Edelbrock 1405 setup for stock IH 392 V8 Off-Road Adventure Rig

[LeeC]

While removing the smog tubes and pluging the holes in the exhaust ports I noticed that my 392 is running very rich. I seem to remember I could smell a lot of unspent fuel in the exhaust when I drove this rig last. The exhaust ports are wet and dark. The PO had installed a brand new Edelbrock 1405 on this stock 392 just before I bought it (I'm guessing, right out of the box). He blew the rear D44 ring gear shortly after and that is when I picked it up for a song...

From what I can gather on the Edelbrock site, the 1406 is setup 2% LEANER than the 1405. IIRC many here have had great luck with the 1406 on their stock 345's. How about on the their stock 392's?

I'm considring purchasing an Electronic Choke Kit (#1478), Off-Road Needle & Seat Assembly kit (#1465) and 1405 Calibration Kit (#1479), then set this carb up the best I can for my stock IH 392 prior to running it again.

Does the Edelbrock Off-Road kit work as well as the Holly Truck Avenger? Or more importantly, will it meet my 68 Travelall Adventure Rig needs?

Here's how the Edelbrock site says the two carbs are setup out of the box:

Edelbrock 1405:
0.100 Primary Jets
0.095 Secondary Jets
0.070-0.047 Metering Rods
Orange (5"Hg) Step-up Spring

Edelbrock 1406:
0.098 Primary Jets
0.095 Secondary Jets
0.075-0.047 Metering Rods
Yellow (4"Hg) Step-up Spring

If there is general agreement on the best way to setup an Edelbrock 1405 for a stock off-road use 392 with a maximum of 4,000RPM, maybe I can get away with just purchasing the exact components I need instead of the complete Calibration Kit???

ADDED: After reading through the Edelbrock Owner's Manual I see altitude plays a larger role than I thought. So, I'm at 1,700 in SoCal and most driving will be between sea level and 6,000 feet.

What are your thoughts?

[JimKoz]

I'm pretty sure that the "2% leaner" is a misprint on their website. At part-throttle cruise, the primaries on the 1406 are more like 22% leaner if you just consider the relative area of the jet minus the metering rod.

1405: 100*100 - 70*70 = 5100
1406: 98*98 - 75*75 = 3979

The 1406 primaries have 3979/5100 = 0.78 times as much jet area for fuel to flow through, or a 22% reduction in jet area from the 1405 calibration.

I'd vote for the 1406 on your 392, but be prepared for it to be a little on the lean side. You may want to get a .070" X .047" metering rod like the 1405 uses to put you somewhere in the middle of the 1405 & 1406 calibrations.

[LeeC]

I don't claim to know much about carborators or their related calculations, so I can't confirm if Edelbrock's "2% LEANER" statement on their site is correct or not.

After reviewing all the posts I could find on this subject here prior to posting this, it appeared that several stock 392 owners had to go 2 stages LEANER. According to their chart that is 8% LEANER for both Cruise Mode and Power Mode. That requires a Primary Jet change to 0.098 and a Metering Rod change to 0.073 x 0.052.

The Calibration Kit looks like it will give me at least 6 different LEANER combinations from their reference chart to work with. The more I read the more I learn and realize that there are a lot of things to check as I get into this more deeply.

I was hoping to find a NORM for what others have found with an Edelbrock 1405 on a stock 392 with a manual trans at 0-3000 feet usage, to start from.

ALSO: need to know if the Edelbrock Off-Road Needle & Seat Assembly work before I start putting out money to setup this brand new crab?

[Will Marsh]

Originally Posted by LeeC

While removing the smog tubes and pluging the holes in the exhaust ports I noticed that my 392 is running very rich. I seem to remember I could smell a lot of unspent fuel in the exhaust when I drove this rig last. The exhaust ports are wet and dark. The PO had installed a brand new Edelbrock 1405 on this stock 392 just before I bought it (I'm guessing, right out of the box). He blew the rear D44 ring gear shortly after and that is when I picked it up for a song...

From what I can gather on the Edelbrock site, the 1406 is setup 2% LEANER than the 1405. IIRC many here have had great luck with the 1406 on their stock 345's. How about on the their stock 392's?

I'm considring purchasing an Electronic Choke Kit (#1478), Off-Road Needle & Seat Assembly kit (#1465) and 1405 Calibration Kit (#1479), then set this carb up the best I can for my stock IH 392 prior to running it again.

Does the Edelbrock Off-Road kit work as well as the Holly Truck Avenger? Or more importantly, will it meet my 68 Travelall Adventure Rig needs?

Here's how the Edelbrock site says the two carbs are setup out of the box:

Edelbrock 1405:
0.100 Primary Jets
0.095 Secondary Jets
0.070-0.047 Metering Rods
Orange (5"Hg) Step-up Spring

Edelbrock 1406:
0.098 Primary Jets
0.095 Secondary Jets
0.075-0.047 Metering Rods
Yellow (4"Hg) Step-up Spring

If there is general agreement on the best way to setup an Edelbrock 1405 for a stock off-road use 392 with a maximum of 4,000RPM, maybe I can get away with just purchasing the exact components I need instead of the complete Calibration Kit???

ADDED: After reading through the Edelbrock Owner's Manual I see altitude plays a larger role than I thought. So, I'm at 1,700 in SoCal and most driving will be between sea level and 6,000 feet.

What are your thoughts?

If you were buying a carb, I'd tell you to get the 1406 since it already has the Electric choke.

