jmortensen

Got this recommendation from a carb builder. Probably just try this first: set emulsion bleeds top to bottom .028 .028 .026. I dle feeds at .033. IAB .072. HSAB at .030-.031 pvrc at .055-.060. Jet primary at 67-68. secondary at 76-78 no pv sec. set primary pv to aprox vacuum at the point where you are just getting into throttle out of the apex.. prob start with around an 8.5. float level at half glass. pump shooter primary at .031 and secondary at .033-.035.. make sure you adjust the pump arms to zero lash at throttle rest.

speedtigger

iTrader: (16)

Sounds like a good starting point. Let us know how it does.

jmortensen

OK, getting closer. Still rich at idle, needs about 3/4 turn out to get to stoich, or at least in that neighborhood. Thinking that having these turned in so tight might affect other things, so I'm going to try downsizing the IFR until I can get closer to 1.5 turns out.

Off idle stumble is still there but better. Went up on the squirters, .033 on primary and .037 secondary. I have a blue cam, thinking about changing the primary side pink to the blue for larger squirt earlier in the stroke.

Also, in an attempt to get the idle down I went ahead and bought a 6010. Got a pretty good deal on it used, so I'm happy about that. The programmed setting on this thing is pretty wacky from what I understand about LS engines. I had heard that they don't need a lot of advance, the guy I bought from had 38 degrees at about 3350 rpm. I thought max should be more like 26 or so. He's got about 30 degrees at a normal idle speed.

He said this was the setup he ran his fastest all motor passes with, so I didn't just want to delete it and start over, but I think I need to use timing to get the idle down, and this just doesn't look like it's going to work.

Suggestions for a decent timing curve and how to lower the idle speed without killing the transition? Was thinking maybe use the MAP sensor. Haven't looked into that too far. I kinda thought it was set up to mimic vacuum advance, in which case it wouldn't do what I want, as I would want a lot of advance with a drop in vacuum when the throttle opens.

jmortensen

Should have searched... looked and found the sticky with a bunch of different timing setups. Still not sure about running 40*, but I did go ahead and save that curve and created my own. I watched a youtube video with a guy who has a boosted LS and he talked about making a pocket or a dip around the idle rpm that you want, so I went ahead and tried it. Worked. Messed around a little and came up with the following. Would need some dyno time to figure out exactly what is ideal, but this should work, and I got the idle down to 950 rpm, which I think is pretty good for having a super light clutch/flywheel setup. Stumble got worse when I adjusted the timing, so now I need to go back and start over.

Was watching other holley tuning vids and they say lightweight cars or cars with low gearing need big squirters. I have both, so I'm going to go back to squirters first as a solution and see what I can do there. Also going to install that blue pump cam on the primary side.

Pop N Wood

iTrader: (1)

Put the 500 RPM timing down to 5° and move the 1000 RPM timing up to 15° or so. Should keep the idle speed but the faster ramp up off idle might help with the stumble.

Idle screws at 3/4 turn tell me there is more to gain from adjusting the IFR and IABs. Go smaller on both.

jmortensen

I dropped to .029 on the IFRs and now I'm running about 1 turn. Haven't moved up on the IABs yet but will do that next. Was at .073, next step is .077. Hoping with that I'll get to somewhere in the 1.5 turns neighborhood on the idle mix screws.

Tried a couple other things too. First was the transfer slots. Seems crazy to me that people set them right, then bolt the carb on and after setting the idle mix screws, they change the idle speed screws which screws up the transfer slot setting. Don't make no sense. So I decided I was going to set the transfer slots and then change the idle speed with the timing. Did that and could only get the idle speed down to about 1300.

I know you don't particularly like it Pop, but I went ahead and tried the 50cc pumps on both sides. I had a blue cam in the primary and brown in the secondary. The blue cam is a 30cc cam, but it still seems to be doing more with the 50cc squirter in place for some reason. It's definitely revving up a lot faster on the primary side. When the secondary kicks in it's ridiculously rich, so I have another blue cam on order for that side too. I had to step down on the squirters. Was at 33 and 37. I have a couple 31s on order going to try them first and see how that works.

That dip in the timing created a hunting idle situation. The thing would idle at the right speed, then slowly speed up and you could watch the AFR fall to about 12:1, then it would slow way down and the AFR would go to 18:1 and it would almost die, then it would go back to normal. I dropped the timing to 5* up to about 1400, then it angles up to 25 degrees at about 2000. Still idling too fast. Hoping that the larger IABs might have some effect there, as I really do want to stick to having the transfer slots set.

What I can say so far is that this thing was hopelessly lean when I started messing with it. Now it's ridiculously fat, so I've at least found where too little and too much are. Now I just need to get to the middle, and see what I can do about that idle speed...

speedtigger

iTrader: (16)

Once I get the primary transfer slot set, I'll often adjust the idle with the rear throttle blades. You might try closing up the rears.

Pop N Wood

iTrader: (1)

Do you have a MAP sensor hooked up? If not be sure to zero out the map table. The box also has an "idle timing control" setting selectable from the lap top page. The box is supposed to default to disabled, most guys say it doesn't work and causes the idle speed to hunt so make sure that is off as well.

Did you check for vacuum leaks? Might be a contributor to your high idle.

