Let me start out by telling you what I have done to the car and what the problem is. I installed a new edelbrock performer RPM intake manifold. The car is a 1971 396 with oval ports and I made sure the manifold had oval ports. The carb is an Edelbrock performer and I'm not sure what type of distributor I have. I know it's an HEI distributor and it could be ACCEL b/c that's the type of plug wires it had on it when I purchased the car about 6 months ago. Also just bought new spark plugs and put them in too.

Anyway got everything bolted on and the timing was off. I got a timing light and set the initial timing at 12 degrees. Hooked up the vacuum advance and set the idle to about 850rpm and took it for a test drive. It was bogging down early when I would get into it, I figured it was to lean. I backed the idle/mixture screws out a half turn and tried again, it was still bogging down. Back the screws out some more and at this point I was a 2 1/4 total turns out. That helped but it was still bogging down, but not as early when I would floor it. Kept trying to adjust the carb and ended up with 4 turns out and it was still bogging down. It seems like 2 turns and 4 turns was no different and I didn't have any black smoke. I also made sure I turned both idle/mixture screws the same amount of turns. Then we decided to pull the vacuum advance and plug it and then take it for another spin, that didn't work either. One problem is I don't have a vacuum gauge yet so I don't know how many hg's it was pulling, but I do know it's working. Then we tried backing the timing down to 8 degrees with the carb at 2 full turns out and that almost seemed worse. We did notice the timing scale where you read the numbers for the timing was chrome like it was a replacement so we are not sure if the past owner had it in the right spot or not. The timing cover is also chrome and if you were looking at the front of the engine the timing cover is at about 2 o'clock position. Does anyone know if this is right? I knew I should have looked at the timing before we pulled the manifold. :mad: Then we tried advancing the timing way past the 16 degree mark probably in the high 20's(if the timing scale is positioned right), obviously the engine sped up faster and we took it for a run which was not much better. We backed it down some but still over 16 maybe lined with the center of the block and took it for a ride and that helped but in the higher RPM range it would still bog down, it seemed like 1st gear was fine but 2nd it would start bogging in the high RPM and 3rd and 4th it would bog down probably running 70 mph. The problem is I'm not sure the exact RPM b/c the tachometer is not working "Sorry!!". This was about the best we had it all day. We thought we were on the right track so we backed the timing down a little more, but still not close to 16 degrees it would maybe be 20 but that seemed to be worse again, which blew my mind b/c if we went higher it was worse or lower it was worse, So I am stuck I'm not sure what the problem is, it seems like I've tried everything. Could it be the spark plugs are gapped to far? we gapped them 40 thousandths. I heard 35 to 40 was fine so I went with 40, the old one's were about 42. Does anyone know the recommended gap on a 1971 396.? Do you guys know what else I could try or do you know what the problem could be?

Sorry about the long post, but I thought I'd give you all the info I had.

Hmmm. Well I know less about Edelbrocks than Holleys...which isn't saying much...sounds like a transition enrichment problem.

I looked at Edelbrocks site, and in the carb owner's manual, there is a procedure for pump setting...my guess would be to try that to get rid of the stumble.
http://www.edelbrock.com/automotive/eps_sect2.html

Scott

The very first thing I'd do is take the top off the carb and check the float levels, new ede's are often not set right.
Then get that vacaum gauge.
It's very possible you're fighting a vacaum leak.

Yeah I do need to get a vacuum gauge. I did find out there is no fuel filter. Also the carb is not brand new, it was working fine before the intake swop. Maybe I got some trash in the carb? But wouldn't trash make is bogg down at low rpm and not just high rpm? Also is .040 to much of a gap for the sprak plugs?

040 is ok with hei.

am I understanding you took this carb off (working fine) swapped the intake, and put it back on?

vacaum leak.

sounds kinda like a weak coil to me...and the bogging in second after timing change, hmm wonder if the vaccum advance is working correctly or at all?

