The Edelbrock 1406 is in fact an enhanced version of what we used to
call a Carter AFB (back in the dark ages), almost identical, and I bet
some of the old gaskets would still interchange. The Quadrajet was a
very different animal. The only similarities I can see is the vacuum
operated metering rods, all else is very different.
Right out of high school I ended up in a Delco factory training school
(they used to train their techs, back then) and was one of the first in
the state (Oklahoma) to be certified to work on that beast (Quadrajet)
and what a beast it was in the first iteration. It improved
magnificently over the years.
All this carb talk does take us back some, doesn't it??
Well... I have a set of the .095" jets... I'm going to put them in
tomorrow and play with my existing meterings rods (I have 3 sets). If
I get time I will pick up another set for experimentation.
I laid all the metering rod and jet combos out in a spreadsheet, and
after running a few formulas to determine the flow area (area of the
jet's hole minus the area of the metering rod) I was able to sort them
in a logical order.
Needless to say, after that, I have little respect for Edelbrock's
Honestly though... I think the one thing that would help more than
anything would be an O2 sensor and a fuel/air meter. At least then I
could actually see what was happening, and when and where in the RPM
and vacuum ranges.
You're not confusing me... I've learned a lot about carbs in the last
year or so, and I keep my nose in the manual and constantly read
websites to try and get a little more insight into what's going on.
Basically, I still think it all comes back to a carb that's not
calibrated for that engine, with that cam, with that kind of (low)
vacuum. I just need to find that balance.
You are 100% correct here. BTW with your current came you want it to
start in enrichen around 8 or 9 inches or so and that fact that the
opwer vale is felt it tell me that you might be a little lean in mid
range and as you richen up jet or metering rods you sometimes need to
size down power valve.You migh also try have power valve come in at
maybe 4.5 too. I agree that a A/F sensor would help a lot here. I had
it down to such a science that I used to run once size in summer
months and two size larger in winter months to keep it at peak
performance. Trust me it is worth the effort to get it right and ift
is very important to watch your plugs too and be prepared to change
the heat range of them if you want best possible performance.
The A/F meter will be the next serious purchase.
Then I gotta get a bung put in the exhaust manifold...that'll be
I may end up trying to find a set of '87-up manifolds and go ahead and
swap them out. That way I'll be set up for the O2 sensor from the
get-go, and it'll probably make the future TBI swap that much less
Either way, I need it running good enough so I can start reconnecting
the emission control equip to get it titled in GA. I'm still running
TN tags (don't have emissions in TN) and as much as I hate to consider
myself anything but a Tennessean, I've been here longer than the law
would prefer without becoming a "proper" citizen.
The best factory exhaust manifold ever made for a SB were made in the
60's and early 70's and they were wheat we called the old "Ram Horn"
style and they flowed well. They came in two sizes 2 ich and 2.5 inch
dump but I am not sure if they would fit/work in your application.
Granted, they would not have a O2 sensor port but you could add one to
the pipe right beow manifold. . On the air fuel sensor probe. You
could drill a hole in exhasut manifold and then tap it to take a bolt
or plug so that you can seal it when done.
I guess a simple question is in order here. Do you have the owners
manual that comes with the 1406 carb?? It contains a very good setup
procedure for your carb. I can't see how it wouldn't contain pertinant
information to get you out of your situation.
If you don't have it, you can go to www.edelbrock.com and download it,
it is a .pdf file.
Oh yes... I know it well, LOL...
I'd like to print up a few hundred copies of the PDF manual--to use as
Actually, the main thing that's not being addressed here is the cruise
mode. The springs are advertised as bringing out Power Mode at a
certain vacuum pressure, but nothing is mentioned about when the cruise
mode comes into play.
Is it 10" Hg??? 8"? 6"?? The carb obviously does not go from idle
circuit to full-on power mode.
I need to figure that part out. Then I can play with rods, jets, and
springs according to find the balance I'm searching for.
The funniest part of the whole thing is...I've literally cost myself in
the thousands of dollars with everything I've been through (some
self-inflicted) with the truck. But in a sick way I like it, LOL...
I'm forcing myself to learn so much about all aspects of it and I love
FYI, the exact link for the manual is here:
Had it bookmarked on both the home PC's as well as the work PC for some
time now ;-)
Also emailed Edelbrock, and I'm still waiting to hear back.
Jon, I used to run these carbs as afb's ( 2) on my 426 S/S Belvedre
Ramcharger and played with jetting and metering rods for 25 years of
competition and did not find theem sensitive to these changes, keeping in
mind I was running flat out, but even driving part throttle around the pits
I did not see a problem. I don't think your entire issue lies with the carb,
it is somewhat large for you gearing and application as mentioned a 650
would be more inline. BTW GM sensors are narrow band for the most part.
600CFM is about right but 3.73 are not the best with that cam and it
would run a lot better with a 4.10 as it would get it on the cam
quicker and make better use of improved RPM range.
