blodi

Here is an image. The curled up line went to the air box. Now what do I do with it?

Yes, I'm talking about the other hose coming off of #57 there that goes up to the back of the air filter box. What do I do with that one? Cap it? It normally "breathes" through the air box. I can keep the one going to to the crankcase breather tube, right? I'm going to run a K&N filter on the tube itself.

Getting ready to install my triple webers. I know the vacuum advance for the webers not hooked up and I have capped off the port at the dizzy. My question is about the other vacuum line that went to the back of my airbox with the SU's. It gots from the airbox down to the small junction box under the dizzy. What do I do with this line now as there is no port for it to go to now? Do I cap it at the junction box? What have you guys done with it? I can't find any images or info by searching.

I am going to be ordering a triple weber setup for my L28. First, my engine basic stats: L28 F54/Flattops, .040 bore, E31 Head which is ported/etc, 500/300 cam, 6-1 header, pertronix igntition, etc. My whole engine install thread here: I've been running the round top SU's with SM needles. They go lean up top despite the needles and repeatedly checking the floats/fuel delivery/etc. Looking to go triples. The good news is my engine was built as a backup for a race car and it came in the crate with jet sizing written on the valve cover. So I have a good starting point. Just hoping you guys can help fill in the blanks. I am learning here. image2 (1) by blodi, on Flickr So what else is missing from those settings? Based on those and what I've learned in some helpful searching it seems I need to go for the 45's and use a 38mm choke? Do the rest of those settings make sense? Thanks!

I'm running the stock springs. I'm going to call Z therapy again today. I think I just need larger nozzles...I've checked everything else out...it's just leaning out progressively above 4.5-5K. It's at 14.6-8ish by the time I hit 6K.

Actually, oddly I seem to be able to run a lot of timing in it and no pinging at all. I can see the advance working with the timing light as I rev the engine, so the advance is working. I started a thread in Carb Central and have been working though it...I think I just need larger nozzles at this point. Gonna call Z therapy today.

OK, good links! I got the carbs balanced last night at 3K rpm. Didn't have a chance to drive it though and observe RPMS. I just had to turn the balance screw in ~1/4 turn to get the rear carb balanced.

I'll have to pick some up and give it a shot. Honestly, I've just synced the carbs at idle. What RPM should I check them at?

Yes, advance is coming from the front carb. The carbs are synced very evenly.

Once I reset the float levels, the difference between the front and rear carb seems to be much more even. The plugs seems to confirm this as well. I've sprayed carb cleaner around the carbs and intake manifold and have seen no evidence of vacuum leaks. Damper dash pots seems to be working correctly. They open evenly when bliping the throttle and fully (by hand). Fluid level is good. I'm using ATF...maybe I need something thicker?

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.

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

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?

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.

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.

Yeah, I'm going to start with the needle seating...as my rear carb needs to be leaned out a couple turns from 2.5 to get it "correct" with my colortune. I'll also double check the float levels too.

Thanks for that. The pump is the K&N unit the MSA sells...low pressure...should be plenty of flow. Found this on seating the needles...might be something i need to try first. The rear carb is only maybe 3/4 of a turn out and the front is closer to 2-2 1/4. At the bottom... http://www.sonic.net/~kyle/su.html

Question is about carb tuning... Running stock round top SU's. Z therapy rebuild kits, ATF in the dashpots, SM needles. 260Z intake manifold. Electronic fuel pump. Again...L28, high compression, E31 head, 500/500 cam. Ported, 6-1 header...etc. I just got an Innovate LM-2 the other day to see how things were looking in the tune. Overall...idle...for some reason...it's reading in the 30-40's...which makes no sense...but regardless... At cruise...things look pretty good...between 15-16. Rolling into throttle at 3.5K at about 30-40% throttle...things go lean...like 17's and there is a slight stutter. But if I push throttle beyond that (50-60%) it richens back up nicely and pulls well. WOT...things progressively get richer down to 12.5-13.0 and hold steady...until I get to maybe 5K+ and then it just starts progressively leaning back out to 14's by 6K...and that's all the revs I'm putting into the engine so far. What are my options for these two issues? Is this engine asking too much of "stock" SU's? to deliver at high RPM? And suggestions for the partial throttle lean out? I think I may eventually want to go to Tripple Webers (40's or 45's?) and fortunately when I bought this engine it came a label for what jets to use! So that will take a lot of guess work out of them down the road hopefully. But I want to get the SU's working well for the time being.

So...update and questions...up to 850 miles on the engine and overall it's been running great! Question is about carb tuning...and maybe I should start a thread in carb central...but I'll start here... Running stock round top SU's. Z therapy rebuild kits, ATF in the dashpots, SM needles. 260Z intake manifold. Electronic fuel pump. Again...L28, high compression, E31 head, 500/500 cam. Ported, 6-1 header...etc. I just got an Innovate LM-2 the other day to see how things were looking in the tune. Overall...idle...for some reason...it's reading in the 30-40's...which makes no sense...but regardless... At cruise...things look pretty good...between 15-16. Rolling into throttle at 3.5K at about 30-40% throttle...things go lean...like 17's and there is a slight stutter. But if I push throttle beyond that (50-60%) it richens back up nicely and pulls well. WOT...things progressively get richer down to 12.5-13.0 and hold steady...until I get to maybe 5K+ and then it just starts progressively leaning back out to 14's by 6K...and that's all the revs I'm putting into the engine so far. What are my options for these two issues? Is this engine asking too much of "stock" SU's? to deliver at high RPM? And suggestions for the partial throttle lean out? I think I may eventually want to go to Tripple Webers (40's or 45's?) and fortunately when I bought this engine it came a label for what jets to use! So that will take a lot of guess work out of them down the road hopefully. But I want to get the SU's working well for the time being.

The breakup/sputtering at 4K+ came back the other night. Since this is a high compression build I put in 7 heat range plugs when I installed it. On a total guess I pulled the old 6 heat range plugs from the old engine and installed them last night. Breakup/sputtering gone! Game on!

Drove it home last night, and this morning and still runs great. Starts right up everytime since that odd time yesterday at lunch. As for that 4K breakup that I experienced that one day...my latest theory is that I possibly didn't take the choke fully off. I noticed this morning when I took the choke off there was a it of a hangup in the cable or something and I had to push it a bit to get the lever fully forward. So maybe on that particular day I thought I had it fully off....but didn't.

Changed to a 6-1 header from the stock exhaust manifold. Heat shield it still in place.

Just replaced it last fall. Drove it over lunch, ran great. But, had a hard time starting when we came back out to it after eating. Vapor lock? Had to floor it while cranking for a while for it to finally fire. Usually fires right up.

Took it for a spin last night and drove it into work this morning....no more sputtering/break up...bizarre. Seems to be running great again!

Still trying to rack up the break in miles...up to 150....bad weather and lack of time has kept me from driving more. Car has been running great...up until the last time I drove it....I'm limiting revs to 4.5-5k overall..but I noticed last time it would start to break up past 4K under load. Didn't have that issue the time I drove it before that.....pulled plugs and they look good....any ideas? Fuel? Timing? Really odd...nothing changed.