Is my carb too big for my 383?

[734406pk]

You can check the fuel delivery system with a manual fuel pressure gage (mounted outside the car) installed just before the carb fuel inlet line. You should see approx 5 psi fuel pressure at full load. This pressure will verify that you have more fuel available than the engine needs at full load.

[Bluemonster71RT]

Your hesitation is instantanious so fuel supply is not the issue at all so the 90* fitting is not the issue . but if the float level is low that could be causing issues , I would try raising it 1/16" or so

So for the edelbrock it is set at 7/16" so go 3/8 then?

[734406pk]

Your hesitation is instantanious so fuel supply is not the issue at all so the 90* fitting is not the issue . but if the float level is low that could be causing issues , I would try raising it 1/16" or so

  also I think there are screens on the 2 float seats inside the carb. If these are plugged up they can cause some problems when you're trying to tune-just like the Holley carbs. Have you had the float seats out and inspected these screen filters? They are tiny, like the size of the button on a click type pen.

[Bluemonster71RT]

also I think there are screens on the 2 float seats inside the carb. If these are plugged up they can cause some problems when you're trying to tune-just like the Holley carbs. Have you had the float seats out and inspected these screen filters? They are tiny, like the size of the button on a click type pen.

Yes they were replaced when I did the rebuild.

[734406pk]

So for the edelbrock it is set at 7/16" so go 3/8 then?

Yes, that's right.

[Denison636]

To give you some easy math. For a carb to fit a engine right it should be at 2 cfm per cubic inch of a motor. So a 383 needs a 766 cfm. If you get a good brand of 750 they will flow better then 766 cfm.

[Chryco Psycho]

So for the edelbrock it is set at 7/16" so go 3/8 then?

See the problem is fuel pumps will put out somewhere between 4-7 PSI , so the float will close off the flow earlier with a lower pressure pump than a higher pressure pump will so the float has to sit higher to close off 7 psi then 4 psi so the level inside th carb will vary ......  Holley style carbs let you see this from the outside while running & you can adjust for it outside too , Eddy Carbs meanwhile not only do not have any external adjustment but don't even let you see where the level is so you know to fix it , so while the jetting may be correct the flow may be harder to draw into the booster if the level is too low causing a hesitation or bog or even just a lazy response where you do not even realize it is not right & could be much better .

[Bluemonster71RT]

So I got to do the test drive yesterday with the float adjustment. Verdict = only a little better. Something must be internally wrong with this carb. Maybe it's still clogged where I wasnt able to clean it. 
I ordered a 770 based on how my old 670 ran. I don't have faith in my 4160. It has a lot of un-doable "mods" done to it. So maybe by next weekend we will have resolution.

[734406pk]

So I got to do the test drive yesterday with the float adjustment. Verdict = only a little better. Something must be internally wrong with this carb. Maybe it's still clogged where I wasnt able to clean it. 
I ordered a 770 based on how my old 670 ran. I don't have faith in my 4160. It has a lot of un-doable "mods" done to it. So maybe by next weekend we will have resolution.

  I think you have something else going on also. Try a better carb see what happens. Is the 770 cfm a Holley Street Avenger by chance?

[Bluemonster71RT]

Yes its the Street avenger. I had awesome fun when I used the 670 SA on my stock motor. So I'm taking a chance on the 770 thinking it will get me in the right path.

[734406pk]

Ok. You will need some tuning parts for the Holley to make it work right. Out of the box, the jetting is a little rich(for safety) and I think it has a 6.5 power valve. May be too high for your set up..I recommend installing the BLACK spring on the secondary diaphragm and tune the primary side first. A wide band AFR is very helpful in dialing in the carb. Saves fuel too and might even pay for itself quickly in fuel savings $$$. Make notes of what is in the carb for reference before you install it, helpful in the tuning process.

[Bluemonster71RT]

Ok. You will need some tuning parts for the Holley to make it work right. Out of the box, the jetting is a little rich(for safety) and I think it has a 6.5 power valve. May be too high for your set up..I recommend installing the BLACK spring on the secondary diaphragm and tune the primary side first. A wide band AFR is very helpful in dialing in the carb. Saves fuel too and might even pay for itself quickly in fuel savings $$$. Make notes of what is in the carb for reference before you install it, helpful in the tuning process.

I still have my jet and spring kit from my 670. I'll have to get a valve kit. I'll see what it does out of the box. I was just watching some tuning videos and one thing about jetting/power valve that was said is to go until you get the black smoke puff. As max rich as I made the edlebrock, I never got black smoke at any time. There must be something clogged in that thing still. I can't believe that I couldnt get more fuel out of it. 

[734406pk]

Very good! The new Holley S-A should come with a set of secondary springs. The power valve is based on 1/2 or less of you idle vacuum to start with and adjust from there. I think the black puff ref is regarding the accelerator pump cam or displacement( 30 or 50 cc size) etc. BTW seat of the pants tuning is possible, but a wide band will save an enormous amount of time in tuning the carb. A Visual black puff of smoke from the rear view mirror on accel is huge rich from my experience.

[Bluemonster71RT]

OK. Test drive with the 770. I warmed it up via the choke to make sure it was good. It was close. It had a good idle and temp was good to take it for a spin. AWESOME! It drove like it should, pulled hard and even felt 100% smoother. THEN when the temp got to about 190 the chugs and pops started and it didn't feel smooth anymore. What am I looking at here? This carb fixed performance fore sure but still not the misfires and chugs. Any help as to where I have to look next would be great. Timing too advanced?   

[734406pk]

OK. Test drive with the 770. I warmed it up via the choke to make sure it was good. It was close. It had a good idle and temp was good to take it for a spin. AWESOME! It drove like it should, pulled hard and even felt 100% smoother. THEN when the temp got to about 190 the chugs and pops started and it didn't feel smooth anymore. What am I looking at here? This carb fixed performance fore sure but still not the misfires and chugs. Any help as to where I have to look next would be great. Timing too advanced?   

Nope. I think it's that "something else going on" theory discussed in a previous post. When the temp gets to 190 deg. The chugs and popping start. I'm thinking it's an ignition issue i.e the distributor pick up having a "hot short" or the ignition coil doing the same. Possible the MSD box, but I'm thinking is an engine mounted ignition component breaking down at 190 deg. temp. I would replace the pick up coil in the distributor first and try it. At least the carb is working nicely.!