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Edelbrock 1409 help tuning

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aday_in_nh

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"I successfully installed my E

"I successfully installed my Edelbrock 1409 onto my M360. As others have commented, very easy and straightforward install. Low idle mixture screws are set but I can't seem to get a smooth transition to higher rpm's. In other words, when I accelerate from 8-900 rpm's, when going through 1100 the engine will stumble. If left at 1100, it will continue to stumble along until you accelerate above 1200, then she's smooth.

Any help from the group would be appreciated.

PS - if you do a skiboat start (idle to WOT), there is no hesitation.

Thanks."
 
"Uh-oh! That sounds like the c

"Uh-oh! That sounds like the clunker I bought off eBay. IF you bought it new, send it back and get another one, for they made it wrong--and Edelbrock KNOWS this by now, for this is not the first case of its kind.

Lead is stuffed into passages drilled in the body to block them off. In my case, too much lead was used and it blocked the flow of fuel. The result was exactly what you are experiencing.

Jeff

PS: I was able to drill out all of the passages and plug them with screws and epoxy--a tricky job. The carb now runs great."
 
"Okay, here's the latest.

"Okay, here's the latest. JEG's replaced my 1409 with a new unit. I installed and adjusted the low idle mixture, and have the exact same problem. To recap; it idles smooth. When accelerating slowly, at 1100 it stumbles and misses. Smoothes out above 1100.

Seems to be the carb is fine? Unless it is a metering/jet/rod problem, of which I am not familiar with. What else should I check on this? Thanks."
 
"1. See if the accelerator pu

"1. See if the accelerator pump linkage is in the hole nearest the pivot. (It should be.)

2. Put a timing light on the mark and see if it advances as it should, THEN comes back as the motor returns to idle.

The metering rods should be fine as received. That said, you can get softer springs for them that enrichen quicker. I'd do that as a last resort, however.

Jeff"
 
Or try this if what Jeff recom

Or try this if what Jeff recomended does not work.
Move the accelerator pump linkage out. One hole
from when you first installed it.
Had the same situation after rebuilding mine.
Worked perfect after.
Let Us know
David
 
"Moving the linkage out makes

"Moving the linkage out makes the pump shot smaller, but that COULD be the reason. Sometimes too much fuel can cause a bog, though usually it's the other way round.

Jeff"
 
"Update - Accelerator pump was

"Update - Accelerator pump was on the hole nearest the pivot. I moved it to the other holes with no improvement - moved it back. The timing was off a few degrees and has been set and is advancing and retarding properly. In the process my voltage regulator crapped out so I replaced that. Got me thinking this might be ignition related so I changed points, cap, rotor, etc. Still no change! Sluggish at about 1100 revs. Smooth everywhere else. I'm stumped."
 
"Andy:

based on your descri

"Andy:

based on your description, its not surprising the accel pump has no effect. It sounds like the issue is in the off-idle transition region. this means changing the power piston spring shouldn't make a difference either.

Two Q's:
1) how did you adjust the idle mixture screws?
2) do you have a vacuum gauge?"
 
"I bought one new 1409, and a

"I bought one new 1409, and a used one off eBay. The new one has been trouble free, but that used one was a pain to get right.

It took most of last year--including rebuilding it 4 times--to get a stumble similar to yours out of it. The reason: Improper manufacture. One (or more) of the lead plugs used to seal off the passages in front of the carb was blocking off the passage. I drilled them all out, then tapped and epoxied screws in the holes. Problem gone!

Jeff"
 
"Makomark - idle was set by th

"Makomark - idle was set by the Edelbrock book. Both sides turned in until rev drop, then opened a 1/4 turn or so. I put a vac gauge on it last weekend and while I don't remember the exact reading, it was where it should be at all rpms and rock solid.

Jeff, how many passages did you need to drill? Sounds like some major quadruple bypass type stuff there. Can you elaborate?

Thanks all."
 
"There's about 4 on each s

"There's about 4 on each side. Not a difficult job, but you'll need a tap, drills, and some compressed air to blow the chips out.

The below photo shows a few of the plugs. (Ignore the "Don't Drill Here" ones-they aren't a problem.) The other ones--and the ones at the top of the vertical passage (just visible in the photo) is a baddie. The top has to come off the body to get at that one.

Jeff
293709.jpg
"
 
"Andy:

Last time I checked,

"Andy:

Last time I checked, the book called for max idle then lean the screws to get a drop in RPM, not to richen it up.

If the vacuum is "where it's supposed to be", I'd suspect a restriction in the transfer slot or the idle channel restriction being a bit small. Some casting flashing at either spot would cause the same result."
 
"Hmmm ? two new carbs ,same pr

"Hmmm ? two new carbs ,same problem? Not likely.
I take it you drilled your new carb for the PCV valve hose? Y/N?.
Try this. Temporarly cap pvc see if still stumbles. May have a bad or wrong pcv
If it still does stumble. While running at 1100 rpms while stumbling. Partly close the choke plate manualy. If it starts to smooth out. It could be the carb, or old fuel?"
 
"Alright - back to basics. Wh

"Alright - back to basics. When setting the idle mixture, the manual calls for setting the idle speed with the "air screw". I'm assuming this is low idle screw on the throttle linkage. Is there another step that I'm missing that is contributing to these issues? Maybe if you could translate the manual step by step I could identify if I've missed a step. Otherwise, still scratching my head. Thanks."
 
"No Idle air adjustment is th

"No Idle air adjustment is the two screws on the front of the carb. with the springs on them.
set them at 2 1/2 turns to start.

Your problem is not the idle circut. but transfer from idle circut to primary fuel dilivey.
to much air ,or not enough fuel or bad fuel or it could be severl other things."
 
"Andy:

there are two parts

"Andy:

there are two parts - the idle SPEED and the idle MIXTURE. the idle speed is set by the screw on the throttle linkage. the idle MIXTURE is controlled per David's description. The tricks to getting a proper setting:

Get the engine thoroughly warmed up. I like 15 minutes past when the thermostat opens.

Set the idle Speed the the engine makers spec - usually about 650-700 rpm.

Adjust the mixture screws for peak vacuum.

Iterate the whole adjusting sequence until no change is noted. Then you can do the lean drop adjustment.

IF the idle speed is too high, the mixture screws won't have any effect.

David's suggestion about the PCV is a good one...a crack in the hose or a stuck open PCV valve may cause that lean out. another scenario is that the valve is stuck closed and you have to open the throttle (idle speed screw) to supply the "missing" air. This case may cause poor off-idle transition."
 
"Andy - the link below is to a

"Andy - the link below is to a video that might answer some of your tuning questions. Note that it's the 4th video in a series of installation instructions.....so you could find 1-3 if you want to go back to square one.

While this is an automotive application, the Edelbrock 1406 is almost identical to the 1409 (I actually used to have one on my boat).

http://www.youtube.com/watch?v=Rg8XHOF4FSw&feature=related"
 
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