Engine and Transmission Tech

Anybody run .080 jets in the primary & the secondary on a Buick/Rover V8 application?

> Anybody run .080 jets in the primary & the secondary on a Buick/Rover V8 application?

Not me. The baseline specs of the 500 CFM manual choke Edelbrock 1404 AFB carb are:

1423 jets (0.086" diameter) in primaries
1460 rod (0.065" x 0.052", stamped 6552)
orange step up springs (5" Hg)
1426 jets (0.095" diameter) in secondaries
center position accelerator pump
0.0935" needle and seat
11/32" float height (+/- 1/4" float drop)
middle accelerator pump link hole
0.028" accelerator pump nozzle diameter
500 CFM rating

At the time, my engine had headers, an Offy Dual Port and a Crane hydraulic flat tappet cam (H-216/285-2S-12). With the above rods and jets it was rich across the board. I tuned it with a wideband O2 sensor and was able to get it so I'm was cruising at 15.5:1 (lean of stoich for better fuel economy) with transition mixtures (climbing a hill, pulling a load, part throttle acceleration) in the 13.5 to 14:1 range and WOT in the 12.5 to 13:1 range. Pretty much ideal.

The Edelbrock carb manual has charts that correlates the rod and jet combinations to changes in mixture but not all possible combinations appear on the chart. Plus Carter makes rods and jets that Edelbrock does not. I wrote a little program to calculate all the possible rod/jet combinations and it helped me find a couple of rod/jet combos that worked better in my application. Using the combos on the Edelbrock chart, I couldn't get the primary power mode lean enough so I had to compensate by leaning down the secondaries a bunch. Getting the right primary rod/jet combo fixed that. I think I ended up with:

0.083" primary jets, Carter #16-241 rods (0.066" cruise step, 0.058" power step)
0.080" secondary jets

I recommend checking the rods with a micrometer. I had a couple of sets of #1461 rods which were machined differently and one pair didn't measure to spec. While they carried the same part number, it was obvious they were from different production batches (different machine step length and different stamped lettering). When I switched to the Edelbrock Performer Rover dual plane intake and a Wedgeshop Erson RV10/RV15 camshaft, I had to go back through the tuning exercise. That engine ended up with 0.089" primary jets and 0.083" secondary jets and either (my notes aren't clear) Edelbrock #1454 rods (0.073" cruise step, 0.037" power step) or #1455 rods (0.073" cruise step, 0.042" power step).

Why do you ask?

Dan Jones

Mine is the Carter 500. A bit fat at WOT (A/F reading drops to 10-11), but sits right at 15-16 on the Interstate. Still sucks for autox, though.

Current setting:

Primary Jet .083
Metering Rod 6852
Set-Up Spring Orange
Secondary Jet .089

I ask because a friend is having problems with his Edelbrock 500 1404. His jetting is set to a recommendation by some who is supposed to be in the know.

His setting:

Primary Jet .080
Metering Rod 6252
Secondary Jet .080

I plan to take my book & go help re-jet it.

[Quote] Mine is the Carter 500. A bit fat at WOT (A/F reading drops to 10-11), but sits right at 15-16 on the Interstate. Still sucks for autox, though.

Carl,

You know what the REAL fix is for that, time to step over to the dark side;-)!!

Bill



Edited 1 time(s). Last edit at 05/16/2015 05:21PM by MG four six eight.

Someday, Bill, someday. :)

> A bit fat at WOT (A/F reading drops to 10-11), but sits right at 15-16 on the Interstate. Still sucks for autox, though.
>
> Current setting:
>
> Primary Jet .083
> Metering Rod 6852
> Set-Up Spring Orange
> Secondary Jet .089

Seems like you could step down the secondary jets a few sizes to lean out the WOT A/F ratio and maybe try a rod that's a little leaner on the power step:

Cruise Power
Step Step
0.0680 0.0570 Carter 16P-330 or Edelbrock #1436)
0.0680 0.0555 (Carter 16P-98)

Dan Jones

Hey Dan,
I too have an Edelbrock Performer Rover dual plane intake, a Wedgeshop Erson RV10/RV15 camshaft with 4-2-1 headers and 2-1 exhaust. If I understand correctly, your current Edelbrock 1404/5 settings are:
• 0.089" primary jets
• 0.083" secondary jets
• (either) Edelbrock #1454 rods (0.073" cruise step, 0.037" power step)
or #1455 rods (0.073" cruise step, 0.042" power step).
• 1460 rod (0.065" x 0.052", stamped 6552)
• orange step up springs (5" Hg)
• center position accelerator pump
• 0.0935" needle and seat
• 11/32" float height (+/- 1/4" float drop)
• middle accelerator pump link hole
• 0.028" accelerator pump nozzle diameter

Yes?

Martin

Yes but I think I may have also tried a pair of Carter 16P-7240 rods (0.072" cruise step, 0.040" power step) which might be a bit safer (to account for cylinder-to-cylinder variation). It's not clear from my notes which set I ended up with. I could check the engine next time I get the chance.

