SU's- lean at partial throttle and high RPM.

[rossiz]

21 hours ago, psdenno said:

Glue the float bowl gaskets?  Curious why.  

the gaskets turn into a pringle the first time they get fuel on them and get increasingly difficult to keep in place when putting the lids back on. put a thin layer of fuel-proof adhesive/sealant on them when they go on for the first time and your life will be so much easier if you have to pop the lids off a dozen times to get the float levels just right.

[siteunseen]

2 hours ago, rossiz said:

the gaskets turn into a pringle the first time they get fuel on them...

Great description!

[siteunseen]

When I get mine set at .55" I put the fuel inlet tube on the lid in my mouth and blow/suck to make sure the float valves are working to allow air in or shut off so air cannot blow through.  Oh yea, you have to turn them upside down and move the float with a finger. Pin in, "none shall pass". 8^)

[psdenno]

30 minutes ago, siteunseen said:

Great description!

OK, thanks, Alesson learned.  I guess I've been lucky the times I've opened and resealed the bowls.  I'll be wiser next time.

Dennis

[blodi]

Thanks for all chiming in guys. I did re-seat the needles and that seems to even out the adjustment for the two a lot. I started at 2.5 turns out. I drove around for a bit last night and kept adjusting evenly.  Ended up at 4 turns out for both for the timing being...rich at cruise ~13.5...and still wants to lean out at partial throttle...WOT it looks good...12.5-13....until about 5-5.5K and it starts leaning out to ~13.8. 

I have checked the rear float previously and it was something like 21-23mm below the cap.  I forgot to check the front last night...I'll get that done. 

Grose jets should be good as they are brand new...just rebuilt the carbs with ZT kit over the winter. 

 

[blodi]

Checked float levels last night. They were at 27.5 and 29 below the mid point of the float bowl cap !....so I adjusted them over and over and finally got them both within a mm of 23. Started with both at 2.5 turns out...and drove and adjusted again. Ended up at 3 1/4 turns out and still felt like it wanted a bit more...so went to 3.5 when I got it home and called it a night. So I'll try again tonight possibly. Car was running well though overall. Just still leaning out a bit at the top end. 

I noticed when I popped the hood to make adjustments (while it was dark out) the first time, #3 header primary was glowing red. I noticed the spark plug wire felt slightly loose so I clamped it down a bit with my fingers. The next time I went to make and adjustment I noticed both #3 and #4 were glowing. The glowing went away shortly after opening the hood and must have built up after running on the highway...but only those two cylinders oddly.  Timing is currently at 35 full FWIW.  

[blodi]

So with some further driving and observation...still the same basic issues. Cruise is too rich...13.5.   HIgh acceleration goes lean....14.0+

Any idea of what needles would correct this? Do I get something that is just richer up top and adjust the cruise with the carb adjusting nuts as needed? 

Or...do I go to larger nozzles? 

Edited June 9, 2016 by blodi

[Patcon]

Have you contacted Ztherapy yet? That is where I'd start...

[blodi]

Actually I just emailed them earlier today. I'll see what they suggest. 

[gundee]

You may also want to try to get a hold of Larry the engine builder and see if he

knows or has an opinion on what works best with that camshaft.

[blodi]

46 minutes ago, Lumens said:

You may also want to try to get a hold of Larry the engine builder and see if he

knows or has an opinion on what works best with that camshaft.

Good point....the engine came with jet settings for tripples taped to it.  Which is fantastic if/when I go to Webers....but for the time being....just want to get the SU's to work as well as they can. 

Maybe I'll shoot Larry a note and he may know off hand what might work. 

 

 

 

 

[Gav240z]

Incidentally which wideband sensor did you go for? I'm interested to see how you progress. Although I think a high compression engine and SU carbs are not the best combo.

In my experience my 72 240z with a high compression L28 block and E88 head tends to feel a bit flat through the mid-range and definitely feels choked at the high end. But until I get a wideband on it I won't be sure if it's not enough fuel or airflow.