jpc647

This past season I was chasing some carburetor problems. I seem to have resolved most of them(can't check now with snow/salt on the ground), but I'm curious how many of you guys are using the 600cmf 1406 carb's on stock or almost stock 350's. Have you guys had to recalibrate this much? Is this normal? I do have the 7111 RPM intake on the car, which from most accounts(except edelbrock) should not matter performance wise over a stock performer intake, until higher rpms.

I've had to recalibrate the carb with new jets, metering rods, step-up springs, etc. I've gone approx 8% richer than off the shelf spec to resolve most of my issues. Which is 2 steps up. Seems odd for my stock 350(probably been rebuilt, but it's nothing to write home about). Granted, all the items come in a calibration kit from Edelbrock, but I wonder if I might have other problems which are being compensated for by the 'drastic' calibration.

Biggest problem was a BOG, off idle, So from a stop to WOT it would sort of bog or slowly accelerate for .5 seconds to a second and then come to life.

Finn5033

I have a 77 350 with a stock 72 intake that I put a 1406 on last summer. It fired right up and actually seems to work just fine. I took the car on a 4 hour road trip the day I put it on and the car ran great with real good gas mileage. I didn't adjust it or have it tuned or anything. I am no expert so I am sure someone else can give you a more technical response.

RetroRanger

I have a 1405 on my bone stock 72 350. the 1405 is set-up slightly richer than the 1406 and has no e choke. I run a stock manifold, I can nail it at a dead stop and I get no bog at all.

I thought the 7111 was for a modified engine and the 2711 for a stock engine.

this summer Im going to put a 2711 maifold on my engine when I change the t chain

edit from ebrocks description re: 7111 "Performer RPM Olds 350; Intake Manifold; Cast; Non-EGR; 1500-6500rpm; 80-85 Olds 330-403; For 4 bbl Carbs; Street/Hi Performance Use Only;"

cutlassefi

Nothing wrong with the RPM intake on most small block applications. See my post of a 9.0:1 380 small block Olds with a mild roller cam. It made almost 400lbft of torque at 3600rpm with an RPM intake.
If you look at the runners/ports on the RPM they're still pretty small.

oldcutlass

The only reason I can see for a big change in jets and major bog would be a vacuum leak. Timing would also play a part in how much fun your big pedal is.

jpc647

Thanks for the post. Could the electric chock be my problem? The 1405 is 2% richer than the 1406. So when I recalibrate the 1406 (+6%) I think, it should be just slightly more rich than the 1405 stock.

I've read on quite a few threads the 7111 RPM is better in the higher rpms but gives up nothing down low. That might have been over on ROP though.

I'm stumped. I'll try the final calibration step on the 1406, but I'm wondering if it'd be better off swapping the intake or the carb. If I swap the carb, I'm thinking I'll go back to a Q-jet and forget about edelbrocks.


Well thats a much higher performing motor than a stock 350. Mine is no where near 400 ft/lbs. Lucky is a stock motor is half that.



I've checked, checked again, and rechecked. Sprayed carb cleaner everywhere looking for a leak. Can't find one. I even replaced the exhuast gaskets because one was leaking a small amount. Checked all around the intake, the carb base, all around the carb, everywhere. I can't find anything. Timing is at like 16 BTDC with the electronic ignition from a newer(75 vintace) 350. (Which is what most people say is about normal. If I move it either way up or down i get adverse affects. Either more off the line and nothing up top or nothing on the get go but a ton up top)

I wish someone had a 1405 local I could borrow for a Saturday. I just don't want to replace both and find out I spend $300 on something I don't need. I'm still leaning towards the carb though. As the more I adjust it and tinker with it, the "closer" I feel I seem to get.

panos

Is it a high mileage engine? Low comp maybe? Worn out engines or those with low comp need more fuel to run decent.

jpc647

I haven't done a compression test on the motor, I can't seem the find a decent reasonably priced tester, the Harbor Freight one is garbage.