Dan Jones

Thanks Dan.

I bought my carb and manifold used, from a crashed Disco, and have never checked to see what the settings are. My engine is running fairly rich across the board, and gets terrible mileage, so I'm going to have to pull it apart this weekend to see what the setup is and get sort it out. Hence my questions.

(Sorry for hijacking your thread temporarily, Carl)

Regards,
Martin

Martin/Dan,

Are the Primary/secondary jets not the other way around?

Not at sea level here but running a 4.6L, Prime 0.083, Rods 1463 (0.067x 0.055) and 2nd 0.086.
Wideband O2, 15 at cruise and 12.5 WOT.

> Are the Primary/secondary jets not the other way around?

I think yours are backwards. You have a smaller primary jet than your secondary jet and the rod reduces the primary jet effective area. If I did the math correctly, when your rods are on the cruise step, the effective primary jet diameter is 0.049. When its on the power step, the effective jet diameter is 0.0622. At wide open throttle, you want the effective diameter of the primary (on the power enrichment step) to be approximately the same as the secondary jet diameter for good mixture distribution. Right now you are much richer in the secondaries than the primaries at WOT. You also want the power enrichment to be approximately 25% richer than cruise. Since we know the effective jet diameter that provides your desired cruise air-fuel ratio and we know the overall jet area that provides your desired WOT A/F ratio, we could figure out which rods and jets would keep your A/F ratios while providing equal mixture distribution. That assumes a square bore carb and equal flowing intake ports. It's not unusual for some cylinders to flow more than others and sometimes stagger jetting is required (different jets and/or rods side-to-side).

Dan Jones

Dan,

Thanks for the details. My setup just came from 3 stages lean on Prime and secondary in the Edelbrock tunning manual. Carb starts out with larger Prime than secondary from the factory too, 0.086 vs 0.089. May have to play some more but it is running well now. Your method does make sense.

> Carb starts out with larger Prime than secondary from the factory too, 0.086 vs 0.089.

The carb has to work on a wide variety of engines. Whether the engine is a 3.5L or a 5.7L, a particular car at cruise only needs deliver enough fuel to support maybe 20 to 25 HP, but there can be a big difference between the amount of fuel required at WOT when the secondaries kick in. To be safe, Edelbrock/Carter installed secondary jets that would be rich so the carb wouldn't lean out (and hole a piston) even on a relatively high HP application.

Dan Jones

Dan,

Using your logic I come out with the following jets:
Prime 0.089, Rods 1455 (0.073 x 0.042) Same as you used.
2nd could be a 0.077 or 0.080.
Mains give me an effective Cruise Diam of 0.0509 and Power of 0.075. So Prime Power and 2nd are close in size and roughly what I had before (ave 0.074). Similarly the Cruise comes out close to before as well (0.049 vs 0.0509).
Now my question is how important is the 25% richer on Primary Power vs Cruise? And what are we calculating? Using your 0.089 main jets and the 0.073 x 0.042 rods we get 47% increase in Diameter. If we take area its a massive 137% increase. Or are you referring to AFR?
Hope I am not total off here.

Mike

Never trust your memory to recall Jets etc!
Turns out I am running 0.083 main and 0.065 X 0.052 Rods. Gives me the 25% enrichment based on diameter I think Dan was referring too. What is strange is that I tried 0.077 secondaries and I am still at 12 AFR on WOT. Sounds like a massive change but I guess its only a 6% reduction based on the average of secondaries and main jets on Power cycle. Now what I find odd is my heads only have minor work but this is a 4.6L after all with Crower 50232 cam. Hard to imagine a 3.5L needing a 0.089 secondary jet.

Carl, did you get it sorted out?

So, two years on.

On my 3.5 - JWR/Offenhauser dual port, Piper 270 cam - I just changed the needles in my Edelbrock 1404 to 6755s. With the stock 086 jets, these are about 8% leaner on cruise and 6.8% leaner on the power step.

Still have the stock 095 secondaries.

Bearing in mind that I can't measure the afr and therefore need to be cautious, any recommendations for secondary jet sizes?
Or, given that the vacuum at WOT won't be very high, should I leave them alone?

Ivor

Heated up the engine for the first time with the 6755 needles.

Didn't need to touch the idle speed, it sat at 790rpm.

The vacuum went up. With the stock needles, the best I could get was 11", Now, I have 12,25"Hg, and although the 6755 needles are weaker, I have the idle screws around a quarter turn tighter.

No fluff off-idle. The idle has a slight lope.

Think that's it until I get to a rolling road.

Ivor

Just to round this off as far as my engine is concerned, see here [forum.britishv8.org]

Ivor

How big is that cam on that li'l 21, Ivor? I would expect a good bit more vacuum than that.

It's a Piper 270.[www.v8engines.com]

I remember the engine in my TR6 with its unknown big cam never made more than 7".

Ivor