Best carb?

[Lattimer]

Originally Posted by Divine 59

Hesitation during the transition between primary and secondary circuits indicate the secondaries are opening too quickly.

Most people will disagree, but I run a Q-jet on my 71 Cutlass. I sent it out to a really good carb rebuilder. It came back in fantastic shape. Only adjustment I had to make was the high idle. Deano asked me questions about my engine set up and built the carb to my specific engine. I have not touched it in over six years.

On the street a Q-jet is my carb preference. Economy if you keep you foot out of it and performance when needed when those big secondaries crack open.

Think about this....GM spent $$$ in research and development on the Q-jet. It was designed to be the best carb choice for a GM engine. Holleys are good, but I give the nod to "Q".

I've heard several others say the same thing. Problem is I don't have a manifold for a q jet and I'm really not interested in changing out my brand new manifold. I was told the q jet can't fit on my manifold.

[Lattimer]

Originally Posted by Divine 59

Hesitation during the transition between primary and secondary circuits indicate the secondaries are opening too quickly.

Most people will disagree, but I run a Q-jet on my 71 Cutlass. I sent it out to a really good carb rebuilder. It came back in fantastic shape. Only adjustment I had to make was the high idle. Deano asked me questions about my engine set up and built the carb to my specific engine. I have not touched it in over six years.

On the street a Q-jet is my carb preference. Economy if you keep you foot out of it and performance when needed when those big secondaries crack open.

Think about this....GM spent $$$ in research and development on the Q-jet. It was designed to be the best carb choice for a GM engine. Holleys are good, but I give the nod to "Q".

also, from what I gather, the only adjustment on the secondaries on the 1406 is jetting.

[FettAffen]

Yea,

Been seeing the same probs on the Edlebog AFB style carbs, seems the primary throttle shafts leak air when you get a little age on them and wobbles around in the throttle shaft bore of the carb body.....

I never had this prob when Carter actually made the AFB, I used alot of AFB's over the years and never a lick of problems,

I have 78 T/A with a poncho 400 and replaced the Edelbrock 1406 with a 1407a couple years ago with same symptoms, adjust this, set that and the idle changes in 10 feet or day by day.........

Push around on the primary throttle shaft lever where the pedal rod attaches, idle will change even when you have everything set, seems to stout of a return spring set up on pulling on one side eats up the throttle shaft bore in the carb base, try a spring on the bottom pulling back and one pulling foreward on the top, maybe that will put the throttle shaft in the same place when back to idle, controlled vacuum leak

I remember years ago you could get the Quadrajet carb throttle shafts rebushed for pretty cheap, I poked around on google and they do sell bushing kits you can do yourself, I think Edlebrock AFB's are 3/8 shaft like the Carter AFB's, but the rebush kit is $169.95...lol...might as well get a new carb

I found this place on the interweb, ask them, maybe a rebush is less then $100..... http://recarbco.com/That is what I am going to do when the 1407 starts to act up.....

Also check to see if the advance weights in your distribator are okay and not a floppy mess or sticking, they will cause weird idle probs also....They do get a work out

Hope I could help.....

[richards72chevy]

I said this in another thread.If you do deciede on a qjet don't get a rebuilt one from auto zone.Im going to get a new carb.I don't know if im going for the eldabrock or holley.That little 390 looks real good.Do they run good in the cold weather?

[Billett]

Just do what I'm doing to solve the problem. LS engine!

[scrappy]

Don't count the little 390 holley out. A friend of mine had one on a 355 sbc in a long travel sand car. He had me rebuild the carb & set it up for off road use which only required spring loaded float needles & jet extensions. The engine was built to nascar spec & it's power range was 4000 to 9000 rpm. It was a nascar spec 390 holley though, not an off the shelf one. The engine made 605hp & 430ft.lbs.tq. As far as the edelbrock carb goes I'm putting money on the electric choke being out of adjustment. On the choke there's an arm that makes contact with a stair stepped bracket that's attached to the throttle shaft. After the truck is warmed up, disconnect the choke(make sure to insulate the power wire) than use a piece of wire to hold the aformentioned choke arm to keep it from being able to make contact with the stepped part of the throttle shaft. After doing this I'd be willing to bet your erratic idle issue goes away. If this solves the problem, put everything back together & loosen the 3 screws on the choke housing to adjust it(i.e. make the choke bi-metal spring tension tighter). As for the slight bog, that's a little more involved because the secondary auxilary air valve needs to be removed & the weights need to be ground a little at a time to tailor the secondary opening rate. Hope all this rambling makes sense & you can get the issues resolved

[hotstuff]

I would change the step up springs to allow more control over fuel flow to vacuum signal The springs are cheap and the fix is fast .