I'm assuming the motor has 144,000 but with a rebuild. It runs strong, and hard. I know the timing chain was replaced at one point, as was the carb/intake. Engine looks really clean inside, which leads me to further believe it's been rebuilt.

panos

Check fuel pressure also,edelbrocks don't like more than 5 psi,also In some applications having too small of a carb will cause it to run rich as the smaller venturies will create higher velocity and hence draw more fuel from the carb.

jpc647

The fuel pressure last summer was 5.2 psi, which edelbrock said was perfect. Between 5 and 5.5 was in their range. .

I've called them a few times, and they just keep recommending a 1405 carb, because it is 2% richer than the 1406. But I recalibrated my 1406 to be 8% richer than stock setting, which surely would more rich than the stock 1405. So to me it seems buying a 1405 car is counter productive. They then recommended part number 1475 which is an acceleration pump kit, which is another $40. Is this worth trying? Edelbrock seems to just keep suggestion spending more money on thier products to no real avail. More progress was made from the calibration kit, than anything else they suggested. Anyone else tried an accelerator pump kit?

Sort of beating my head against the wall here. My biggest problem is going WOT from a stand still from a light or whatnot. The car seems to hesitate, like take a second to wake up.

jpc647

Wanted to bump this. I keep reading through old threads trying to find a culprit. Keep reading people say "Ignition problems can sometimes seem like carb problems". Not really sure what that means.

People are saying stock motors are breaking the tires lose at WOT, with the same configuration as mine. But mine seems to be running lean. I'm missing something. Besides looking at the plugs, how are all of you measuring A/F ratio with a carb? I've seen kits to weld a bung into the exhaust, but that seems like a very expensive route to go.

TripDeuces

If it were running lean you'd notice the car 'surging' while cruising. It would feel like someone pushing the car from the rear intermittently.
What makes you think it's lean? You said you made it 8% richer than the baseline.
I only know of two ways to check the mixture. An air/fuel ratio meter and an old school tool called a Color Tune. I actually own a Color Tune but it's not designed to be used for extended periods. Personally I don't think you need either. I'd invest in a vacuum gauge though and learn how to use it.
I find it hard to believe the carb is that far off right out of the box. Those are fairly simple carbs and work very similar to Quadrajets with the variable cfm secondaries. As several have already said they work just fine as is. Your bog issue has me perplexed without more info.

jpc647

The only thing leading me to thinking it's still lean is that everytime I richen up the rods the car gets better. Wondering if crusing at 1500 rpms there is enough fuel flowing through the carb to go WOT and not run out, but from a stop the carb isn't supplying enough fuel fast enough. I don't think I need anything for extended periods of time. I would love to take a minute ride up the road and see what the A/F ratios are so that I can move in the right direction to fix the problem. At this point I'm sorta guessing. The plugs aren't black, so it's not running too rich.

I have a vacuum gauge, and have checked at idle, it seems to have the highest Hg right where it is, the Hg drops down if I turn the mixture screws out either way. What other information can I provide for you to help you help me?

plugs:same two plugs different camera angle.
photo2_zpsc58770e1.jpgphoto_zps128be22c.jpg

TripDeuces

With the engine off. Open the throttle all the way while looking into the primaries. Can you see two streams of fuel shooting into the venturis? Although a bog at initial WOT is usually a bad accelerator pump it could be other things also so I'll start there.
What you're describing is a big slug of air that's getting dumped into the engine but no fuel to go with it or not enough fuel. You get a huge lean moment until the fuel can actually get flowing and then the bog ends. This can also happen if the secondaries just flop open like on a Quadrajet when someone tinkers with the air valve wrap spring. If I'm not mistaken that carb uses a weighted secondary air valve that opens gradual based on demand. Since the secondaries don't have a accelerator pump that opening needs to proceed gradually to work. Is that working properly?
Let's start with this. Normally I wouldn't even attempt to try and diagnose stuff over the internet. It's just easier when it's in front of you.

cutlassefi

Jut an fyi, a bog can be too rich as well.
Try another hole in the accelerator pump arm, see what happens. Plugs don't look bad, you're close.

jpc647

Should I open the throttle fast or slow and watch for the stream of fuel? The accelerator pump was replaced last year as one of the first steps. No real noticeable different between the old and the new.

