Also got to messing with my Edelbrock 1406 600cfm carb. I have a hesitation at about 1/2 throttle. Full throttle and no problem, runs great, between 50% and 75% it starts to hesitate and if I leave it there and don't push it to the floor, it sounds like it isn't getting any gas...like it is starving and refusing to accellerate just popping and sputtering. If I gun it down from there, the secondaries open up and it takes right off. I have the metering rod/jet kit for this carb and was running it at stock configuration until last week, then riched it up one "step" with improvement, then riched it up as much as I can with the calibration kit and almost fixed all the hesitation. Then I started messing with the springs and after I started swapping them all out and testing it, it just got worse, then I noticed that I had lost my instructions and didn't know which was the 8"Hg spring... Can I have maxed out my 600 cfm carb on this motor? The motor just seems to want MORE and I can't seem to get enough into it fast enough... Got onto JEGS and figured out which spring needs to go in there now, but haven't swapped it out yet...
My Edelbrock dies if I try to go full throttle from a standstill. Falls flat on its face......Very frustrating. I know of 2 other guys in this area that had Edelbrocks that did the same thing....Both of them switched to Holleys and went on about their business.....Me- I'm in college! I can't just BUY another carb! If I go to part throttle and get the RPM's up to about 3000 or so.....I can nail it and get very little hesitation. I don't know what the answer is......I guess now we're both wondering now why I even posted this huh? Good Luck to you!! Preston
Could it be that the carb is dumping too much, too soon at the lower RPM, temporarily flooding the engine and causing the hesitation? I know the Edelbrock 1405 on the 302 in my truck does this.
If it dies from an idle it is probably your accelerator pump. Repair it and set it to push the maximum amount of fuel. The mid-range hesitation is due to too strong a spring. Compre your springs and put them each in a baggy with numbers going from 1 up with the number 1 the lightest and the highest number the heaviest spring. Making note of the one you have in the car now you can go to the next lighter spring until it all works well.
Next time I go to the track, Rolandag is going to meet me and we will slap on a 700 double pump holley and see if I just maxed out my carb on this engine.
I have been thinking about how mine is acting. I think what is going on is just before the secondaries open up, it bogs down because the engine is essentially "choked". I have tried all the springs and the 8"Hg ones work the best. These are the "highest" springs I have in my calibration kit. So I think I will just have to live with this "hiccup" until I go to a bigger/different carb. So basically, I have the highest springs installed, and the highest jet/rod combo installed, and cannot go anymore without swapping the carb (or doing some mods to it that I don't know how to do).
You setup is alot like an engine I had in my 75... It really got down and boogied with the T289 and 700 DP! All the carbs I tried on that engine, it loved that one. I never had a chance to run at the track with the 2" open spacer, but it seemed to like that too... seat of the pants. The only problem was hood clearance, so I didn't run it much. If that 700DP is set up decent, I bet you want one after you run it. However, it will get crappy MPG. Set up a 3310 or similar, and you will gain some economy. There is a chance that the 600 is outclassed by your engine, but unlikely. Does it produce any black smoke from the exhaust under sudden throttle and load? If so, you might need to increase accel pump duration. I know how to do that on a Holley, but not a Ebrock. Most 700s came with 50cc primary accel pumps, that helps alot. I used the 50cc pump on mine, however I didn't use the 50cc cam. I used the 330 cam, lined up in hole #1 on the cam AND the bellcrank. You don't get the full 50cc like that, however the 330 is rated at like 40cc when used at those settings with the 50cc pump. Running 4.11 gears, the 32 squirter worked perfect with the cam setting/50cc pump. When I had 3.00 gears, the 25 worked better. I think you have 3.55s? I would go with the 28 squirter. Don't underjet either... The 700 comes with too small jets from Holley. I ran 76 prim/78 sec IIRC... Works real well with your intake!
Your engine may want a bit more carb.Lookiing at your engine build it looks like you have alot more than me,and i have a 650 holley on mine.Had a 600 on it but with the 650 it pulls alot harder and will rev to the moon!Before around 6000 rpm it felt like it was working hard to get there now with the 650 it winds up easily to it's 7000 rpm valve float.Which is completly unessasary since it only makes power to about 5700.
My Torker 289 is VERY heavily ported, about as ported as you can go with. And I am running a 3.80 rear. I am not sure where to go at this point as most of the suggestions are Holley-specific. The Edelbrock is very easy to tune if you buy the $30 kit, but I think that my engine is asking for me to tune it beyond the settings that the kit will let me go. Just need to test out a larger carb and see what happens. The re-jetting used to work on a seasonal basis, but with the 1.7 rockers, I seem to have had to move the entire jetting "curve" richer to keep the engine happy. Not sure of the black smoke, as I tend to keep my eyes in front of me in case the a$$-end decides to squirrel around on meBut none that I am aware of.
Found a video camera at work. Fairly new, so maybe I can get the wife to take some videos and I can see how it is taking off and if there is any smoke. Might take it to the track next weekend if they dry out... I don't think there is any smoke though. I put the 8"HG springs back in so most of my hesitation should be gone now.
I was just concerned that you were running out of pump shot too fast. If you have the pump set for short duration, you are likely dumping fuel too fast. This will cause black smoke while it is dumping, then hesitation when pump shot runs out too soon. I believe in Ebrock speak, the "springs" you are speaking of open the secondarys sooner... I this right? If so, you could be opening the secondarys too soon. In Holley speak, that is called "crashing" the secondarys. Meaning that the engine is not ready for it. Happens when vacuum secondary is set to open too soon.
Fwiw, you can't crash the secondarys in a DP! That is why it has a secondary pump... you open the secondarys and it crams a pump shot of fuel down your engine's throat. No questions asked.
I am thinking it is the exact opposite...it will run like crap if I accelerate just to the point before the 2ndaries open. If it gets to that point where is it falling on it's face, and I hit it a little harder, the secondaries open and it runs just fine from there on. Yes, those springs adjust when the 2ndaries open.