JimM: Yes that's exactly what I did, carb was working fine, took it off swapped the intake put it back on. So I guess we can throw the spark plug gap thought out the window, since .040 is fine. I know the vacuum line in the front middle of the carb that goes to the pcv valve seems to be working fine. The other hole to the right of it on the carb we have plugged. What's the best way to find the vacuum leak?

wiskeesour: I know the vacuum advance is working b/c if I pull the vacuum line from the front of the carb while the motor is running the vacuum line makes a high pitch noise and the motor slows down some. Then when I hook it back to the carb the motor slowly speeds up some.

Do you guys think something could be a miss inside the carb? How could I test the coil?

Original manifold was a ? Spray some WD40 into the airhorn with engine running and notice if engine speeds up. If it does, intake charge is lean. If engine dies, too rich.

Spray most anything, WD-40, Brakleen, etc., at all joints and hoses to find a leak. listen for rpm change when leak is found.

Also, look for Edel model number on carb, it may be too small to fill the void/volume added by the new intake.

I'd do like JimM suggests and check float level.

The Original manifold was the stock manifold. The carb is an Edelbrock Performer 750 cfm, part #1411, would that be too small?

I'll give those float levels a check after I try the WD40 test.

No, 1411 should be good size for the CID. However, OE manifold is a spreadbore design, since engine is 350 HP, new manifold is square bore design and present carb is spreadbore design. You will need an adapter plate.

Do WD40 test before doing floats, easy job first.

oh no I hope I don't need an adapter plate b/c I don't think I have a half inch at the most of hood clearance:mad:

I do already have an adapter b/c that's what was on it when it was bolted to the stock manifold.

I'll make sure I do the WD40 test first, and then the floats. I wish I could try that today but I'll be to busy.:(

Summit Racing, as well as others, maybe the local speed shop, does sell a 3/16 inch thick plate designed for this adaption.

What part number is your new manifold? Also you should get a piston stop so that you can correctly find TDC. You need to know your timing to prevent overheating and or engine damage. ALWAYS check and mark your timing/distributor setting prior to removing you manifold. Make very sure that you read up on how to use one properly before attempting it. You can do damage. If you have a spreadbore carb on a square bore manifold as Everett mentioned then that is your problem.

The new manifold is #7161 which is a square bore carb flange. When I look up the carb on edelbrock's site #1411 says it's a square flange. Do you still think I'll need a spacer?:confused:

no spacer is needed for an EDEL carb to sit on an EDEL manifold. both are squarebore.

To check the coil(stock, aftermarket?), U need an ohmmeter/voltmeter. Do you have one? Know how to use one? Check the voltage with the car running....

Are you sure the vaccum advance 'on the distributor' is working properly and moves freely w/o resistance? Just trying to help.....

Yes I have a ohmmeter, I'll check the coil and I'll check the vacuum advance and make sure it's moving freely.

Personnally, I think your chasing ghosts. Sounds to me like it's leaning out. Idle mixture screws are just that.... IDLE MIXTURE screws. They won't have a large impact when you dump the throttle open. Edelbrock carbs are funny. They work great until they don't. I'm a Holley guy. But someone who is good at tuning AFB's can tell you how to richen that thing up. I believe it's just an adjustment to do that. The larger plenum and runners got you lean, fatten it up and you should be ok. IMO.

Personnally, I think your chasing ghosts. Sounds to me like it's leaning out. Idle mixture screws are just that.... IDLE MIXTURE screws. They won't have a large impact when you dump the throttle open. Edelbrock carbs are funny. They work great until they don't. I'm a Holley guy. But someone who is good at tuning AFB's can tell you how to richen that thing up. I believe it's just an adjustment to do that. The larger plenum and runners got you lean, fatten it up and you should be ok. IMO.
Agree, and I'm a Holley guy too. Once you set your idle screws with your NEW VACUUM gauge, that's it. Leave them alone.
The first rule in problem solving is to ask 'what changes were made'. Huh,,,,? The manifold, right? Get in there and make sure that the carb is torqued down properly. Tighten gradually like you were installing lug nuts. Move from corner to opposite corner. Then check both throttle shafts for FREE AND COMPLETE MOVEMENT.
Timing; Remove the vacuum hose from the distributor and plug it to avoid a vacuum leak. Start the engine and set the timing to about 10-12 degrees advanced. Then hook up the hose again to the distributor. You're now in the ballpark. What else,,,??? Oh, test drive it and report back. But FIX that tach. Not good being blind.