I've tried the bottom hole, as close to the intake manifold as I can. It seems to hit softer all around. Not as much giddy up and go. Middle hole hits like bam, chirp into second gear and take of. Haven't tried the top hole closest to the hood, a family member parking in front of my garage this weekend and left. Tonight I can probably try.

TripDeuces

Whether you open it fast or slow you should see the two streams enter the primaries with any kind of throttle movement. I'm just trying to find out if the accelerator pump is working as intended to start with.

KDV

Lots of good edelbrock troubleshooting info .

jpc647

Just checked. Car on or off looking in over the choke plate pushing the throttle both of the edelbrock "pump jets" squirt a stream of fuel. After doing it a couple of times though, I did notice it seems the passenger side sprays harder and more eradic. What I mean is the driver side is a solid medium velocity stream, but the passenger side is a high velocity spray. Like it goes into the barrel but not all in the same place.

Sorry if that doesn't make sense. Going to try and get a video now.

Can't embed video, feel free to watch. Looks like one side is spraying a lot more than the other. Might go take the top off the carb and clean the needles out. That sounds like a good project.
http://s478.photobucket.com/user/jpc...tml?sort=3&o=0

TripDeuces

You may have dirt in there or the casting is damaged. It should be two basically equal streams that hit the booster in the middle. Although your description isn't the ideal stream I'm not convinced that's totally your problem though.
You mentioned that the carb has been apart several times or at least worked on. There is a needle and seat arrangement under those shooters that holds fuel up in that shooter cavity. If the needle wasn't put back there is nothing to hold the fuel in there and it will drain back into the bowl. What happens is your initial movement of the throttle may have no fuel to shoot into the venturi. Could be dirt in there also holding the needle off the seat and allowing fuel to drain back. Just something else to check. Here's a pick of an old one out of a original Carter which the Edelbrock is based off of. I'm assuming the arrangement is still the same.

jpc647

I cleaned them both out and called edelbrock too. It appears the #28 pump jets in my car are on the older side, as they have since been replaced with #31 series, which are .003" larger. Not sure if .006 of total fuel will be enough, but well see. I had the needel and seats out before when I re-adjusted the floats to the proper 7/16 measure. They seem to move pretty free. When the new pump jet comes, I'll take it apart again, one stuck one time and the car wouldn't run worth crap, but they both seem to move up/down okay with the float. I changed the accelerator pump notch to give it more of a shot, it certainly seems to hit harder when moving. If I'm at 25-30mph and I nail it there is a definite improvement.

The car runs good after about 2000(guess, no tach) rpms and keeps on pulling until 3rd gear, where it sort of seems to hit a wall and not want to accelerate as fast.

The car maybe doesn't "bog" so much from an idle anymore as it just slowly accelerates until higher rpms where it starts to really pull. I originally thought that was the 7111 intake, but others on the board with stock motors are saying they can peel out from a stop with lower gears and the same intake.

I've got 3.33's, dual exhaust, and a higher jetted carb and it seems slower than others stock cars, single exhaust with 2.73 gears.

Still confused, as to how a 600cfm(1405 or 1406) Edelbrock carburetor is designed to work well and be an improvement for for the OEM Quadrajet rated at 750cfm. Wouldn't the extra 750 cfm at WOT be a big improvement? So many things running through my head at the moment.

TripDeuces

Glad it's getting better now. Maybe the rest of that bog is just timing related.
The Edelbrock (Carter) and Qjet are variable cfm carbs. Although rated at 750 cfm the Qjet is only going to give you what you need. That secondary air valve only opens as far as needed to supply the demand. That is why the carb was on everything from 6 cylinders up to 500 ci Cadillacs.
I still wonder about your lean/rich condition. Regarding the plugs in your pics the ones on the left look correct while the ones on the right look rich to me. The black at the top of the threads is wet looking instead of dry like the other. Who told you it was lean to start with and why did you come to that conclusion? Other than the intake your engine is basically stock (?). The addition of headers might have required a richer mixture but that is not a given. 8% increase in enrichment is huge, especially on a stock no frills engine.

jpc647

I have a hard time conveying my message. Thank you for bearing with me. I know the quadrajet is a variable cfm, but if at max it opens to 750cfm on a 72 350(factory), and the edelbrock will only open to 600 max, could this inheriantly be the problem?