[Sloan66]

Do they make the holley 390 with a manual choke?

[OregonNed]

just a subscribe

[scrappy]

Originally Posted by Sloan66

Do they make the holley 390 with a manual choke?

Yes, I have one on the straight 6 in my fj40 landcruiser with an offenhauser dual port intake. The 390 holley I got from summit came with a manual choke. I'm not sure if an electric choke is even an option from the factory on a 390 but an electric choke from any 1850/4160 holley should bolt right on.

[Lattimer]

Originally Posted by Billett

Just do what I'm doing to solve the problem. LS engine!

No way. The 327 is my favorite small block, and its staying!!!!!

[Lattimer]

Originally Posted by FettAffen

Yea,

Been seeing the same probs on the Edlebog AFB style carbs, seems the primary throttle shafts leak air when you get a little age on them and wobbles around in the throttle shaft bore of the carb body.....

I never had this prob when Carter actually made the AFB, I used alot of AFB's over the years and never a lick of problems,

I have 78 T/A with a poncho 400 and replaced the Edelbrock 1406 with a 1407a couple years ago with same symptoms, adjust this, set that and the idle changes in 10 feet or day by day.........

Push around on the primary throttle shaft lever where the pedal rod attaches, idle will change even when you have everything set, seems to stout of a return spring set up on pulling on one side eats up the throttle shaft bore in the carb base, try a spring on the bottom pulling back and one pulling foreward on the top, maybe that will put the throttle shaft in the same place when back to idle, controlled vacuum leak

I remember years ago you could get the Quadrajet carb throttle shafts rebushed for pretty cheap, I poked around on google and they do sell bushing kits you can do yourself, I think Edlebrock AFB's are 3/8 shaft like the Carter AFB's, but the rebush kit is $169.95...lol...might as well get a new carb

I found this place on the interweb, ask them, maybe a rebush is less then $100..... http://recarbco.com/That is what I am going to do when the 1407 starts to act up.....

Also check to see if the advance weights in your distribator are okay and not a floppy mess or sticking, they will cause weird idle probs also....They do get a work out

Hope I could help.....

I just messed around with the shafts and got no change.

I won't rebuild this thing, I'll just replace it.

I rebuilt the distributor when I first got it, so it has new weights and springs.

[Lattimer]

Originally Posted by scrappy

Don't count the little 390 holley out. A friend of mine had one on a 355 sbc in a long travel sand car. He had me rebuild the carb & set it up for off road use which only required spring loaded float needles & jet extensions. The engine was built to nascar spec & it's power range was 4000 to 9000 rpm. It was a nascar spec 390 holley though, not an off the shelf one. The engine made 605hp & 430ft.lbs.tq. As far as the edelbrock carb goes I'm putting money on the electric choke being out of adjustment. On the choke there's an arm that makes contact with a stair stepped bracket that's attached to the throttle shaft. After the truck is warmed up, disconnect the choke(make sure to insulate the power wire) than use a piece of wire to hold the aformentioned choke arm to keep it from being able to make contact with the stepped part of the throttle shaft. After doing this I'd be willing to bet your erratic idle issue goes away. If this solves the problem, put everything back together & loosen the 3 screws on the choke housing to adjust it(i.e. make the choke bi-metal spring tension tighter). As for the slight bog, that's a little more involved because the secondary auxilary air valve needs to be removed & the weights need to be ground a little at a time to tailor the secondary opening rate. Hope all this rambling makes sense & you can get the issues resolved

Not entirely sure what you are talking about with the piece of wire. I'll have to look at it closer.

I've messed with it a lot with the air cleaner off, and the choke is always staying open then once the truck is warm. Never messed with an electric choke before this. I adjusted the way Edelbrock's instructions show, and it seems to work fine in terms of starting.

[scrappy]

Originally Posted by Lattimer

Not entirely sure what you are talking about with the piece of wire. I'll have to look at it closer.

I've messed with it a lot with the air cleaner off, and the choke is always staying open then once the truck is warm. Never messed with an electric choke before this. I adjusted the way Edelbrock's instructions show, and it seems to work fine in terms of starting.

I appolagise, I was was thinking about the function of a holley not an edelbrock. The part I was talking about in my previous post is on the throttle linkage side of the carb not on the choke side. It's the part on the top plate of the carb in the center. There's a rod going from that down to a stepped bracket. It's function is to hold the throttle blades open until the bi-metal spring in the choke housing heats up & than when you blip the throttle the choke disengages. Wire that back so that it cannot touch the screw thats on the throttle shaft. I've had the same problem with edelbrocks & carter afb's before & adjusting the choke is what fixed it.