So you guys think I should richen it up more. I tried 4 full turns backing the screws out and I didn't see a change b/w 2 1/4 and 4 turns the other day. Do you think I should keep going and see what happens? I'll make sure the carb is snug, but as far as I remember it was tight! Should I keep riching the carb until I don't see an increase in vacuum? Basically what if I get 5 total turns out and it doesn't help and I'm not getting anymore vacuum, should I go to 6 total turns or not?

I'll try whatever to get this thing working.

Going more than 2 1/2 turns is doing nothing except wasting your energy turning. You might borrow a Holley carb and see what results you get.

Otherwise, order a Tuning kit for the model of carb you have and follow directions.
Do you own/use a vacuum gauge?

Stop playing with the idle screws, they are for IDLE. If your problem exsists up top, your only wasting time. You have to richen the MAIN JETS! Like I said I think it has some thing to do with three holes and a rod somewhere. Ask an AFB guy, he'll know.

You have to richen the MAIN JETS! Like I said I think it has some thing to do with three holes and a rod somewhere. Ask an AFB guy, he'll know.On top of the air horn, side-to-side, there are two covers, oblong, 1/2 inch wide by 3/4 inch long, each held by a screw.

Underneath the screw & cover, be careful in removal as everything is spring-loaded, is a piston, metering rod, and a spring, spring may be in the hole. Don't lose any pieces. Pull out the rod & piston as an assembly. You will see the rod is clipped to the piston. The piston may have extra holes for the rod position.

The lower holes are to lean the fuel mixture, as going up the piston richen the fuel mixture. You may need to place the rod in the upper hole and do a trial run to see if this action helped. this would be richening the mixture.

Also, another contributing factor is the amount of vacuum created by the engine. The lower the vacuum, the pistons rise thus engaging the power circuit(s), making the carb rich. There are different springs to buy to correct this phenomon if needed. They come in the tune-up kit.

After moving the rod to piston relationship, insert the assembly back into the carb body and be sure the piston does go down into its bore, the spring is seated inside the piston and the cylinder, the rod is in the metering jet hole, and replace the cover. Test drive.

Remember, rod up the piston richens the mixture, the lower the rod, the leaner the mixture.

I've had many problems in the past with boggs etc. How's the accelerator pump? This may not help, but hows your centrifical advance? Are your wieghts snapping back? These along with sticking power pistons (on Q jets, never had an Edlebrock, don't know if they have them) have been problems for me in the past.


Good luck!

I have played with alot of EDEL carbs. They are EASY to tune. Everett is 100% correct. With my carb I was dum enuff to drill out the jet/main, pilot hole(s) with a bit that was just a hair larger. MOPAR eng builder said I could. Turned out I was TOO rich and the motor didnt like it. So he says remove the top of the carb and pull out the back 2 butterflies(they are weighted with counterbalance, not bolted in). So I did, to this day that was the best carb Ive owned....maybe I got lucky...383 stroker...

I'm getting a vacuum gauge today, and I might just have to try what Everett#2390 and wiskeesour says!

If you need to, edelbrock sells a tuning kit that contains a selection of rods, jets, and springs. You can also download the manual for the carb if you don't have it.

That said, if it ran good before, I still thing you have a vacaum leak. Have you pulled the plugs? Are any of the "white"?

I haven't pulled the plugs but I was planning on it. I was thinking about dropping them back to .035 on the gap size.