I thought the plug on the left looked white or lean, while the one on the right was closer to "normal". I thought light brown was the ideal color, while white is lean, black is rich. I agree they look wet too. I don't know about that. I've had people follow me on trips to look for smoke out the tail pipes. It smokes very little if I go WOT and let off. A little bluish tint, but not a lot of smoke. Less than you see from a new car when it's idling in traffic and not completely warmed up was how it was described to me.

I thought it was learn in the beginning because of the original problems. Surging, popping out exhaust on 0 throttle deceleration.(which richening up the idle screws took care of 95%), and the bog going from stop to WOT. Bog like, the engine almost dies, bog.

Yes, besdies the 7111 high rise intake and the 1406 carb, the car is stock(best I can tell). There can't be a high lift cam in it, it idles too well. 18lb vacuum at idle. Stock heads, although they did look very clean when I had the valve covers off. That leads me to think it was rebuilt, or at least the heads were off at one time. Well I have 73 valve covers, and a dynomax(no other info on muffler) exhaust. It's a dual system. Not sure of the diameter, I could look if it helps. 3.33 single trac rear. Transmission doesn't have a shift kit or anything. Just a plain jane cutlass, no frills motor.

I agree 8% is huge. I don't understand it. I've started wondering if its better not to understand and just get it to burn rubber. ha.

I just found this link. http://vb.foureyedpride.com/archive/...p/t-74438.html
I'm going to spend a half hour tonight trying to follow this and see if hes legit, or Full of crap.

TripDeuces

The carb cfm formula is this:

CARB CFM = CU.IN. X RPM divided by 3456 X VE%

So if you had a stock or street performance production engine of 350 cubic inches and you wanted to spin it to 5000 RPM max and it had a VE% of 80%, the formula would determine a required carb CFM of 405 CFM. If you had a warmed over street performance motor of the same size, but it was capable of 7000 max RPM and it had better heads, camshaft, headers and a performance intake that raised the VE% to 95%, the formula would give you a minimum required carb CFM size of 673 CFM.

My point on the Qjet is it never opens completely to allow the full 750 cfm if the engine doesn't require it. The above formula is not an absolute but it will get you in the ballpark. I like my carbs about 10% larger than the formula states. But if you do the math for your engine I think you'll find that 600 cfm is more than enough.
On the plugs I think perfect is probably right between the two but leaning more toward that whiter one. I only say that because I'd rather err on the side of rich than lean for the piston and rings sake. It still shows a trace of brown on the center electrode porcelain with a nice dry black ring on the top of the threads. The other shows a blackened porcelain and a wet top thread. Personally I would set it back to it's stock settings which are listed on the Edelbrock site. They list what the rods and jets are for every carb they make. The difference between the 1405 and the 1406 is slight so you could even go with the performance model settings.
Regardless if it is rich or lean at cruise speed the bog still isn't right so I'm wondering if you have enough timing in it. That's probably your next step. Hopefully you know someone nearby who knows the old school stuff that can help you out.

jpc647

Thank you for the explanation on CFM's. I'm learning! I was at stock Edelbrock Settings when I started and I had all sorts of problems. Hesitations and a bad bog right of idle. A bog where the engine would actually stumble and want to shut off. I can't say the plugs really looked much different.

This is one of the plugs when the car was hesitating and stumbling:
20121023_131942.jpg


The timing is off the timing tab by about an inch or a little more. It'd say it's around 17/18 at idle. I tried tweaking it up/down and found one way I got more up top, one way I got more down low, but where it is seemed like a good medium.