Its me again lol

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R3N0

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So... if you haven't read my last post that's okay... it was long and a pain in the butt. I have a new issue that has arisen but I dont think it will be as difficult to solve. I hope. So here we go.

My engine is set to 12* BTDC I'm idling at 900 rpm, and my idle mixture screws are working. Now I'm get this nasty stumble when coming off idle to a light throttle. At WOT my truck charges ahead... but if I dont hammer it it struggles. The motor is making 14 -15 Hg at idle. I'll post video. My thought... and forgive me if I call it a wrong name, but i think my blades are sitting wrong and covering the " idle lean in" it's a term my friend used. The rectangular opening in the main bores that assist when when coming off a stop. I havnt pulled the carb yet, as I wanted some ideas before i go through and disconnect everything. But I think the last time I chem dipped the edelbrock 1406 I may have sat the blades wrong. Am I right on this? Or is there an easier fix I'm missing?
 
does the accelerator pump squirts as soon as you hit the throttle? is the distributor vacuam advance working?
 
Everything I've read about timing and carb is to nail down your timing 1st(get your va setup if you plan on using it). Then move onto carb.
That being said those "transfer slots" should pretty much be square if that makes sense. Adjust idle screw to achieve square-"ish"
 
Yup, if the accelerator pump is giving you a full, steady shot; it's time to look at your transfer slots- especially since you've had the carb apart.
With the carb off, back off your idle screw so it doesn't contact the linkage. Loosen up the screws on the butterflies and work the linkage a bit to get the blades settled into the bores snugly, then tighten the screws back up making sure the butterflies don't move around. Now observe how much of your transfer slots are exposed- they should look "square", or just a tad tall.
If you still have hesitation, you may have the accel pump delivering too big of a shot- back it off a hole and see if it improves. If it's worse, go the other way.
 
Okay. I will give this a try tomorrow. Have to wait till the wife goes to work then I'll pull it and check. Thanks yall.
 
4spdragtop said:
Everything I've read about timing and carb is to nail down your timing 1st(get your va setup if you plan on using it). Then move onto carb.
That being said those "transfer slots" should pretty much be square if that makes sense. Adjust idle screw to achieve square-"ish"
Click to expand...
Transfer slots... okay I thought that term my friend used was a bit "odd" lol
 
It probably needs some more initial timing. I'd pull in like 16 and if it likes that, maybe try 18.
 
Do you have the accelerator pump rod in the right hole, usually the middle
 
You may need more timing. What are you running for a cam? 15 initial "or more" is not unheard of. You can NOT run a performance, cammed up engine on a "stock" distributor AKA long stock mechanical curve and slow advance AKA strong springs
 
900 rpm idle & 14-15" of vac suggests a non-std cam, ie a cam with increased duration/overlap.

That requires more timing at idle.

This may not make sense, but PLEASE try it anyway, easy to do, takes 5min.
Engine idling, increase initial timing to 20-22* [ actual amount is not critical ]. Idle rpm WILL increase. Reset idle rpm & mixture screws. Test drive to see if flat spot is improved/cured...
 
Make sure the step up rods and springs are free. I think that's the direction you will end up.
Transition on a Edelbrock/Carter is tailored through the step up rods and springs.
 
The cam is a XE256H Comp cam, yes the pump is in the right hole and centered. I'm going to pull the carb tomorrow just to make sure the transfer slots are correct. Wont take but a minute. Afterwards I'll bump up the timing slowly, as it's a Summit Distributor and adds 20* of mechanical timing. This 8,900 lb truck likes to make the engine rattle at higher * of timing.4.10 gearing on 35s So ill take it slow. Until I can figure out how to limit the mechanical timing I may have to keep the timing low. How do yall feel about mechanical timing kits from box stores? Should I not even bother with them?
 
I checked the springs and rods as they are easily accessible, under revving they drop and lift pretty easily with out shuddering. I'm using silver springs with I think they are the 4037 rods... but dont quote me on that I may have the number wrong and running the stock jets.
 
Bewy said:
900 rpm idle & 14-15" of vac suggests a non-std cam, ie a cam with increased duration/overlap.

That requires more timing at idle.

This may not make sense, but PLEASE try it anyway, easy to do, takes 5min.
Engine idling, increase initial timing to 20-22* [ actual amount is not critical ]. Idle rpm WILL increase. Reset idle rpm & mixture screws. Test drive to see if flat spot is improved/cured...
Click to expand...
I will give this a try before pulling the carb.
 
And I'm using the blue springs in the distributor, maybe I should slip a black spring in to delay timing? Or a silver to bring it in faster?
 
You are all over the map. Try what I said in post #13. Forget about centri curves etc for now.
The test drive is at low rpms to see if the off idle stumble is fixed/improved.
 
Bewy said:
You are all over the map. Try what I said in post #13. Forget about centri curves etc for now.
The test drive is at low rpms to see if the off idle stumble is fixed/improved.
Click to expand...
You mean post 10, right?
 
You Again.jpg
 
Bewy said:
You are all over the map. Try what I said in post #13. Forget about centri curves etc for now.
The test drive is at low rpms to see if the off idle stumble is fixed/improved.
Click to expand...
I will absolutely try this first.
 
Bewy said:
You are all over the map. Try what I said in post #13. Forget about centri curves etc for now.
The test drive is at low rpms to see if the off idle stumble is fixed/improved.
Click to expand...
I'm just replying to questions. But I understand.
 
Like we talked about in your other thread, you might need more initial timing (to bring the idle speed up and be able to close down the throttle blades and square up the transfer slots) but you can’t do that yet because the mechanical advance brings in too much timing and it rattles. This is all part of tuning. You need to limit the mechanical advance in the distributor and bump the initial up a few degrees. Then test, and do it all over again.
 
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