[budman k20]

I have been tuning with the vacuum gauge to set the idle mixture. What I read was max out the vacuum at the correct idle speed and back off 1/8 turn.

I'm pretty sure the process you described is incorrect. You can download the tuning instructions for your carb from the edelbrock website. I remember the instructions saying adjust idle until max vac then adjust the other side go back a couple times and reset idle speed as needed. Just curious what your vacuum readings were? Sounds like you have a stock cam so it should have been over 18in. I would like to know how much your vacuum changed when you backed out the idle screw 1/8 turn. I have a 1407 so my instructons (and memory) may be off a little. If you have a stock fuel pump you should be OK... not for sure but the odds are in your favor that you dont need a fuel reg. What is your base timing set to? If its not around 12-14 btc you need to put it in that range and when you do it make sure the engine is not spinning fast enough to add mechanical advance <700 rpm to be sure. The other thing I found playing with my edelbrock is it needs a non metal spacer. This really helps out after hot shut down to keep the fuel from boiling. If you shafts are not worn you should be able to make your carb work. Finally what do you know about your dist timing... like the total advance it delivers and at what rpm? This has a big effect on how your engine runs and needs to be sorted out before you complete any carb fine tuning. Hopefully I gave you something to think about. Good luck I think you can make your carb work with a little research.

[Lattimer]

Originally Posted by budman k20

I have been tuning with the vacuum gauge to set the idle mixture. What I read was max out the vacuum at the correct idle speed and back off 1/8 turn.

I'm pretty sure the process you described is incorrect. You can download the tuning instructions for your carb from the edelbrock website. I remember the instructions saying adjust idle until max vac then adjust the other side go back a couple times and reset idle speed as needed. Just curious what your vacuum readings were? Sounds like you have a stock cam so it should have been over 18in. I would like to know how much your vacuum changed when you backed out the idle screw 1/8 turn. I have a 1407 so my instructons (and memory) may be off a little. If you have a stock fuel pump you should be OK... not for sure but the odds are in your favor that you dont need a fuel reg. What is your base timing set to? If its not around 12-14 btc you need to put it in that range and when you do it make sure the engine is not spinning fast enough to add mechanical advance <700 rpm to be sure. The other thing I found playing with my edelbrock is it needs a non metal spacer. This really helps out after hot shut down to keep the fuel from boiling. If you shafts are not worn you should be able to make your carb work. Finally what do you know about your dist timing... like the total advance it delivers and at what rpm? This has a big effect on how your engine runs and needs to be sorted out before you complete any carb fine tuning. Hopefully I gave you something to think about. Good luck I think you can make your carb work with a little research.

29" of vacuum idling at 700-800. 12 degrees initial advance, I set that at about 600 rpm. No clue what cam is in this, I haven't had a reason to look inside the engine.

I rebuilt the distributor using an Accel kit I bought at the local speed shop. It had cap/rotor/springs/module/weights/etc. I haven't tried to see what the total advance is, as I have no way of reading past 15 where the timing tab ends.

I did the setting by idle RPM a couple of times, then found instructions from someone else saying how to do it with the vac gauge. Supposedly using the vac gauge is more accurate.

I just put in the special thick gasket from Edelbrock under the carb to help with hot starts. So far that seems to have helped.


Just driving around tonight starting and stopping the truck a few times, I saw it idle at 1400, 1200, 600, 900, 1000, etc. Every time I stop at a light or restart the engine I get a different idle speed. Otherwise it runs great. Only got it to hesitate once hitting the 4-barrels, after that they kicked in smoothly.

[budman k20]

Using a vac gauge is more accurate than a tach but you don't turn out the screw 1/8 more once you have max vac. I take it you have a manual trans. Any chance your distributor springs are loose or one has come off alowing the mechanical advance to come in early? This would cause the engine to pick up speed. Did you plug the vac advance to the dist when you timed the engine? Have you set the float height? FYI this is all covered in the edelbrock carb tuning instructions. See below for idele adjustment

http://www.edelbrock.com/automotive_...ers_manual.pdf


Read this from the online instructions

IDLE MIXTURE
The Edelbrock Performer Series carburetor has conventional Idle Mixture Screws (IMS) that provide a leaner A/F when turned clockwise and richer A/F when turned counter clockwise.
The idle air flow is controlled by a conventional screw that opens the Primary Throttles. The following procedure should be used to set the idle mixture and speeds.