But since you already have the 1405, I'd start with the same setup I use in a 1406. .098 main jets and .070x.037 rods should work fine for you. #26 on the 1405 calibration chart.

If you just want to start with one set of rods, I'd buy a set of .075x.047 rods and go to #25 on the chart.

Definitely put the offroad needle/seats in it.

The tuning kit is up to you. If you don't have any tuning parts I'd buy one. Once you've bought 3-4 individual pieces you paid more than the kit costs.


My $.02.

Will Marsh

[LeeC]

Thanks Will, your $0.02 is worth $$$'s!

The needles for position 26 on the chart are not in the $56 #1479 Calibration Kit. That is exactly why I asked.

Electric Choke kit ~$52
Off-Road Kit ~$12
0.075 x 0.047 Rods ~$8

INITIAL TOTAL: ~$72!

Your suggestion on moving to position 25 with just one set of 0.075 x 0.047 Metering Rods appears to be a good one. If that doesn't do it, then a pair of 0.098 Primary Jets are cheap.

Any thoughts on the Step-up Springs?

[Will Marsh]

Originally Posted by LeeC

Thanks Will, your $0.02 is worth $$$'s!

The needles for position 26 on the chart are not in the $56 #1479 Calibration Kit. That is exactly why I asked.

Electric Choke kit ~$52
Off-Road Kit ~$12
0.075 x 0.047 Rods ~$8

INITIAL TOTAL: ~$72!

Your suggestion on moving to position 25 with just one set of 0.075 x 0.047 Metering Rods appears to be a good one. If that doesn't do it, then a pair of 0.098 Primary Jets are cheap.

Any thoughts on the Step-up Springs?

I suspected they might not be. That's why I suggested #25 instead. You might notice that #26 is the ONLY place they use those rods on the 1405 chart.

If you compare the 1406 chart to the 1405 chart, you'll see that only the combinations #24 and higher on the 1405 appear on the 1406 chart. And those are in the Upper right (rich/rich) on the 1406 while they're bottom center on the 1405 chart (lean/neutral).

IME, every engine I've run one of these carbs on wants to be in the Top/center-right on the 1406 chart and Bottom/center on the 1405 chart.

And once you get the carb right for that altitude, it generally is pretty close on any engine in the 300-400ci range.

I run the stiffest (Silver or Purple) springs in all of mine or they hesitate when you punch the throttle. Lighter springs will give you better cruise mileage if you can tune out the hesitation with the jets/rods/accel pump settings.

I'll be in chat shortly if you want more direct feedback.


Will Marsh

[LeeC]

Good, I'm already one spring color stiffer than the 1406 at Orange.

One odd thing about the 1405 and 1406 charts is that neither show the other settings on there charts. It would be nice to know where the 1406 base sits on the 1405 chart, and the 1405 on the 1406.

One last question:
I'm having trouble understanding were I would fall on the 1405 chart if I set up the 1405 just like a 1406 (0.098 Primary Jets and 0.075 x 0.047 Metering Rods - only difference being the stiffer Orange springs). That would be just a change of Primary Jets from 0.100 to 0.098, from the 1405 position 25. Everything jumps all over the place when you just change the primarys. The closest I see on the 1405 chart is position 28 with 0.098 / 0.073 x 0.047. I'm guessing even leaner???

Can you help with that?

[LeeC]

Never mind... I found a couple common cross references:

28 on the 1405 chart = 24 on the 1406 chart

&

29 on the 1405 chart = 23 on the 1406 chart

That gives me enough to cross reference the two charts and puts a 1405 setup like a 1406 about 4 stages (16%) leaner on the Cruise Mode and about 1 stage (4%) leaner on the Power Mode on the 1405 chart.

Cool Edelbrock Owners Manual!

[LeeC]

After compeleting my research of how others have calibrated their stock 392's for the Edelbrock 1405(1406) the grouping of settings appear to be right were Will has stated. The Calibration Charts for the 1405 and the 1406 are below. The two groupings of four are the same Primary and Rod settings for each carb. At the bottom of the 1405 chart I have placed a circle where I believe the base setting for the 1406 is on the 1405 chart.

1405 positiion 25 = 1406 position 18
1405 position 26 = 1406 position 19 (the 1"9" is missing on the chart)
1405 position 28 = 1406 position 24
1405 position 29 = 1406 position 23

A 1405 calibrated like the base 1406 (Primary, Secondary and Rod) comes in all the way down at the bottom of the 1405 chart at about 4 stages leaner (16%) for Cruise Mode and about 1 stage leaner for Power Mode (4%).





Based on what I have researched, I plan the start with position 25 on the 1405 chart by changing the Metering Rods to 0.075 x 0.047 for my currently rich running stock 392 at 1,700 altitude. This 1405 position is 2 stages leaner for Cruise Mode and about neutral for Power Mode. I will initially leave the (stiffer than the 1406 Yellow) Orange springs in place.

It is worth noting that there is not a direct relationship between the "stages" on the 1405 and 1406 charts. I'm not sure why that is? Is it possible that the comment on the Edelbrock site that states the 1406 is designed 2% leaner than the 1405 is independent of the calibration components?

Hope this helps some others going down this road. The Edelbrock Owner's Manual is the best source for information on calibration I have found. Go figure...

1405 Owners Manual:
http://www.edelbrock.com/automotive_...405_manual.pdf

NOTE: There is about a $20 difference between the Calibration Kit for the 1405 and 1406. Look at the components you think you need.

[Doc Stewart]

Thank you, Lee. Good report.