First start today!

[rcv]

After almost 2 years of slowly rebuilding the engine, I finally got my '70 240Z to start up today!  This is the first time I've ever seen the car run, so I'd love some feedback from you all with more experience on how it sounds. 

The car starts up pretty easily, even with the choke completely disengaged.  The RPM seems to drift all over the place though, so I had to keep messing with the fast idle screw to keep it around 2,000 (just above Tom Monroe's recommended 1,500 minimum).  It sounds kind of rough to my ears, but again I've never heard the car run properly so I really have no idea.  This was originally my (soon-to-be) father in law's car and he thought it sounded a little rough but not terrible.  I messed with the timing a little bit and settled on ~15 degrees of advance, but the RPM is wandering around so much that it's hard to know if any adjustments are helping or hurting. 

I only got around 10 minutes of runtime today because I was running out of a gas can rather than the tank, and I emptied 2 gallons of gas in 10 minutes. I'm pretty sure all of that gas is just going back in the tank through the return line though, as there's no noticeable smoke from the exhaust.

 

Questions:

• How's it sound? Any concerns from you all?
• Any concerns about the RPM wandering around, or is this normal for a newly rebuilt engine?
• I was running water from my garden hose through the open radiator.  After my runs today, I just let it drain out and put on the cap and drain plug. Any issues with leaving the remnants of hose water in there?  I'm planning on continuing my break-in next weekend, so I'd rather not fill it up with coolant just yet. I also don't want the thing to rust solid over the week.
• What are your favorite guides for setting timing?  Should I try to set timing before or after synchronizing my carbs and getting the mixture set?

Thanks everyone - you've all been a huge help so far!

Videos:

- Very first start! After a few unsuccesful cranks, I handed the keys to my father-in-law-to-be who started it up almost immediately.  He claims the car remembers him.

 

- Here's me starting it. I reved it to ~3,500RPM before I got ahold of myself and dropped it back down to 2,000

 

- Here's a quick walkaround of the car.  I'm watching the RPM with my timing light, then bring it in closer to get some engine sound.  I then walk around to the exhaust to capture that as well.

 

 

[siteunseen]

I guess I would get the carbs balanced first off then if it idles steady set the valves. Then do the carbs again and the timing.

[siteunseen]

On second thought maybe set the valves to spec first. You won't be running the moror during that process so the carbs are irrelevant. Take the plugs out and write out a "go by" board. Some come up together or damn close and you can do them out of sequence just X them off as you go.

 

[rcv]

Sure that sounds reasonable. Think it’s worth doing before I run the car any more, or should I let it run for another 20min or so to break it in further before seeing the lash again?

[Zed Head]

The cam lobes are the part that usually gets damaged after a rebuild, on these engines for sure, and others.  Usually it's recommended to let it sit at about 1500-2000 RPM for 20 minutes to let the lobes and pads wear in with good lubrication.  You guys compressed 20 minutes at 1500-2000 down to about three at 3000-4000 it looks like but it's probably fine.  p.s. it does sound good though...

p.s. #2 it's not going to rust over a week with just water in it.  Actually, if you fill it with water you might find some leaks by next weekend.  It's not the water that causes rust it's the oxygen in the air.  So, filled with water would be no big deal unless you get a freeze in Sherman Oaks.

https://www.melling.com/wp-content/uploads/2017/03/Camshaft-Break-In-Proced-Rev4-12-07.pdf

Edited September 21, 2020 by Zed Head

[rcv]

The camshaft is original - I haven’t had the budget to replace it yet but I had the head rebuilt by a local reputable shop (Valley Head in Northridge) so it does have new pads. I only ran it above 3k briefly, the rest of the time was between 1500-2500, so hopefully it’s ok. I’m also using the high zinc break in oil from Lucas so hopefully that’s helping things ease in. 

[rcv]

So I’ve been tinkering with the tuning trying to get it to idle well, but haven’t made a lot of good progress. It seems like it’s been running rich - there’s some darkish smoke coming out of the exhaust, and it really doesn’t want to start with the choke on. I readjusted the lash cold this morning hoping that would help, but the adjustments were minimal and it hasn’t seemed to make much of a difference. I also sprayed some starting fluid around the manifold and carbs and didn’t get any change while running, so I don’t think there’s a vacuum leak. 
 

I’ve been pressing on those maintenance buttons below my carbs to adjust the mixture, and the RPMs go up every time I do, so I’ve been screwing my mixture knobs in and in and in.  At this point they’re screwed all the way in and the car seems happier for it. It’s starts up immediately and idles around 1000-2000 with both my idle screws all the way out.  That doesn’t seem right. My carbs were rebuilt by Paltech but I’m wondering if something is wrong there - maybe the needles aren’t seated, or something is wrong with the jet tube. Any thoughts on where I should start looking?
 

Here’s how it starts up now with the mixture knobs as lean as they’ll go:

PS before you ask, yup I’m sure the chokes are pushed all the way in 😋

Edited October 11, 2020 by rcv

[siteunseen]

The disable button makes the rpm raise? That is odd, it makes mine run half on everything. 

My easy thing first suggestion would be to poke on the floats through the fuel inlet with the red straw that comes with WD-40. They maybe  stuck in the bowls from shipping dry?

[Patcon]

If the mixture nuts are all the way up, the needle valves are stuck open or the floats are set too high

[rcv]

@siteunseen yup from what I’ve watched/read this means I’m too rich. 

Your theory is that the floats aren’t ever shutting off the fuel supply, and so the pump is just force feeding fuel through the jets?

When you say “...through the fuel inlet” how do you mean? The fuel inlet is bent and there should be that grosse (sp?) jet there. Do you mean go in from the bottom?

I poked my straw through the bowl vent, and on the rear carb I can feel it bounce a bit but it feels rock solid on the front. I think you may be on to something. I’ll open up the float bowls tomorrow and see what I can see. 

 

[siteunseen]

I'm sorry! The vents will work just as well and much easier. The "ins" have the jets on the other side. STUPID, STUPID, STUPID!

Thank you, I get confused on Saturdays in the fall. I'm lying. I'll be confused Monday a.m

Those are some beautiful carbs, Paltech does good work.

Edited October 11, 2020 by siteunseen

[Captain Obvious]

1 hour ago, rcv said:

I’ve been pressing on those maintenance buttons below my carbs to adjust the mixture, and the RPMs go up every time I do, so I’ve been screwing my mixture knobs in and in and in.  At this point they’re screwed all the way in and the car seems happier for it. It’s starts up immediately and idles around 1000-2000 with both my idle screws all the way out.  That doesn’t seem right. My carbs were rebuilt by Paltech but I’m wondering if something is wrong there - maybe the needles aren’t seated, or something is wrong with the jet tube. Any thoughts on where I should start looking?

So all of that sounds like a significant rich condition. What needles are you running? Stock N-27 or something else?

Also, your comment about the needle seating is important... It is possible to install the needles too deep in the suction pistons and if that happened, it can result in a rich mixture.