Ignition and carb gurus, help me out
 

Ok, here is the story. I've been working on getting an Edelbrock performer carb tuned on my S4 6 port. I've been having some trouble with the high rpm tuning though. Cruise and part throttle are fine, but once the engine hits 5000 rpm it seems to want to just spit and sputter, no acceleration at any throttle amount. Its almost like an on/off switch. Fine at any throttle amount, including WOT up till 5000rpm then it just dies, like hitting a brick wall. When that happens the A/F ratio goes through the floor below 10, my AEM wideband doesn't go below that.

Now, I think it might be the ignition thats causing a problem. I noticed one time when I tried to go over 5000 the tach just went crazy on me, jumping all over the place. This tells me that something was going on with the ignition. What do you all think? Would it be fuel related or ignition?

What are you using for an air filter set up??

I've done lot's of tuning with my Edelbrock and it is flawless.

I had a 10" round with a 2" high element, but I am going to a 14" round with a 3" element and drop base, MUCH bigger.

Here is the setup with the carb and ignition as it stands right now. I got .089 in the secondaries, .095 in the primaries, 7347 metering rods, silver springs (gotta bring that down to a pink i think), and the secondary air valve removed. I've got stock ignition with the stock 2nd gen spark plugs, brand new. The plugs are BUR7EQ leading and BUR9EQ trailing.

Mine did this when I tried a carb hat and larger cone filter. Take a test run on a clean dry road with the airfiter off and see if it does the same thing, perhaps your filter is too restrictive. And make sure you remove the carb stud so your engine doesn't swallow it. My friend injected the stud and the motor survived, only because the camden swallowed it first.

I thought this would work great, but it sucked. Sad thing was someone else told me it worked great for them.

Wow, thats gotta suck. The camden was probably trashed after that. But I haven't heard alot of good things about carb hats, only really good for turbos or show cars.

I'll try that though. I won't have a chance tomorrow as its supposed to be raining, but we'll see.

Ok, it turned out to be a pretty nice day, and I did some cruising around. Turns out the problem is just fuel related, my secondary jets are just too big. I have to go out and buy some smaller .086's I think. The engine seems to pull pretty good as long as I don't really open the secondaries too much. I figure 1 or 2 sizes smaller on the secondaries will solve the problems and put me pretty close to a good tune.

Well, I'll bump this up to the top, if anyone else wants to give their opinion.

I've ordered some .083 jets for the secondaries, hopefully that leans it out enough. If not, I'll have to go all the way down to .080's, which is just 1 step up from the smallest available. I find it kinda weird that I would have to go so small. A thread by rototiller used a 625 carter AFB (basically an edelbrock performer series), he ended up with huge .101 secondary jets in his carb. Its amazing I would have to go so small on a 13B instead of a 12A, which had the .101's.

You have the plugs backwards. The leading should be the BUR9EQ. The BUR7EQ's are 2 steps hotter than the 9's.
I don't know if that is hampering anything but under hard throttle the plugs are going to be running very hot.
Also I have found when I got my Se and was having some RPM issues. I found the previous owner had put in 2nd gen plugs. I changed then back to the regular BR9EQ-14 and it ran fine.
I am now using the BUR9EQ in the leading but with a 2nd gen coil. I am using the stock BR9EQ-14 ones in the trailing side.
The car pulls all the way thru the RPM very smoothly.

Part of the reason you are having to lean your secondaries is that that air filter cannot get enough air through. One you go to the 14" you may need to richen things up. I would get the edelbrock strip kit, it has an abundance of jets and metering rods in it. I had my metering rods modified on a jewelers lathe to improve the transition and cruise.

I won't be doing any tuning for a little bit as I just fried my leading ignitor. I did already put the 14" filter on it and didn't make much difference. But anyway, I fried the ignitor by hooking up my TT box wrong to switch to the 2nd gen leading coil.

Ok, figured I would get this thread going again. I've got the TT box working and everything, ignition is all in order. Got some more tuning done with the 14" filter on it. Got my part throttle cruise and acceleration all figured out, no stumbles anywhere. I'm still having problems with the WOT acceleration. Even with edelbrock's smallest jets, .077", its going way rich up top. As rich as 10.8:1. I wanna see that around 12.5 at least, preferably 13:1. You have any suggestions for modifying things to get this into spec at all? I was thinking mabey enlarging the secondary air bleeds, but I don't know enough about air bleeds to really mess around with that stuff.

