HEI tuning and timing....need help selecting springs and initial timing!

[thefarmboy21]

I have not tuned on the carb for a while. My buddy ran it and messed with the mixture screws and adjusted the secondaries , he may have also messed with the floats. I changed the fuel pump already thinking that may be a possible cause just didn't have an oil change yet.....I'll change the oil this evening if the rain holds off and try to adjust some carb stuff.

Rich, how many turns out should the mixture screws be for a starting point? I've got a vac gauge I can use. Also where do the floats need set? I don't have a book on it.....maybe I can find a manual on the web.

[rich weyand]

Here's the owner's manual:
http://www.edelbrock.com/automotive/misc/tech-center/install/1000/1404_manual.pdf

You need the gasket to adjust the floats because you have to take the top off the carb.
http://www.summitracing.com/parts/edl-1499/overview/

Here's a post of mine on my tune.  Includes how I set my idle mixture screws initially, though I tweaked them with an A/FR meter.
http://www.fullsizechevy.com/forum/general-discussion/classics/514682-just-got-1978-k-20-where-do-i-start-5.html#post5758323

That whole thread should be pretty interesting to you.

[thefarmboy21]

When adjusting the idle fuel mix, for example "3 1/2 turns" means full revolutions correct, not in 1/2's? I know that sounds stupid but me carb literally idles the highest and pulls the most vacuum at ONE full revolution OUT per screw. 1 turn each from dead closed?!?! I'm thinking it has to be pouring an absurd amount of fuel if it only wants 1 turn per side. Also I adjusted my vacuum secondary flap back to the edelbrock spec (turn screw til it barely opens then back off 1.5 turns" and somewhere between the idle mix and secondaries I've developed an exhaust "flutter" It's like it puffs and has a lisp after I let off the fuel? I haven't checked the floats yet because I don't have a top gasket, but I'm thinking I may rebuild one of my 1406 600cfm carbs for it instead. Sigh........I just want a reliable daily driver lol.

[rich weyand]

Yeah, it means full revolutions.  One revolution out is amazing. 

Which truck is this?  The '77, right?  You are running the mechanical fuel pump on the block, right?

[thefarmboy21]

No the 86......I just dropped a basically fresh 350 in it. It's a 70-72ish bottom end from a truck that I rebuilt a couple years ago and had been running as my derby motor with some heavily worked 2.05 double hump heads......the heads need new bronze valve guides, so I put a spare set of centerbolt heads on the motor and dropped it in my 86. Has a manual fuel pump with the return port, Comp 4x4 cam (.447x.462) Eddy performer intake, HEI dist, AC Delco R45TS plugs.

But yea it kinda threw me for a loop when it just wanted leaner and leaner.......and the exhaust will still burn your eyes!

[rich weyand]

You must be leaking fuel somewhere in the carb.  Choke not opening all the way?  Float valve stuck open or not closing properly?  Piece of grit in a float valve?  Floats set wrong?  Someone mentioned on a forum that the Edelbrock floats are always wrong, right out of the box, so I checked mine and sure enough they were set low, overfilling the bowls.

The floats are easy to check, but you do need to replace the air horn gasket when you take the top off the carb.  Edelbrock 1499 I think.  Set of five in the package.  Don't drop one of those little snap clips when you take off the linkage rods.  They're a bugger to find.

[thefarmboy21]

Well the choke is currently wired open, so it's not that. I'm thinking there's something going on with the needle valves or floats. I've got a gasket kit on the way, so hopefully I can get it straightened out.

[Dan75k20]

I bought the edelbrock trick kit for my edelbrock 1405 performer intake flat tops 4 valve reliefs 0 76cc 882s 2.02 1.60 0.30 over same comp extreme 4x4 extreme cam you are running it is absolutely perfect the truck runs amazing  ill let you know what size metering rods i am running we set the carb up with an air fuel meter and 02 sensor

[thefarmboy21]

Yea I'd like to know. I'm going to try and tear the carb down today. I have two 600's on the shelf I may try if I can't find the issue with my 650.

[rich weyand]

This thread I posted earlier includes my rods/jets/etc.  I also dialed it in with an AF/R meter.
http://www.fullsizechevy.com/forum/general-discussion/classics/514682-just-got-1978-k-20-where-do-i-start-5.html#post5758323

[thefarmboy21]

Did you buy an Air/fuel gauge and sensor combo, or just cobble your own system together?

[rich weyand]

I bought a complete kit.  NGK AFX Powerdex.  It has the wideband sensor.  Not a cheap unit -- you can find them for about $300.  But well worth it to get the mixture spot on the numbers for idle, cruise circuit, power circuit, and secondaries.  Makes it a snap to tune a carb, or to re-tune it when you change something.  And a perfectly tuned carb is a joy to drive.

There are cheaper units, but for accurate readings you want one with a wideband sensor that includes a heater circuit, a thermostat circuit (to control the heater with), and the sensor circuits.  This is a seven-wire sensor.

I had the local muffler shop braze the (provided) bung in the drivers side exhaust and chase the threads.  When I have the unit installed (only when tuning), I run the cable up the firewall, hook it over the wiper, and run it in through the vent window (which will still close and latch).  I plug the unit into the cigar lighter for power.  The unit itself fits in the little glove pocket in the dash (I don't have A/C, so instead of the A/C vent I have a little glove tray in the dash) with a piece of packing foam around it to keep it from rattling around.