Does your Demon carb have the "idle eze" option like on page 14 of the mighty demon instruction sheet?

http://static.speedwaymotors.com/pdf/91012054.pdf

Funny how every car is so different. Maybe you just need a fatter cam, LOL. That will get the idle speed down.

jmortensen

I do have the MAP hooked up, and I think I switched on the idle timing control. I am pretty sure no vacuum leaks, but will check again. No idle eze.

I called Texas Speed and they suggested a cam, then I said no give me a bigger one, and they did, and now I wish I had gone bigger yet. Typical for me...

speedtigger

iTrader: (16)

That idle timing control was not good for me. It made the idle very erratic.

jmortensen

Turns out idle control was off. Sprayed brake cleaner around and found a vacuum leak between the carb and the manifold. Kinda surprised because I have a 1/4" thick pretty squishy insulator there so I figured that would be the last place for a leak. Will take it out and bolt carb straight to manifold with gasket and see if that solves it.

jmortensen

Tried to bolt it back on without the spacer, acc pump hits manifold. Bought another 1/2" spacer which just arrived and tried again. No more vacuum leak, which is nice, but still can't seem to get the idle set just right. I took a video, and of course it wasn't really doing what it had been, which was speeding up as the AFRs went down to about 12:1, then slowing down as the AFR went to about 20, then returning to about 15:1.

Kinda getting annoyed, but I think this is so much better than what it was doing when I started that I'll probably just try to take it out, maybe to a track day where I can pit and adjust stuff and go back out, and see what it does. Of course, being in Seattle I'm running out of viable track days, so might have to leave it sitting in the shop until spring... again.

Here's a little video. Goes super rich on the AFR when I snap the throttle open, but that happened on my old triple sidedraft carbs on the old inline 6 and so (maybe incorrectly) I kind of expect that. If that's wrong, please advise. Now has the 50cc squirters, 31 nozzle primary and 33 secondary, blue cams.

speedtigger

iTrader: (16)

You could richen that idle a little with the mixture screws. Idle mixture hunting can sometimes be caused by the throttle blade/idle transfer slot adjustment being out of whack. Also, check to make sure your throttle blades do not stick a little just above idle. This can make a carb idle high after you have activated the throttle. The secondaries can do this too.

jmortensen

I set the slots then adjusted the rear only as you suggested and tried to set idle speed with timing more than anything, so they should be pretty close.

What does one do to fix sticky throttle shafts? Lube?

speedtigger

iTrader: (16)

Lube won't hang in that environment for long and probably wont fix it anyway. It is typically binding or wear causing friction, but I have seen carbs where the seconday actuator link was bent too short.

Pop N Wood

iTrader: (1)

Most guides I read claim throttle sticking is in the linkage to the carb.

I fought a sticky throttle for a year. Tried everything I could think of, even replaced the baseplate. Finally noticed the primary accel pump arm was bent. This caused it to hit the the pump cam at an angle causing the throttle to hang ever so slightly when returning slowly to idle. A quick blip of the throttle would drop the idle back down.

Weird.

Hate to say it but your too rich on snap throttle could be too much squirter. All the guides say just enough accel shot to cover the bog and no more.

ALSO now that you fixed a vac leak you need to lean out the idle circuits and maybe even the main jets. They were undoubtedly set too rich to compensate for the air leaking past the carb.

Nice exhaust rumble. Also pretty good throttle response. What flywheel are you running?

jmortensen

Flexplate/button clutch with 7.25" dual disks.



REALLY appreciate the help guys. I'll check the linkage, and see where that goes. I might order up a couple more squirters. Getting quite a collection at this point. Maybe I'll try 31s on both sides. It's defintely responding a lot better than it was when I started.

Pop N Wood

iTrader: (1)

Nice. That is probably my next upgrade, a lighter flywheel. Went with stock LS2/7 and it is way too heavy for such a lightweight car.

jmortensen

Just went and checked linkage. The only thing hitting was the primary side acc pump lever was just barely touching the throttle linkage. I hit it with a belt sander real quick and took maybe .020" off of it, now there is a little gap there. I can't imagine that was actually causing it to hang up, but that was all that I saw. Looked at the transfer slots and they were a little too far closed, so I opened that back up, and changed down the IFRs too. No time to test today, but will probably give it a shot this weekend.

jmortensen

Fast forward 7 months, rain is almost gone and I'm back at it. Original problem was that I couldn't get the idle down, today it wouldn't idle at all. Frustrated, I grabbed some starting fluid and started checking for leaks again. Had a strong hit when I missed the carb and hit the manifold where the Edelbrock timing module bolts to it. WTF? Stick my finger on the hole, there is vacuum there! I guess it was always like that, with the hole drilled right through. I didn't put a longer than stock bolt in there and push through the manifold so it must have been made that way. I guess I didn't realize and didn't find it previously. Kinda embarrassed actually.

Once I realized what was going on I grabbed an extra little rubber insulator off of the old Edelbrock unit and screwed it in, and now it idles, but the idle mix is really lean even with the screws out 2 turns. I think I was chasing the leak previously when I made all of those other changes. DOH! I guess it's time to change those IFRs back up and try again.

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Who is an idiot? This guy.