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Topic Review (Newest First)
04-01-2012 03:04 PM
91chevyss so do i need to put the .113 jets back in? i was trying to save a little gas but the .107 with the 7147 rod could give me worse mileage not sure. where exactly do i hook up to get a reading for the stepup spring to use? I misplaced the manual, but i found one online and it still doesnt make since lol. is it suppose to give a reading low enough to equal the hg on the spring at idle? as far as timing i need to get a tab for the cover because im using the aftermarket chrome cover and it didnt come with one.
04-01-2012 09:04 AM
cobalt327 Hey freakin seuss.

Baseline the carb back to STOCK SETTINGS! Step up springs to suit the vacuum at idle and for tip in of the enrichment circuit (it's in the manual).

Set the timing correctly- be sure the total doesn't exceed 36 degrees.

Run it (you'll love it) and check the plugs to see what- if anything- needs to be done w/the carb settings.
03-31-2012 11:41 PM
91chevyss i finally found the problem, well i purchased the spring kit and installed the yellow spring and it made it worse, although it was shorter than the one i pulled out it was also stiffer. so i tried the blue springs even worse. it was just popping and bogging down starting at around 2000 rpms. the next day i pulled all the spark plugs out a about half were a tan color and a couple plugs were two tone white on side and tan on the other. so i figured it wasnt getting enough gas, but it didnt make since because it seem to run better on the lowest hole on the accel pump even though it was still popping and bogging down. so today i pulled the top of the carb off to make sure the jets werent clogged and i got to looking at the jet holes and the size of the rod through each jet, the .101 with the rod through it didnt look very big. so i switch the jets around. i took the .095 out of the secs and put the .101 in place and put .107 in the prims. and checked the floats and then i put everything back together. i also put my stock springs back in which where identical to the orange springs (mine were plain, guess they lost their color). well i cranked it and it ran even worse come to find out i mixed up the #6 and #8 wires when i checked the plugs, switched them back and fired it up and it ran like brand new lol, took it down the road with out any popping and bogging, but it did have a little hesistation when i stepped on it so i moved the linkage to the middle hole and that fixed that. so now its running 100 times better and im guessing the rod was to big for the .101 jets. im still gonna check the vac advance and get the timing set correctly. thanks everyone for all the help.
03-23-2012 02:48 PM
91chevyss let me correct that, i just looked at the description for the 1407 carb on the same web site and it comes with .071 x .047 rod which that one is a recondition. thanks. sorry for all the replies.
03-23-2012 02:39 PM
91chevyss just looked at the page you sent in the commet "centerline", the calibration kit for the 1406 with .101 uses .073 x .047 which is the same rod thats in the carb now but was wondering why the 1407 with .101 use a .065 x .037. thanks again for the help.
03-23-2012 02:31 PM
91chevyss ok thanks centerline you help me understand some more. what will happen if i dont change the rods when i change springs, i mean i think it will reduce gas, but would the rods be to big for the jets to where i dont get enough fuel, if so could the .107 jets work. I read some where that engine will only take in the cfm that it needs so saying that the carb is a 750 doesnt mean that engine is taking that much in so could i use the springs, jets, and rods that come with a 600 or 650 and it be fine correct me if im wrong. as far as the intake its my only option right now but i will try to get a dual plane soon. i'll mess with the screws today. thanks again.
03-23-2012 09:16 AM
Centerline Simply screw the idle mixture screws in till they stop. Don't try to tighten them. Then back them out 1 1/2 turns. At this point you don't need to change the metering rods out, just the springs. The reason you wan to change the springs is that the stock springs are too heavy for the amount of vacuum your engine is producing (based on your cam) which is causing an over-rich condition at idle and is probably also contributing to your hesitation problem. These springs come in Calibration Kits and you'll want to use the lighter ones, probably yellow or orange. However, you can tune the carb all you want and it still won't help your streetability much because you're using the wrong intake manifold for your engine combination.

Centerline
HotRodsAndHemis.com

"When buying a used car, punch the buttons on the radio. If all the stations are rock and roll, there's a good chance the transmission is shot." - Larry Lujack
03-23-2012 12:31 AM
91chevyss ok at what point would not be forcing them should they just be finger tight or a little more or less. i also took them out to make there was no dirt. also should i change the rods to smaller ones or will the stock ones be fine. do the rods happen to raise when you give it gas or do they stay in the same spot. And does any one have an opinion on springs the diagram for the 1407 doesnt show .101 and .95 or could i go by the 1405 or 06 diagram. thanks for the help.
03-22-2012 12:11 PM
Centerline You've been given some good advice in this thread. Let me summarize for you.

You have three basic problems.

1. carb is too big for the engine.
2. wrong intake manifold
3. wrong pressure regulator

If you intend to keep the 750 carb, switch to the lighter metering rod springs which will help alleviate the over rich idle. A spacer will help but you really need to replace that manifold with a good quality dual plane high rise. A torker manifold is suited for the track but doesn't do well on the street. If you want to continue using the in tank pump get a regulator with a return line. All you're going to do now is burn up the pump, and its a pain to replace. Also running an electric water pump on the street is not the best idea... again another item best suited for the track.

