First I'm running a E4ME Series carb

I bought a set of #58 rods and #76 jets out of a 1985 GMC commercial truck 350 V8 w/ computer carb

Would running this set be better for a ZZ3?

At this moment the carb has #54 rods and #74 jets.

I would appreciate your opinions.
Thank you.




note:
The Secondarys are modded with a 90* AV set @ 1/2 turn tension, "CK" secondary rods, and "H" hanger
Still may consider "DR" rods and "G" hanger for Fuel economy

The Secondarys are just fine but I would like a little better part throttle response. Timing is set at 8 degrees BTC. Computer is ZZ3 with PROM and ESC so that part is ok.

 

Is this a test?

CC q-jets don't have primary jets & rods. They have a mixture control solenoid ( http://www.carbs.net/Quads/E4MC.htm , #'s 221-229).

 

No this is not a test. I'm quite aware there is a MCS.
What do you think the mixture control solenoid meters
on E4ME 4 bbl and Dual Jet 2bbls? I see Two rods and Jets .

You must be thinking of varajets with stand alone MCS.

 

Guess I failed. Mine has been so trouble-free, I've never actually had it apart. I did have a CC dual jet for my California-emissions '81 V6 Malibu apart, but that was over 10 years ago.

Sorry. I'll shut up now (a little late, huh?).

 

If everything is working properly, the ECM will vary the duty cycle to maintain its prescribed 14.7:1 air/fuel ratio. Of course, if the new rods and jets force the ECM to correct beyond certain parameters, it may throw a code and go into limp-home mode.

 

Yeah, they got primary jets and rods but you can't change them out for earlier stuff. The primary rods are different in design and length from others and they have a hard "step" in them from the lean to the rich parts of the rod- not a gradual taper. The jets are also very different from earlier ones- they have a "tower" built on top fo them to keep the primary rods centered in the jet as they jump up and down.

Don't mess with 'em. Concentrate on the secondary side of the computer controlled carb.

 

Ok I gotta share what I learned


I made a tool to grasp the double D Jet/ tower combo by drilling out the center of a 1/4" nut driver and grinding down the socket to where there was only two places to grasp onto the jet.

Instead of the truck carb parts, I tried a 58u Rod and #76 jet towers out of a 1984 Olds Tornado E4ME center fuel feed carb (straight out gas line) . The springs that came with the tornado rods had more pressure than my stock Rods. Idle is exactly the same, mixture control solenoid setting is also the same.

When I hit part throttle on a test drive, it no longer had a dead spot and it hit 5800 RPM much quicker. :lala:

My old Jet/Rod combo 54/74 was fine for idle but was just simply too lean for my engine. I also learned NOT to use the #54 rod and #76 jet combo since it would run too rich.

It seems that the tips on both rods are the same except for the taper. (Note hardly any adjustment on MCS) The #58 rods has .058 taper to fill in the bigger hole of the #76 jet to keep it at stoich. So only at certain engine loads is when it takes advantage of the bigger #76 jet

 

Keep this in your bag of tricks if you want to try it in the future: Buy a set of "DA" secondary rods and a "B" hanger and install them along with the STOCK primary rods/jets.

You have essentially richened up only the near-WOT part of your fuel curve with your primary-side mods which is why it feels much stronger when you first nail it.

However, your current secondary rods are very lean on the initial part of their taper. Which is the part that memters fuel when you first mash it. So your primary mods are making up for the too-lean part of your current secondary rods.

That's a perfectly valid way of doing it but going to a set of DAs (or even the DRs you mention) in the secondaries will give you the same resuts without all the primary-side effort.

Give it a try. You'll kick yourself for not trying it first! Regardless, I'm lad to hear you're happy with the results so far.

 

Hi Damon

Thanks for responding. I probably have taken the long route to end with the same result. The reason I was going the long way is I thought I had a problem with the mixture control solenoid. I replaced the MCS with a new one. I didn't have to back out the MCS set screw nearly as much to idle just right. The carb was totaly clean diped and blown out with compressed air. Also the idle mixture screws take 4 1/2 turns out just to idle is this normal? I heard it should only have to take 3 1/2 turns. I guess I was a little worried that my primary rods and jets were too small . But now the carb seems to work well. I'll should still buy a set of DA rods and a B hanger that you mentioned Damon

BTW I've accumlated some sets of secondary rods but I don't know if they would be even close to the DA's you mentioned.

Would CV be close?The other set are out of early carbed turbo buicks and are probably too rich.
DG DU

again thanks

 

I'll check on the CV rods when I get home but I don't think they're close to the DAs.

Having the idle screws way the heck out is normal for an emissions QJet. It's fine on a stock motor but if you're going for performance they get to be too lean as soon as you put in a bigger cam, large-port intake, etc. If you shoot me an email I'll send you back some tech articles on how to richen up the idle circuits on a QJet. I like to have the screws no more than about 2 turns out when I'm done tuning.