Yeah, but...I just had the rear axle rebuilt 7 or 8 months ago. I
don't want to do that again. I kind of consider the 3.73 a bit more
ideal than the 3.08's I had, or 4.10's. Just seems like a good
compromise between economy and power.
And I don't want to have to rev it up to get moving.
This why I keep coming back to swapping the cam for something better
suited to my truck.
I wholeheartedly agree. However I'm going to try to make due.
I did finally talk to Edelbrock's tech support folks. They answered
the question that has been bugging me: At what vacuum level do the rods
pop up into Cruise Mode?
They said with my 4" springs, that the onset of Cruise mode should
happen around 8" Hg of vacuum.
This pretty much coincides with what I have been observing on the
vacuum gauge. While driving down the road, the lean spot is basically
between 5" and 8" of vacuum. At 5", it isn't great, but it's really
noticable around 5.5"-8".
Oh well... Gonna try to pick up a couple of sets of metering rods on
the way home. Gonna get a set with the .068" cruise step. That should
take it almost all the way back to stock cruise settings, even with my
current jets (which are smaller than stock).
If this doesn't work, I'm going to go ahead and start cam shopping.
Will I need to remove the heads to do that, or just the intake,
rockers/rods/lifters, and any and everything else from the front of the
Try a 6 or 6.5 inch power valve. You might also reduce the size of
power valve to if possible. You may not find the fuel flow you need in
main jets for smooth transition without being too rich at times. You
could also try polishing the road with emery cloth to take a few
thousandth of on them and tweak the flow a bit.
Power valve? I thought Edelbrocks didn't have them!?
I did the following Google search: "power valve" site:edelbrock.com
Which searches the entire Edelbrock website for the exact phrase "power
valve". I got one link in return, and it was in regards to an
On a site, I found this: "Briefly though I can expound on a few things
regarding how the "power mode" interacts with the main metering system,
which I didn't think was explained well enough in the manual. I learned
this information through trial and error and through talking to
Edelbrock Technical Support. What they call the power mode is the same
thing Holley accomplishes by using a power valve."
Got my carbs mixed up sorry. I do reacll that what I wound up doing
with my Qjets was to use large jets and large metering rods so that
they leaned out well at cruise butfattened up nicely with foot in it.
Larger dia rods still have same min diameter at bottom of rod so a
biiger rod in a bigger jet allows for lean cruise and more fuel when
foot is in it. Maybe you should stick with 98's and find a larger
diameter rod. It is a thought anyway.
you should not have to go with smaller jets on a 600 CFM carb with a
I use to run some various Holleys on a quasi hot-rod i had at one
time. Mostly stock 350 , a holley 600 ran very well, later when added
a completely different modified engine went to a 750.
I agree with your advice or whomever made the point about make small
changes at the time. Seems like you would want to get your idle
scquared away first.
I'm guessing on a stock engine that one or two jet sizes would be as
much as even would make sense to do. I would think a 600CFM carb would
power a stock small block just fine, without modification. As i recall
a minor change in metering rod or jet size can really get you too much
fuel when you can't handle it. YOu would need some steep gears to
take the fuel if you changed it much at all as far as jets or I'm
guessing this carb uses metering rods on the secondaries like a
quadrajet? been a long time since I even thought about carbs.... but
it would be nice to have an old school hot-rod
to mess around with. I'm thinking that might be one of my future
No metering rods on the Secondaries...just jets.
I admit I did go too far with the changing of the jets, and I need to
make it richer on cruise mode.
I talked to Edelbrock's tech support yesterday. I wasn't thrilled with
the results. The dude kept putting me on hold each time I'd ask a
question. He'd come back 30 seconds later with the answer, so I don't
feel confident that I was speaking with a real expert. Having done
tech support and assisted with training, I can say that a good script
to read from can allow newbie tech agents handle *most* calls. But
this guy didn't seem to really know what was going on.
I don't know whether to agree or disagree with the statements he made
about the gas fumes from the pipe. I haven't checked the plugs in a
while, but he said that's the ONLY way to know if it's rich or lean. I
disagree. Regardless of what the plugs look like, if you're gassing
yourself and everyone within 100 yards of you truck to death with gas
fumes, then you're rich!
I was gonna mess with it last night. I left work early to get to the
local speed shop to get 2 sets of metering rods. They close at 5:30pm,
and like Noon on Saturdays. Traffic was horrendous so I called ahead.
I got there right at closing time--doors locked.
I called, got the same dude. Told him I was there and REALLY needed
those metering rods. He said "hold on". I got put on hold, then
transferred to somebody's voice mail, then automatically disconnected.
An hour and 45 minutes later I managed to fight through traffic to get
home--with no A/C.
Needless to say, I was pissed off, hot and tired, and didn't feel like
screwing with it.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.