Anyone running an Edelbrock 750 CFM carb? I am partial to the Q-jet myself. However, after discovering that the Q-jet on my brothers Lark was fatally warped he decided to go with an Edelbrock. I was reluctant at first, but I told him I would go ahead and put one on for him. The old 70 Lark has never run better! After some minor adjustments/tuning we got that "taped to your seat feeling" we have been missing for the last few months. The engine is basically stock internals with a T/A intake and dual 2.5" w/ Flowmasters. I am just curious what other people have to say about Edelbrock Carbs on their small block Buick.
I ran a 750 on my car for a while. I did'nt have to much luck with it. Could'nt get it tuned to suit me. I was running it on a Poston intake. Going to do a little porting in a few weeks. I may give it a another try. At wot it ran good. A little better than the qjet i'm running now. Just did'nt do as well as the qjet does at low rpm's. I sure do like the easy tuning with the edelbrock.
Hey David - I found that my low rpm driving was greatly improved with the Edelbrock over the Q-jet and the top end stayed about the same, maybe a bit better with the Edelbrock. Do you happen to remember what jet and rod combinations you used when you were running the Edelbrock? The carb was pretty lean when I got it out of the box. I had to go up two stages in the primaries and secondaries just to get the car to stop pinging. I used a Poston intake for a while also. I just couldn't get any carb I had to run well on that thing. I hope the porting helps out a lot.
I don't remember the rods I used. Jetting was .104's & .101's. Got it all wrote down in my book that came with the carb. I've got other issues do take care of before I give it another try though. Intake as got a leak. Soon as all my parts come im going to go to work. New oil pump setup from TA. Got the high volume pump now. New Comp. 268h cam. Mild headporting and portmatching. You think I ought to contact Jim Burek to see if there is any tricks I could do to the Poston intake other than port matching? Anyway, I 've got to take care of the oiling issue first. Way to much oil pressure. 85 to 90 #'s. I'm going to try the edelbrock one more time when everything else is done. I sure do like how it performs at wot. :grin:
Hey David - Sounds like you are running that thing super lean. Are you sure it is a 750cfm carb? Mine came stock with .110 jets and 7547 rods in the front and .107 jets in the rear. It was way too lean, and my engine is basically stock. I had to change to a 7337 rod in the front and a .113 jet in the secondaries:shock:. What is the part number stamped on the left front of the lower part of the carburetor. It should be 1407 or 1411. Let me know
Mine is a model 1411. I'm going to play with jetting again when I put it back on. I was fowling plugs before I jetted it down. I can't seem to find any combo that works well. Not many options in there jetting kit for a 1411. When I get through with the heads, and put the new cam in, I'll see what I can do with it. I don't think I got a good seal on the intake when I installed it the first time. That could cause a big problem. Anyway I hope the rest of my parts come in tomorrow. I'm ready to get started.
OK ken. I did'nt have nothing better to do, so I jetted the edelbrock back to stock specs. and put it back on. Cranked right up. Idel was fine. I'll take it for a drive tomorrow and see how it does. Took it apart, rejetted it, put it on the car in in less than a hour. All carbs should be so easy. :grin: Last time I tried it with stock jets my float drop was bad off. Maybe i'll have better luck with it this time.
I have a 1407 and it is running really rich, fouling the plugs. I have no idea where the jets are at. I guess I will pull the carb and start digging into it. Any idea where a good jet to start would be? Thanks, Kevino No:
Remove the metering rods first. You access them under the two stepup spring covers. There in the middle of the airhorn on top. Just losen the screws and turn the covers and pull the pistons and rods out. There is also 3 small retainer pins, one is on the throttle linkage, one on the fuel pump, and one I think one on your chock linkage. Then remove the 8 screws and take the airhorn off. Your primary jets will be in the middle, bottom of the carbs body and secondarys in the back. Remove them with a flat screw driver. I say all this assuming you do have the stripper kit for rejetting your carb. If you have your owners manual i would suggest you study it before taking the carb apart and proceeding to breaking down your carb. Once you've done your homework take your time tearing it apart. You find its a pretty simple proceedure. Edelbrocks are pretty easy. Follow the jetting chart in your manual for your model. good luck.:TU:
Hey Kevin - If my memory serves me correctly the 1407 has .113 jets, 7147 rods, and an orange step-up spring on the primaries, with .107 secondary jet. The rod and jet in this set up are REALLY rich in cruise mode (metering rod down) causing plugs to turn nasty. My suggestion would be to try leaning out the cruise mode. This can be done by either a jet change or finding a metering rod that is leaner in cruise mode but the same in power mode (i.e. 7347). And as you probably know, you don't even have to take the carb apart to change a metering rod. If that still doesn't correct the problem you will have to go down a jet size or two. You may have to try changing to a different step-up spring. This is especially true if you have an aftermarket camshaft and you don't have a lot of vaccum at idle. If this is the case you will have to go with a lighter spring so that the metering rods don't "pop-up" so early and cause a rich condition. All this tuning stuff is spelled out pretty well in the owners manual, but it still takes a little "intuition" to get it right. To give you an idea, here is the combination I ended up with. My "out of the box" configuration was as follows: .110 jets, 7547 rods, and orange step-up spring in the primaries, .107 jets in the secondaries. Here is what I ended up with: .110 jets, 7337 rod, silver step-up spring in the primaries, .113 jets in the secondaries. In other words, I had to go 1 stage richer in cruise mode, 2 stages richer in power mode, and 2 stages richer in the secondaries. This still didn't cure my lean condition (car was pinging a little). I discovered that because I still had the stock camshaft my engine was holding a lot of vaccum (20 in. Hg) at idle. This meant that the rods were staying down too long. I changed to a heavier spring and voila, problem solved. If you let me know some details about your car, camshaft, intake, etc. and how the carburetor is currently set-up I can give you some ideas that will get you in the "ballpark". I have tuned more of these carbs than I would like to admit. On occasion I have discovered that these carbs just plain don't work with some engine combos.