1. Fully warm engine and ensure choke is fully open.
2. Air cleaner in place.
3. Set desired speed with the air screw.
4. Adjust the IMS on ONE side to get the maximum possible RPM.
Do not go rich beyond the maximum speed point.
5. If the above changed the idle speed more than 40 RPM, then readjust the speed.
6. Adjust the side OPPOSITE of that in Step 4 to get maximum RPM.
7. Reset the speed.
8. Carefully trim each IMS to again get the maximum idle RPM.
9. Go leaner just enough to get a 20 RPM drop in speed.
10. Reset the speed to the desired RPM.
11. This is a Lean-Best Idle Set. Setting richer than this will not
improve idle quality or performance, but could tend to foul plugs.

Proper fuel pressure should be verified and cracked or brittle vacuum lines should be eliminated. Many so-called “carburetor calibration” problems have been traced to another part of the
engine system that was not functioning properly.
Winter Fuel Idle Sets
During the winter months (in most parts of the country) the local fuel will be a “winter” blend that is very volatile, as an assist to cold-engine starting and driveability during warm-up.
However, the high volatility has the disadvantage of allowing excessive vaporization of the fuel if the vehicle is operated in a heated area such as a garage. This can result in problems in the
idle-set procedures since the carburetor’s internal vents will allow this excess vapor to be drawn into the throats and enrichen the mixture. The idle will be erratic and not seem to be able to
hold a set. To resolve this type of problem, it is advisable to perform the final settings outdoors after the vehicle has been stabilized with a drive of several miles.

[Lattimer]

Originally Posted by budman k20

Using a vac gauge is more accurate than a tach but you don't turn out the screw 1/8 more once you have max vac. I take it you have a manual trans. Any chance your distributor springs are loose or one has come off alowing the mechanical advance to come in early? This would cause the engine to pick up speed. Did you plug the vac advance to the dist when you timed the engine? Have you set the float height? FYI this is all covered in the edelbrock carb tuning instructions. See below for idele adjustment

http://www.edelbrock.com/automotive_...ers_manual.pdf


Read this from the online instructions

IDLE MIXTURE
The Edelbrock Performer Series carburetor has conventional Idle Mixture Screws (IMS) that provide a leaner A/F when turned clockwise and richer A/F when turned counter clockwise.
The idle air flow is controlled by a conventional screw that opens the Primary Throttles. The following procedure should be used to set the idle mixture and speeds.

1. Fully warm engine and ensure choke is fully open.
2. Air cleaner in place.
3. Set desired speed with the air screw.
4. Adjust the IMS on ONE side to get the maximum possible RPM.
Do not go rich beyond the maximum speed point.
5. If the above changed the idle speed more than 40 RPM, then readjust the speed.
6. Adjust the side OPPOSITE of that in Step 4 to get maximum RPM.
7. Reset the speed.
8. Carefully trim each IMS to again get the maximum idle RPM.
9. Go leaner just enough to get a 20 RPM drop in speed.
10. Reset the speed to the desired RPM.
11. This is a Lean-Best Idle Set. Setting richer than this will not
improve idle quality or performance, but could tend to foul plugs.

Proper fuel pressure should be verified and cracked or brittle vacuum lines should be eliminated. Many so-called “carburetor calibration” problems have been traced to another part of the
engine system that was not functioning properly.
Winter Fuel Idle Sets
During the winter months (in most parts of the country) the local fuel will be a “winter” blend that is very volatile, as an assist to cold-engine starting and driveability during warm-up.
However, the high volatility has the disadvantage of allowing excessive vaporization of the fuel if the vehicle is operated in a heated area such as a garage. This can result in problems in the
idle-set procedures since the carburetor’s internal vents will allow this excess vapor to be drawn into the throats and enrichen the mixture. The idle will be erratic and not seem to be able to
hold a set. To resolve this type of problem, it is advisable to perform the final settings outdoors after the vehicle has been stabilized with a drive of several miles.

Its not 1/8 more, it was back off 1/8.

yes to manual trans. Yes to plugging the vac advance. I haven't touched the float height. I don't feel particularly qualified to open up the carb. Bad past experiences.

I've double checked the timing about 20 times at idle. I have not had the cap off since I rebuilt the distributor, I can check to make the springs are still on there.

I have those instructions, and I followed them to set up the carb. Truck ran great but still had idle issues. Tried setting the idle several more times with the same procedure.

Read somewhere (can't remember where) about setting with vac gauge, so I printed it out and tried that. Vacuum came way up and the truck runs just as good. Still has the same idle issues.

Everything except the carb on this has been installed by me since I bought the truck 3 months ago. Carb was already on the truck.