Try it without the spacer.
Eddy 1405 tuning advice
- Thread starter 4spdragtop
- Start date
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Low speed light throttle only uses the idle circuit so it could be that you need to use lighter springs. The metering rod might be bouncing up and down . I dont think timing is an issue . I run a very similar cam and it will run OK anywhere between 12-18 intitial. I also think your lash is fine .
Try the lighter springs and see what they do .
Try the lighter springs and see what they do .
Orange springs in it, and down tight at idle. Pop up when throttled.
The spacer was needed when we 1st got the car for percolation. I honestly never thought about removing it.
The spacer was needed when we 1st got the car for percolation. I honestly never thought about removing it.
So basically a rod change?
I've been saying it all along.
Do you have a complete Edelbrock tuning kit?
it may be bouncing in drive though . Cant hurt to try .
I can’t imagine the spacer is causing this unless there is massu vacuum leak.
Anytime you add a spacer the calibration needs to be adjusted, usually needs richening up.
Yes ez to spring swap. No gasket required with spacer correct?
Ez enuf to remove spacer also.
I think the springs are about right, Steve. I wouldn't mess with those again right now. If the pistons are staying down SOLID at idle and not bouncing, leave the springs alone for now.
What else could cause the surging .
It's too lean.
If the rods/pistons stay down at idle, they will stay down at cruise speed because the vacuum is higher.
This will be my last post on this thread because I see my advice [ posts 26 & 43 ] of 40+ yrs years on these carbs is being ignored.
For the umpteenth time, do the idle screw test in post #43 because you may well be still on the idle cct at cruise & THE MET RODS/ MAIN JETS WILL HAVE NO AFFECT IF THIS IS THE CASE, SO CHANGING THEM DOES NOTHING. And it needs more idle timing.
Here is my last piece of help:
T slot is checked from under the blades. Carb would normally have to be removed each time to check this. A pain in the a**. To check without removing the carb....with carb on the bench, set t slot to 0.040" [ ideal/perfect ] with speed screw. Using vernier calipers, measure from screw boss to head of screw & record it. Now open blades for a 0.060" gap. Measure again & record. With carb on the car, you can check your gap. More than 060 would require bypass air [ only after correct idle timing is established ]. Less than 040 is OK & no corrective action is needed. Your surging problems are quite likely T slot related. I would also set the valve lash to 0.030" which will improve idle vac.
This will be my last post on this thread because I see my advice [ posts 26 & 43 ] of 40+ yrs years on these carbs is being ignored.
For the umpteenth time, do the idle screw test in post #43 because you may well be still on the idle cct at cruise & THE MET RODS/ MAIN JETS WILL HAVE NO AFFECT IF THIS IS THE CASE, SO CHANGING THEM DOES NOTHING. And it needs more idle timing.
Here is my last piece of help:
T slot is checked from under the blades. Carb would normally have to be removed each time to check this. A pain in the a**. To check without removing the carb....with carb on the bench, set t slot to 0.040" [ ideal/perfect ] with speed screw. Using vernier calipers, measure from screw boss to head of screw & record it. Now open blades for a 0.060" gap. Measure again & record. With carb on the car, you can check your gap. More than 060 would require bypass air [ only after correct idle timing is established ]. Less than 040 is OK & no corrective action is needed. Your surging problems are quite likely T slot related. I would also set the valve lash to 0.030" which will improve idle vac.
Metering rods are supposed to be down/lean in cruise and idle, sir. That's when vacuum is highest. When vacuum drops, the springs overcome the low vacuum and push the rods UP into the small (rich) part of the rods enriching the mixture for acceleration, similar to a power valve. But at a steady cruise while NOT under load, the rods are in the down (lean) position since vacuum is high. Sorry your gettin your panties in a wad, but thats how these carburetors work. He has the springs what I would call just about right.
Well, I did turn the IMS out as mentioned in #43, sorry you feel you're being ignored, you ain't the only one with advice here. Doing this by myself takes time. So unwad yerself and relax, or not...
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Take your time and have fun. Try different things and learn as you go. Ignore the EGO's........
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Forgive me if I'm gettin this wrong, but the one time you made it richer, it got better, right?
Also Steve, just like Edelbrock says. as you get closer to the optimal tune, the vacuum reading will continue to climb. So that's one other way to tell your heading in the right direction. But again, that's not set in stone, yet, because your timing may not be optimal for the tune yet. I don't know what method you've been using to adjust the idle air screws, but here's how I do it.
