Hey guys, trying to get my street hemi inatke with 2-600 cfm eddys dialed in.I have the 1406 in rear and 1405 up front. I have a 472 that's 10.5-1 with a hydraulic .581/.567 with 254@.050 of duration. I have the jetting as follows 92's all the way around in front carb. I have 92's in primaries and left secondary is a 95, while the right secondary is 90 in the rear carb. I have the accelerator pump in the furthest hole down the rod on both carbs. My LM-1 is doing screwy things so I'm trying to set these up by feel. I seem to be close but at cruise rpm's it's giving me a lean stumble. I have installed the smallest metering rods in my kits and went to the stiffest springs. So, that being said... Am I looking at just rear carb jetting changes in the primaries or am I off base here??? Any thought or help would be greatly appreciated!!! TIA

It looks like the primary jets are much smaller than what the carbs come with. I found a good manual from Edelbrock that might help you sort it out.

http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf

How many holes on your accelerator pump arms? If there all the way down that is the minumum pump shot, not the most I would try the middle hole in the warm weather months and move it to the top hole(most shot) in cold weather. Have you tried changing the squirter nozzles to smaller or bigger? If not you may want to As far as the wide ban readings make sure you have no exhaust leaks and then go from there I use to cut the primary metering rod springs so the rods would stay down idling in gear in the automatic cars and the same on stick shift cars idling in nuetral On the rear carb right side secondary jet it may like a lot smaller jet like a .071 to maybe a .063 IHTHs

I guess my biggest question is, at cruise rpm's are you running just off the back carb on this setup????

Yes, you should be still on the idle circuit on the front carb. You have the factory progressive linkage connecting the two carbs?

Sheldon

Sheldon, I do have the factory progressive linkage style... I'm trying to do all this with my LM-2 reading very erratic A/F ratios??? Can't get a good baseline...

The front carb..lets call it the secondary carb looks to be OK. I made a plate that covers the manifold and I mount the carb on that so it has no effect on setting the primary carb. Then I tune that carb. You drive on it the most of the time so it's absolutely necessary to get that right. What kind of vacuum are you pulling? That will dictate the springs to use for the metering rods. If you're using the strongest springs the vacuum may not be enough to pull the metering rods down into the jets for a leaner mixture, you are essentially tuning the idle on the idle mixture screws and it will always be erratic. I loosen the screw holding the metering rod cover and swing it out of the way. Have someone start the car while you hold a finger in place of the cover. The metering rod should be pulled down and stay down. If it isn't or jumps up and down the spring is to heavy. Tuning those carbs takes a little patience but you will love the results. My car has an O2 gage mounted with my other gages so I monitor it all the time. After getting the primary carb set up remove the plate under the secondary. If the idle jumps or goes erratic, you need to make sure the idle mixture screws are closed and the throttle plate is closing all the way and the carb is not leaking fuel into the manifold. Good luck. "Edit" I forgot to mention if the secondary carb is leaking fuel remove the fuel line and cap it before running the plate under it, you don't need gas running all over yor engine. Take it off and find out why it's leaking gas.

I am running 11" hg. The springs are down til I blip the throttle. I may end up trying the single carb method to get it absolutely right. Just was hoping to get it resolved without doing all that... But we'll see??? Just looking for opinions and help like you've provided! Thanks!

I'll tell you what happened to me today. I suspected the fuel was boiling on my setup so I got some heat wrap and wrapped the fuel line at the back near the exhaust and up front beside the header as well as where the fuel line comes up the front of the block.
I combed over both carbs making sure everything was up to snuff and then mounted the wideband. After two hits with the aircleaner off I had them dead on taking it for a 10 mile run with WOT and cruise.
I mounted the shaker back on and went out again, car ran perfect until I hit it and she went 15.0 right away at WOT. So with the shaker on it's boiling the fuel causing it to go lean.
I don't know if this will help you but if you're trying to tune it with the shaker on it may be your problem.

Sheldon

No shaker, Sheldon. Have kept it off cause I hate removing that thing... Lol

I think I would leave the metering rods as-is and try .03 larger jets in every position except the right secondary rear, I would leave that one.
That sort of mimics the factory Hemi carb jetting only fatter everywhere and you say it's lean.
I wish Edelbrock jets went up .001 at a time like a Holley but they don't.

Sheldon

It should have more vacuum that that. Check for vacuum leaks, double check the timing, make sure that there is not an obstructed idle curcuit.

Well... I had spoken to Dwayne Porter and he had expressed concern with that much duration on a hydraulic cam. He was thinking 10" hg would be normal.... So, I feel lucky with 11". He tried to deter me from hydraulic, but I'm not racing this thing and I didn't want the hassle of adjusting every so often... So I have to live with short comings of a hydraulic flat tappet...

I would try going bigger on the primary jets, and bigger on the metering rods. that way when you roll into the throttle at cruise, you'll be getting more fuel.

Update: I went up to .098 jets and .065/.052 metering rods, and it seemed better but still had a stumble at 2750-3000 rpm's at light cruise throttle. It seems it only happens went I'm at the max throttle before opening the front carb???? Any added input to throttle and it powers on no problem... Just at that max cruise rpm on back carb??? So, I went up to .101 jets and same metering rods and it seems to be too rich. Doesn't seem to be as smooth through the rpm ranges. So, that's where I'm at.... still no answers yet? Any input? Is there something I can add to the .098 jets and .065/.052 rods that would help this condition? Seemed to be way better but I still felt the stumble as explained above. Really getting frustrated at this point...

Do you have vacuum advance? If so, try plugging it. YOu may need to bump up the idle setting to compensate. Drive it and see if it helps.

Already eliminated that....

the clusters are different between a 1406 and 1405. the 1405, or at least the one i have, has a smaller idle jet than the 1406 and the secondaary clusters are different. i've been messing with a ch28 on a 440 (and whether this is apples to grapefruits is another question) but one thing i did was try to make the clusters the same, opened up the idle jets, and jetted the carbs down. really drives nice.

I guess I'm going to need to get some dyno time and try adjusting from there.... Any good recommendations on dyno tuners close to my area(Lexington,Ky)???? Cincy isn't very far for me either.....

After taking some time off and talking to Tim Banning a few weeks ago.... My problem is solved. It was in the distributors.(yes plural on two different units.) One being my custom FBO and a factory MP unit. I put a MSD billet unit in and like magic it runs fine. I did have to back down the jetting though. So, HUGE props to Tim Banning at FHO. He took the time to hear my complaints and helped me out with some advice. He's definitely a stand up guy in my book! Just like to give credit where credit is due....