Setting the idle mixture screws on an AFB is pretty simple and can be ball-parked by using the following procedure. With the engine shut off, screw the idle mixture screws all the way in (clockwise)... but DO NOT force them. Once they're all the way in, back each one out 1 1/2 turns. This should give you a basic setting. Any further adjusting should be done in very small increments while the engine is running.

Good luck.

Centerline
HotRodsAndHemis.com

"Old age and treachery will always trump youth and exuberance." - Anonymous
03-22-2012 09:36 AM
Dannyringo
i have an idea for u

Quote:
Originally Posted by 91chevyss
hi everyone i have 91 chevy tbi engine that i switched to carb and its in a 91 silverado. I had the motor rebuilt a few years ago it was bored .060 over due the rod bearing overlaping, the cam has .488 lift, it also has electric water pump and fans, edelbrock shorty headers, edelbrock torker intake, edelbrock 1407 750 with spacer, and a holley regulator set at about 5-5.5 psi. also an accel coil in cap hei with msd wires. once i first got it running it wouldnt rev past 2500-3000 rpms got that fixed by changing module in dist. i took down the road and to town a few times and by normal driving i guess you could say light throttle it would be hesitate or bog down not sure but if you stomp on it wouldnt be as bad and it will also rev fine in park well i fixed most of the problem by relizing the choke wasnt all the way open "about half way" lol new to carb. also when i had the revving up problem i thought the carb was to big and was getting to much gas so i took out the .113 prim and .107 secs and put in .101 and .95 and that was all i changed and i still have them in there, but im still having the hesitation or bog cant really tell and it does it the most right when im creeping up around 2000 rpms. it smells like it could be running rich and theres also a little wetness around the pump at the top of the carb. one other thing my wife was behind me one day when i got on it and she said it had llke this burnt smell but no smoke came out. any help would be greatly appreciated.
first pull the carb off after you run it around the block and it is warmed up...see if there is a puddle of fuel under the carb at the bottom of the intake. If this is the problem, your carb is too big....down size to a 600cfm carb.
Next check to see that the vacuum hoses are in new condition to the distributor and that infact the vacuum advance is working...Simple method is to suck on the hose to the advance unit and hold your tip of the tongue on it for a time to see if it moves, as well as hold vacuum....insure all vacuum lines are in good condition and are in the right place...a vacuum leak will do the same thing, if it is cracked, but not seen...idle will be erratic also, or higher than normal and shifting may, or may not work as it should.

Did you pull the distributor, when you did the intake manifold? If you did, then make sure you did it at TDC....To find this correctly, pull the #1 plug out and spin the motor by hand and wait until finger is blown off the cylinder head than take a look at the dampner and put it on the timing mark dead center, then pull the cap off and check to see that the rotator is pointing to #1 cylinder....\

I think if you do these things, you will find your problem...

Lastly, insure fuel pressure is there from the pump and that your pressure reading really is 5-5.5psi.
Good luck and I think the 600cfm will work better for you,
03-22-2012 12:23 AM
91chevyss thanks for the inputs guys and f-bird 88 would a 3000 stall be to high for a street vehical would it affect gas mileage also its been starting fine sometimes as soon as i hit the key lol but its been idling fine for the most part. if i would need a stall now which i still want to get one in the near future for takeoff will i have problems shutting off in gear. i will post a vid on youtube if someone is willing to take a look. also will this cam lift be able to produce 400-450hp or tq. thanks again.
03-21-2012 11:54 PM
OMARS67 every eddy ive ever owned ran rich. weather brand new or rebuilt or from a swap meet. mechanical or electric fuel pump didnt matter nor did the regulator. but then one day i bought a holley at the swap meet, a 4150 double pumper 650 for the stroker in my vette. WOW!!!!! with only bout 4-5 psi. youll say the same thing once you ditch that eddy. beautiful throttle response.
03-21-2012 11:40 PM
F-BIRD'88 .488" cam

get a 10" 3000+ stall converter

Recurve the distributor for 24-26deg base inital at idle and 34-36deg at max mech advance. ( 10deg advance curve)

Now that you have the correct timing curve reset the carb idle mix screws
for best idle. about 800rpm.
reinstall the stock jetting and rods but swap the metering rod step spring for a 4" rated

The bog and spark plug fouling will be gone.

Fuel pump Carter electric #4070 5psi no regulator is required.
03-21-2012 10:55 PM
91chevyss Ok thanks, now if any one can help me with idle mixture screws. Im not sure how to set them. Is there a guage or something to help with that.
03-21-2012 09:28 PM
400muscle The open spacer has its merits. Namely it increases volume so if you're engine is starved for air because your carb is too small the open spacer will make your monitor think the carb got bigger
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