If it's an auto, I adjust IN gear with the wheels blocked and parking on. Don't wanna run anybody over. With the engine up to temp and your vacuum gauge hooked to a manifold vacuum source, I adjust them 1/4 turn IN (lean) at the time, until the vacuum on the gauge begins to drop and the engine starts to stumble. Next, I adjust OUT (rich) 1/4 turn at a time until I reach the highest reading on the vacuum gauge. The engine will smooth out once that highest reading is met. Rinse and repeat for the other screw. Opinions vary, but I prefer to make this adjustment with the idle "a little" lower then normal, because you can hear the differences in the way the engine runs and normally see the differences on the vacuum gauge easier, too. Not necessary, but it can help if you haven't done it enough to get used to hearing how the engine responds. If the idle is normal, say about 750, sometimes it will "cover up" so to speak the differences you need to be listening for while making those adjustments.....if that makes sense.
If it's an auto, I adjust IN gear with the wheels blocked and parking on. Don't wanna run anybody over. With the engine up to temp and your vacuum gauge hooked to a manifold vacuum source, I adjust them 1/4 turn IN (lean) at the time, until the vacuum on the gauge begins to drop and the engine starts to stumble. Next, I adjust OUT (rich) 1/4 turn at a time until I reach the highest reading on the vacuum gauge. The engine will smooth out once that highest reading is met. Rinse and repeat for the other screw. Opinions vary, but I prefer to make this adjustment with the idle "a little" lower then normal, because you can hear the differences in the way the engine runs and normally see the differences on the vacuum gauge easier, too. Not necessary, but it can help if you haven't done it enough to get used to hearing how the engine responds. If the idle is normal, say about 750, sometimes it will "cover up" so to speak the differences you need to be listening for while making those adjustments.....if that makes sense.
Thanks Rob, the one time I went 1 step up rich it was "better" but still had SOME surging/stumble.
So my next "changes" were
1- Set valve lash a little looser .018 int and .022 ex(comp says .022 for both)
2- reduce timing to 12* from 16*(mentioned on here)
3- increased idle(rpm dropped with timing) approx 1/4 turn.
4- opened IMS up another 1/2 turn to chk for changes.
This was my drive last night, nfg lol.
Honestly the ims screws make no difference until approx 1 1/2- 1 1/4 turns out....from 1 1/2- 2 turns there is next to no difference.
So my next "changes" were
1- Set valve lash a little looser .018 int and .022 ex(comp says .022 for both)
2- reduce timing to 12* from 16*(mentioned on here)
3- increased idle(rpm dropped with timing) approx 1/4 turn.
4- opened IMS up another 1/2 turn to chk for changes.
This was my drive last night, nfg lol.
Honestly the ims screws make no difference until approx 1 1/2- 1 1/4 turns out....from 1 1/2- 2 turns there is next to no difference.
Did you say you also had a 1406? I wonder if you should pop it on there just to see if there's a quirk in the 1405. 1406s come set up a little lean, so if you have a set of 7347 or 7147 rods, you may want to pop them in. If not, you can still do a comparison.
He should check the timing while he's at it.
Kick the timing back up to 16, then check in gear.
I set my initial in gear
So not much time to tinker with 2 grandbabies for the day lol, but I was able to bump timing up to 18, which increased idle speed. I backed out the idle screw 1/4 turn(closing up t-slots some). I then messed with IMS screws. I know a lot of what I've read says to start at 2 or 2 1/2 turns out, but I see MINIMAL change till I hit around 1 1/2 turns out(approx).
I got max vac at 14" in park, 650 rpm.
No helper, so limited with what I can do. I'll see I'd the bride can resist running me over tomorrow while I'm under the hood.
Drove great tonight, not one bog surge or backfire. My thoughts are the idle quality(in gear)is low due to 340 cam in 273....
Well to raise up rpm I either increase timing or increase idle screw, which opens up the T-slots causing the symptoms/erratic bs.
Thoughts?
Hope to drive the pi$$ outta it tomorrow and get some more readings.
I got max vac at 14" in park, 650 rpm.
No helper, so limited with what I can do. I'll see I'd the bride can resist running me over tomorrow while I'm under the hood.
Drove great tonight, not one bog surge or backfire. My thoughts are the idle quality(in gear)is low due to 340 cam in 273....
Well to raise up rpm I either increase timing or increase idle screw, which opens up the T-slots causing the symptoms/erratic bs.
Thoughts?
Hope to drive the pi$$ outta it tomorrow and get some more readings.
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