CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
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I just got my 350 running, I'm pretty excited! Seems like it survived the cam break in without too much trouble, and now it's just a matter of getting it driveable. But before I can drive it, I've got to get it to idle. Just a mild 350 with a 650 DP on it.
It WILL idle, it's just on the virge of stalling out at any given moment, and I cant get it to idle at anything less than about 20 degrees advanced without stalling out. I had it at around 700 RPMs and just turning on my electric fan stalled it out. Seems like it could be nearly ANYTHING causing this, since it's such a fresh build and there's so many things to dial in, and I'm a litlte over my head with it.
So I wondering if you guys had any suggestions on some books or something that I could read to explain a lot of this stuff to me.
Otherwise, feel free to add some suggestions here on things I should look at. I just found out that setting the mixture screws can make a big difference. I also am considering adjusting hte secondary idle screw. I hear with large cams thats a good idea, with small cams, it's unnecessary. My cam is very mild. 218/224 @ .050. I don't know whether that means I'm barking up the wrong tree with that or not. I'm also going to go hunting for vacuum leaks.
Also, is 750 RPMs a bit high for it to idle? Or should I try to get it running closer to around 600 or so?
And again, if anyone knows of some good reference material that will run me through what common adjustments are and how they're made and what tehy affect and so forth.... I'd be glad to hear it.
vacuum guage is all you need for setting idle screws. Start with 1.5 turns out for a 2 corner idle system and .75 turn out for a 4 corner idle system. there is a holley setup sticky with all the info you'll ever need on this board.
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Take the carb off, flip it over, and look at the transition slot. You want less than .050" of it exposed below the pri throtle blades. If more of it is exposed than that (it will be), open the sec throttles with their idle screw, 1/8 turn; put the carb back on; re-set the idle speed and mixture; then pop the carb back off and look at it. Repeat until you have between .030" and .050" of the transition slot showing.
Do you set the primaries AND secondaries to have .030~.050 of the slot showing, or is it that you are trying to get the secondaries open enough to allow only .030~.050 of the primary transfer slots showing?
I did som searches and heard some mentionings of getting all 4 equal, but the sticky thread doesnt seem to indicate anything like that at all...
Adjusting your idle screws to your engine makes a huge diffrence in throttle response, off-idle power and basically more power througout all rpm. Get the holley tuning kit and try out some diffrent pump cams and jet sizing, You'll be amazed at what a little tuning can do for you. It wouldnt hurt to get an air/fuel ratio gauge or fuel pressure gauge either.
Adjusting your idle screws to your engine makes a huge diffrence in throttle response, off-idle power and basically more power througout all rpm. Get the holley tuning kit and try out some diffrent pump cams and jet sizing, You'll be amazed at what a little tuning can do for you. It wouldnt hurt to get an air/fuel ratio gauge or fuel pressure gauge either.
THe question to me is should I be concerned if it's in the lean area? I know it runs off a narrowband O2 sensor, and the range in which it operates is very, very, very small, so I wonder if just running in the top half of the gauge is close enough to stoichiometric that I should be hapy with it.
But I dont know that it's getting warm enough to get a decent signal in the collectors of my long tubes anyway.
