help with tuning an AED 750 Ho

-
S

sparkie573

Well-Known Member
Joined
Jan 14, 2013
Messages
97
Reaction score
1
Location
missouri
So I'm a bit of a novice when it comes to carb tuning. And I am trying to get this tuned in. It's a newer AED 750 Ho carb. I have a wideband kit on it which is helping a lot. I am trying to get my cruising rpm air/fuel ratio a bit leaner as it is running at about 11.5 to 12.5 and in between.

The car is a 4 speed with 3.23 gears.
Here are the specs on the engine. 408 stroker all forged, edelbrock heads, rpm air gap, 1 inch spacer between the carb.. The cam specs are comp cams adv dur 282 290 & @ .050 244 252 lobe sep 110 valve lift .520 .540

it has all msd ign, and I have the black bushing in for 18* of swing, and the lightest springs in it.

the carb specs right now are 73 primary's 80' on the secondary, a 4.5 power valve, .055 pvrc, high speed bleed are .031's, idle bleed is .070, primary idle restriction is .035 and secondary is .033, it's got a .031 primary squirter and a .035 secondary

I have the idle speed set at about 800 rpm and I have the idle mixture set at around a 14.0 best I can tell due to the wideband bouncing around at idle.

Any help would be greatly appreciated. thanks
 
Try a .031-.032 primary IFR. With 3.23's, you should still be on the transition slot so the IFR is where I would concentrate time and effort. You will need to readjust the mixture screws.

What is initial timing? Should be up close to 20* with a XS282s camshaft. Might need a bushing that limits advance to less than 18. I have some 10 and 14* bushings available.

I usually never run the two lightest springs in an MSD distributor. Light and medium is what I run most of the time on stuff like this.

Sound like a solid build and should run real strong.
 
I have the initial timing set at 17-18* with an 18* bushing in so it's 36 all in.. Sorry, what is the IFR? is that the idle feed restriction? and where is that at? sorry "novice" I have been trying to educate myself as much as I can.... Which springs did you say? 1 of the medium "blue" and 1 of the "light" silver? Thanks a lot.
 
Medium blue and light silver is usually what I run on most stuff. Initial timing sounds in a good range for nice idle manners.

Go here.
http://members.tccoa.com/392bird/carbtech.htm

Look at the pic of of metering block with PV in front of it. The IFR (idle feed restrictor) should be in location 6 or 25.

Once you get it close, you may fine tune it with an Idle Air Bleed (IAB) change.
 
This may be a stupid question, but... Should My timed park port should be plugged and not left open since my MSD distributer doesn't have a vacuum advance????

also, I'm going to be ordering some idle feed restrictions. Should I also order some idle air bleeds as well, and what size? Thanks.
 
The port on the carb should be plugged when not in use. It's a vacuum leak when the throttle plates are open.
 
I was checking my spec sheet on the carb where it states all of the bleeds. It shows an interm air bleed but then states N/A. just curious about that... I ordered some .030, .031, 0.032, bleeds and some .071 and .073 bleeds. I also did a bit of tinkering, I put a vacuum gauge on and at idle and as best I could tell with the cam it was between 7-9. I thought possibly the power valve may be to large so I went down to a 3.5, it didn't seem to help my cruise rpm a/f but it did seem to slightly make it slightly snappier when you mash it. I also tried tightening the mixture screws another 1/4 turn. which made them 3/4 out or less, still nothing. and I also tried to adjust the rear butterflies open a hair, no real help but made it a lot harder to start so I adjusted them back.... There is no shop I can find around that had idle restrictors to I had to order them, hopefully they hurry up and get here so I can get this thing tuned in...
 
Help, and question?! So, I got my idle feed restrictors in. But I think I may not have the kind that I need. I got the quick fuel brand which is a 6/32 but has a head with a flat screw driver slot. I got my old idle feeds drilled out and tapped for the 6/32 but when I screwed the new ones in I saw that they cover the hole for idle fuel from the main well. Am I correct in saying that I have the wrong type and need to get some Allen set screw type??? Also where the heck can I get them if that is what I need? Thanks.. I'll try to post a pic or 2.
 
That's not gonna work!

How deep did you tap those? If you went all the way through you are in for some fun. The set screws need to bottom on the threads you cut. You may have to score the outer threads of the set screws if you went all the way through.

I have some 6-32 set screws and 8-32's as well.
 
I just drilled the old ones out slowly to the depth that they were and them tapped them ... After doing some research on the old interweb.. I pretty much figured out/ or at least see that everyone else that has done this use the set screw type.
 
Get some .125 or 1/8" length cup tip set screws and run them into the current hole. If they stop above the surface, you are OK. Figure out how many more threads you need to run in to get them down/flush. Tap them incrementally until they are flush.

If they get flush and don't stop, you'll need to either go up to the next size or score the brass.
 
Ok, so I got some cup tip set screws a while back and drilled them for .031s' I put them in and drove around and still getting a slight stumble at cruise 2500 ish. I disconnected the secondary linkage to see what would happen cruised around and the stumble seems very slightly less. while I had the secondary unhooked cruising around the AFR gauge was showing 13.2 to 13.8 I'm not sure how well I trust the thing. seems if it were that close it would cruise and have no stumble at all. Also, with the secondary disconnected and at operating temp, sitting in the garage, if I run it up to say 3500 to 4000 and hold it level It will seem to run smooth and then get a pop. wondering if that has anything to do with it or what is going on there, I'm thinking it is from whatever is going on with the IFR or AIB. Just trying to give enough info for anyone that can help. Is there anything I can check or do to figure this out more? Questions; Should I go down on the IFR in the secondary as well? Should I try going down a bit more on the primary? or should I go up on the IAB ?? And if so do I need to do the secondary as well? any help at all would be great. I am trying to get this running and cruising well to take to Branson cruising lights in a few weeks.
 
You must log in or register to reply here.
-

Back
Top