Mabey rx7carl or Sterling could give me some insight into how air bleeds work? I've done some research, and as far as I can see, the bigger the air bleed for a jet, the less fuel that gets pulled through the jet. Mabey I'm wrong on this, but my knowledge of physics says that liquid is harder to pull by vacuum than air and if you allow more air into the passages through the air bleed, it won't suck up as much fuel. The edelbrock doesn't have changable air bleeds, but it does have air bleeds and I may be able to enlarge them if my theory is good.

^^ Not sure about the mod, but I believe you are correct on the air bleeds and their function. I have been playing around a lot with the jets on my weber, and recently I was running too big a size of air correctors and that resulted in me leaning out up top and fouling a plug. I swapped in smaller airs and that did the trick for me.

Thats good to know that I'm on somewhat the right track.

Even with the very rich WOT conditions the car is very quick. Its definately faster than my 02 alero, which is about 150hp right now. I figure by seat of the pants its making about 140hp with more in it too. A little more tuning could gain me another 15hp I think.

85 rotarypower: You are on the right track as far as leaning out the secondaries, exactly what I ended up doing with the same symptoms. The Edelbrock is jetted for a V8 and just doesn't need that much fuel on the top end.

Still too rich? Hmmm; maybe drop your float level a little (easy to do). If that doesn't work you might have to lower your fuel pressure a little. Let us know.

An easy way to set your primary mixture: disconnect the secondary linkage and run it as a two barrel!! This will allow you tune without interference from the secondaries...

BTW; how is your fuel mileage/kilometerage? Mine got up to 21+ when I was working 30+ miles away in mixed traffic.

P.S.: how does your dual magnaflow run/sound? I'm curious about your setup; could you include a description?

Sanspistons: Edelbrock RA, RA, RA!!!

I used to have an edelbrock carb and I had the exact same issues you had. What I did to correct is was to jet down the the secondaries a little and also you have to open up your intake to make a small plenum under the carb. That way the carb gets a stronger vacuum signal. Worked great after that.

I've dropped the fuel pressure already, and I can't jet it down any further. I've already got the smallest possible jets in the secondaries, .077. I'll see about the tune on the primaries though. That may be a little out of whack yet, but it seems to be great under part throttle acceleration and cruise, runs right in the range I want it to. I can adjust the float level down too, see if that makes any difference.

As far as fuel mileage, I've done about 120miles to 7/8ths of a tank. Far from great, but remember I've been tuning the carb on this, starting with it running extremely rich. I'd rather do it that way than start lean and detonate the engine. I'd expect about 250miles to a tank when tuned properly.

As far as the exhaust, check out the vid I posted in another thread. It sounds great as far as I'm concerned, and its working great too it seems. Even with the carb in its untuned state, the engine makes loads of power, and torque is not bad either. It is loud though, I gotta either add a couple 4" round magnaflows as presilencers or put something different on. Its not bad at idle or cruise, but regular acceleration makes me light headed actually.

Your problem is you are using a carburetor designed for a plenum, on an intake manifold that has independent runners. I don't even need to ask you if you're using a box-stock Racing Beat manifold, because those are the exact problems you will have and the reason why RB modifies the hell out of the Holleys that they sell.

Here's a quick fix that will work. Put a 1/2" open-hold sarb spacer on it, or better yet, put a 4-hole carb spacer on it and cut it so #1 secondary and #2 secondary are one big hole. You may have to do this to the primary side as well but maybe not.

If you reply with what you are using for a spacer (if any) and air filter we can help a little more. Post pics too if you have them. You issue may be way simpler to solve than you think.

Ok, I'm using a standard 14" drop base air cleaner with 3" tall element. I've got no spacer at this point. I can take the insert out of my manifold to make an open plenum. I'll give that a try then report back on the changes.

BTW, I've got a jaytech manifold, taller than a RB so no room for an actual spacer any height.

Ok, here are a couple pics of the intake manifold, showing the insert and how the manifold was before.

Tell you what, I ran my Edelbrock w/o a spacer and it ran like crap. I then added the spacer w/o independent runners and she's been running smooth ever since!

That insert is your problem. Take that thing out. I would add a 1/2 " open spacer as well and just get a shorted filter if need be. BTW, if you do add the spacer don't forget to cut the carb stud down a tad as well.