pump off the car), but I can't figure out how to connect the coolant hard line that runs by the thermostat to the manifold.

 

It looks like the right place would be at the center of the manifold on the bottom, below where the PCV valve sits. That port is blocked off on my manifold with a bolt. Does anyone know where to get a connector that I can screw in there (or maybe have a part number? The parts manual I have only shows the US manifold setup) to connect the coolant line? Or did I guess wrong and should I look elsewhere on the manifold?

 

Thx!

[datzenmike]

14800-N5810 about $6 at the dealer, is the outlet pipe for the L20B intake for the coolant line. There are different outlets for different engines but I imagine the threads are the same. Failing that get the one on the thermostat housing... same thing.

The coolant by pass hard line may have been removed and the hose down at the lower rad fitting maybe has a bolt and gear clamp on the end???? I see that the 510 did not have the thermostat by pass on them like the later cars.

 

 

The fitting with the hose and gear clamp is for the PCV connection The fitting just above it with the blue cap and wire is the vacuum source for the brake booster.

 

 

 

 

 

The water outlet hose goes to the front of the intake  (far right in this picture just inside that loop of rubber tubing lower right) I just went out and checked it.

 

[rundwark]

Thanks Mike! I contacted a local dealer to see if they still have that part available. I couldn't find it at any of the online Nissan parts sellers.

 

Now that I know where it's supposed to go, I'll also try if the coolant connector from the original manifold (the one that I just pulled off the car) fits this manifold.

[datzenmike]

That part number is for an L series fitting.  After looking at the K-14 fitting it looks much larger.

[rundwark]

Took the plug that was in the manifold to an Autozone, I now know it's got an 1/2"-20 thread.

 

They didn't have anything that would work (of course), but I'm going to look for generic 1/2" thread to 3/8" hose connectors while I wait for the Nissan dealer to get back to me.

[datzenmike]

I would expect metric and pipe threads.

[rundwark]

Just ordered this: http://www.jegs.com/webapp/wcs/stores/servlet/m20ProductDisplayView?productId=379712

 

Fingers crossed...

[rundwark]

Yeah, me too. I was really surprised to find a non-metric thread. Maybe some previous owner re-tapped it.

[rundwark]

Oics!

 

It's coming together (mocking it up):

 

 

None of this really fits together well yet, but after I get a connector for the intake, I might be able to just modify the hard line by shortening it. And I'll put a little loop between hard line and thermo housing. I'll need to replace the coolant connector on the thermostat housing as well as drill open the thin connector on the hard line or just replace it. The thin connections are so rusty, that they appear to no longer be hollow. Looking at it, I'm really surprised the car was running good temperature most of the time.

 

Replaced the floats with composite ones:

[rundwark]

Received the JEGS plug today, it fits perfectly.

 

Pic with plug installed:

 

I cut down the metal bypass line a little bit, it's now just long enough to fit a 3/8" coolant hose after the 3/16" split off for the thermo housing and improvised this coolant line setup. Not sure how much this will get flow to the thermostat housing but it's gotta be better than what I had. The whole thing was completely clogged up.

 

 

[datzenmike]

Yes, that's perfect.

[rundwark]

So I put it all together today.

 

The good news: it runs! no leaks!

 

The bad news: it dies once the engine gets hot, and after that I can only restart it if I hold the throttle almost full down while running the starter for a while.

 

I adjusted the carbs to full lean, but no luck. Exhaust smoke is pretty black too, so definitely running rich. While running, I sprayed some carb cleaner on the throttle shafts and didn't hear the engine slow down so I'm pretty sure there are no leaks there.

 

My guess is that the carbs are running needles for a bigger engine (I believe the previous owner had an L-18), I'm just running a stock L-16, so I'll get a new set from ztherapy.

 

Could the not starting hot issue be explained by needles for an L-18, or should they not make that much or a difference?

 

Just to make sure I'm not doing something stupid, here are some pics. Is it an issue that I'm running my fuel return line so high?

 

 

[rundwark]

After cooling down for a bit, I was able to drive it (more like jump it) around our culdesac. The throttle feels like an on/off switch when driving, it's either almost dying or accelerating like a rocket even with a little bit of gas.

 

Mike, does this indicates anything to you?

[datzenmike]

Throttle geometry wrong? Sealik is the guy to ask.

[rundwark]

Yeah, now that you mention it, the throttle geometry is kinda messed up right now.

 

[rundwark]

What's weird though is that any pics I find online seem to have a similar setup, with the throttle rod going somewhat diagonal.

 

The throttle doesn't feel on/off-ish when I'm just sitting around in neutral. It only acts weird when there's some load, so maybe not geometry.

[rundwark]

Just renamed the topic, since it's kinda evolving.

[Sealik]

The bad news: it dies once the engine gets hot, and after that I can only restart it if I hold the throttle almost full down while running the starter for a while.

 

I adjusted the carbs to full lean, but no luck. Exhaust smoke is pretty black too, so definitely running rich. While running, I sprayed some carb cleaner on the throttle shafts and didn't hear the engine slow down so I'm pretty sure there are no leaks there.

 

My guess is that the carbs are running needles for a bigger engine (I believe the previous owner had an L-18), I'm just running a stock L-16, so I'll get a new set from ztherapy.

 

Could the not starting hot issue be explained by needles for an L-18, or should they not make that much or a difference?

 

Just to make sure I'm not doing something stupid, here are some pics. Is it an issue that I'm running my fuel return line so high?

 

 

 

 

I doubt the needles have any thing to do with not starting when hot

Fuel return line???  Don't see one

All you need is a couple of feet of fuel line for each vent routed towards the bottom of the car and secured into place.

Did you set the floats and then check fuel level after the fuel pump/engine was fired?

You leaned out the carbs......meaning you raised the jets up?

Wideband is a must when tuning SUs

 

Notice the fuel line tee is centered between the carbs.....<.......and the fuel lines are of the same length

Return line.......in front of the spark plug leads

 

 

I'm not running a bar from the firewall.....converted to trunnion and throttle cable

[rundwark]

Thanks for the reply Sealik! I have a fuel return line, but I hooked it up to the tops of the float bowls, are those the breathers?

 

Since that's not where you're running yours, that's probably not the right place :)

 

Is your fuel line split off from the same fuel rail that leads into the floats? It just goes up a bit first, so that fuel actually makes it to the floats and then goes down?

[rundwark]

Oh and yeah, I raised the jets all the way up, and didn't measure the float levels yet.

 

But I guess the first problem to fix right now is to unplug the float breathers and run the return line in the right place..

[rundwark]

I found a couple of old posts here on fuel return lines, including this post from Mike, with a pic of the stock fuel return restrictor for L20B's: http://community.ratsun.net/topic/55210-fuel-pressure-regulator/?p=915132

 

Since work and family will keep me away from wrecking yards for the next couple of weeks (and I am not that patient), I ordered this restrictor to work into the fuel hose: https://www.watcon.com/return-fuel-line-restrictor

 

My plan is to add a T-connector in the fuel supply hose between the pump and the carbs, connect the stem of the to the return hose, with this restrictor in it. It seems to me like it would be better to put the return split-off somewhere after the supply line has gone by the carbs, but since no one seems to have it set up that way, I'm just gonna put it in front like everyone else.

[rundwark]

It's alive!

 

Got the engine to run properly today, after completely redoing the fuel hose setup. It's a lot more tidy now, with shorter lines.

 

Thanks for the advice Mike and Sealik